DELCATH SYSTEMS, INC. (DCTH) Business

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Item 1. Business.

Unless the context otherwise requires, all references in this Annual Report on Form 10-K to the “Company”, “Delcath”, “Delcath Systems”, “we”, “our”, and “us” refers to Delcath Systems, Inc., a Delaware corporation, incorporated in August 1988, and all entities included in our consolidated financial statements. Our corporate offices are located at 566 Queensbury Avenue, Queensbury, New York 12804. Our telephone number is (518) 743-8892 and our internet address is www.delcath.com. The information found on, or otherwise accessible through, our website is not incorporated by reference into, and does not form a part of, this Annual Report on Form 10-K.

Company Overview

We are an interventional oncology company focused on the treatment of cancers primary or metastatic to the liver. Our lead product, the HEPZATOTM KIT (melphalan for Injection/Hepatic Delivery System), a drug/device combination product (“HEPZATO” or “HEPZATO KIT”), was approved by the US Food and Drug Administration (the “FDA”) on August 14, 2023, indicated as a liver-directed treatment for adult patients with uveal melanoma with unresectable hepatic metastases affecting less than 50% of the liver and no extrahepatic disease, or extrahepatic disease limited to the bone, lymph nodes, subcutaneous tissues, or lung that is amenable to resection, or radiation. The first commercial use of the HEPZATO for the treatment of metastatic hepatic dominant uveal melanoma (“mUM”) took place in January 2024.

In the United States, HEPZATO is considered a combination drug and device product and is regulated as a drug by the FDA. Primary jurisdiction for regulation of HEPZATO has been assigned to the FDA’s Center for Drug Evaluation and Research. The FDA has granted us six orphan drug designations (five for melphalan in the treatment of patients with ocular (uveal) melanoma, cutaneous melanoma, intrahepatic cholangiocarcinoma, hepatocellular carcinoma, and neuroendocrine tumor indications and one for doxorubicin in the treatment of patients with hepatocellular carcinoma).

We have sufficient raw material and component constituent parts of the HEPZATO KIT to meet anticipated demand and we intend to manage supply chain risk through stockpiled inventory and contracting with multiple suppliers for critical components.

In Europe, the hepatic delivery system is a stand-alone medical device having the same device components as HEPZATO, but without the melphalan hydrochloride and is approved for sale under the trade name CHEMOSAT Hepatic Delivery System for Melphalan, or CHEMOSAT, where it has been used at major medical centers to treat a wide range of cancers in the liver. On February 28, 2022, CHEMOSAT received Medical Device Regulation (“MDR”) certification under the European Medical Devices Regulation (EU) 2017/745, which may be considered by jurisdictions when evaluating reimbursement. As of March 1, 2022, we assumed direct responsibility for sales, marketing and distribution of CHEMOSAT in Europe.

We operate as one operating segment. See Note 16 - “Segment Information” in the accompanying notes to our consolidated financial statements for further detail.

Cancers in the Liver—A Significant Unmet Medical Need

According to the American Cancer Society’s (“ACS”) Cancer Facts & Figures 2025 report, cancer is the second leading cause of death in the United States, with more than 618,000 deaths and over 2 million new cases expected to be diagnosed in 2025. Cancer is one of the leading causes of death worldwide, accounting for approximately 10 million deaths and 20 million new cases in 2022 according to GLOBOCAN, the database of the International Association of Cancer Registries. The financial burden of cancer is enormous for patients, their families and society. The liver is often the life-limiting organ for cancer patients and cancer that spreads to the liver is one of the leading causes of cancer death. Cancer that begins in one area of the body often metastasizes to the liver. Patient prognosis is generally poor once cancer has spread to the liver. Consequently, cancers in the liver remain a major unmet medical need globally.

