Atea Pharmaceuticals, Inc. (AVIR) Business

Item 1. Business.

Overview

We are a late-stage clinical biopharmaceutical company leveraging our deep understanding of antiviral drug development, medicinal chemistry, biochemistry and virology to discover, develop and commercialize novel, orally administered antivirals to treat serious viral diseases. Our current product candidate pipeline includes the regimen of bemnifosbuvir and ruzasvir which we believe has the potential to improve the current standard of care (“SOC”) for the treatment of patients with hepatitis C virus (“HCV”) infection and AT-587 which we believe has the potential to be the first direct-acting antiviral (“DAA”) for the treatment of patients, particularly immunocompromised patients, with chronic hepatitis E virus (“HEV”) infection.

HCV - Our Goal and our Program

The objective of our HCV development program is to improve upon the current SOC by offering bemnifosbuvir and ruzasvir as a differentiated pan-genotypic protease inhibitor-free, short-duration regimen for patients infected with HCV, if successfully developed and approved. We believe that a novel treatment regimen that can be easily prescribed will benefit today’s HCV population, which is predominately young (20-49 years old) and non-cirrhotic, and it would be a significant improvement to the current SOC.

Presently, there are no short-course (i.e., 8 week) nucleotide inhibitor-based, pan-genotypic HCV treatment regimens. Clinical and nonclinical results from studies conducted to date, including a global Phase 2 clinical trial which enrolled 275 HCV infected patients, have shown that the regimen of bemnifosbuvir and ruzasvir has high potency and has been well tolerated. These studies have also shown that the regimen has a low risk for drug-drug interactions (“DDIs”) with many commonly prescribed medications including proton pump inhibitors and offers the convenience of being able to be taken with or without food. This is a profile that we believe will offer a significant improvement to the current SOC, if approved.

The global HCV Phase 3 program we are conducting consists of two randomized, open label studies: C-BEYOND which has clinical trial sites in the US and Canada, and C-FORWARD which has clinical trial sites in countries outside of North America. In these Phase 3 trials we are comparing our regimen of bemnifosbuvir and ruzasvir to an active comparator, the regimen of sofosbuvir and velpatasvir, in patients with chronic HCV infection. We are conducting the Phase 3 program in geographically diverse regions in order to enroll patients with a broad array of HCV genotypes (“GT”).

C-BEYOND is fully enrolled with over 880 patients, and we expect to report topline results mid-2026. We are actively progressing enrollment of an additional 880 patients in C-FORWARD and expect to report topline results from C-FORWARD at year-end 2026. Pending successful results from these Phase 3 clinical trials, we are targeting submission to US Food and Drug Administration (“FDA”) of a New Drug Application (“NDA”) for marketing approval in March 2027.

We are executing a focused chemistry, manufacturing and controls (“CMC”) strategy to provide fixed dose combination (“FDC”) tablets for the completion of the Phase 3 program and to prepare us for potential launch with commercial supply sufficient for projected initial sales if the regimen of bemnifosbuvir and ruzasvir is approved for marketing.

Given the large number of patients currently infected with HCV, which is reported by the US Centers for Disease Control and Prevention to be as many as four million persons in the US, and the incidence of newly reported chronic infections continuing to outpace rates of treatment, we expect that a substantial global market will exist for the foreseeable future. In 2025, global net sales of branded HCV therapeutics

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known in the US as Epclusa® (including the authorized generic copy of Epclusa) and Mavyret® exceeded $2.5 billion with the US accounting for approximately 50% of these sales.

HEV – Our Goal and Our Program

We are developing AT-587 for the treatment of chronic HEV infection in immunocompromised patients. In this high-risk patient population, infection with HEV can rapidly progress to cirrhosis and other serious complications.

There are no DAAs currently available for the treatment of HEV. The most frequent interventions include reduction of immunosuppressive agents which, in solid organ transplant recipients, increases risk of transplant rejection, or off-label treatment with ribavirin which is indicated for treatment of other viruses but hindered by serious adverse events (“SAEs”) and limited HEV efficacy. The severity of disease in high-risk patients combined with the lack of approved HEV therapies is a substantial unmet medical need which we believe can be addressed if AT-587 is successfully developed.

AT-587 has demonstrated potent nanomolar antiviral activity against HEV in vitro. In single-dose in vivo nonclinical pharmacokinetic (“PK”) studies, high plasma concentrations of the surrogate to the active intracellular triphosphate metabolite were observed in all animal species tested. Results from in vitro toxicology, pharmacology and drug metabolism and pharmacokinetic (“DMPK”) studies indicate the potential for a favorable clinical profile for AT-587. Additional Investigational New Drug Application/Clinical Trial Application (“IND/CTA”) enabling studies are ongoing. Currently, we anticipate initiating clinical development of AT-587 with a first-in-human Phase 1 study in mid-2026.

We believe that developing a treatment for HEV, particularly a product candidate derived from our proprietary platform, is a potentially important and advantageous strategic expansion of our antiviral pipeline. If both product candidates are successfully developed and approved, we will have a hepatology portfolio that we anticipate will improve upon the current SOC for HCV and introduce the first DAA for HEV.

Our Technology Platform and Nucleos(t)ides Role in Antiviral Therapy

Leveraging our deep understanding of virology, medicinal chemistry and antiviral drug development, we have built a proprietary platform of nucleosides and nucleotides (together “nucleos(t)ides”) to develop novel product candidates to treat single stranded ribonucleic acid (“ssRNA”) viruses, which are a prevalent cause of serious viral diseases. Bemnifosbuvir and AT-587 have been derived from this platform.

Over the last 40 years, nucleos(t)ide analogs have been developed to mimic naturally occurring nucleic acids and disrupt viral replication and they are the foundation of many currently commercialized DAAs used to treat serious viral infections, including human immunodeficiency virus (“HIV”), hepatitis B virus (“HBV”), and HCV.

By leveraging this proven foundational modality, together with our virology, medicinal chemistry and antiviral drug development experience and expertise, we continue to expand and position our platform to generate next‑generation nucleos(t)ide antivirals with broad applicability across high‑burden ssRNA viruses.

Our Team

We have assembled and are utilizing the expertise and experience of a team with a demonstrated track record of efficiently and successfully discovering, developing, obtaining global regulatory approvals and commercializing innovative oral DAAs. Our team has very specific expertise in the identification of unmet patient needs, virology, medicinal chemistry, particularly nucleos(t)ide chemistry and optimization, drug discovery, preclinical and clinical development, regulatory affairs and commercialization.

We have relied on that expertise to:

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discover bemnifosbuvir, the investigational, novel, double prodrug nucleotide analog, which we are developing in combination with ruzasvir for the treatment of HCV;

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identify and in-license ruzasvir, the investigational NS5A inhibitor, which we are evaluating in combination with bemnifosbuvir for the treatment of HCV; and

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discover AT-587, the investigational, novel double prodrug nucleotide analog, which we are developing for the treatment of HEV.

We are also relying on this expertise as we expand and leverage our proprietary nucleos(t)ide platform in our efforts to discover and develop other innovative product candidates for the treatment of serious viral diseases for which no DAAs are approved or for which the SOC may be significantly improved.

Our Product Pipeline

The chart below depicts key information regarding the development of the regimen of bemnifosbuvir and ruzasvir for the treatment of HCV and the development of AT-587 for the treatment of HEV, including development status and anticipated milestone events.

Antiviral Therapy

Background on viruses and infection

Viruses are cellular parasites that lack the machinery needed to survive and replicate independently. They rely on a host cell’s replication systems to reproduce. Unlike living organisms, such as humans, which universally use DNA as their genetic material, viruses may use either DNA or RNA. Approximately 70% of known viruses are RNA viruses. These can be further classified as ssRNA or double-stranded RNA viruses depending on the type of RNA that constitutes their genome. HCV and HEV are ssRNA viruses.

Infection begins when a virus binds to a specific receptor on the host cell membrane through attachment proteins. Once inside the host cell, RNA viruses use their RNA as a template to produce both new genomic RNA and viral messenger RNA (“mRNA”). These mRNAs then encode nonstructural proteins responsible for viral replication and transcription, as well as structural proteins needed to assemble and secrete new virions. These newly formed virus particles then exit the host cell via a secretion process and continue the infection cycle.

Viral polymerase as an antiviral target

Viral polymerases are essential, highly conserved enzymes upon which viruses rely to replicate their genomes, making them one of the most validated and strategically attractive antiviral targets. RNA-dependent RNA polymerase (“RdRp”) is used for replication by all ssRNA viruses. Because human cells lack RdRp, inhibitors can selectively block viral replication with reduced toxicity and lower risk of resistance. Advances in technology have enabled intensive structural and functional studies of viral RNA polymerases and have opened avenues for the development of new and more effective antiviral therapies.

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Viral resistance and variants

Viral resistance remains a major challenge for DAAs, driven by the ability of viruses, especially RNA viruses, which lack proofreading abilities, to mutate at up to six orders of magnitude higher than human cells. These rapid genetic changes can reduce susceptibility to existing therapies and lead to the continual emergence of new viral variants with distinct genetic profiles. Such variants may differ in transmissibility or virulence and, in some cases, cause more severe disease. Importantly, these mutations can also diminish the effectiveness of vaccines and therapeutics, underscoring the need for antiviral therapeutics that maintain potency despite ongoing viral evolution.

Nucleos(t)ide analogs and prodrugs

Naturally occurring nucleic acids – DNA and RNA - are composed of nucleosides and nucleotides that store and transmit genetic information in both human and viral cells. Nucleos(t)ide analogs are synthetic compounds that mimic the structure of naturally occurring nucleosides and nucleotides that directly target viral polymerases, leading the enzyme to mistakenly incorporate the analogs into nascent nucleic acids, causing inhibition of viral replication. Because viral polymerases must maintain highly conserved structural features to replicate and produce viable virions, nucleos(t)ide analogs exhibit a higher barrier to resistance compared to other antiviral classes. These agents are often delivered as prodrugs, which enhance cellular uptake, improve bioavailability, reduce toxicity, and bypass rate-limiting activation steps. As a result, nucleos(t)ide analog prodrugs form the backbone of many frontline antiviral regimens for life-threatening infections such as HIV, HBV, and HCV.

Our Development Programs

The regimen of Bemnifosbuvir and Ruzasvir for the Treatment of HCV

HCV – Disease Overview

HCV is a blood-borne, positive sense, ssRNA virus, that primarily infects liver cells. HCV is a leading cause of chronic liver disease, liver transplants and liver cancer. It is most commonly transmitted through the reuse or inadequate sterilization of medical equipment (especially syringes and needles in healthcare settings), the transfusion of unscreened blood and blood products, and injection drug use through sharing of contaminated syringes and needles. HCV infection becomes chronic in 75% to 85% of acute cases, with an incubation period lasting from two to 26 weeks.

HCV is classified into seven GTs (GT-1 through GT-7) and 67 subtypes that vary in distribution worldwide. In the US, HCV GT-1 is the predominant GT followed by GT-2 and GT-3 with other GTs accounting for less than 2% of the cases. Patients with HCV are also categorized by liver function: no cirrhosis (or non-cirrhotic) refers to no liver scarring; compensated cirrhosis refers to liver scarring without clinically significant functional impairment; or decompensated cirrhosis refers to liver scarring with moderate to severe loss of liver function.

According to the World Health Organization (“WHO”), an estimated 50 million people globally live with chronic HCV infection, with approximately one million new infections occurring each year. The WHO estimated that approximately 242,000 people died in 2022 (its most recent estimate) from HCV-related liver diseases. Most HCV-related deaths are due to liver scarring (cirrhosis) and liver cancer (hepatocellular carcinoma).

However, it is reported that there is a wide gap between the number of reported cases versus estimated cases. Most individuals who become infected with HCV remain unaware that they are infected because HCV can go undetected until the condition progresses to symptomatic disease or until specific clinical tests are performed to confirm diagnosis. Consequently, cases are underreported, skewing actual disease prevalence rates. The burden of underreporting is realized when high medical expenditures (comorbid treatment costs, liver transplants) and mortality rates from advanced chronic liver disease do not proportionally align with reported prevalence rates.

Diagnosis of HCV and Expanding Adoption of the Test-and-Treat Model of Care

Traditionally, HCV diagnosis has relied on a two‑step laboratory process that begins with an HCV antibody test to determine whether a person has ever been exposed to the virus. A reactive antibody

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result is then followed by nucleic acid testing to detect HCV RNA, which confirms whether an active infection is present. Although accurate, this approach depends on access to healthcare, phlebotomy services and laboratories, and multiple patient visits, which can lead to delays, incomplete testing, and loss to follow‑up. As a result, many people with active HCV infection, particularly high-risk patients who may lack standard and routine healthcare, may remain undiagnosed, and if diagnosed, fail to start HCV treatment in a timely manner or at all.

Newer diagnostic tools, including point‑of‑care nucleic acid testing, which now are a part of HCV treatment guidelines for certain patient populations, are addressing these challenges. These point-of-care diagnostic tools frequently use finger stick testing rather than venipuncture requiring phlebotomy services, with droplet samples then screened at the point-of-care for immediate identification of active HCV infection. This prompt diagnosis can then be followed by immediate initiation of therapy occurring all in in one visit, rather than multiple patient visits. This model of care, referred to as the “test-and-treat” model, has been shown to reduce delays and increase treatment starts for HCV patients. Expanding adoption and use of the test-and-treat model of care is recognized as a critically important element to further HCV eradication efforts.

Antivirals for the treatment of HCV

While no vaccine exists for the prevention of HCV, several sequentially improved oral antiviral therapeutics have been introduced beginning in 2014. Currently, the leading HCV products are combination therapies comprised of agents with differing mechanisms of action and therapeutic targets: NS3/4A protease inhibitors, NS5A inhibitors, and NS5B nucleos(t)ide polymerase inhibitors. The patient’s cirrhotic status, concomitant medications, co-infection status and any prior HCV treatment are factors used by healthcare providers to determine the appropriate antiviral to be used in treatment. In the US, the two leading therapeutics for treatment of chronic HCV are:

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Epclusa® (sofosbuvir and velpatasvir): a fixed-dose combination regimen consisting of sofosbuvir, an HCV nucleotide analog NS5B polymerase inhibitor, and velpatasvir, an HCV NS5A inhibitor, was first approved by the FDA in 2016. It is indicated for the treatment of adults and pediatric patients ≥3 years with chronic HCV GT-1, -2, -3, -4, -5 or -6 infection, without cirrhosis or with compensated cirrhosis. For patients with decompensated cirrhosis, Epclusa is approved for use in combination with ribavirin (a guanosine analog which is a broad-spectrum antiviral). The recommended dosage in adults is one tablet (400 mg of sofosbuvir and 100 mg of velpatasvir) taken orally once daily with or without food for 12 weeks.

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Mavyret® (glecaprevir and pibrentasvir): a fixed-dose combination regimen consisting of glecaprevir, an HCV NS3/4A protease inhibitor, and pibrentasvir, an HCV NS5A inhibitor, was first approved by the FDA in 2017. It is indicated for the treatment of adults and pediatric patients ≥3 years with chronic HCV GT-1, -2, -3, -4, -5 or -6 infection, without cirrhosis or with compensated cirrhosis. The recommended dosage in adults is three tablets (100 mg glecaprevir and 40 mg pibrentasvir in Mavyret was the first and remains the only 8-week treatment approved for HCV GT-1, -2, -3, -4, -5 or -6 in adult patients without cirrhosis and with compensated cirrhosis who have not been previously treated. Longer treatment durations (up to 16 weeks) are indicated for some treatment-experienced HCV populations. Mavyret is not approved for use in patients with decompensated cirrhosis.

Our HCV Product Candidate Development

We are developing the regimen of bemnifosbuvir and ruzasvir for the treatment of HCV. Based on our preclinical and clinical data to date, we believe that this regimen, if approved, has the potential for use within the expanding test-to-treat model of care by offering the following potential benefits:

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convenient (no food effect) protease inhibitor-free treatment with an 8-week duration in HCV-infected patients without cirrhosis and a 12-week duration for HCV-infected patients with compensated cirrhosis;

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high efficacy across all HCV GTs, including GT-3, regardless of cirrhosis status;

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low risk of DDIs including with commonly prescribed agents such as proton pump inhibitors; and

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well tolerated.

We believe the high potency of the bemnifosbuvir and ruzasvir combination across all HCV GTs will reduce the need for prescribers to identify in the diagnostic process, the infection GT and the low risk of DDIs will simplify patient management by reducing the need for co-medication adjustments. Additionally, we believe that patient adherence will be enhanced by a potential treatment course that can be taken with or without food and is 8-weeks in duration for non-cirrhotic patients.

Modeling data indicating a dual mechanism of action of bemnifosbuvir against HCV

The established mechanism of action of bemnifosbuvir, a nucleotide analog HCV NS5B polymerase inhibitor, is the inhibition of HCV RNA and chain termination which blocks viral replication of HCV virions inside the host cell. Recent modeling of HCV viral kinetics from a bemnifosbuvir Phase 1B monotherapy study suggests that bemnifosbuvir may also block the assembly and secretion of progeny HCV virions into the bloodstream, further inhibiting viral infectivity as a result of a reduction in extracellular HCV virus titers. We believe that this inhibition by bemnifosbuvir of the assembly/secretion of new HCV virions, an additional distinct mechanism of action, may further explain the high antiviral potency of bemnifosbuvir and the regimen combining bemnifosbuvir and ruzasvir for the treatment of HCV.