Cancers in the Liver—Incidence and Mortality

Cancers in the liver consist of primary liver cancer and cancers metastatic to the liver. Primary liver cancers, hepatocellular carcinoma and intrahepatic cholangiocarcinoma, originate in the liver or biliary tract and are particularly prevalent in populations where the primary risk factors for the disease, such as hepatitis-B, hepatitis-C, high levels of alcohol consumption, aflatoxin, cigarette smoking and exposure to industrial pollutants, are present. Cancers metastatic to the liver, also called liver metastasis, or secondary liver cancer, result from the spread or “metastases” of a primary cancer into the liver. These metastases often continue to grow even after the primary cancer in another part of the body has been removed or successfully treated. Given the vital biological functions of the liver, including processing nutrients from food and

filtering toxins from the blood, it is not uncommon for metastases to settle in the liver. In many cases patients die not as a result of their primary cancer, but from the tumors that metastasize to their liver. In the United States, metastatic liver disease is more prevalent than primary liver cancer. We estimate that the total potential addressable market for liver cancer (primary and metastatic) is approximately 200,000 in the United States per year. Based on industry reports, it is estimated the total addressable market (“TAM”) in the United States for mUM, metastatic cholangiocarcinoma (“mCCA”), metastatic neuroendocrine tumor (“mNET”), metastatic colorectal cancer (“mCRC”), metastatic breast cancer (“mBC”), metastatic non-small cell lung cancer (“mNSCLC”), metastatic pancreatic cancer (“mPC”) and HCC, is well over $1.0 billion.

Treatment of liver cancer is difficult. Current liver cancer treatment options include surgery, systemic treatment with anticancer drugs, and liver directed treatment options. Surgery options include surgical resection, liver transplant, and isolated hepatic perfusion (“IHP”). While surgical resection and liver transplant, when feasible, offer best possible outcomes for liver cancer patients, the percentage of patients that qualify for these procedures is low, generally 10% or less of the total liver cancer population. Clinical efficacy observed with IHP provided the rationale for using percutaneous hepatic profusion (“PHP”) in mUM, as well as other tumor types, including colorectal cancer. Systemic options include systemic chemotherapy and immunotherapy agents. Minimally invasive options include external beam radiation therapy and liver directed procedures.

Procedures in the liver, and liver directed treatments (interventional oncology) are performed by an interventional radiologist. These procedures include trans-arterial chemoembolization (TACE, DEBTACE) and Radioembolization (SIRT, TARE, or Y90). We believe that CHEMOSAT and HEPZATO represent an important advancement in the potential liver-directed treatment of primary liver cancer and other cancers metastatic to the liver. Two key factors differentiate PHP with HEPZATO and CHEMOSAT from other liver directed therapies: the ability to treat the entire liver, including radiologically invisible micrometastases, and the repeatability of the procedure. We believe PHP with HEPZATO and CHEMOSAT is uniquely positioned either as a standalone therapy or as a complement to other therapies. In clinical studies with HEPZATO and CHEMOSAT, both treatment-naive and pretreated patients have benefited from the treatment, thus expanding the use to multiple lines of treatment.

Uveal Melanoma

Uveal melanoma frequently metastasizes to the liver. Based on third party research that we commissioned approximately 5,000-6,200 cases of uveal melanoma are diagnosed in the United States and Europe annually, and approximately 50% of these patients will develop metastatic disease. Of metastatic cases of uveal melanoma, approximately 90% of patients develop liver involvement. According to Lane et al., JAMA Ophthalmol. 2018 Sep 1;136(9):981-98, once uveal melanoma has spread to the liver, median overall survival for these patients is up to 12 months. There is no one standard of care for patients with uveal melanoma liver metastases. Based on our research, an estimated 800 patients with uveal melanoma liver metastases in the United States, and 1,200 patients in Europe may be eligible for treatment with HEPZATO or CHEMOSAT annually. Eligible patients are those with limited extrahepatic disease that can be treated with resection or radiation, who are able to safely undergo general anesthesia, and who have metastases involving less than 50% of the liver parenchyma. Currently 55% of the patients are not eligible for KIMMTRAK, the only approved uveal melanoma systemic therapy, and most patients are treated with multiple lines of therapy. We estimate the annual addressable market for this indication in the United States and Europe is approximately $600 million per year.

Colorectal Cancer

Colorectal cancer (“CRC”) is one of the most prevalent cancers in the United States and Europe and has a high metastatic rate to the liver. GLOBOCAN 2022 estimates that there are 516,452 CRC diagnoses per year in the United States and the European Union. According to the ACS, in the United States there are approximately 160,186 diagnoses leading to 54,614 deaths.

Recent advances in the treatment of primary CRC have shown encouraging increases in 5-year survival; however, the presence of metastasis is an indicator for increased mortality probability. We estimate approximately 98,000 CRC patients in the United States, the United Kingdom and the European Union annually could be candidates for treatment with HEPZATO (if it received FDA approval for such treatment) and CHEMOSAT.

Breast Cancer

Breast cancer (“BC”) is the most diagnosed cancer in women in the United States and worldwide. The ACS estimates that 319,750 women will be diagnosed with BC in the United States annually. BC is the second leading cancer-related cause of death for women (behind lung cancer) in the United States. GLOBOCAN 2022 estimates that there are, annually, 708,210 women diagnosed with BC in the United States, the European Union and the United Kingdom. Recent advances in primary

BC treatments have given patients a high 5-year survival rate. The prognosis for patients with BC liver metastasis, however, remains poor.

Approximately 18% of all women diagnosed with BC will also have distant metastatic disease, in which 5% of these patients will have liver only metastasis. Eventually 50% of all metastatic patients will see their disease progress to the liver in addition to their initial diagnosed metastatic site and in 20% of these patient’s liver progression is the cause of mortality (Deipolyi AR, et al.J Vasc Inter Radiol. 2018;29(9):1226-1235). Treatment options for patients with multiple sites of metastatic disease vary. We estimate that approximately 6,000 BC patients with hepatic involvement in the United States and the European Union could be candidates for treatment with HEPZATO KIT and CHEMOSAT. An additional 10,000 patients could benefit from treatment with HEPZATO (if it received FDA approval for such treatment) and CHEMOSAT in the palliative setting based on local treatment guidelines.

Neuroendocrine Cancer

Neuroendocrine Tumors (“NETs”) or neuroendocrine neoplasia are a rare group of cancers that originate from neuroendocrine cells. NETs can originate anywhere in the body, the most common sites include the digestive tract, rectum, lungs, pancreas, or appendix. The American Society of Clinical Oncology estimates that there are 12,000 new diagnoses of NETs each year in the United States, and a total of 21,500 in the United States and Europe.

According to Pape et al. 2008. Endocrine-Related Cancer. 15(4), 1083-1097, NETs have a metastasis rate of between 60-80% and the majority of these accrue in the liver (85%). We estimate that approximately an aggregate of 7,500 NETs patients in the United States, the United Kingdom and the European Union each year could be candidates for treatment with HEPZATO (if it received FDA approval for such treatment) and CHEMOSAT.

Pancreatic Cancer

Pancreatic adenocarcinoma has a poor prognosis. The ACS estimates that pancreatic cancer will affect 62,210 patients annually, with 49,830 annual deaths in the United States. Along with GLOBOCAN estimates for Western Europe, pancreatic cancer affects a total of 132,442 patients annually with 105,638 annual deaths.

Upon diagnosis, nearly 75% of patients will have liver metastasis and 58% of those patients will have liver only metastasis. Metastatic pancreatic cancer leaves the patient with limited treatment options (Oweira, et al. World J Gastroenterol. 2017;23(10):1872-1880). We estimate there are approximately 57,600 new pancreatic cancer patients each year in the United States and European Union with hepatic only involvement. Given the rapid progression of the disease and rapid decline in the overall patient status it is unknown at this time the estimated number of candidates for treatment with HEPZATO KIT (if it received FDA approval for such treatment) and CHEMOSAT.

Cholangiocarcinoma

According to GLOBOCAN 2022, an estimated 68,500 new cases of primary liver cancer, or Cholangiocarcinoma (“CCA”), are diagnosed in the United States and Europe annually. According to the ACS, approximately 42,240 new cases of these cancers are expected to be diagnosed in the United States, leading to approximately 30,090 deaths.