Non-clinical data supporting the clinical development of the regimen of bemnifosbuvir and ruzasvir for the treatment of HCV

To support the clinical development of the bemnifosbuvir and ruzasvir regimen, we conducted multiple in vitro experiments and studies.

Viral resistance has emerged as an important consideration since it may impact the effectiveness of antiviral treatments for HCV infection. We profiled the antiviral activity of AT-511, the free base of bemnifosbuvir, and ruzasvir against major HCV NS5A and NS5B Resistance-Associated Substitutions ("RASs ") selected in vitro or identified in HCV patients with hard-to-treat sub-genotypes who have failed treatment with currently available DAAs.

In these in vitro studies, AT-511 was approximately 10-fold more active than sofosbuvir against a panel of laboratory strains and clinical isolates of HCV GTs tested (GT-1, -2, -3, -4, and -5) and bemnifosbuvir was not resistant to known sofosbuvir RASs such as S282T and L159F/S282T. AT-511 also retained antiviral activity against most HCV GT-1a and HCV GT-3a NS5A single RASs tested.

In GT-1a, ruzasvir was 10 times more active than velpatasvir, and retained single-digit picomolar potency against a panel of RASs selected by previous NS5A inhibitors and was 10 times more potent than velpatasvir against selected double mutants. In HCV GT-3a, one of the most difficult to treat HCV GTs,

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ruzasvir was six times more active than velpatasvir and retained sub-nanomolar potency against select NS5A RASs which were treatment-emergent in HCV GT-3 patients failing currently available DAAs.

Ruzasvir and a panel of other NS5A inhibitors were profiled for antiviral activity against seven difficult-to-treat HCV sub-genotypes using the HCV GT-1b replicon backbone. Both ruzasvir and velpatasvir maintained picomolar potency over the majority of these difficult-to-treat sub-genotypes such as HCV GT-1l, -4r, and -6v. All tested NS5A inhibitors exhibited 100- to 1000-fold EC50 shifts for HCV GT-3b and GT-3g.

Clinical Development

Summary

In 2025, after aligning with each of the FDA at an End-of Phase 2 meeting and the European Medicines Agency (“EMA”), on the design, endpoints and statistical plans, we initiated Phase 3 clinical development comparing the regimen of bemnifosbuvir and ruzasvir to the regimen of sofosbuvir and velpatasvir for the treatment of chronic HCV infection.

Our Phase 3 program continues to progress with two ongoing clinical trials. We expect to complete and announce Phase 3 topline results from C-BEYOND, which is fully enrolled with over 880 chronically infected HCV patients, in mid-2026. We expect to complete and report topline results for C-FORWARD at year-end 2026 with patient enrollment actively progressing on schedule. Pending successful results from these Phase 3 clinical trials, we currently anticipate submitting an NDA to the FDA in March 2027 with submission of a Marketing Authorization Application (“MAA”) to the EMA thereafter.

Our advancement to Phase 3 development has been supported by several earlier stage trials including a global Phase 2, single-arm, open-label trial in 275 treatment-naïve patients with chronic HCV infection (both with and without compensated cirrhosis) who received bemnifosbuvir (550 mg) and ruzasvir (180 mg) once daily for eight weeks. Patients with HCV GT -1, -2, -3 and -4 enrolled in the trial. In this study, the regimen met its primary endpoint of sustained virologic response (“SVR”) at 12 weeks post-treatment (“SVR12”) and was well-tolerated.

In the Phase 2 study’s primary analysis population, which was the per-protocol treatment adherent population (n=215), the overall SVR12 rate was 98%. The efficacy evaluable patient population (n=259), which included 17% treatment non-adherent patients, achieved a 95% SVR12 rate. High SVR12 rates (99%) were observed in patients without cirrhosis (n=181) with the 8-week regimen. Treatment adherent patients with cirrhosis (n=34) achieved an 88% SVR12 rate. Although viral kinetics were slower in cirrhotic patients, all patients with cirrhosis (100%; 34/34) achieved an end of treatment response at Week 8. Based on these Phase 2 results, including viral kinetic modeling of such results, the ongoing Phase 3 clinical trials are evaluating the regimen of bemnifosbuvir and ruzasvir for eight weeks of treatment for patients without cirrhosis and for 12 weeks of treatment for patients with compensated cirrhosis. We believe that the longer treatment duration of bemnifosbuvir and ruzasvir being studied in patients with compensated cirrhosis in the Phase 3 clinical trials will improve SVR12 rates, as compared to those rates observed in the Phase 2 study for patients with cirrhosis.

Other earlier clinical studies conducted with bemnifosbuvir as monotherapy or in combination with daclatasvir (a first generation NS5A inhibitor) and ruzasvir as monotherapy or in combination with other DAAs also supported the advancement to Phase 3 development. Dose-related HCV RNA reductions in HCV-infected subjects were observed in a bemnifosbuvir monotherapy study, with the once daily bemnifosbuvir doses of ~550 mg showing the highest HCV RNA reductions. Bemnifosbuvir exhibited equally potent antiviral activity regardless of GT (including GT-3 infected subjects) or cirrhosis status, with HCV RNA reductions of 4.4 - 4.6 log10 IU/mL with 7-day dosing. In the first Phase 2 treatment study of bemnifosbuvir with a first-generation NS5A inhibitor (daclatasvir), similar potent viral kinetics were observed with eight of nine GT-1-infected subjects achieving SVR12 after eight weeks of treatment. For ruzasvir, results from a Phase 1b proof-of-concept ("POC") study in HCV-infected subjects (GT-1, -2 and -3) conducted by Merck showed HCV viral load reductions greater than 3 log10. High SVR12 rates were

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subsequently observed in Phase 2 studies conducted by Merck evaluating 180 mg ruzasvir as part of a prior combination not including bemnifosbuvir.

Phase 1 clinical pharmacology studies conducted in healthy subjects also supported the advancement of the regimen of bemnifosbuvir and ruzasvir to Phase 3 clinical development and support a potentially competitively advantaged product profile which in addition to high potency includes a low risk of DDIs and convenience of administration as the regimen can be taken with or without food.

The PK of combined bemnifosbuvir and ruzasvir were evaluated in studies conducted in healthy subjects, both as individual formulations and as the fixed dose combination (“FDC”) tablet being used in the ongoing Phase 3 clinical trials. In addition, the PK of bemnifosbuvir and ruzasvir administered separately and in combination with other concomitant medications has been studied in multiple phase 1 studies. These studies demonstrated the combination of bemnifosbuvir and ruzasvir has low potential for DDIs with the concomitant medications that have been studied, including gastric acid reducing agents (omeprazole, a proton pump inhibitor, and famotidine, an H2-blocker), Biktarvy®, a commonly prescribed HIV antiretroviral, and therapeutics that are sensitive substrates of CYP3A, efflux or hepatic uptake transporters. A standard high-fat/high-calorie test meal did not reduce the plasma exposure to bemnifosbuvir or ruzasvir, supporting dosing of the regimen with or without food.

Prior to commencing the ongoing Phase 3 program, over 2,300 human subjects had been exposed to bemnifosbuvir collectively across the HCV program and a prior Coronavirus Disease 2019 ("COVID-19") development program, at differing doses (single doses up to 1100 mg twice per day ("BID")) and durations up to 12 weeks. Additionally, over 2,100 human subjects had been exposed to ruzasvir in clinical studies conducted by Merck initially and more recently by us, including the Phase 2 study of the bemnifosbuvir and ruzasvir combination.

Both bemnifosbuvir and ruzasvir either alone or in combination have been well-tolerated. Across our completed studies, there have been no study drug-related serious adverse events (“SAEs”) reported for either bemnifosbuvir or ruzasvir.

Global Phase 3 Clinical Development

The global HCV Phase 3 program we are currently conducting includes two randomized, open label Phase 3 non-inferiority trials comparing the FDC regimen of bemnifosbuvir and ruzasvir (“BEM/RZR FDC”) to the FDC regimen of sofosbuvir and velpatasvir (“SOF/VEL FDC”) in patients with chronic HCV infection. C-BEYOND, is being conducted in the US and Canada, and C-FORWARD is being conducted outside of North America. We are conducting the Phase 3 program in geographically diverse regions to enroll patients with a broad array of HCV genotypes.

Each Phase 3 trial is designed to enroll approximately 880 treatment-naïve patients, both with and without compensated cirrhosis. Patients are stratified by GT and cirrhosis status, and patients with controlled HIV co-infection are allowed to enroll in the trials. For patients without cirrhosis, bemnifosbuvir and ruzasvir is being given for eight weeks and sofosbuvir and velpatasvir is being given for 12 weeks. For patients with compensated cirrhosis, patients in both treatment arms are receiving 12 weeks of treatment.

In the Phase 3 trials, we are using a FDC tablet, consisting of 275 mg of bemnifosbuvir and 90 mg of ruzasvir. Two tablets are being administered once daily for a total daily dose of 550 mg of bemnifosbuvir and 180 mg of ruzasvir.

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Global HCV Phase 3 Program: C-BEYOND (US/Canada) and C-FORWARD (Outside North America)

Each trial in the Phase 3 program is an open label study. While blinding the clinical trial sites and the patients to the treatment assignment is not possible due to the varying lengths of treatment and the necessity to provide the active comparator, the regimen of SOF/VEL FDC, in its commercially available packaging, staff at Atea who are monitoring the clinical trials, are and expect to remain blinded to individual patient treatment assignments until completion of the respective study, including during any internal cumulative data reviews and reviews of data by the studies’ data safety monitoring board.

The primary efficacy endpoint in each Phase 3 trial is HCV RNA less than the lower limit of quantification (“LLOQ”) at 24 weeks from the start of treatment (“SVR at Week 24”). However, the primary analysis population in which the endpoint is to be assessed will differ for each trial. In C-BEYOND, the trial being conducted in the US and Canada, the primary efficacy endpoint will be measured in a modified intent-to-treat (“mITT”) population. In agreement with the FDA, the mITT population includes all patients randomized and dosed. In C-FORWARD, the trial outside North America, the primary efficacy endpoint will be measured in a per-protocol (“PP”) population. In agreement with the EMA, the PP population includes all patients randomized, study drug compliant (≥80% based on pill count) and who have an assessment at the Week 24 timepoint. However, for each trial, the key secondary endpoint will be SVR at Week 24 in the opposite analysis population (i.e., the PP population for C-BEYOND, and the mITT population for C-FORWARD). The differing primary analysis populations for each trial are a result of differing feedback from regulatory authorities (e.g., the FDA prefers the mITT analysis, and the EMA prefers the PP analysis.)

Measurement of sustained viral response at the Week 24 study visit was selected to ensure the primary endpoint occurs at the same relative time point from start of treatment in all patients. As the treatment duration is eight weeks for patients without cirrhosis in the bemnifosbuvir and ruzasvir study arm and 12 weeks for all other study arms, the primary endpoint also encompasses the period at least through the SVR12 timepoint for each treatment arm.

Global Phase 2 Clinical Trial

We have completed a global Phase 2 study of bemnifosbuvir in combination with ruzasvir which enrolled 275 treatment-naïve patients infected with HCV GT -1, -2, -3 and -4, both with and without compensated cirrhosis. This study, which met its primary endpoints, evaluated the safety and efficacy of eight weeks of treatment with the regimen consisting of once daily bemnifosbuvir 550 mg and ruzasvir 180 mg.

The primary endpoints of the Phase 2 study were safety and SVR12 in the PP treatment adherent population (population which was adherent to the treatment). Secondary and other endpoints included

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SVR12 in the efficacy evaluable population (a broader analysis population which included treatment of non-adherent patients), SVR24, virologic failure and resistance.

Phase 2 Open Label Study of Bemnifosbuvir + Ruzasvir in HCV-Infected Patients

The study met its primary endpoints of safety and SVR12. The regimen was generally well-tolerated with no drug-related SAEs.

Primary efficacy endpoint results demonstrated a 98% (210/215) SVR12 rate in the PP treatment adherent patient population after eight weeks of treatment with the regimen of bemnifosbuvir and ruzasvir. The efficacy evaluable patient population, which included 17% treatment of non-adherent patients, achieved a 95% (245/259) SVR12 rate.

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SVR12 Rates with 8 Weeks Bemnifosbuvir + Ruzasvir in Treatment Adherent Patients (Primary Endpoint Analysis) and Regardless of Treatment Adherence

Furthermore, 99% (180/181) of treatment adherent patients who were non-cirrhotic and infected with GT-1, -2, -3, and -4 achieved SVR12, supporting the pan-genotypic potency of the regimen and our selection of an 8-week treatment for non-cirrhotic patients in the Phase 3 program.

SVR12 Rates by Genotype with 8 Weeks Bemnifosbuvir + Ruzasvir in Non-cirrhotic Treatment Adherent Patients

High SVR12 rates were also observed in non-cirrhotic patients regardless of treatment adherence, including in patients with GT-3 infection.

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SVR12 Rates with 8 Weeks Bemnifosbuvir + Ruzasvir in Non-cirrhotic Patients Regardless of Treatment Adherence (Overall and GT-3)

Treatment adherent patients with compensated cirrhosis achieved an 88% (30/34) SVR12 rate. While viral kinetics were slower in cirrhotic patients, all (100%; 34/34) achieved an end of treatment response (at Week 8). Based on these Phase 2 results, including viral kinetic modeling of the results, the ongoing Phase 3 clinical trials are evaluating treatment durations for the regimen of bemnifosbuvir and ruzasvir of eight weeks in patients without cirrhosis and 12 weeks in patients with compensated cirrhosis.

Viral Kinetics in Treatment Adherent Patients with Cirrhosis

There were 14 patients who experienced virologic failure in the Phase 2 study, five of whom were in the PP treatment adherent patient population and relapsed at four weeks post treatment (one non-cirrhotic; four cirrhotic). Resistance analyses indicated that SVR12 rates were not impacted by resistance associated substitutions. Rather, viral kinetic and pharmacokinetic analyses indicated that most of the viral failures were due to treatment non-adherence. These analyses further supported the regimen’s high barrier to resistance in patients infected with HCV. The long-term durability of response was sustained as there were no virologic failures between 12 and 24 weeks post treatment.

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Multiscale Viral Kinetics Modeling

To further inform the design of the Phase 3 clinical trials, the Phase 2 results were further evaluated in a multiscale viral kinetics model of HCV infection and treatment to estimate the efficacy of the regimen of bemnifosbuvir and ruzasvir. In this model, the population estimate for the time to achieve HCV RNA LLOQ in the blood plasma was approximately 12 to 16 days while the corresponding time to achieve cure, defined as HCV viral load below 6.67×10-4 IU/mL, was approximately seven to eight weeks. We believe these modeling data, which are shown below, provide further support for the regimen of bemnifosbuvir and ruzasvir being evaluated in the ongoing Phase 3 program with treatment durations of eight weeks in patients without cirrhosis and 12 weeks in patients with compensated cirrhosis.

Predicted Median Time to Viral Clearance by Fibrosis Stage Based on Phase 2 Results

Early HCV Phase 1 and Phase 2 Clinical Trials with Bemnifosbuvir

Other clinical studies conducted with bemnifosbuvir as monotherapy or in combination with daclatasvir (a first generation NS5A inhibitor) also supported the advancement to Phase 3 development of the regimen of bemnifosbuvir and ruzasvir. In a Phase 1 bemnifosbuvir monotherapy study, dose-related HCV RNA reductions in HCV-infected subjects were observed with the once daily bemnifosbuvir doses of ~550 mg showing the highest HCV RNA reductions. Bemnifosbuvir exhibited equally potent antiviral activity regardless of HCV GT (including HCV GT-3 infected subjects) or cirrhosis status, with HCV RNA reductions of 4.4 - 4.6 log10 IU/mL with 7-day dosing.

In a Phase 2 treatment study of bemnifosbuvir with a first-generation NS5A inhibitor (daclatasvir), similar potent viral kinetics were observed with 8 of 9 HCV GT-1-infected subjects achieving SVR12 after eight weeks of treatment.

Early HCV Phase 1 and Phase 2 Clinical Trials with Ruzasvir

Ruzasvir is an investigational oral, pan-genotypic NS5A inhibitor that we licensed from MSD International GmbH, an affiliate of Merck & Co., Inc. (“Merck”), in December 2021. In studies conducted by Merck, ruzasvir demonstrated in vitro potent antiviral activity with an EC50 in the sub- to low picomolar range against all GTs (10 pM against GTs 1-7). The antiviral activity of ruzasvir was evaluated in a POC study in HCV-infected patients, where viral load reductions 3 log10 were observed in HCV GT-1, GT-2 and GT-3 infected patients after treatment with monotherapy. This clinical antiviral activity is on par with what was achieved, as single agents, with pibrentasvir and velpatasvir, the NS5A inhibitor components of Mavyret

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and Epclusa, respectively. These POC data supported evaluation of ruzasvir in larger Phase 2 multiple drug combination studies (including two and three drug regimens) previously conducted by Merck. These studies included treatment-naïve and interferon-experienced patients with or without compensated cirrhosis. In general, high SVR12 rates (90%) were observed in two-drug combination studies (ruzasvir plus uprifosbuvir, a pyrimidine nucleotide prodrug, for 12 weeks) conducted by Merck in GT-1, -2, -4 and -6-infected patients (C-Breeze 1 and 2). A lower SVR12 rate was observed in GT-3 subjects with compensated cirrhosis (40% SVR12; C-Breeze 1). We believe this lower rate is attributed to the reduced antiviral activity associated with the nucleotide uprifosbuvir in GT-3 cirrhotic subjects as an increase in ruzasvir dose to 180 mg substantially increased the SVR12 rate in this population (68% SVR12; C-Breeze 2), highlighting the observed dose-related clinical antiviral activity of ruzasvir in GT-3 subjects with cirrhosis.