Hepatocellular Carcinoma

Hepatocellular Carcinoma (“HCC”) is the most common form of primary liver cancer and remains a significant cause of cancer-related mortality globally. According to GLOBOCAN 2022 and updated 2026 projections, there are approximately 110,740 new cases of primary liver cancer diagnosed annually in the United States, the European Union, and the United Kingdom combined. While surgical resection and liver transplantation offer the best hope for a cure, approximately 80% of patients present with unresectable disease at the time of diagnosis or are ineligible for surgery due to underlying cirrhosis or tumor location. For these patients, regional, liver-directed therapies are critical as the disease is inherently confined to the liver parenchyma. We estimate that approximately 65,000 HCC patients annually in the United States and Europe could be candidates for treatments with HEPZATO (if it received FDA approval for such treatment) and CHEMOSAT, representing the largest segment of our addressable primary liver cancer market.

Intrahepatic Cholangiocarcinoma

Intrahepatic Cholangiocarcinoma (“ICC”) is the second most common form of primary liver cancer and according to Wang et al., 2013 J Clin Oncol 31:1188-1195 accounts for 5-30% of primary liver cancers diagnosed in the United States and Europe annually. We believe that 80% of ICC patients are not candidates for surgical resection, and may be candidates for certain local treatments. According to third party research that we commissioned, including ICC and extrahepatic liver cancers that have liver involvement, we estimate that approximately 9,000 ICC patients in the United States, the United

Kingdom and the European Union annually could be candidates for treatment with HEPZATO KIT (if it received FDA approval for such treatment) and CHEMOSAT.

Non-small cell lung cancer

Lung cancer is the leading cause of cancer-related death in the United States and Europe, with Non-Small Cell Lung Cancer (“NSCLC”) accounting for approximately 85% of all lung cancer diagnoses. We estimate that approximately 240,000 new cases of lung cancer will be diagnosed in the United States annually, with GLOBOCAN 2022 estimating over 640,000 annual diagnoses across the United States, the European Union, and the United Kingdom. While recent advances in systemic immunotherapy and targeted agents have significantly improved 5-year survival rates for mNSCLC, the liver remains a frequent “escape site” for disease progression. Approximately 30% to 40% of patients with mNSCLC will develop liver metastases during the course of their disease, which is often associated with a significantly poorer prognosis and resistance to systemic checkpoint inhibitors. We estimate that a subset of these patients, approximately 34,000 individuals in the United States and Europe annually, present with liver-dominant metastatic disease and could be candidates for treatment with HEPZATO (if it received FDA approval for such treatment) and CHEMOSAT to achieve regional control of their hepatic burden.

About HEPZATO KIT and CHEMOSAT

HEPZATO KIT™ (HEPZATO (melphalan) for Injection/Hepatic Delivery System) and CHEMOSAT® Hepatic Delivery System for Melphalan percutaneous hepatic perfusion (“PHP”), are designed to administer high-dose chemotherapy to the liver while controlling systemic exposure and associated side effects during a PHP procedure.

In the United States, HEPZATO KIT is considered a combination drug and device product and is regulated and approved for sale as a drug by the FDA. HEPZATO KIT is comprised of the chemotherapeutic drug melphalan and Delcath’s proprietary Hepatic Delivery System (“HDS”). In Europe, the device-only configuration of the HDS is regulated as a Class III medical device and is approved for sale under the trade name CHEMOSAT Hepatic Delivery System for Melphalan. During the PHP procedure the HDS is used to isolate the hepatic venous blood from the systemic circulation while simultaneously filtrating hepatic venous blood during melphalan infusion and washout. The use of the HDS results in loco-regional delivery of a relatively high melphalan dose, which can potentially induce a clinically meaningful tumor response with minimal hepatotoxicity and reduce systemic exposure.

The PHP procedure is an outpatient procedure performed in an interventional radiology suite in approximately two to three hours. Patients may remain in a post-anesthesia care unit, surgical intensive care unit or step-down unit overnight for observation following the procedure. Treatment with CHEMOSAT and HEPZATO KIT is repeatable, and a new disposable system is used for each treatment. Patients treated in clinical trial settings were permitted up to six treatments. In commercial treatment settings, patients have received up to ten treatments. HEPZATO KIT received regulatory approval by the FDA in August 2023 for adult uveal melanoma patients with unresectable liver metastases only, and patients with unresectable liver metastases and extrahepatic disease limited to the bone, lymph nodes, subcutaneous tissue or lung that is amenable to resection or radiation. HEPZATO KIT’s indication is not limited to specific human leukocyte antigen (“HLA”) phenotypes or to a specific line of treatment. In Europe, CHEMOSAT is approved for the percutaneous intra-arterial administration of melphalan hydrochloride to the liver, where it has been used in the conduct of percutaneous hepatic perfusion procedures at major medical centers to treat a wide range of cancers to the liver.

The FOCUS Trial

To support the New Drug Application (“NDA”) for HEPZATO, we conducted the FOCUS Clinical Trial for patients with metastatic hepatic dominant Uveal Melanoma (the “FOCUS Trial”), a global registration clinical trial that investigated objective response rate in patients with mUM. The FOCUS Trial evaluated the safety and efficacy of treatment with the HEPZATO KIT for patients with mUM. The primary endpoint of overall response rate (“ORR”) was assessed by an Independent Review Committee per RECIST v1.1. The primary endpoint of the trial, ORR was met with a wide margin and the safety profile was acceptable. Results from the FOCUS Trial were reviewed by the FDA and were the basis for approval of HEPZATO KIT on August 14, 2023. On May 6, 2024, we announced the publication of results from our Phase 3 FOCUS Trial, including an ORR of 36.3%, which included 7.7% of patients with Complete Response, as determined by an Independent Review Committee. An ORR of 36.3% in the FOCUS study was statistically significantly better than the pooled ORR estimate (a weighted mean of the observed ORR) of 5.5% in the historical control group. Two additional publications with FOCUS trial results were published, including results from the first, randomized portion of the FOCUS trial (Zager et al., Ann Surg Oncol 2025) and the results from key subgroup analyses of the FOCUS trial (Zager et al., J Cancer Res Clin Oncol 2025). We expect that these publications will support increased clinical adoption of and reimbursement for CHEMOSAT in Europe, and support reimbursement in various jurisdictions, including the United States.

CHOPIN Trial

The Leiden University Medical Center conducted an investor-initiated Phase 1b/2 trial (the “CHOPIN trial”) on the use of CHEMOSAT in combination with the immune checkpoint inhibitors (“ICI”) ipilimumab and nivolumab to treat patients with mUM with liver metastases.

The goal of the CHOPIN trial was to evaluate the safety and efficacy of systemic ICI therapy with ipilimumab plus nivolumab (“IPI+NIVO”) when combined with Delcath’s liver-targeted percutaneous hepatic perfusion treatment in mUM patients. Ipilimumab and nivolumab are approved by the FDA and European Union for the treatment of unresectable metastatic melanoma. Published results from the Phase 1b portion of the trial include updated safety and efficacy results which were presented in June 2022 at the American Society of Clinical Oncology Annual Meeting. The Phase 1b portion of the trial enrolled seven patients each of which were treated with two cycles of PHP (melphalan 3mg/kg, max 220 mg per cycle) combined with four cycles of IPI+NIVO, escalating the dosing from 1mg/kg each IPI+NIVO (cohort 1) to IPI 1mg/kg + NIVO 3mg/kg (cohort 2). In the seven patients, best tumor responses included 1 complete response, 5 partial responses and 1 stable disease accounting for an Objective Response Rate of 85.7% and a Disease Control Rate of 100%. At the cut-off date of November 15, 2022, the median follow-up was 29.1 months (range 8.9 – 30.2), the median Progression Free Survival (“PFS”) was 29.1 months (95% CI 11.9 – 46.3) and the median Duration Of Response (“DOR”) was 27.1 months (range 7.4 – 28.5). At the time of the cut-off date all patients were still alive and three of four patients who subsequently experienced progressive disease continued with treatment in the form of repeated PHP cycles.

On October 18, 2025, independent investigators presented results from the Phase 2 portion of the CHOPIN trial. The randomized Phase 2 trial was designed to compare the safety, tolerability, and efficacy of CHEMOSAT with melphalan for percutaneous hepatic perfusion (PHP) when used alone versus when combined with the systemic ICI therapy.