In studies conducted by Merck, over 1,200 HCV-infected participants received ruzasvir at daily doses up to 180 mg for durations up to 12 weeks as part of 2-drug and 3-drug regimens with or without ribavirin. The overall safety data indicates that ruzasvir was generally well-tolerated with no consistent treatment-related changes in laboratory, vital signs, or electrocardiogram parameter values. SAEs and discontinuations due to adverse events (“AEs”) were rare in all studies conducted by Merck.

Phase 1 Trials Supporting the Combination of Bemnifosbuvir and Ruzasvir and Their Use as the Fixed Dose Combination

A Phase 1 clinical study in healthy participants was initially conducted to evaluate the potential DDIs between bemnifosbuvir and ruzasvir. The study drugs were well-tolerated and did not meaningfully affect the plasma PK profiles of each other. The lack of DDIs between bemnifosbuvir and ruzasvir supported the evaluation of the combination regimen in HCV-infected patients in the Phase 2 study using individual formulations of bemnifosbuvir and ruzasvir. The bemnifosbuvir and ruzasvir FDC being used in the ongoing Phase 3 program has been evaluated in a Phase 1 study in healthy participants for relative bioavailability and food effect. Results of the Phase 1 study showed a high bioavailability of the FDC tablet relative to the co-administered reference individual formulations of each of bemnifosbuvir and ruzasvir. In addition, a high-fat/high-calorie test meal did not reduce the plasma exposure to bemnifosbuvir or ruzasvir, supporting dosing of the FDC with or without food.

Phase 1 Trials Assessing Potential Risk of DDIs and Characterizing PK Properties of Bemnifosbuvir Alone and In Combination with Ruzasvir

A series of Phase 1 trials have been conducted in healthy participants and special populations to comprehensively evaluate and characterize the PK properties of bemnifosbuvir alone and in combination with ruzasvir.

DDIs

DDIs are one of the most common causes of adverse drug reactions, particularly in patients taking concomitant medications which includes many HCV patients receiving DAAs. DDIs increase the risk of altered clinical efficacy and undesirable therapeutic outcomes. A low risk of DDIs simplifies a prescriber’s management of HCV patients and choice of HCV therapeutic by reducing the need for co-medication adjustments.

CYP3A Substrates

A series of Phase 1 studies have demonstrated an overall low DDI potential associated with bemnifosbuvir, including no dosage adjustment needed for co-administration with drugs that are CYP3A substrates or for drugs that are sensitive substrates of efflux and hepatic uptake transporters. CYP3A is an enzyme that metabolizes many classes of medicines and supplements, and the efflux and hepatic uptake transporters regulate cellular trafficking of many drugs that are commonly prescribed.

In these studies, bemnifosbuvir was administered with index drugs for CYP3A4 (midazolam as a substrate), P-glycoprotein (digoxin as a substrate, cyclosporine as an inhibitor, carbamazepine as an inducer), breast cancer resistance protein and organic anion transporter polypeptide 1B1 (rosuvastatin as a substrate). Based on the results of these studies, which showed a low potential for DDIs, we believe

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bemnifosbuvir has the potential to be co-administered with commonly prescribed therapeutics that are CYP3A4 substrates or are sensitive substrates of efflux and hepatic uptake transporters.

Gastric Acid Reducing Agents

Gastric acid reducing agents can substantially decrease absorption of currently marketed oral HCV antivirals resulting in reduced effectiveness. The effect of famotidine, an H2-blocker, or omeprazole, a proton-pump inhibitor, on the plasma PK of bemnifosbuvir and ruzasvir administered as FDC tablets was evaluated in healthy participants as part of Phase 1 trials. Results from these trials showed that famotidine 20 mg, when administered simultaneously with the bemnifosbuvir and ruzasvir FDC, or concomitant omeprazole 20-40 mg, did not affect the plasma exposure of bemnifosbuvir or ruzasvir. We believe these results support the use of H2-blockers or proton pump inhibitors concomitantly with the administration of the regimen of bemnifosbuvir and ruzasvir in patients with HCV.

HIV Therapeutic - Biktarvy®

We have conducted a Phase 1 study demonstrating in healthy participants the absence of clinically significant DDIs between the combination of bemnifosbuvir and ruzasvir and the HIV antiretroviral FDC of bictegravir/emtricitabine/tenofovir alafenamide marketed in the US as Biktarvy. The co-administered bemnifosbuvir and ruzasvir regimen and the HIV FDC combination were generally safe and well tolerated. These results support the inclusion of HCV/HIV co-infected patients receiving these HIV therapies in our ongoing Phase 3 program.

Phase 1 Trials in Special Populations - Bemnifosbuvir

Hepatic Impairment

A Phase 1 PK study evaluating a single dose of bemnifosbuvir in participants with varying degrees of hepatic impairment showed increased drug exposure in individuals with moderate to severe liver dysfunction. However, these changes did not meaningfully affect levels of AT-273, the plasma marker for the active intracellular antiviral metabolite of bemnifosbuvir. No safety concerns were identified. We believe these results support the use of bemnifosbuvir without dose adjustment in HCV-infected patients with hepatic impairment.

Renal Impairment

A Phase 1 renal impairment study showed that a single dose of bemnifosbuvir was safe and well-tolerated across participants with normal kidney function, moderate-to-severe renal impairment, and those with end-stage renal disease on hemodialysis. We believe these results showed that bemnifosbuvir may be used without dose adjustment in HCV-infected patients with renal dysfunction, including those undergoing dialysis.

Safety Results for Bemnifosbuvir, Ruzasvir and the Regimen of Bemnifosbuvir and Ruzasvir

Prior to the commencement of the ongoing Phase 3 program, over 2,300 human subjects had been exposed to bemnifosbuvir collectively between the HCV development programs and a prior COVID-19 development program, at differing doses including single doses up to 1100 mg BID and durations (up to 12 weeks). Additionally, over 2,100 human subjects had been exposed to ruzasvir.

Both bemnifosbuvir and ruzasvir, alone and in combination, have been well-tolerated and have shown favorable safety profiles. To date, there have been no study drug-related SAEs reported for bemnifosbuvir, ruzasvir or the combination of bemnifosbuvir and ruzasvir.

In the Phase 2 study evaluating the regimen of bemnifosbuvir and ruzasvir, 275 HCV-infected subjects with HCV GT -1, -2, -3 and -4 received the combination of bemnifosbuvir 550 mg and ruzasvir 180 mg once daily for up to eight weeks. AEs were reported in 43% (118/275) of patients. Most were mild to moderate in intensity, with headache (9%) and nausea (8%) being the most commonly reported. Treatment-emergent SAEs were reported in 3% (9/275) of patients, with one resulting in death (carcinoma). An additional 10 patients (4%) reported SAEs that occurred at least four weeks after discontinuation of study drug, four of which resulted in death. None of the SAEs were assessed as related to the study drug. There were no clinically relevant trends in laboratory or electrocardiogram abnormalities.

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Phase 2 Study– Safety Primary Endpoint Met - Generally Safe and Well Tolerated in HCV-infected Patients With or Without Cirrhosis.

In the prior COVID-19 program, with doses of bemnifosbuvir greater than 550 mg twice daily, an increased incidence of mild to moderate gastrointestinal related non-serious AEs, specifically nausea and to a lesser extent vomiting, were observed. However, treatment-limiting, bemnifosbuvir-related gastrointestinal AEs were not apparent at the 550 mg once daily dose being evaluated for HCV.

Thorough QT Study – Bemnifosbuvir

A dedicated thorough QT Phase 1 trial was conducted in healthy participants who were randomized to receive a single oral dose of bemnifosbuvir 550 mg (clinical dose), 1100 mg (supratherapeutic dose), matching placebo (negative control) and open-label moxifloxacin 400 mg (positive control), in a four-way crossover design. Results, announced in November 2024, showed that bemnifosbuvir had no clinically relevant effects on cardiac repolarization, heart rate, PR interval, or QRS duration, which are all related to heart function. A QTc effect exceeding 10 milliseconds, the established threshold of concern, can be excluded across the observed plasma concentrations of bemnifosbuvir and its metabolites at the therapeutic and supratherapeutic doses.

Collectively, clinical data were consistent with the preclinical in vitro and in vivo study results, which demonstrated bemnifosbuvir has a low potential for cardiotoxicity with no predicted arrhythmic QTc-interval prolongation (a heart condition that occurs when the heart’s ventricles take longer than normal to repolarize) or inhibition of the human mitochondrial DNA-directed RNA polymerase.

AT-587 for the Treatment of HEV

HEV – Disease Overview and Current SOC

HEV is an ssRNA virus which infects the liver and remains an under-recognized global health challenge with an estimated 19.5 million acute infections annually. While typically self-limiting in healthy individuals, HEV can cause chronic disease in those with compromised immunity, including recipients of solid organ and stem cell transplants, people living with HIV, and those with hematologic or rheumatic conditions, often progressing rapidly to cirrhosis. HEV GT-1 and -2 drive waterborne, acute epidemics in developing regions, whereas HEV GT-3 and -4 predominate in high-income countries through zoonotic, foodborne transmission that can lead to chronic infection in markets with expanding at-risk populations. Despite this burden, no DAA is approved for the treatment of HEV, and current off-label treatments have limited efficacy and tolerability.

Based on the number of patients receiving solid organ or stem cell transplants or with hematologic malignancies in the US and Europe each year (up to 450,000 patients), the annual incidence of chronic

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HEV is estimated to be ~13,500 in this at-risk population, which assumes that roughly 3% develop chronic HEV infection. Among solid organ transplant recipients, HEV infection has been increasingly recognized as a potentially life-threatening viral infection, as rapid progression of liver fibrosis has been documented, often culminating in cirrhosis and, in some instances, decompensation and death.

Although awareness of HEV is increasing, particularly regarding its impact on immunocompromised individuals, the true burden of disease may be underestimated. We believe that clinical overlap with other viral infections and persistent challenges in diagnostic testing contribute to substantial underreporting. Serological assessment often fails to detect HEV infection even when present and in such cases, nucleic acid testing remains the only reliable method for establishing the diagnosis.

Treatment Guidelines for HEV

There currently are no approved DAA therapeutics for HEV infection. The European Association for the Study of the Liver (“EASL”) outlines a stepwise approach for managing chronic HEV in immunocompromised individuals. The initial strategy involves reducing immunosuppression to help restore the host immune control, although this carries risks such as organ rejection or reinfection. If viral clearance is not achieved, a 3-month course of ribavirin, a broad-spectrum antiviral, is recommended. Ribavirin therapy, however, can be associated with adverse effects including dose-dependent anemia, dry cough, teratogenic effects and dermatologic reactions. In cases of relapse following initial ribavirin therapy, EASL recommends extending ribavirin treatment for an additional six months.

Our HEV Product Candidate Development

We are developing AT-587 for the treatment of HEV. Based on our preclinical data to date, we believe AT-587, if successfully developed and approved, could offer the following potential benefits:

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first DAA therapy;

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favorable safety profile; and

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well tolerated with fewer side effects than current treatments.

The chemical structure of AT-587, a modified guanosine nucleotide prodrug, is very similar to bemnifosbuvir with only limited substitutions. Like bemnifosbuvir, AT-587 is converted after multi-step activation to an active triphosphate (TP) metabolite (AT-9068).

Non-clinical data supporting the clinical development of AT-587 for the treatment of HEV

AT-587 has shown potent pan-genotypic antiviral activity against HEV in both in vivo and in vitro studies. AT-587 has also shown favorable safety results in in vitro studies.

AT-587 has been screened for anti-HEV activity in an in vitro subgenomic replicon and infection system and was greater than 30-fold more potent than sofosbuvir and ribavirin against HEV GT-1 and -3, including clinically resistant viral strains.

Inhibition of HEV Replication by Nucleotide Analogs (EC50values [nM] against HEV strains in Huh7 cells)

In vivo antiviral activity of AT-587 was confirmed in primary human hepatocytes infected with HEV GT-3.

In vitro toxicology data obtained to date present a favorable safety profile for AT-587. The active triphosphate metabolite (AT-9068) did not inhibit human DNA polymerases. AT-587 was not cytotoxic to

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human iPS cardiomyocytes (IC50 100 uM), has no effect on the viability of bone marrow CD34+ cells (IC50 30 uM), and demonstrates no phototoxic potential in BALB/c 3T3 cells. AT-587 was negative for genotoxicity in Ames, chromosomal aberration, and in vitro micronucleus assays. AT-587 also demonstrated minimal inhibition in a screening hERG assay. AT-9068 was found to be a substrate and inhibitor of human mitochondrial RNA polymerase (POLRMT). However, based upon comparison of the relative efficiencies, AT-9068 is expected to be utilized 1.5-fold less than the triphosphate of sofosbuvir.

Additional IND/CTA enabling studies are being completed.

Clinical Development

We are planning to initiate clinical development of AT-587 for the treatment of chronic HEV in mid-2026. The clinical program is expected to begin with a Phase 1 study which will evaluate single and multiple doses of AT-587 as a single agent in healthy subjects for up to seven days. The principal objectives of this study will be to further assess safety, tolerability and PK of AT-587. This study will also assist us in the selection of the AT-587 dose strength to be subsequently evaluated in patients with chronic HEV. Antiviral activity/efficacy and safety would subsequently be evaluated in treatment studies in high-risk immunocompromised patients with chronic HEV.

Discovery efforts for other RNA virus infections

We have an extensive library of compounds that have been designed and generated by our medicinal chemists. Currently, we are evaluating select compounds derived from this library in in vitro and in vivo studies to assess the antiviral activity and other properties of such compounds against other RNA viral infections.

In all our discovery and preclinical efforts, we assess where there is a compelling market opportunity and then we aim to identify and advance only those candidates that we believe may have first- or best-in-class profiles with the potential to either become the SOC, or disrupt the existing SOC, and in each case, dramatically improve patient outcomes.

COVID-19

In September 2024 we announced the outcome of the global Phase 3 SUNRISE-3 trial evaluating bemnifosbuvir versus placebo for the treatment of COVID-19. The trial did not meet the primary endpoint of a statistically significant reduction in all-cause hospitalization or death through Day 29 in the monotherapy cohort of 2,221 high-risk patients with mild to moderate COVID-19. We believe that the unfavorable results from this study were impacted by the constantly evolving variants of COVID-19 and rapidly changing natural history of the disease, which trended toward a milder disease during the study period. This led us to discontinue efforts to develop bemnifosbuvir for the treatment of COVID-19. In SUNRISE-3, bemnifosbuvir was generally safe and well tolerated. In April 2025, we completed the close out of the SUNRISE-3 clinical trial.

Merck License Agreement

In December 2021, we entered into a license agreement with Merck (“Merck License Agreement”) for the development, manufacture and commercialization of ruzasvir. Ruzasvir is the HCV NS5A inhibitor we are developing in combination with bemnifosbuvir for the treatment of HCV.

Pursuant to the terms of the Merck License Agreement, we obtained from Merck an exclusive (subject to certain reserved rights to conduct internal research), sublicensable, and worldwide license under certain Merck patents and know-how to research, develop, manufacture, have manufactured, use, import, export, sell, offer for sale, and otherwise commercialize ruzasvir (“Compound"), or products containing the Compound (each a “Product”) for all therapeutic or prophylactic uses in humans (“Field”).

In consideration for the rights we acquired under the Merck License Agreement, we paid Merck an upfront payment in the amount of $25.0 million and agreed to pay Merck milestone payments up to $135.0 million in the aggregate upon our achievement of certain development and regulatory milestones and up to $300.0 million in the aggregate upon our achievement of certain sales-based milestones. The first development milestone, in the amount of $5.0 million, was paid upon initiation of the first clinical trial in

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our Phase 3 program. The next milestone, in the amount of $10.0 million will be due upon acceptance of the bemnifosbuvir and ruzasvir regimen NDA in the US. The related expense will be recorded when the contingency is resolved and the milestone becomes payable. We currently anticipate submission and acceptance of the NDA in the first half of 2027.

Additionally, we have agreed to pay Merck tiered royalties based on annual net sales of Products ranging from high single digit to mid-teens percentages, subject to certain adjustments. Our royalty payment obligations will continue on a country-by-country and Product-by-Product basis until the later of (i) the expiration of the last to expire valid claim of a licensed Merck patent claiming such Product and (ii) a period of years after the first commercial sale of such Product in such country.