The Phase 2 trial included 76 patients randomized 1:1 to receive two PHP treatments alone at weeks one and seven (PHP group) or four cycles of ICI every three weeks over approximately nine weeks with two PHP treatments at weeks one and seven (combination group). The primary study endpoint of one-year progression-free survival rate was met with 54.7% in the combination group versus 15.8% in the PHP group. The secondary endpoints included Safety, Overall Survival (“OS”), Progression Free Survival (“PFS”) and Overall Response Rate (“ORR”). The combination group saw an increase in median OS of 23.1 months versus 19.6 months (HR = 0.39; p = 0.006), median PFS 12.8 months versus 8.3 months (HR = 0.34; p0.001) and ORR of 76.3% in the combination group versus 39.5% (p0.001). Grade 3 or higher treatment-related adverse events were more frequent in the combination group (81.6% versus 40.5%, P0.001), but most were manageable with standard care. The combination treatment adverse events were consistent with the types, rates and frequencies of adverse events in individual use of PHP and checkpoint inhibitors. No new safety signals were identified.

Clinical Development Program

In addition to HEPZATO’s FDA approved use to treat mUM, we believe that HEPZATO has the potential to treat other cancers in the liver, such as mCRC, mBC, mCCA, mNET, mNSCLC, mPC and HCC. The focus of our current and planned clinical development program is to generate clinical data for CHEMOSAT and HEPZATO in a broader set of liver cancer indications either as monotherapy or in combination or sequenced with current standard of care therapeutics, including immunotherapy. The ongoing and planned trials may support eventual regulatory submissions for label expansion in the United States as well as support increased clinical adoption and reimbursement in various jurisdictions including the United States and Europe.

We expense research and development costs as they are incurred. We expect our research and development expenses to increase for the foreseeable future relating to the costs required to complete these Phase 2 clinical trials.

Our expected research and development expenses will consist primarily of:

•salaries and related overhead expenses for personnel in research and development functions, including stock-based compensation;

•fees paid to trial sites, consultants, and the contract research organization (CRO) for the clinical trials, along with other related clinical trial fees, including, but not limited to, clinical trial database management, clinical trial material management and statistical compilation and analysis; and

•costs related to compliance with regulatory requirements.

At this time, we cannot reasonably estimate or know the exact nature, timing and estimated costs of the efforts that will be necessary. Non-refundable advance payments that are made for future research and development activities are recorded as prepaid expenses. The prepaid amounts are expensed as the services are performed, or when it is no longer expected that the services will be rendered.

Metastatic Colorectal Cancer

Our Investigational New Drug (“IND”) application for a Phase 2 clinical trial evaluating HEPZATO in combination with SOC for metastatic breast cancer (“mCRC”) was cleared by the FDA in December 2024.

The Phase 2 trial will evaluate the safety and efficacy of HEPZATO in combination with trifluridine-tipiracil and bevacizumab compared to trifluridine-tipiracil and bevacizumab alone in patients with liver-dominant mCRC receiving third-line treatment. Approximately 90 patients will be enrolled in this randomized, controlled trial. Patient enrollment began during the third quarter of 2025, with the study expected to take place at more than 20 sites across the United States and Europe. In July 2025, we received authorization from the European Union and United Kingdom regulatory authorities for the clinical study of Melphalan for Injection/Hepatic Delivery System in patients with refractory metastatic colorectal cancer with the liver dominant disease. The trial’s primary endpoint, hepatic progression-free survival (“hPFS”), is anticipated to read out by the end of 2027, while OS, a secondary endpoint, is expected in 2028.

We estimate that the TAM for liver-dominant mCRC receiving third-line treatment is between 6,000 and 10,000 patients annually in the United States. This market includes patients who present with significant liver disease burden, with liver-dominant status determined through radiological and clinical criteria. By targeting this patient population, we aim to provide a novel treatment option for those with limited therapeutic alternatives.

Metastatic Breast Cancer

Our IND application for a Phase 2 clinical trial evaluating HEPZATO in combination with SOC in liver-dominant metastatic breast cancer (“mBC”) was cleared by the FDA in April 2025.

The Phase 2 trial will evaluate the safety and efficacy of HEPZATO in combination with SOC versus SOC alone in patients with liver-metastatic HER2-negative mBC following the failure of previous treatments. The SOC options will be the physician’s choice of eribulin, vinorelbine or capecitabine. We expect approximately 90 patients will be enrolled in this randomized, controlled trial. The study will take place at more than 15 sites across the United States and Europe, with patient enrollment expected to begin in the first quarter of 2026. The trial’s primary endpoint, hPFS, is anticipated to read out by the end of 2028, while results for OS, a secondary endpoint, is expected in 2029.

We estimate that approximately 7,000 patients annually in the United States are affected by HER2-negative metastatic breast cancer with liver metastases and are candidates for third line treatment. This population includes patients with a significant burden of liver metastases, which are likely to be the primary cause of mortality. By focusing on this demographic, we intend to offer a novel therapeutic option to those patients with limited treatment alternatives.

Market Access and Commercial Clinical Adoption

United States

The first commercial use of HEPZATO KIT for the treatment of mUM occurred in January 2024. We are working with numerous leading cancer centers across the United States which have treated with HEPZATO or indicated interest in HEPZATO to treat patients and provide access to the treatment for patients nationwide. HEPZATO is available for cancer centers to treat patients upon completion of required training as documented in our Risk Evaluation and Mitigation Strategy (“REMS”). REMS focuses on preventing, monitoring, and/or managing specific risks associated with a product.

Our commercial and medical field teams are comprised of liver directed therapy managers, clinical specialist representatives, oncology area managers and medical science liaisons who work directly with the cancer centers to obtain the required training. In conjunction with the first commercial treatment, we also launched websites relating to the HEPZATO KIT, including www.HEPZATOKIT.com, www.HEPZATOKITREMS.com, and www.HEPZATOKITACCESS.com, to support the commercialization. On www.HEPZATOKIT.com, we have a healthcare setting locator which identifies certified healthcare facilities that have expressed an interest in performing the HEPZATO KIT procedure, have conducted most of the required training and are actively seeking patient referrals. In addition, www.HEPZATOKITREMS.com contains a healthcare setting locator that lists facilities that have completed and filed all documentation required under REMS. The information found on, or otherwise accessible through, our HEPZATO KIT websites is not incorporated by reference into, and does not form a part of, this Annual Report on Form 10-K.

Upon activation of the cancer center, the center is able to commercially treat patients with HEPZATO. As of December 31, 2025, there were 32 sites accepting referrals, with 25 active sites.

United States Reimbursement

A facility at which HEPZATO is used will seek reimbursement for the cost of the HEPZATO and the attendant procedure. Usage of HEPZATO by the cancer centers will depend on the availability of coverage and reimbursement from third-party

payors, such as government health administration authorities, private health insurers and managed care organizations. For products administered under the supervision of a physician, particularly in a hospital setting, the ability of a treating facility to obtain adequate reimbursement is dependent on the type of health insurance coverage a patient has and the treating facility’s agreement (or lack of agreement) with such insurance. Additionally, separate reimbursement for the product itself or the treatment or procedure in which the product is used may not be available, which may impact physician utilization. Furthermore, the classification, as either outpatient or inpatient, of the treatment procedure associated with the administering of a product will impact a treating facility’s reimbursement. Many United States hospitals receive a fixed reimbursement amount per procedure for certain surgeries and other treatment therapies they perform, or a predetermined rate for all hospital inpatient care provided as payment in full. Because this amount may not be based on the actual expenses the hospital incurs, hospitals may choose to use therapies which are less expensive when compared to HEPZATO.

On January 30, 2024, Centers for Medicare and Medicaid Services (“CMS”) announced an established permanent and product-specific J-Code for HEPZATO. The J-Code (J9248) became effective on April 1, 2024. Delcath applied for and was granted transitional drug pass-through status for HEPZATO under the Outpatient Prospective Payment System for hospital outpatient services beginning on April 1, 2024 and expiring on March 31, 2027. On August 5, 2024, CMS announced that it had has granted New Technology Add-on Payment (“NTAP”) status for HEPZATO, effective October 1, 2024. The NTAP designation under the CMS Inpatient Prospective Payment System (“IPPS”) is designed to support the adoption of innovative medical technologies that provide substantial clinical improvement over existing treatments. HEPZATO is used primarily in the outpatient setting, however there are instances where it is used in the inpatient setting. This additional payment is intended to help to cover the costs associated with HEPZATO for eligible Medicare inpatients, ensuring that more patients can benefit from this advanced liver-directed therapy.