Under the terms of the Merck License Agreement, we are obligated to use commercially reasonable efforts to develop and commercialize at least one Product in the Field in certain countries.

The term of the Merck License Agreement will continue, on a Product-by-Product and country-by-country basis, until expiration of all royalty payment obligations arising under the Merck License Agreement. We may terminate the Merck License Agreement for convenience upon 90 days prior written notice. Each party has the right to terminate the Merck License Agreement in the event of the other party’s material breach of the terms of the Merck License Agreement subject to a 60-day cure period and in the event of the other party’s bankruptcy or insolvency. Merck has the right to terminate the Merck License Agreement immediately if we commence any interference or opposition proceeding or other challenge to the validity or enforceability of any Merck patent licensed to us under the Merck License Agreement or if we otherwise oppose any extension of, or the grant of any supplementary protection certificate with respect to, any such Merck patent.

Upon any termination of the Merck License Agreement, the license granted to us by Merck will terminate. Upon termination of the Merck License Agreement by us for convenience other than as a result of a safety issue, or upon any termination by Merck, Merck will have an exclusive, fully paid, perpetual, sublicensable license to certain of our patents and know-how that are reasonably necessary to develop, manufacture or commercialize a Product that contains ruzasvir as the sole active agent, as such Product exists at termination. Additionally, if requested by Merck, during a period of time after delivery of the notice of termination of the Merck License Agreement by Merck or by us for convenience other than as a result of a safety issue, we will have the obligation to negotiate with Merck for the grant to Merck of a non-exclusive, royalty bearing license to certain of our patents and know-how that are reasonably necessary to develop, manufacture or commercialize a Product that is comprised of the combination of ruzasvir and bemnifosbuvir, as such Product exists at termination, with certain license terms pre-specified in the Merck License Agreement.

Manufacturing

In parallel with our clinical development program, we are executing an integrated CMC strategy intended to provide sufficient drug substance and drug product to support the completion of the global HCV Phase 3 development of the bemnifosbuvir and ruzasvir regimen, and, if approved, supply product for commercial launch and subsequent commercial sales. Additionally, we are engaged in efforts to manufacture cGMP-compliant material required for the initiation of the clinical trials of AT-587 for the treatment of HEV.

We do not currently own or operate manufacturing facilities to produce preclinical or clinical product candidates or commercial supply, nor do we have plans to develop or operate our own manufacturing operations in the future. We currently rely upon third party contract manufacturing organizations (“CMOs”) to produce our product candidates for both preclinical and clinical use and anticipate relying upon these or other CMOs or other third parties for commercial supply if any of our product candidates is successfully developed and approved for sale. Because we rely on these CMOs, we have personnel with pharmaceutical development and manufacturing experience who are responsible for maintaining our CMO relationships.

Although there are a limited number of suppliers and manufacturers that can produce the raw materials and active pharmaceutical ingredients in the quantities and with the quality and purity that we require for our product candidates, we believe our current network of suppliers and manufacturers are able to fulfill

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these requirements and can continue to expand capacity as needed. Simultaneously, we have and will continue to evaluate engagement with other suppliers and manufacturers to increase overall capacity as well as further reduce risks associated with reliance on a limited number of suppliers and manufacturers.

Currently, we are manufacturing commercial launch supply in quantities that we believe will be sufficient to support the launch and commercial sale in the period immediately following market introduction. We expect our HCV commercial presentation to include simple, weekly dosing blister packs to bolster convenience, adherence and commercial competitiveness.

We have not yet entered into long term commercial supply agreements and are relying upon time and materials contracts which are currently in place to procure the raw materials, synthetic intermediates and formulation excipients together with the manufacturing capacity necessary to manufacture product for commercial launch.

Our contract manufacturing agreements give us visibility into the expected future cost of producing the bemnifosbuvir and ruzasvir FDC on a commercial scale and based on our knowledge of the prices of currently marketed therapies indicated for HCV, we believe that our cost of goods will be competitive

Commercialization

We currently believe that we can maximize the value of our product portfolio by retaining global development rights to our product candidates. However, to further maximize the value of product candidates that are authorized or approved for sale, we may seek collaborations that allow us to access and leverage commercialization expertise and resources of collaborators in certain markets. To assist in the commercialization in the US of any product candidates we successfully develop, we may enter arrangements with third parties that have existing commercial infrastructure including a pharmaceutical sales force and expertise in managed care. Outside the US, we anticipate that commercialization of our products, if approved or authorized for use, would be undertaken by third party collaborators. Currently, we do not have any sales, marketing or commercial product distribution infrastructure and we do not have any existing arrangements with third parties to commercialize our product candidates in the US or elsewhere.

Competition

As a clinical-stage biopharmaceutical company, we face competition from a wide array of companies in the pharmaceutical and biotechnology industries. These include both small companies and large companies with much greater financial and technical resources and far longer operating histories than our own. We may also compete with the intellectual property, technology, and product development efforts of academic, governmental, and private research institutions.

Our competitors may have significantly greater financial resources, established presence in the market, expertise in research and development, manufacturing, preclinical and clinical testing, obtaining regulatory approvals and reimbursement, and marketing approved products than we do. These competitors also compete with us in recruiting and retaining qualified scientific, sales, marketing, and management personnel, establishing clinical trial sites and patient registration for clinical trials, as well as in acquiring technologies complementary to, or necessary for, our programs. Smaller or early-stage companies may also prove to be significant competitors, particularly through collaborative arrangements with large and established companies.

The key competitive factors affecting the success of any product candidates that we develop, if approved, are likely to be their efficacy, safety, convenience, price, and the availability of reimbursement from government and other third-party payors. The commercial opportunity for any product candidate we develop, if any are approved, could be reduced or eliminated if such product fails to achieve market acceptance from patients, prescribers and payors, our competitors develop and commercialize products that are more effective, have fewer or less severe side effects, are more convenient, or are less expensive than any products that we may develop. Our competitors also may obtain FDA or other regulatory approval for their products more rapidly than we may obtain approval for ours and may commercialize products more quickly than we are able to.

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HCV

Since 2014, many direct-acting antiviral therapies have been approved for use for the treatment of HCV in the US and globally. Orally administered, FDA-approved treatments for patients with chronic HCV include:

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Sovaldi® (sofosbuvir) (Gilead Sciences, Inc.), an HCV nucleotide analog NS5B polymerase inhibitor approved for the treatment of adult patients with GT-1, -2, -3, or -4, chronic HCV infection without cirrhosis or with compensated cirrhosis as a component of a combination antiviral treatment regimen; pediatric patients ≥3 years old with HCV GT-2 or -3 infection without cirrhosis or with compensated cirrhosis in combination with ribavirin.

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Epclusa® (sofosbuvir and velpatasvir) (Gilead Sciences, Inc.), a FDC regimen of sofosbuvir and velpatasvir, an HCV NS5A inhibitor, approved for the treatment of adults and pediatric patients ≥3 years old with chronic HCV GT-1, -2, -3, -4, -5, or -6 infection without cirrhosis or with compensated cirrhosis, or with decompensated cirrhosis for use in combination with ribavirin.

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Harvoni® (ledipasvir and sofosbuvir) (Gilead Sciences, Inc.) a FDC regimen of ledipasvir, an HCV NS5A inhibitor, and sofosbuvir approved for the treatment of adult and pediatric patients ≥3 years old with HCV GT-1, -4, -5 or -6 infection without cirrhosis or with compensated cirrhosis; GT-1 infection with decompensated cirrhosis in combination with ribavirin; and GT-1 or -4 infection who are liver transplant recipients without cirrhosis or with decompensated cirrhosis, in combination with ribavirin.

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Vosevi® (sofosbuvir, velpatasvir, and voxilaprevir) (Gilead Sciences, Inc.) a FDC regimen of sofosbuvir, velpatasvir and voxilaprevir, an HCV NS3/4A protease inhibitor approved for the treatment of adult patients with chronic HCV infection without cirrhosis or with compensated cirrhosis who have HCV GT-1, -2, -3, -4, -5, or -6 infection and have previously been treated with an HCV regimen containing an HCV NS5A inhibitor; HCV GT-1a or -3 infection who have previously been treated with an HCV regimen containing sofosbuvir without an HCV NS5A inhibitor.

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Mavyret® (glecaprevir and pibrentasvir) (AbbVie, Inc.) a FDC regimen of glecaprevir, an HCV NS3/4A protease inhibitor and pibrentasvir, an HCV NS5A inhibitor, approved for the treatment of adult and pediatric patients ≥3 years old with acute or chronic HCV GT-1, -2, -3, -4, -5, or -6 infection without cirrhosis or with compensated cirrhosis. Mavyret as an eight-week treatment is approved for patients who have not been previously treated. Longer treatment durations (up to 16 weeks) are indicated for some treatment-experienced populations. It is recommended that Mavyret be taken with food. Mavyret is not approved for use in patients with decompensated cirrhosis.

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Zepatier® (elbasvir and grazoprevir) (Merck) a fixed-dose combination of elbasvir, an HCV NS5A inhibitor and grazoprevir, an HCV NS3/4A protease inhibitor approved for the treatment of chronic HCV GT-1 or -4 infection in adult and pediatric patients ≥12 years old or weighing at least 30 kg. Zepatier is indicated for use with ribavirin in certain patient populations.

In addition to the branded products, Gilead Sciences, Inc. markets in the US authorized generic copies of Epclusa and Harvoni through its wholly-owned subsidiary, Asegua Therapeutics, LLC.

With the exception of the regimen of bemnifosbuvir and ruzasvir, we are not aware of any HCV investigational agents in late-stage development in the US. There may be other HCV investigational agents in various stages of clinical development, including late-stage development, in other parts of the world.

HEV

There are no approved therapeutic agents for the treatment of HEV and there are only two licensed and available recombinant hepatitis E vaccines: Hecolin (HEV239) in China since 2011 and in Pakistan since

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2020 and Hevaxin in India since 2026. We are not aware of any HEV investigational agents in late-stage development.

Intellectual Property

Our commercial success will depend in part on our ability to obtain and maintain proprietary protection for our therapeutic products for viral diseases. We seek to protect our proprietary compounds and methods of treatment for viral diseases using our compounds, alone and in combination with other therapeutic agents, in addition to dosage forms, dosing regimens and formulations for their administration. We also seek protection on the manufacturing process for the production of our compounds. Our success also depends on our ability to operate without infringing, misappropriating or otherwise violating the proprietary rights of others and to prevent others from infringing, misappropriating or otherwise violating our proprietary rights.

Our policy is to seek to protect our proprietary position by filing US and foreign patent applications covering our proprietary technologies, inventions, and improvements that are important to the development and implementation of our business. In addition, we currently plan to seek patent term adjustments, restorations, and/or patent term extensions where applicable in the US, Europe and other jurisdictions. We also rely on trade secrets, know-how, continuing technological innovation and potential in-licensing opportunities to develop and maintain our proprietary position. Additionally, we expect to benefit, where appropriate, from statutory frameworks in the US, Europe and other countries that provide a period of regulatory data exclusivity to compensate for the time required for regulatory approval of our drug products.

As of March 1, 2026, we are the sole owner of seventeen patent families covering our product candidates and proprietary compounds, which include composition of matter, pharmaceutical compositions, methods of use, and processes of manufacture as described in more detail below. Our owned patent estate as of March 1, 2026, on a worldwide basis, includes more than 300 pending, granted, or allowed patent applications with twenty four issued US patents, twelve pending US non-provisional applications and more than 250 pending or granted patent applications that have entered the national phase of prosecution in countries outside the US.

As of March 1, 2026, we are the exclusive licensee of three patent families from Merck covering composition of matter, process of preparation, and formulations of ruzasvir, the NS5A inhibitor which we are developing in combination with bemnifosbuvir for the treatment of HCV. These three patent families collectively include two issued US patents, granted patents in France, Great Britain, and Germany and one pending US patent application and one pending patent application in the European Patent Office ("EPO").

The exclusivity terms of our patents depend upon the laws of the countries in which they are obtained. In the countries in which we currently file, the patent term is 20 years from the earliest date of filing of a non-provisional patent application. The term of a US patent may be extended to compensate for the time required to obtain regulatory approval to sell a drug (a patent term extension) or by delays encountered during patent prosecution that are caused by the US Patent and Trademark Office (referred to as patent term adjustment). For example, the Drug Price Competition and Patent Term Restoration Act of 1984, referred to as the Hatch-Waxman Act, permits a patent term extension for FDA-approved new chemical entity drugs of up to five years beyond the expiration of the patent. The length of the patent term extension is related to the length of time the drug is under regulatory review and diligence during the review process. Patent term extensions in the US cannot extend the term of a patent beyond a total of 14 years from the date of product approval. Only one patent covering an approved drug, or its method of use may be extended, and only those claims covering the approved drug, or an approved method for using it may be extended. A similar kind of patent extension, referred to as a Supplementary Protection Certificate, is available in the European Union ("EU"). Legal frameworks are also available in certain other jurisdictions to extend the term of a patent. We currently intend to seek patent term extensions on any of our issued patents in any jurisdiction where we have a qualifying patent and the extension is available; however, there is no guarantee that the applicable regulatory authorities, including the FDA in the US, will agree with our assessment of whether such extensions should be granted, and even if granted, the length of such extensions. Further, even if one or more of our patents is extended, the patent, including the

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extended portion of the patent, may be held invalid or unenforceable by a court of final jurisdiction in the US or a foreign country.

Current issued patents and patent applications covering the composition of matter for AT-511, the free base of bemnifosbuvir, and our product candidate, bemnifosbuvir, will expire on dates ranging from 2036 to 2038, if the applications are issued and held valid by a court of final jurisdiction if challenged, and without regard to any possible patent term adjustments or extensions. Current issued patents and patent applications covering the use of AT-511 and bemnifosbuvir for the treatment of HCV will expire on dates ranging from 2036 to 2046, if the applications are issued and held valid by a court of final jurisdiction if challenged, and without regard to any possible patent term adjustments or extensions.

However, any of our patents, including patents that we may rely on to protect our market for products if any are approved, may be held invalid or unenforceable by a court of final jurisdiction. Alternatively, we may decide that it is in our interest to settle a litigation in a manner that affects the term or enforceability of our patent. Changes in either the patent laws or in interpretations of patent laws in the US and other jurisdictions may diminish our ability to protect our inventions and enforce our intellectual property rights. Accordingly, we cannot predict the breadth or enforceability of claims that have been or may be granted on our patents or on third-party patents. The pharmaceutical and biopharmaceutical industries are characterized by extensive litigation regarding patents and other intellectual property rights. Our ability to obtain and maintain a proprietary position for our product candidates and the use of these product candidates will depend on our success in enforcing patent claims that have been granted or may grant. We do not know whether any of the pending patent applications that we have filed or may file or license from third parties will result in the issuance of any additional patents. The issued patents that we own or may receive in the future may be challenged, invalidated, or circumvented, and the rights granted under any issued patents may not provide us with sufficient protection or competitive advantages against competitors with similar technology. Furthermore, our competitors may be able to independently develop and commercialize products with similar mechanisms of action and/or duplicate our methods of treatments or strategies without infringing our patents. Because of the extensive time required for clinical development and regulatory review of any product candidate we may develop, it is possible that, before any of our product candidates can be commercialized, any related patent may expire or remain in force for only a short period following commercialization, thereby reducing any advantage of any such patent. For more information regarding risks relating to intellectual property, see the section titled “Risk Factors—Risks Related to Intellectual Property.”

Our patent families, as of March 1, 2026, are further described below.

AT-511 and Bemnifosbuvir

We own a first patent family that describes AT-511 or a pharmaceutically acceptable salt thereof (for example, bemnifosbuvir), pharmaceutical compositions of AT-511 or the pharmaceutical salts thereof, and methods to treat HCV using AT-511 or a salt thereof. This family consists of nine issued US patents (US Patent Nos. 9,828,410; 10,000,523; 10,005,811; 10,239,911; 10,815,266; 10,870,672; 10,870,673, 10,875,885 and 12,084,473) covering AT-511 or a pharmaceutically acceptable salt thereof, related compounds and their pharmaceutical compositions. This patent family is now also in the national stage of prosecution or granted in the African Regional Intellectual Property Organization (“ARIPO”), Australia, Brazil, Canada, China, Colombia, the Eurasian Patent Office (“EAPO”), Egypt, the EPO, Georgia, Hong Kong, Indonesia, Israel, India, Japan, Korea, Mexico, Macao, Malaysia, Nigeria, New Zealand, the Philippines, Russia, Saudi Arabia, Singapore, Thailand, Vietnam, Ukraine, South Africa, and the United Arab Emirates. We have over 75 foreign patents granted or allowed, and more than 15 pending patent applications. The expected year of expiration for this patent family, where issued, valid and enforceable, is 2036, without regard to any extensions, adjustments, or restorations of term that may be available under national law.

We also own a second patent family that specifically covers bemnifosbuvir (the hemisulfate salt of AT-511), related compounds, pharmaceutical compositions, process of preparation, and methods to treat HCV using bemnifosbuvir. This family includes three issued US patents (US Patent Nos. 10,519,186; 10,894,804; and 12,006,340) covering bemnifosbuvir or a process to prepare bemnifosbuvir. This family is currently in the national phase of prosecution in Argentina, ARIPO, Australia, Brazil, Canada, China,

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Colombia, the EAPO, Georgia, Hong Kong, Indonesia, Israel, India, Japan, Korea, Mexico, Malaysia, Nigeria, New Zealand, the Philippines, Russia, Singapore, Taiwan, Thailand, Vietnam, Ukraine, Uzbekistan, and South Africa. The patent has now been granted by the European Patent Office. We have over 75 granted foreign patents and over 20 pending applications. The expected year of expiration for this patent family, if issued, valid and enforceable, is 2038, without regard to any extensions, adjustments, or restorations of term that may be available under US or other national laws.

We own two patent families that disclose methods for the treatment of coronaviruses. These families include five granted US patents (US Patent Nos. 10,874,687; 11,707,480; 11,783,038; 11,813,278; 12,226,429; and 12,551,499). Patent applications in this family have been granted in China, Japan and the EPO, and applications are pending in Australia and Canada. The expected year of expiration for patents issued from these families, if valid and enforceable, is 2040 or 2041, without regard to any extensions, adjustments, or restorations of term that may be available under US or other national laws.

We own a fifth patent family that discloses the use of AT-511 or a pharmaceutically acceptable salt thereof for the treatment or prevention of a positive-stranded RNA virus infection, including a Flaviviridae viral infection such as dengue, West Nile, or yellow fever. This family consists of two issued US patents (US Patent Nos. 10,946,033 and 11,975,016) and is currently pending or granted in Australia, Brazil, Canada, China, the EAPO, the EPO, Hong Kong, Indonesia, Japan, Korea, Malaysia, Nigeria, Russia, Singapore, Thailand, Vietnam, and South Africa. We have over 50 foreign patents granted and eight pending patent applications. The expected year of expiration for this patent family, if issued, valid and enforceable, is 2037, without regard to any extensions, adjustments, or restorations of term that may be available under US or other national laws.

We own a sixth patent family that discloses the use of AT-511 and bemnifosbuvir for the treatment of HCV in patients with cirrhosis of the liver. This family includes one granted US patent (US Patent No. 11,690,860). The expected year of expiration for this patent family, if issued, valid and enforceable, is 2039, without regard to any extensions, adjustments, or restorations of term that may be available under US or other national laws.

We own a seventh patent family that describes methods to treat mutant or resistant forms of the SARS-CoV-2 virus. This family consists of one pending application in the US. The expected year of expiration for patents issued from non-provisional patent applications filed on the basis of this patent application, if valid and enforceable, is 2041, without regard to adjustments of term that may be available under US or other national laws.

We also own an eighth patent family that discloses methods for manufacturing AT-511 and bemnifosbuvir. This family consists of one pending US application. The expected year of expiration for patents issued from non-provisional patent applications filed on the basis of these provisional patent applications, if valid and enforceable, is 2041, without regard to adjustments of term that may be available under US or other national laws.

We also own a ninth patent family that discloses additional processes for the manufacture of AT-511 and bemnifosbuvir. This family consists of one pending patent application in the US in addition to pending applications in Argentina, Australia, Canada, China, the EPO, Hong Kong, India, Japan, Korea, Mexico, New Zealand, and Taiwan. The expected year of expiration for patents issuing from these non-provisional patent applications, if valid and enforceable, is 2041, without regard to any adjustments of term that may be available under US or other national law.

We also own a tenth patent family that discloses new morphic forms of bemnifosbuvir. This family consists of one pending patent application in the US, as well as pending applications in Australia, Brazil, Canada, China, the EAPO, the EPO, Israel, India, Japan, Korea, Mexico, Russia, and Taiwan. The expected year of expiration for patents issued from non-provisional patent applications filed on the basis of this patent application, if valid and enforceable, is 2042, without regard to adjustments of term that may be available under US or other national laws.

Ruzasvir and the Combination of Bemnifosbuvir and Ruzasvir

We have exclusively licensed three patent families from Merck covering composition of matter, process of preparation, and formulations of ruzasvir, a pan-genotypic NS5A inhibitor which we are combining with

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bemnifosbuvir in the regimen we are developing to treat HCV. The family covering the ruzasvir composition of matter includes one granted US patent (US Patent No. 9,555,038), and granted patents in France, Great Britain, and Germany. The expected expiration date is in 2034. The family describing a process of preparation includes one granted US patent (US Patent No. 10,457,690), with an expected expiration date in 2036. The family describing formulations includes one pending US patent application and one pending patent application in the EPO, which if granted, is expected to expire in 2039.

We also solely own an eleventh patent family covering the combination of bemnifosbuvir and ruzasvir. This family consists of one granted US patent (US Patent No. 12,458,656) two pending US patent applications, and currently pending or granted applications in the United Arab Emirates, Argentina, Australia, Brazil, Canada, China, Colombia, the EAPO, the EPO, Indonesia, Israel, India, Japan, Korea, Mexico, Malaysia, New Zealand, the Philippines, Qatar, Russia, Saudi Arabia, Singapore, Thailand, Taiwan, and South Africa. The expected year of expiration for this patent family, if issued, valid and enforceable, is 2042, without regard to any extensions, adjustments, or restorations of term that may be available under US or other national laws.

We also solely own a twelfth patent application covering the FDC regimen of bemnifosbuvir and ruzasvir. The expected year of expiration for patents issuing from this application, if valid and enforceable, is 2046, without regard to any adjustments of term that may be available under US or other national law.

AT-587

We own a patent family that describes AT-587 or a pharmaceutically acceptable salt thereof, pharmaceutical compositions of AT-587 or the pharmaceutical salts thereof, and methods to treat HEV using AT-587 or a salt thereof. This family currently consists of pending PCT and Taiwanese applications. The expected year of expiration for this patent family, if issued, valid and enforceable, is 2046, without regard to any extensions, adjustments, or restorations of term that may be available under US or other national law.

Government Regulation and Product Approval

Government authorities in the US, at the federal, state and local level, and other countries extensively regulate, among other things, the research, development, testing, manufacture, quality control, approval, labeling, packaging, storage, record-keeping, promotion, advertising, distribution, marketing and export and import of products such as those we are developing. A new drug must be approved by the FDA through the NDA process before it may be legally marketed in the US.

US Drug Development Process

In the US, the FDA regulates drugs under the Federal Food, Drug and Cosmetic Act (“FDCA”) and its implementing regulations. The process of obtaining regulatory approvals and the subsequent compliance with appropriate federal, state, local and foreign statutes and regulations require the expenditure of substantial time and financial resources.

The process required by the FDA before a drug may be marketed in the US generally involves the following:

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completion of certain preclinical laboratory tests, animal studies and formulation studies in accordance with FDA’s good laboratory practice requirements and other applicable regulations;

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submission to the FDA of an IND, which must become effective before human clinical trials may begin;

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approval by an independent institutional review board (“IRB”), or ethics committee at each clinical site before each trial may be initiated;

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performance of adequate and well-controlled human clinical trials in accordance with good clinical practice requirements (“GCPs”) to establish the safety and efficacy of the proposed drug for its intended use;

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submission to the FDA of an NDA after completion of all pivotal trials;

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satisfactory completion of an FDA advisory committee review, if applicable;

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satisfactory completion of an FDA inspection of the manufacturing facility or facilities at which the drug is produced to assess compliance with current good manufacturing practice (“cGMP”), requirements to assure that the facilities, methods and controls are adequate to preserve the drug’s identity, strength, quality and purity, and satisfactory completion of potential inspections of selected clinical investigation sites to assess compliance with GCPs; and

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FDA review and approval of the NDA to permit commercial marketing of the product for particular indications for use in the US.

Prior to beginning the first clinical trial with a product candidate in the US, a sponsor must submit an IND to the FDA. An IND is a request for allowance from the FDA to administer an investigational drug product to humans. The central focus of an IND submission is on the general investigational plan and the protocol(s) for clinical studies. The IND also includes results of animal and in vitro studies assessing the toxicology, pharmacokinetics, pharmacology, and pharmacodynamic characteristics of the investigational product; chemistry, manufacturing, and controls information; and any available human data or literature to support the use of the investigational product. An IND must become effective before human clinical trials may begin. Once submitted, the IND automatically becomes effective 30 days after receipt by the FDA, unless the FDA, within the 30-day time period, raises safety concerns or questions about the proposed clinical trial. In such a case, the IND may be placed on clinical hold and the IND sponsor and the FDA must resolve any outstanding concerns or questions before the clinical trial can begin. Submission of an IND therefore may or may not result in FDA allowance to begin a clinical trial.

Clinical trials involve the administration of the investigational product to human subjects under the supervision of qualified investigators in accordance with GCPs, which among other things include the requirement that all research subjects provide their informed consent for their participation in any clinical study. Clinical trials are conducted under protocols detailing, among other things, the objectives of the study, the parameters to be used in monitoring safety and the effectiveness criteria to be evaluated. A separate submission to the existing IND must be made for each successive clinical trial conducted during product development and for any subsequent protocol amendments. While the IND is active, progress reports summarizing the results of the clinical trials and nonclinical studies performed since the last progress report, among other information, must be submitted at least annually to the FDA, and written IND safety reports must be submitted to the FDA and investigators for serious and unexpected suspected adverse events, findings from other studies suggesting a significant risk to humans exposed to the same or similar drugs, findings from animal or in vitro testing suggesting a significant risk to humans, and any clinically important increased incidence of a serious suspected adverse reaction compared to that listed in the protocol or investigator brochure.

Furthermore, an independent IRB or ethics committee for each site proposing to conduct the clinical trial must review and approve the plan for any clinical trial and its informed consent form before the clinical trial begins at that site and must monitor the study until completed. Some studies also include oversight by an independent group of qualified experts organized by the clinical study sponsor, known as a data safety monitoring board ("DSMB"), which provides authorization for whether or not a study may move forward at designated check points based on access to certain data from the study and may halt the clinical trial if it determines that there is an unacceptable safety risk for subjects or other grounds, such as no demonstration of efficacy. Each of our HCV Phase 3 clinical trials are being monitored by a DSMB.

The FDA or the sponsor may suspend a clinical trial at any time on various grounds, including a finding that the research subjects or patients are being exposed to an unacceptable health risk. Similarly, an IRB can suspend or terminate approval of a clinical trial at its institution if the clinical trial is not being conducted in accordance with the IRB’s requirements or if the investigational product has been associated with unexpected serious harm to patients.

Human clinical trials are typically conducted in three sequential phases that may overlap or be combined:

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Phase 1: The product candidate is initially introduced into healthy human subjects, and in some cases, patients with the target disease or condition. These studies are designed to test the safety, dosage tolerance, absorption, metabolism and distribution of the investigational product in humans, the side effects associated with increasing doses, and, if possible, to gain early evidence on effectiveness.

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Phase 2: The product candidate is administered to a limited patient population with a specified disease or condition to evaluate the preliminary efficacy, optimal dosages and dosing schedule and to identify possible adverse side effects and safety risks. Multiple Phase 2 clinical trials may be conducted to obtain information prior to beginning larger and more expensive Phase 3 clinical trials.

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Phase 3: The product candidate is administered to an expanded patient population to further evaluate dosage, to provide statistically significant evidence of clinical efficacy and to further test for safety, generally at multiple geographically dispersed clinical trial sites. These clinical trials are intended to establish the overall risk/benefit ratio of the investigational product and to provide an adequate basis for product labeling.

Post-approval trials, sometimes referred to as Phase 4 studies, may be conducted after initial marketing approval. These trials are used to gain additional experience from the treatment of patients in the approved therapeutic indication. In certain instances, the FDA may mandate the performance of Phase 4 clinical trials as a condition of approval of an NDA.

During the development of a new drug, sponsors are given opportunities to meet with the FDA at certain points. These points may be prior to submission of an IND, at the end of Phase 2, and before an NDA is submitted. Meetings at other times may be requested. These meetings can provide an opportunity for the sponsor to share information about the data gathered to date, for the FDA to provide advice, and for the sponsor and the FDA to reach alignment on the next phase of development. In January 2025, we met with the FDA at an end of Phase 2 meeting to review the Phase 2 study results and align on the design and parameters of the HCV Phase 3 clinical program we are currently conducting.

Concurrent with clinical trials, companies usually complete additional animal studies and must also develop additional information about the chemistry and physical characteristics of the drug and finalize a process for manufacturing the product in commercial quantities in accordance with cGMP requirements.

The manufacturing process must be capable of consistently producing quality batches of the product candidate and, among other things, the manufacturer must develop methods for testing the identity, strength, quality and purity of the final drug. In addition, appropriate packaging must be selected and tested, and stability studies must be conducted to demonstrate that the product candidate does not undergo unacceptable deterioration over its shelf life.

US Review and Approval Process

Assuming successful completion of all required testing in accordance with all applicable regulatory requirements, the results of product development, including results from preclinical and other non-clinical studies and clinical trials, along with descriptions of the manufacturing process, analytical tests conducted on the chemistry of the drug, proposed labeling and other relevant information are submitted to the FDA as part of an NDA requesting approval to market the product. The submission of an NDA is subject to the payment of substantial user fees; a waiver of such fees may be obtained under certain limited circumstances. Additionally, no user fees are assessed on NDAs for products designated as orphan drugs, unless the product also includes a non-orphan indication.

In addition, the Pediatric Research Equity Act (“PREA”), requires a sponsor to conduct pediatric clinical trials for most drugs, for a new active ingredient, new indication, new dosage form, new dosing regimen or new route of administration. Under PREA, original NDAs and certain supplements must contain a pediatric assessment unless the sponsor has received a deferral or waiver. The required assessment must evaluate the safety and effectiveness of the product for the claimed indications in all relevant pediatric subpopulations and support dosing and administration for each pediatric subpopulation for which the product is deemed safe and effective. The sponsor or FDA may request a deferral of pediatric clinical

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trials for some or all of the pediatric subpopulations. A deferral may be granted for several reasons, including a finding that the drug is ready for approval for use in adults before pediatric clinical trials are complete or that additional safety or effectiveness data needs to be collected before the pediatric clinical trials begin. The FDA must send a non-compliance letter to any sponsor that fails to submit the required assessment, keep a deferral current or fails to submit a request for approval of a pediatric formulation.

The FDA conducts a preliminary review of all NDAs within the first 60 days after submission, before accepting them for filing, to determine whether they are sufficiently complete to permit substantive review. The FDA may request additional information rather than accept an NDA for filing. In this event, the NDA must be resubmitted with additional information. The resubmitted application also is subject to review before the FDA accepts it for filing. Once filed, the FDA reviews an NDA to determine, among other things, whether a product is safe and effective for its intended use and whether its manufacturing is cGMP-compliant to assure and preserve the product’s identity, strength, quality and purity. Under the Prescription Drug User Fee Act (“PDUFA”) guidelines that are currently in effect, the FDA has a goal of ten months from the date of “filing” of a standard NDA for a new molecular entity to review and act on the submission. This review typically takes twelve months from the date the NDA is submitted to FDA because the FDA has approximately two months to make a “filing” decision after it the application is submitted.

The FDA may refer an application for a novel drug to an advisory committee. An advisory committee is a panel of independent experts, including clinicians and other scientific experts, that reviews, evaluates and provides a recommendation as to whether the application should be approved and under what conditions. The FDA is not bound by the recommendations of an advisory committee, but it considers such recommendations carefully when making decisions.

Before approving an NDA, the FDA will typically inspect the facility or facilities where the product is manufactured. The FDA will not approve an application unless it determines that the manufacturing processes and facilities are in compliance with cGMP and adequate to assure consistent production of the product within required specifications. Additionally, before approving an NDA, the FDA may inspect one or more clinical sites to assure compliance with GCPs.

After the FDA evaluates an NDA, it will issue an approval letter or a Complete Response Letter ("CRL"). An approval letter authorizes commercial marketing of the drug with prescribing information for specific indications. A CRL indicates that the review cycle of the application is complete, and the application will not be approved in its present form. A CRL usually describes the specific deficiencies in the NDA identified by the FDA and may require additional clinical data, such as an additional clinical trials or other significant and time-consuming requirements related to clinical trials, nonclinical studies or manufacturing. If a CRL is issued, the sponsor must resubmit the NDA addressing all of the deficiencies identified in the letter or withdraw the application. Even if such data and information are submitted, the FDA may decide that the NDA does not satisfy the criteria for approval.

If regulatory approval of a product is granted, such approval will be granted for particular indications and may entail limitations or restrictions on the indicated uses for which such product may be marketed. For example, the FDA may approve the NDA with a Risk Evaluation and Mitigation Strategy (“REMS”), to ensure the benefits of the product outweigh its risks. A REMS is a safety strategy to manage a known or potential serious risk associated with a medicine and to enable patients to have continued access to such medicines by managing their safe use, and could include medication guides, physician communication plans, or elements to assure safe use, such as restricted distribution methods, patient registries, and other risk minimization tools. The FDA also may condition approval on, among other things, changes to proposed labeling or the development of adequate controls and specifications. The FDA may also require one or more post-approval studies and surveillance to further assess and monitor the product’s safety and effectiveness after commercialization and may limit further marketing of the product based on the results of these post-approval studies.

Expedited Development and Review Programs

The FDA offers a number of expedited development and review programs for qualifying product candidates. For example, the FDA Fast Track program is intended to expedite or facilitate the process for reviewing product candidates that meet certain criteria. Specifically, investigational drugs are eligible for

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Fast Track designation if they are intended to treat a serious or life-threatening disease or condition and demonstrate the potential to address unmet medical needs for the disease or condition. The sponsor of a Fast Track product candidate has opportunities for more frequent interactions with the applicable FDA review team during product development and, once an NDA is submitted, the application may be eligible for priority review. With regard to a Fast Track product candidate, the FDA may consider for review sections of the NDA on a rolling basis before the complete application is submitted, if the sponsor provides a schedule for the submission of the sections of the NDA, the FDA agrees to accept sections of the NDA and determines that the schedule is acceptable, and the sponsor pays any required user fees upon submission of the first section of the NDA.

A product candidate intended to treat a serious or life-threatening disease or condition may also be eligible for Breakthrough Therapy designation to expedite its development and review. A product candidate can receive Breakthrough Therapy designation if preliminary clinical evidence indicates that the product candidate, alone or in combination with one or more other drugs or biologics, may demonstrate substantial improvement over existing therapies on one or more clinically significant endpoints, such as substantial treatment effects observed early in clinical development. The designation includes all of the Fast Track program features, as well as more intensive FDA interaction and guidance beginning as early as Phase 1 and an organizational commitment to expedite the development and review of the product candidate, including involvement of senior managers.

Moreover, an NDA is eligible for priority review if the product candidate is designed to treat a serious condition, and if approved, would provide a significant improvement in safety or effectiveness compared to marketed products. The FDA will attempt to direct additional resources to the evaluation of an NDA designated for priority review in an effort to facilitate the review. The FDA endeavors to review applications with priority review designations within six months of the filing date as compared to ten months for review of new molecular entity NDAs under its current PDUFA review goals.

In addition, depending on the design of the applicable clinical trials, a product candidate may be eligible for accelerated approval. Product candidates intended to treat serious or life-threatening diseases or conditions may be eligible for accelerated approval upon a determination that the product candidate has an effect on a surrogate endpoint that is reasonably likely to predict clinical benefit, or on a clinical endpoint that can be measured earlier than irreversible morbidity or mortality, that is reasonably likely to predict an effect on irreversible morbidity or mortality or other clinical benefit, taking into account the severity, rarity, or prevalence of the condition and the availability or lack of alternative treatments. As a condition of approval, the FDA generally requires that a sponsor of a drug receiving accelerated approval perform adequate and well-controlled confirmatory clinical trials to verify and describe the predicted clinical benefit and may require that such confirmatory trials be underway prior to granting any accelerated approval. Products receiving accelerated approval may be subject to expedited withdrawal procedures if the sponsor fails to conduct the required clinical trials in a timely manner, or if such trials fail to verify the predicted clinical benefit. In addition, the FDA currently requires pre-approval of promotional materials as a condition for accelerated approval, which could adversely impact the timing of the commercial launch of the product.

Fast Track designation, Breakthrough Therapy designation, priority review and accelerated approval do not change the standards for approval but may expedite the development or approval process. Even if a product qualifies for one or more of these programs, the FDA may later decide that the product no longer meets the conditions for qualification or decide that the time period for FDA review or approval will not be shortened.

Post-approval Requirements

Any products manufactured or distributed pursuant to FDA approvals are subject to pervasive and continuing regulation by the FDA, including, among other things, requirements relating to record-keeping, reporting of adverse experiences, periodic reporting, product sampling and distribution, and advertising and promotion of the product. After approval, most changes to the approved product, such as adding new indications or other labeling claims, are subject to prior FDA review and approval. There also are continuing, annual program fees for any marketed products.

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Drug manufacturers and their subcontractors are required to register their establishments with the FDA and certain state agencies and are subject to periodic unannounced inspections by the FDA and certain state agencies for compliance with cGMP, which impose certain procedural and documentation requirements upon drug manufacturers. Changes to the manufacturing process are strictly regulated, and, depending on the significance of the change, may require prior FDA approval before being implemented. FDA regulations also require investigation and correction of any deviations from cGMP and impose reporting requirements upon NDA holders and any third-party manufacturers that NDA holders may decide to use. Accordingly, manufacturers must continue to expend time, money and effort in the area of production and quality control to maintain compliance with cGMP and other aspects of regulatory compliance.

The FDA may withdraw approval if compliance with regulatory requirements and standards is not maintained or if problems occur after the product reaches the market. Later discovery of previously unknown problems with a product, including adverse events of unanticipated severity or frequency, or with manufacturing processes, or failure to comply with regulatory requirements, may result in revisions to the approved labeling to add new safety information, imposition of post-market studies or clinical studies to assess new safety risks, or imposition of distribution restrictions or other restrictions under a REMS program. Other potential consequences include, among other things:

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restrictions on the marketing or manufacturing of the product, complete withdrawal of the product from the market or product recalls;

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fines, warning letters, or untitled letters;

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clinical holds on clinical studies;

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refusal of the FDA to approve pending applications or supplements to approved applications, or suspension or revocation of product approvals;

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product seizure or detention, or refusal to permit the import or export of products;

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consent decrees, corporate integrity agreements, debarment or exclusion from federal healthcare programs;

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mandated modification of promotional materials and labeling and the issuance of corrective information;

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the issuance of safety alerts, Dear Healthcare Provider letters, press releases and other communications containing warnings or other safety information about the product; or

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injunctions or the imposition of civil or criminal penalties.

The FDA closely regulates the marketing, labeling, advertising and promotion of drug products. A company can make only those claims relating to safety and efficacy, purity and potency that are approved by the FDA and in accordance with the provisions of the approved label. The FDA and other agencies actively enforce the laws and regulations prohibiting the promotion of off label uses. Failure to comply with these requirements can result in, among other things, adverse publicity, warning letters, corrective advertising and potential civil and criminal penalties. Physicians may prescribe, in their independent professional medical judgment, legally available products for uses that are not described in the product’s labeling and that differ from those tested and approved by the FDA. Physicians may believe that such off-label uses are the best treatment for many patients in varied circumstances. The FDA does not regulate the behavior of physicians in their choice of treatments. The FDA does, however, restrict marketers’ communications on the subject of off-label use of their products. The federal government has levied large civil and criminal fines against companies for alleged improper promotion of off-label use and has enjoined companies from engaging in off-label promotion. The FDA and other regulatory agencies have also required that companies enter into consent decrees or permanent injunctions under which specified promotional conduct is changed or curtailed. However, companies may share truthful and not misleading information that is otherwise consistent with a product’s FDA-approved labeling.

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Marketing Exclusivity

Marketing exclusivity provisions authorized under the FDCA can delay the submission or the approval of certain marketing applications. The FDCA provides a five-year period of non-patent data exclusivity within the US to the first applicant to obtain approval of an NDA for a new chemical entity. A drug is a new chemical entity if the FDA has not previously approved any other new drug containing the same active moiety, which is the molecule or ion responsible for the action of the drug substance. During the exclusivity period, the FDA may not approve or even accept for review an abbreviated new drug application (“ANDA”), or an NDA submitted under Section 505(b)(2) (“505(b)(2) NDA”), submitted by another company for another drug based on the same active moiety, regardless of whether the drug is intended for the same indication as the original innovative drug or for another indication, where the applicant does not own or have a legal right of reference to all the data required for approval. However, an application may be submitted after four years if it contains a certification of patent invalidity or non-infringement to one of the patents listed with the FDA by the innovator NDA holder.

The FDCA alternatively provides three years of non-patent exclusivity for an NDA, or supplement to an existing NDA if new clinical investigations, other than bioavailability studies, that were conducted or sponsored by the applicant are deemed by the FDA to be essential to the approval of the application, for example new indications, dosages or strengths of an existing drug. This three-year exclusivity covers only the modification for which the drug received approval on the basis of the new clinical investigations and does not prohibit the FDA from approving ANDAs or 505(b)(2) NDAs for drugs containing the active agent for the original indication or condition of use. Five-year and three-year exclusivity will not delay the submission or approval of a full NDA. However, an applicant submitting a full NDA would be required to conduct or obtain a right of reference to any preclinical studies and adequate and well-controlled clinical trials necessary to demonstrate safety and effectiveness.

Pediatric exclusivity is another type of marketing exclusivity available in the US. Pediatric exclusivity provides for an additional six months of marketing exclusivity attached to any existing periods of regulatory exclusivity or patent terms if a sponsor conducts clinical trials in children in response to a written request from the FDA. The issuance of a written request does not require the sponsor to undertake the described clinical trials, and a grant of pediatric exclusivity does not require the sponsor to obtain approval for the product candidate for pediatric use.

Other Healthcare Laws

Pharmaceutical companies are subject to additional healthcare regulation and enforcement by the federal government and by authorities in the states and foreign jurisdictions in which they conduct their business. Such laws include, without limitation, US federal and state anti-kickback, fraud and abuse, false claims, pricing reporting, and physician payment transparency laws and regulations regarding drug pricing and payments or other transfers of value made to physicians and other licensed healthcare professionals as well as similar foreign laws in the jurisdictions outside the US. Such foreign laws and regulations may be broader in scope than the provisions described above and may apply regardless of payor. These laws and regulations may differ from one another in significant ways, thus further complicating compliance efforts. For instance, in the EU, many EU member states have adopted specific anti-gift statutes that further limit commercial practices for medicinal products, in particular vis-à-vis healthcare professionals and organizations. Additionally, there has been a recent trend of increased regulation of payments and transfers of value provided to healthcare professionals or entities and many EU member states have adopted national “Sunshine Acts” which impose reporting and transparency requirements (often on an annual basis), similar to the requirements in the US, on pharmaceutical companies. Certain countries also mandate implementation of commercial compliance programs or require disclosure of marketing expenditures and pricing information. Violation of any of such laws or any other governmental regulations that apply may result in significant penalties, including, without limitation, administrative civil and criminal penalties, damages, disgorgement fines, additional reporting requirements and oversight obligations, contractual damages, the curtailment or restructuring of operations, exclusion from participation in governmental healthcare programs and/ or imprisonment.

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Coverage and Reimbursement

Significant uncertainty exists as to the coverage and reimbursement status of any product candidate for which we may seek regulatory approval. Sales in the US and in foreign jurisdictions will depend, in part, on the availability of sufficient coverage and adequate reimbursement from third-party payors, which include government health programs such as Medicare, Medicaid, TRICARE and the Veterans Administration, as well as managed care organizations and private health insurers. Prices at which we or our customers seek reimbursement for our product candidates can be subject to challenge, reduction or denial by third-party payors.

The process for determining whether a third-party payor will provide coverage for a product is typically separate from the process for setting the reimbursement rate that the payor will pay for the product. In the US, there is no uniform policy among payors for coverage or reimbursement. Decisions regarding whether to cover any of a product, the extent of coverage and amount of reimbursement to be provided are made on a plan-by-plan basis. Third-party payors often rely upon Medicare coverage policy and payment limitations in setting their own coverage and reimbursement policies, but also have their own methods and approval processes. Therefore, coverage and reimbursement for products can differ significantly from payor to payor. As a result, the coverage determination process is often a time-consuming and costly process that can require manufacturers to provide scientific and clinical support for the use of a product to each payor separately, with no assurance that coverage and adequate reimbursement will be applied consistently or obtained in the first instance.

Third-party payors are increasingly challenging the price and examining the medical necessity and cost-effectiveness of medical products and services, in addition to their safety and efficacy. Adoption of price controls and cost-containment measures, and adoption of more restrictive policies in jurisdictions with existing controls and measures, could further limit sales of any product that receives approval. Third-party payors may not consider our product candidates to be medically necessary or cost-effective compared to other available therapies, or the rebate percentages required to secure favorable coverage may not yield an adequate margin over cost or may not enable us to maintain price levels sufficient to realize an appropriate return on our investment in drug development. Additionally, decreases in third-party reimbursement for any product or a decision by a third-party payor not to cover a product could reduce physician usage and patient demand for the product.

Healthcare Reform

In the US and in foreign jurisdictions, there has been, and continues to be, several legislative and regulatory changes and proposed changes regarding the healthcare system that could prevent or delay marketing approval of product candidates, restrict or regulate post-approval activities, and affect the profitable sale of product candidates.

Among policy makers and payors in the US, there is significant interest in promoting changes in healthcare systems with the stated goals of containing healthcare costs, improving quality and/or expanding access. In the US, the pharmaceutical industry has been a particular focus of these efforts and has been significantly affected by major legislative initiatives. In March 2010, the Patient Protection and Affordable Care Act, as amended by the Health Care and Education Reconciliation Act (collectively, the “ACA”) was passed, which substantially changed the way healthcare is financed by both governmental and private insurers, and significantly affected the pharmaceutical industry. The ACA increased the minimum level of Medicaid rebates payable by manufacturers of brand name drugs from 15.1% to 23.1%; required collection of rebates for drugs paid by Medicaid managed care organizations; imposed a non-deductible annual fee on pharmaceutical manufacturers or importers who sell certain “branded prescription drugs” to specified federal government programs, implemented a new methodology by which rebates owed by manufacturers under the Medicaid Drug Rebate Program are calculated for drugs that are inhaled, infused, instilled, implanted, or injected; expanded eligibility criteria for Medicaid programs; created a new Patient-Centered Outcomes Research Institute to oversee, identify priorities in, and conduct comparative clinical effectiveness research, along with funding for such research; and established a Center for Medicare and Medicaid Innovation at the Centers for Medicare & Medicaid Services (“CMS”) to test innovative payment and service delivery models to lower Medicare and Medicaid spending, potentially including prescription drug spending.

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Since its enactment, there have been judicial and political challenges to certain aspects of the ACA. On June 17, 2021, the US Supreme Court dismissed the most recent judicial challenge to the ACA without specifically ruling on the constitutionality of the ACA. In addition, other legislative changes have been proposed and adopted since the ACA was enacted. These changes included aggregate reductions to Medicare payments to providers, which went into effect on April 1, 2013 and, due to subsequent legislative amendments to the statute, will remain in effect through 2032, with the exception of a temporary suspension from May 1, 2020 through March 31, 2022, unless additional Congressional action is taken. In addition, on January 2, 2013, the American Taxpayer Relief Act of 2012 was signed into law, which, among other things, reduced Medicare payments to several providers, including hospitals, and increased the statute of limitations period for the government to recover overpayments to providers from three to five years. In addition, on March 11, 2021, the American Rescue Plan Act of 2021 was signed into law, which eliminated the statutory Medicaid drug rebate cap, beginning January 1, 2024. The rebate was previously capped at 100% of a drug’s average manufacturer price.

Moreover, there has recently been heightened governmental scrutiny over the manner in which manufacturers set prices for their marketed products, which has resulted in several Congressional inquiries and proposed and enacted federal and state legislation designed to, among other things, bring more transparency to product pricing, review the relationship between pricing and manufacturer patient programs, and reform government program reimbursement methodologies for pharmaceutical products. On August 16, 2022, the Inflation Reduction Act of 2022, or ("IRA"), was enacted into law. Among other things, the IRA requires manufacturers of certain drugs to engage in price negotiations with Medicare (beginning in 2026), imposes rebates under Medicare Part B and Medicare Part D to penalize price increases that outpace inflation (first due in 2023), and replaces the Part D coverage gap discount program with a new discounting program (which began in 2025). The IRA permits the Secretary of the US Department of Health & Human Services (“HHS”) to implement many of these provisions through guidance, as opposed to regulation, for the initial years. HHS has issued and will continue to issue guidance implementing the IRA. CMS has published the negotiated prices for the initial ten drugs, which went into effect in 2026, and the subsequent 15 drugs, which will first be effective in 2027, although the Medicare drug price negotiation program is currently subject to legal challenges. While the impact of the IRA on the pharmaceutical industry cannot yet be fully determined, it is likely to be significant.

The One Big Beautiful Bill Act, which was enacted in July 2025, imposes significant reductions in the funding of the Medicaid program. Such reductions are expected to decrease the number of persons enrolled in Medicaid and reduce the services covered by Medicaid, which could adversely affect our sales of any product candidate that we commercialize.

The Trump administration is pursuing a two-fold strategy to reduce drug costs in the US. While it is unclear whether and how the Trump administration proposals will be implemented, the Trump administration policies are likely to have a negative impact on the pharmaceutical industry and on our ability to receive adequate revenues for our product candidates, if approved. On the one hand, President Trump has threatened to impose significant tariffs on pharmaceutical manufacturers that do not adopt pricing policies such as most favored nation pricing, which would tie the US price of a drug to the lowest price in a group of other countries. In response, multiple pharmaceutical manufacturers have reportedly entered into confidential pricing agreements with the federal government. On the other hand, the Trump administration is pursuing traditional regulatory pathways to impose drug pricing policies, although final regulations have not yet been published. Even regulatory proposals or executive actions that are ultimately deemed unlawful could negatively impact the US pharmaceutical sector and our business. In addition, pharmaceutical pricing and marketing has long been the subject of considerable discussion in Congress and among policymakers, and it is possible that Congress could enact additional laws that negatively affect the pharmaceutical industry.

Individual states in the US have also become increasingly active in implementing regulations designed to control pharmaceutical product pricing, including price or patient reimbursement constraints, discounts, restrictions on certain product access and marketing cost disclosure, drug price reporting and other transparency measures, and, in some cases, designed to encourage importation from other countries and bulk purchasing. Some states have enacted legislation creating so-called prescription drug affordability boards, which ultimately may attempt to impose price limits on certain drugs in these states. In addition, certain individual states as well as regional healthcare authorities and individual hospitals are increasingly

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using bidding procedures to determine which drugs and suppliers will be included in their healthcare programs. The states of Louisiana and Washington used bidding procedures in 2019 and more recently Minnesota did so in 2021 to secure contracts with suppliers of HCV antiviral therapeutics for certain populations including those covered by Medicare and those in correctional institutions. Other states are currently engaged in similar discussions and legislation including bidding procedures for procurement of HCV therapies for certain federally insured populations is proposed at the federal level. Furthermore, there has been increased interest by third party payors and governmental authorities in reference pricing systems and publication of discounts and list prices.

In the EU, on December 13, 2021, Regulation No 2021/2282 on Health Technology Assessment (“HTA”) was adopted. The Regulation entered into force in January 2022 and has been applicable since January 2025, with phased implementation based on the type of product, i.e. oncology and advanced therapy medicinal products as of 2025, orphan medicinal products as of 2028, and all other medicinal products by 2030. The Regulation intends to boost cooperation among EU member states in assessing health technologies, including new medicinal products, and provide the basis for cooperation at the EU level for joint clinical assessments in these areas. It will permit EU member states to use common HTA tools, methodologies, and procedures across the EU, working together in four main areas, including joint clinical assessment of the innovative health technologies with the highest potential impact for patients, joint scientific consultations whereby developers can seek advice from HTA authorities, identification of emerging health technologies to identify promising technologies early, and continuing voluntary cooperation in other areas. Individual EU member states will continue to be responsible for assessing non-clinical (e.g., economic, social, ethical) aspects of health technology and making decisions on pricing and reimbursement.

We expect that additional state, federal and foreign healthcare reform measures will be adopted in the future, any of which could limit the amounts that federal and state governments will pay for drug products and healthcare services, which could result in reduced demand for our product candidates once approved or additional pricing pressures.

Data Privacy and Security

Numerous state and federal laws, regulations and standards govern the collection, use, access to, confidentiality and security of health-related and other personal information and could apply now or in the future to our operations or the operations of our partners. In the US, numerous federal and state laws and regulations, including data breach notification laws, health information privacy and security laws and consumer protection laws and regulations govern the collection, use, disclosure, and protection of health-related and other personal information. Further, certain foreign laws govern the privacy and security of personal data, including health-related data. Privacy and security laws, regulations, and other obligations are constantly evolving, may conflict with each other to complicate compliance efforts, and can result in investigations, proceedings, or actions that lead to significant civil and/or criminal penalties and restrictions on data processing. For additional information, see Part I, Item 1A, “Risk Factors”.

Government Regulation Outside of the US

In addition to regulations in the US, we are subject to a variety of regulations in other jurisdictions, such as the EU, governing, among other things, clinical trials, marketing authorization and any commercial sales and distribution of our products once approved. Whether or not we obtain FDA approval for a product candidate, we must obtain the requisite approvals from regulatory authorities in foreign countries prior to the commencement of clinical trials or marketing of the product in those countries. The requirements and processes governing the conduct of clinical trials, approval process, product licensing, pricing and reimbursement vary from country to country. Failure to comply with applicable foreign regulatory requirements may be subject to, among other things, fines, suspension or withdrawal of regulatory approvals, product recalls, seizure of products, operating restrictions and criminal prosecution.

Non-clinical Studies and Clinical Trials

Similar to the US, the various phases of non-clinical and clinical research in the EU are subject to significant regulatory controls.

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Non-clinical studies are performed to demonstrate the health or environmental safety of new chemical or biological substances. Non-clinical (pharmaco-toxicological) studies must be conducted in compliance with the principles of good laboratory practice (“GLP”) as set forth in EU Directive 2004/10/EC (unless otherwise justified for certain particular medicinal products – e.g., radio-pharmaceutical precursors for radio-labeling purposes). In particular, non-clinical studies, both in vitro and in vivo, must be planned, performed, monitored, recorded, reported and archived in accordance with the GLP principles, which define a set of rules and criteria for a quality system for the organizational process and the conditions for non-clinical studies. These GLP standards reflect the Organization for Economic Co-operation and Development requirements.

Clinical trials of medicinal products in the EU must be conducted in accordance with EU and national regulations and the International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use (“ICH”) guidelines on Good Clinical Practices (“GCP”) as well as the applicable regulatory requirements and the ethical principles that have their origin in the Declaration of Helsinki. If the sponsor of the clinical trial is not established within the EU, it must appoint an EU entity to act as its legal representative. The sponsor must take out a clinical trial insurance policy, and in most EU member states, the sponsor is liable to provide ‘no fault’ compensation to any study subject injured in the clinical trial.

The regulatory landscape related to clinical trials in the EU has been subject to recent changes. The EU Clinical Trials Regulation (“CTR”) which was adopted in April 2014 and repeals the EU Clinical Trials Directive, became applicable on January 31, 2022. Unlike directives, the CTR is directly applicable in all EU member states without the need for member states to further implement it into national law. The CTR notably harmonizes the assessment and supervision processes for clinical trials throughout the EU via a Clinical Trials Information System, which contains a centralized EU portal and database.

While the EU Clinical Trials Directive required a separate clinical trial application (“CTA”) to be submitted in each member state in which the clinical trial takes place, to both the competent national health authority and an independent ethics committee, much like the FDA and IRB respectively, the CTR introduces a centralized process and only requires the submission of a single application for multi-center trials. The CTR allows sponsors to make a single submission to both the competent authority and an ethics committee in each member state, leading to a single decision per member state. The CTA must include, among other things, a copy of the trial protocol and an investigational medicinal product dossier containing information about the manufacture and quality of the medicinal product under investigation.

The assessment procedure of the CTA has been harmonized as well, including a joint assessment by all member states concerned, and a separate assessment by each member state with respect to specific requirements related to its own territory, including ethics rules. Each member state’s decision is communicated to the sponsor via the centralized EU portal. Once the CTA is approved, clinical study development may proceed.

As of January 31, 2025, except in limited circumstances, all clinical trials conducted in EU member states (and related applications) are subject to the provisions of the CTR.

Medicines used in clinical trials conducted in EU member states must be manufactured in accordance with Good Manufacturing Practice (“GMP”). Other national and EU-wide regulatory requirements may also apply.

Marketing Authorization

In order to market our future product candidates in the EU and many other foreign jurisdictions, we must obtain separate regulatory approvals. More concretely, in the EU, medicinal product candidates can only be commercialized after obtaining a marketing authorization (“MA”). To obtain regulatory approval of a product candidate under EU regulatory systems, we must submit a MAA. The process of doing this depends, among other things, on the nature of the medicinal product. There are two types of MAs:

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“Centralized MA” are issued by the European Commission through the centralized procedure, based on the opinion of the Committee for Medicinal Products for Human Use (“CHMP”) of EMA and are valid throughout the EU. The centralized procedure is mandatory for certain types of product candidates, such as: (i) medicinal products derived from biotechnology

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processes, such as genetic engineering, (ii) designated orphan medicines, (iii) medicinal products containing a new active substance indicated for the treatment of certain diseases, such as HIV/AIDS, cancer, neurodegenerative diseases, diabetes, auto-immune and other immune dysfunctions and viral diseases and (iv) advanced therapy medicinal products (“ATMPs”) such as gene therapy, somatic cell therapy or tissue-engineered medicines. The centralized procedure is optional for product candidates containing a new active substance not yet authorized in the EU, or for product candidates that constitute a significant therapeutic, scientific or technical innovation or which are in the interest of public health in the EU.

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“National MAs” are issued by the competent authorities of the EU member states, only cover their respective territory, and are available for product candidates not falling within the mandatory scope of the centralized procedure. Where a product has already been authorized for marketing in an EU member state, this national MA can be recognized in another member state through the mutual recognition procedure. If the product has not received a national MA in any member state at the time of application, it can be approved simultaneously in various member states through the decentralized procedure. Under the decentralized procedure an identical dossier is submitted to the competent authorities of each of the member states in which the MA is sought, one of which is selected by the applicant as the reference member state.

Under the centralized procedure the maximum timeframe for the evaluation of a MAA by the EMA is 210 days.

In the EU, innovative products that target an unmet medical need and are expected to be of major public health interest may be eligible for a number of expedited development and review programs, such as the PRIority MEdicines (“PRIME”) scheme, which provides incentives similar to the Breakthrough Therapy designation in the US. Launched by EMA in March 2016, the PRIME scheme is a voluntary scheme aimed at enhancing the EMA’s support for the development of medicines that target unmet medical needs. It is based on increased interaction and early dialogue with companies developing promising medicines, to optimize their product development plans and speed up their evaluation to help them reach patients earlier. Product developers that benefit from PRIME designation can expect to be eligible for accelerated assessment, but this is not guaranteed. Many benefits accrue to sponsors of product candidates with PRIME designation, including but not limited to, early and proactive regulatory dialogue with the EMA, frequent discussions on clinical trial designs and other development program elements, and accelerated MAA assessment once a dossier has been submitted. Importantly, a dedicated contact and rapporteur from the CHMP is appointed early in the PRIME scheme facilitating increased understanding of the product at EMA’s committee level. An initial meeting initiates these relationships and includes a team of multidisciplinary experts at the EMA to provide guidance on the overall development and regulatory strategies.

Moreover, in the EU, a “conditional” MA may be granted in cases where all the required safety and efficacy data are not yet available. The conditional MA is subject to conditions to be fulfilled for generating the missing data or ensuring increased safety measures. It is valid for one year and has to be renewed annually until fulfillment of all the conditions. Once the pending studies are provided, it can become a “standard” MA. However, if the conditions are not fulfilled within the timeframe set by the EMA, the MA ceases to be renewed. Furthermore, MA may also be granted “under exceptional circumstances” when the applicant can show that it is unable to provide comprehensive data on the efficacy and safety under normal conditions of use even after the product has been authorized and subject to specific procedures being introduced. This may arise in particular when the intended indications are very rare and, in the present state of scientific knowledge, it is not possible to provide comprehensive information, or when generating data may be contrary to generally accepted ethical principles. This MA is close to the conditional MA as it is reserved for medicinal products to be approved for severe diseases or unmet medical needs and the applicant does not hold the complete data set legally required for the grant of a MA. However, unlike the conditional MA, the applicant does not have to provide the missing data and will never have to. Although the MA “under exceptional circumstances” is granted definitively, the risk-benefit balance of the medicinal product is reviewed annually, and the MA is withdrawn in case the risk-benefit ratio is no longer favorable.

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Under the above-described procedures, in order to grant the MA, the EMA or the competent authorities of the EU member states make an assessment of the risk benefit balance of the product on the basis of scientific criteria concerning its quality, safety and efficacy. MAs have an initial duration of five years. After these five years, the authorization may be renewed for an unlimited period on the basis of a reevaluation of the risk-benefit balance.

Data and Marketing Exclusivity

The EU also provides opportunities for data and market exclusivity. Upon receiving MA, reference products generally receive eight years of data exclusivity and an additional two years of market exclusivity. If granted, the data exclusivity period prevents generic or biosimilar applicants from relying on the pre-clinical and clinical trial data contained in the dossier of the reference product when applying for a generic or biosimilar MA in the EU during a period of eight years from the date on which the reference product was first authorized in the EU. The market exclusivity period prevents a successful generic or biosimilar applicant from commercializing its product in the EU until 10 years have elapsed from the initial MA of the reference product in the EU. The overall 10-year market exclusivity period can be extended to a maximum of eleven years if, during the first eight years of those 10 years, the MA holder obtains an authorization for one or more new therapeutic indications which, during the scientific evaluation prior to their authorization, are held to bring a significant clinical benefit in comparison with existing therapies. However, there is no guarantee that a product will be considered by the EU’s regulatory authorities to be a new chemical entity, and products may not qualify for data exclusivity.

Pediatric Development

In the EU, MAAs for new medicinal products have to include the results of studies conducted in the pediatric population, in compliance with a pediatric investigational plan ("PIP") agreed with the EMA’s Pediatric Committee ("PDCO"). The PIP sets out the timing and measures proposed to generate data to support a pediatric indication of the drug for which the MA is being sought. The PDCO can grant a deferral of the obligation to implement some or all of the measures of the PIP until there are sufficient data to demonstrate the efficacy and safety of the product in adults. Further, the obligation to provide pediatric clinical trial data can be waived by the PDCO when these data is not needed or appropriate because the product is likely to be ineffective or unsafe in children, the disease or condition for which the product is intended occurs only in adult populations, or when the product does not represent a significant therapeutic benefit over existing treatments for pediatric patients. Once the MA is obtained in all the EU member states and study results are included in the product information, even when negative, the product is eligible for six months’ supplementary protection certificate extension (if any is in effect at the time of approval) or, in the case of orphan pharmaceutical products, a two-year extension of the orphan market exclusivity is granted.

The aforementioned EU rules are generally applicable in the European Economic Area (“EEA”) which consists of the 27 EU member states plus Norway, Liechtenstein and Iceland.

Failure to comply with EU and member state laws that apply to the conduct of clinical trials, manufacturing approval, MA of medicinal products and marketing of such products, both before and after grant of the MA, manufacturing of pharmaceutical products, statutory health insurance, bribery and anti-corruption or with other applicable regulatory requirements may result in administrative, civil or criminal penalties. These penalties could include delays or refusal to authorize the conduct of clinical trials, or to grant MA, product withdrawals and recalls, product seizures, suspension, withdrawal or variation of the MA, total or partial suspension of production, distribution, manufacturing or clinical trials, operating restrictions, injunctions, suspension of licenses, fines and criminal penalties.

Brexit and the Regulatory Framework in the United Kingdom

Since the end of the Brexit transition period on January 1,2021, and the implementation on January 1, 2025, of the Windsor Framework (as defined below), the United Kingdom (“UK”) has not generally been directly subject to EU laws with respect to medicinal products. The EU laws that have been transposed into UK law through secondary legislation remain applicable in the UK, however, new legislation such as the (EU) CTR is not applicable in the UK. Under the Medicines and Medical Devices Act 2021, the

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Secretary of State or an ‘appropriate authority’ has delegated powers to amend or supplement existing regulations in the area of medicinal products and medical devices. This allows new rules to be introduced in the future by way of secondary legislation, which aims to allow flexibility in addressing regulatory gaps and future changes in the fields of human medicines, clinical trials and medical devices.

Since January 1, 2021, the Medicines and Healthcare products Regulatory Agency (“MHRA”) has been the UK’s standalone medicines and medical devices regulator. As a result of the Northern Ireland Protocol, different rules applied in Northern Ireland than in Great Britain (“GB”); broadly, Northern Ireland continued to follow the EU regulatory regime. However, on January 1, 2025, a new arrangement called the “Windsor Framework” came into effect and reintegrated Northern Ireland under the regulatory authority of the MHRA with respect to medicinal products. The Windsor Framework removes EU licensing processes, and EU labelling and serialization requirements in relation to Northern Ireland and introduces a UK-wide licensing process for medicinal products.

The UK regulatory framework in relation to clinical trials is derived from pre-existing EU legislation (as implemented into UK law, through secondary legislation). In April 2025, the UK government adopted the Medicines for Human Use (Clinical Trials) Amendment Regulations. The amendment, which will take full effect from April 2026, aims to provide a more flexible regime to make it easier to conduct clinical trials in the UK, increase the transparency of clinical trials conducted in the UK and make clinical trials more patient centered.

The MHRA has introduced changes to national licensing procedures, including procedures to prioritize access to new medicines that will benefit patients, including a 150-day assessment and a rolling review procedure. All existing EU MAs for centrally authorized products were automatically converted or grandfathered into UK MAs, effective in GB (only), free of charge on January 1, 2021, unless the MA holder opted out. In order to use the centralized procedure to obtain a MA that will be valid throughout the EEA, companies must be established in the EEA. Therefore, since Brexit, companies established in the UK can no longer use the EU centralized procedure and instead an EEA entity must hold any centralized MAs. In order to obtain a UK MA to commercialize products in the UK, an applicant must be established in the UK and must follow one of the UK national authorization procedures or one of the remaining post-Brexit international cooperation procedures to obtain an MA to commercialize products in the UK. An international recognition framework has been in place from January 1, 2024, whereby the MHRA will have regard to decisions on the approval of MAs made by the EMA and certain other regulators when determining an application for a new UK MA.

There is no pre-MA orphan designation in the UK. Instead, the MHRA will review applications for orphan designation in parallel to the corresponding MA application. The criteria are essentially the same, but have been tailored for the market, i.e., the prevalence of the condition in the UK, rather than the EU, must not be more than five in 10,000. Should an orphan designation be granted, the period of market exclusivity will be set from the date of first approval of the product in the UK.

Human Capital Resources

As of March 4, 2026, we had 55 full-time employees, including 19 employees with M.D., Ph.D. or Pharm.D. degrees. Of these full-time employees, 38 employees are engaged in research and development activities. None of our employees are represented by a labor union or covered by a collective bargaining agreement. We consider our relationship with our employees to be good.

Our top priorities for human capital resources are to attract, recruit, retain, incentivize, and seamlessly integrate both our current and new employees in an engaging manner. The principal purpose of our competitive equity and cash compensation and benefits programs is to promote and support these priorities. We consider our human capital resources strategy to be comprehensive and built to foster our core way of working which is grounded on the principles of scientific rigor in a collaborative, entrepreneurial, and results-oriented manner.

Organization

Atea Pharmaceuticals, Inc. was incorporated in July 2012 and began principal operations in March 2014. Our principal office facilities are in Boston, Massachusetts. Atea Pharmaceuticals Securities Corporation,

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a Massachusetts corporation incorporated in 2016, is a wholly owned subsidiary of Atea Pharmaceuticals, Inc. Our website is www.ateapharma.com. Information that is contained on, or that can be accessed through, our website is not incorporated by reference into this Annual Report on Form 10-K, and you should not consider information on our website to be part of this Annual Report on Form 10-K.

Available Information

We make available free of charge on the investor relations portion of our website our Annual Reports on Form 10-K, Quarterly Reports on Form 10-Q, Current Reports on Form 8-K, Proxy Statements for our annual meetings of stockholders, and amendments to those reports, as soon as reasonably practicable after we file such material with, or furnish it to, the Securities and Exchange Commission (“SEC”). These filings are available for download free of charge on the investor relations portion of our website located at https://ir.ateapharma.com. The SEC also maintains a website that contains reports, proxy statements and other information that we and other issuers file electronically with the SEC. The address of that website is https://www.sec.gov.

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Information about our Executive Officers and Directors

The following table sets forth the name, age and position of each of our executive officers and directors as of the date of this Annual Report on Form 10-K.

(1) Member of the Audit Committee.

(2) Member of the Compensation Committee.

(3) Member of the Nominating and Corporate Governance Committee.

(4) Member of the Strategy and Public Policy Committee.

Executive Officers

Jean-Pierre Sommadossi, Ph.D., is the founder of our Company and has served as our President, Chief Executive Officer and Chairman of our Board since July 2012. Prior to that, he co-founded and held several roles at Idenix Pharmaceuticals, Inc., a biopharmaceutical company, from 1998 to 2010, including Principal Founder and Chief Executive Officer and Chairman. Dr. Sommadossi also co-founded Pharmasset, Inc., a biopharmaceutical company, in 1998. Dr. Sommadossi has also served as Chairman of the board of directors of Panchrest, Inc., a privately held marketing authorized representative in healthcare, since 2013, and Chairman of the board of directors of Biothea Pharma, Inc., a privately held biotechnology company, since 2021. Dr. Sommadossi has also served as a member of the board of directors of The BioExec Institute since 2004. Previously, Dr. Sommadossi served on the board of directors of ABG Acquisition Corporation from February 2021 to February 2023, as Chairman of the board of directors of Kezar Life Sciences, Inc., a biopharmaceutical company, from June 2015 to May 2022, Vice Chairman of the board of directors of Rafael Pharmaceuticals, Inc., a biopharmaceutical company, from October 2016 to November 2020 and as Chairman of the board of directors of PegaOne, Inc., a biopharmaceutical company, from September 2020 to January 2021. Dr. Sommadossi also served as a member of the Harvard Medical School Discovery Council from 2010 to 2021. Dr. Sommadossi received his Ph.D. and Pharm.D. degrees from the University of Marseilles in France. We believe that Dr. Sommadossi’s extensive scientific, operational, strategic and management experience in the biopharmaceutical industry qualifies him to serve on our Board.

Andrea Corcoran has served as our Chief Financial Officer since October 2020, Secretary since September 2014 and Executive Vice President, Legal since December 2013. Ms. Corcoran previously served as our Executive Vice President, Administration from September 2014 to October 2020. Prior to joining us, Ms. Corcoran served as Senior Vice President, Strategy and Finance at iBio, Inc., a

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biotechnology company, from 2011 to 2012, as General Counsel and Secretary at Tolerx, Inc., a privately held biopharmaceutical company, from 2007 to 2011, and as Executive Vice President of Idenix Pharmaceuticals, Inc. from 1998 to 2007. Ms. Corcoran received her J.D. from Boston College Law School and her B.S. from Providence College.

Janet Hammond, M.D., Ph.D., has served as our Chief Development Officer since August 2020. Prior to joining us, Dr. Hammond served as Vice President and Therapeutic Area Head for General Medicine and Infectious Disease Development at AbbVie, Inc., a biopharmaceutical company, from November 2016 to August 2020, and as Senior Vice President, Global Head of Infectious Diseases and Head of Pharmaceutical Research and Early Development China at F. Hoffmann-La Roche from March 2011 to November 2016. Dr. Hammond has also served on the board of directors of Enterprise Therapeutics Ltd., a privately held biopharmaceutical company, since May 2024. Dr. Hammond received her M.D. and Ph.D. from the University of Cape Town, South Africa, and her Sc.M. in Clinical Investigation from Johns Hopkins University School of Hygiene and Public Health.

Maria Arantxa Horga, M.D., has served as our Chief Medical Officer since January 2021 and previously served as our Acting Chief Medical Officer since October 2020 and as Executive Vice President, Clinical Sciences since August 2020. Prior to joining us, Dr. Horga served as Vice President, Pharmacovigilance and Medical Affairs at Biohaven Pharmaceuticals, Inc. from October 2019 to August 2020. Prior to that, Dr. Horga served as Vice President, Global Head of Clinical Program Execution, Site Head of the Roche NY Innovation Center from July 2017 to August 2019, and as Global Head of Translational Medicine, Infectious Diseases at F. Hoffmann-La Roche from 2012 to 2016. Dr. Horga received her M.D. from the Santander School of Medicine and completed her residency in Pediatrics and a fellowship in Pediatric Infectious Diseases at the Mount Sinai School of Medicine.

John Vavricka has served as our Chief Commercial Officer since October 2018. Prior to joining us, Mr. Vavricka co-founded and served as the Chief Executive Officer of Biothea Pharma, Inc., a privately held biotechnology company, from March 2018 to June 2021. Prior to that, Mr. Vavricka founded and served as the Chief Executive Officer and President of Iroko Pharmaceuticals, Inc., a global pharmaceuticals company, from 2007 to 2015. Mr. Vavricka received his B.S. from Northwestern University.

Wayne Foster has served as our Executive Vice President, Finance and Chief Accounting Officer since January 2022 and previously served as Senior Vice President, Finance and Administration from December 2019 to January 2022. Prior to joining us, Mr. Foster served as Vice President of Finance at Mersana Therapeutics, Inc., a biopharmaceutical company, from January 2012 to September 2019. Mr. Foster received his B.B.A. from the University of Massachusetts Amherst.

Directors

Franklin Berger has served as a member and the Lead Director of our Board since September 2019. Mr. Berger has served as Founder and Managing Director at FMB Research LLC, a consulting firm, since June 2005. Mr. Berger has also served on the boards of directors of Satellos Bioscience Inc. since September 2023 and Kezar Life Sciences, Inc. since January 2016. Mr. Berger previously served on the boards of directors of ESSA Pharma Inc. from March 2015 to October 2025, Rain Therapeutics Inc. from May 2020 to January 2024, Atreca Inc. from October 2014 to May 2024, BELLUS Health, Inc. from May 2010 to June 2023, Five Prime Therapeutics, Inc. from October 2014 to April 2021, Tocagen, Inc. from October 2014 to December 2020 and Proteostasis Therapeutics, Inc. from February 2016 to December 2020. Mr. Berger received his B.A. and M.A. from Johns Hopkins University and his M.B.A. from Harvard Business School. We believe that Mr. Berger’s financial background and experience as an equity analyst in the biotechnology industry combined with his experience serving on the boards of directors of multiple public companies qualifies him to serve on our Board.

Jerome Adams, M.D., has served as a member of our Board since May 2021. Dr. Adams also has served as Presidential Fellow and Executive Director of the Center for Community Health Enhancement and Learning and Distinguished Professor of Practice in the departments of Pharmacy Practice and Public Health at Purdue University and Associate Professor of Anesthesia at Indiana University since October 2021. Dr. Adams served as the 20th Surgeon General of the US from September 2017 to January 2021. Prior to that, Dr. Adams served as the Commissioner of the Indiana State Department of Health from November 2014 to September 2017, where he served as a cabinet advisor on public health matters and

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led Indiana’s response to Ebola, Zika and HIV crises. Dr. Adams has held numerous roles in academia and medicine, including General Anesthesiologist at Walter Reed Medical Center from 2018 to 2021 and at Ball Memorial Hospital from 2006 to 2017 and Associate Professor of Anesthesia at Indiana University from January 2008 to September 2017. Earlier in his career, Dr. Adams was a Clinical Research Assistant at Eli Lilly and Company. He has served in leadership positions at a number of professional organizations, including the American Medical Association, the Indiana State Medical Association, and the Indiana Society of Anesthesiologists. Dr. Adams received his B.S. in Biochemistry and B.A. in Psychology from the University of Maryland, Baltimore County, his M.D. from the Indiana University School of Medicine and his M.P.H. from the University of California, Berkeley. We believe that Dr. Adams’ extensive leadership and public sector experience qualifies him to serve on our board.

Howard Berman, Ph.D., has served as a member of our Board since June 2025. Dr. Berman is the founder of Coya Therapeutics, Inc., a biotechnology company, where he has served as Executive Chair since November 2024 and previously served as Chief Executive Officer and Chairman of the board of directors from March 2020 to November 2024. Dr. Berman has also served on the board of directors of Bertex, LLC since 2006. Previously, Dr. Berman founded and served on the board of directors of Imaware Inc., a private at-home health testing and diagnostics company from March 2018 to March 2024. Dr. Berman has also previously served in positions of increasing responsibility as a Senior Medical Liaison at Abbvie Inc. from April 2013 to June 2020, at Eli Lilly and Company from May 2009 to March 2013, and at Novartis Pharmaceuticals, Inc. from April 2003 to May 2006. Dr. Berman received his B.S. from the University of Michigan and Ph.D. from Weill Cornell Medical School. We believe that Dr. Berman is qualified to serve on our Board due to his experience in the biotechnology industry and service as a public company executive and board member.

Barbara Duncan has served as a member of our Board since October 2020. Ms. Duncan served as Chief Financial Officer and Treasurer at Intercept Pharmaceuticals, Inc. from May 2009 to June 2016. Ms. Duncan has also served on the boards of directors of Ovid Therapeutics, Inc. since June 2017, Halozyme Therapeutics, Inc. since February 2023, Convergent Therapeutics, a privately held biopharmaceutical company, since December 2024 and PhoreMost Ltd., a privately held biopharmaceutical company since June 2025. Previously, Ms. Duncan served on the boards of directors of Fusion Pharmaceuticals Inc. from October 2020 to May 2024, Jounce Therapeutics, Inc. from February 2016 to April 2023, Adaptimmune Therapeutics plc from June 2016 to May 2023, Immunomedics, Inc. from March 2019 to October 2020, Innoviva, Inc., from November 2016 to April 2018, Aevi Genomic Medicine, Inc., from June 2015 to January 2020, and ObsEva S.A. from November 2016 to May 2021. Ms. Duncan received her B.A. from Louisiana State University and her M.B.A. from the Wharton School, University of Pennsylvania. We believe Ms. Duncan is qualified to serve on our Board due to her financial expertise, experience in the biotechnology industry and service as a public company executive and board member.

Arthur Kirsch has served as a member of our Board since February 2025. Mr. Kirsch has served as a Senior Advisor at Alvarez & Marsal Life Science Industry Group, a global professional services firm, since 2019. Previously, Mr. Kirsch was a Managing Director and Senior Advisor at GCA Global, LLC, a global investment banking firm, from 2005 to 2019, where he was responsible for healthcare investment banking activities. From May 1994 to May 2004, Mr. Kirsch served as Executive Vice President, Head of Research at Vector Securities, LLC, a brokerage firm. From February 1990 to May 1993, Mr. Kirsch served as President of Natwest Securities Limited, a brokerage firm. From June 1979 to February 1990, Mr. Kirsch served at Drexel Burnham Lambert, Inc., an investment banking firm, where he held the position of Executive Vice President, Head of Equity Division. Mr. Kirsch has served on the board of directors of Liquidia Corporation, a biopharmaceutical company, since December 2016 and Evommune, Inc. since November 2025. Mr. Kirsch has previously served on the boards of directors of Kadmon Holdings, Inc. from May 2019 to November 2021, Immunomedics, Inc. from August 2015 to October 2016, POZEN Inc. from May 2004 to May 2015 and Aralez, Inc. from February 2016 to May 2019. Mr. Kirsch received his B.S. from the University of Rhode Island and his M.B.A. from Bernard M. Baruch College, Columbia University. We believe Mr. Kirsch’s extensive experience in the healthcare and life sciences industries and as a strategic advisor qualifies him to serve on our Board.

Bruno Lucidi has served as a member of our Board since September 2014. Mr. Lucidi has served as an independent consultant to biotechnology companies since July 2013. Mr. Lucidi served as a Life Sciences Expert at Wallonia Trade and Foreign Investment Agency, an economic development agency, from

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January 2017 to June 2020. Mr. Lucidi also founded and served as Chief Executive Officer at AgenTus Therapeutics (now Mink Therapeutics), a pre-clinical stage biopharmaceutical company, from October 2017 to September 2019. Previously, Mr. Lucidi served as Chief Executive Officer at Karolinska Development AB, an investment company investing in and managing a portfolio of Nordic life science companies from 2014 to 2015, Vice President of Pediatric Vaccines at GSK Biologicals from 2009 to 2012, Worldwide Vice President of Oncology & Virology at Johnson & Johnson from 2002 to 2005, and held leadership roles at Bristol-Myers Squibb from 1994 to 1998, including Senior Director Virology Europe and Director, Oncology Europe. Mr. Lucidi received his B.S. from Saint Romain en Gal and was trained in Oncology at the Villejuif Gustave Roussy Institute, Villejuif, France, in Marketing and Strategic Management of Companies at the École Supérieure de Commerce, Paris, France, and in Finance, Merger and Acquisitions at the Investment Banking Institute in New York. We believe that Mr. Lucidi is qualified to serve on our board due to his extensive leadership experience in the life science industry as an executive of pharmaceutical companies and other organizations at various stages of development and his expertise commercializing antiviral and other drug products on a global basis.

Polly A. Murphy, D.V.M., Ph.D. has served as a member of our Board since August 2020. Previously, Dr. Murphy served as the Chief Business Officer of Avadel Pharmaceuticals plc from May 2024 to February 2026 and UroGen Pharma, Inc. from August 2020 to May 2024. Dr. Murphy also previously served in various leadership roles at Pfizer, Inc. from September 2008 to August 2020, including as Vice President and Head of Oncology Early Commercial Development from January 2019 to August 2020, Vice President and Head of Oncology Global Marketing and Commercial Development from June 2017 to December 2018, Vice President and Head of Strategy and Business Development in China from November 2013 to May 2017, and Vice President Worldwide R&D Business Development from 2009 to 2012. Dr. Murphy has served on the board of directors of Celcuity Inc. since September 2022. Dr. Murphy received her D.V.M. and Ph.D. from Iowa State University and M.B.A. from Nova Southeastern University. We believe Dr. Murphy is qualified to serve on our Board due to her experience in the pharmaceutical industry in business development and commercialization.

Bruce Polsky, M.D., MACP, FIDSA, has served as a member of our Board since November 2014. Dr. Polsky is the Chairman of the Department of Medicine at NYU Langone Hospital – Long Island in Mineola, New York, where he has practiced since May 2015. He also has served as Professor and Chairman of the Department of Medicine and as an Associate Dean at NYU Grossman Long Island School of Medicine since February 2019. During the period from December 1998 to May 2019, Dr. Polsky held positions at several institutions, including Professor of Medicine at Stony Brook University School of Medicine from 2017 to 2019, Chair of the Department of Medicine and Senior Attending Physician, Departments of Medicine and Laboratory Medicine at Mount Sinai St. Luke’s and Mount Sinai Roosevelt Hospitals from 2009 to 2015, Professor of Medicine and Pathology at Icahn School of Medicine at Mount Sinai from 2014 to 2015, John H. Keating Sr. Professor of Clinical Medicine at Columbia University College of Physicians and Surgeons from 2009 to 2013, Medical Director, Clinical Virology Laboratory, Department of Pathology and Laboratory Medicine at St. Luke’s-Roosevelt Hospital Center from 1998 to 2013 and Chief, Division of Infectious Diseases and Senior Attending, Departments of Medicine and Pathology and Laboratory Medicine at St. Luke’s-Roosevelt Hospital Center from 1998 to 2012. Dr. Polsky received his B.S. from University of Michigan and M.D. from Wayne State University. We believe that Dr. Polsky is qualified to serve on our Board due to his extensive medical and scientific knowledge and the depth and breadth of his experience as a leading practicing infectious disease physician.