On October 23, 2025, the Company entered into a National Drug Rebate Agreement (“NDRA”) with CMS, which also subjected the Company to entering into a Pharmaceutical Pricing Agreement (“PPA”) with the Public Health Service and a master agreement with the U.S. Department of Veterans Affairs (“VA”). Pursuant to the NDRA, the Company must pay mandated rebates to states for Medicaid usage. Under the PPA, beginning on July 1, 2025, the Company began selling HEPZATO to eligible covered entities at the statutory 340B price. The Company is also obligated to make any sales to the VA at the Federal Ceiling Price. The NDRA, the PPA, and the agreement with the VA requires the Company to calculate and submit pricing information to the Government and subjects the Company to potential penalties for failing to make timely and/or accurate reports of the required values.

We expect that payors will follow decisions made by the CMS, as the administrator for the Medicare program, regarding HEPZATO reimbursement.

Even if a cancer center obtains coverage for a given product by a third-party payor, the third-party payor’s reimbursement rates may not be adequate to make the product affordable to patients or profitable, or the third-party payors may require co-payments that patients find unacceptably high. Patients who are prescribed medications for the treatment of their conditions, and their prescribing physicians, generally rely on third-party payors to reimburse all or part of the costs associated with their prescription drugs. Patients are unlikely to use our products unless coverage is provided, and reimbursement is adequate to cover all or a significant portion of the cost of our products. Therefore, coverage and adequate reimbursement is critical to new product acceptance. Coverage decisions may depend upon clinical and economic standards that disfavor new drug products when more established or lower cost therapeutic alternatives are already available or subsequently become available. Additionally, reimbursement by a third-party payor may depend upon a number of factors including the third-party payor’s determination that use of a product is:

•a covered benefit under its health plan;

•safe, effective and medically necessary;

•appropriate for the specific patient;

•cost-effective; and

•neither experimental nor investigational.

For many third party payors, we expect that each patient candidate for treatment with HEPZATO will likely have to go through a medical pre-authorization process, which may require the healthcare provider to provide scientific, clinical and cost effectiveness data for the use of our products to the payor. Further, no uniform policy requirement for coverage and reimbursement for drug products exists among third-party payors in the United States. Therefore, coverage and reimbursement for drug products can differ significantly from payor to payor. The coverage determination process may require providing scientific and clinical support for the use of our products to each payor separately. As such, in order to assess available benefits and coordinate the treatment pathway before a patient is treated with HEPZATO, we have

engaged a third-party benefits coordinator to guide the patient and a treating healthcare provider through the pre-authorization and reimbursement process.

Although private third-party payors often use CMS as a model for their coverage and reimbursement decisions, they also have their own methods and approval process apart from CMS’s determinations. Therefore, even if the cancer center obtains coverage for a given product by a third-party payor, the third-party payor’s reimbursement rates may not be adequate to make the product affordable to patients or profitable to us, or the third-party payors may require co-payments that patients find unacceptably high.

Government authorities and other third-party payors are developing increasingly sophisticated methods of controlling healthcare costs, such as by limiting coverage and the amount of reimbursement for particular medications. Increasingly, third-party payors are requiring that drug companies provide them with predetermined discounts from list prices as a condition of coverage, are using restrictive formularies and preferred drug lists to leverage greater discounts in competitive classes and are challenging the prices charged for medical products.

In addition, recently there has been heightened governmental scrutiny over the manner in which manufacturers set prices for their marketed products, which has resulted in several U.S. Congressional inquiries and proposed and enacted federal and state legislation designed to, among other things, bring more transparency to drug pricing, reduce the cost of prescription drugs under government payor programs, and review the relationship between pricing and manufacturer patient programs. For example, the Inflation Reduction Act (“IRA”) among other things, (1) requires the U.S. Department of Health and Human Services (“HHS”) to negotiate the price of certain single-source biologics that have been on the market for at least 7 years covered under Medicare as part of the Medicare Drug Price Negotiation Program (the “Medicare Drug Price Negotiation Program”), and (2) imposes rebates under Medicare Part B and Medicare Part D to penalize price increases that outpace inflation on an annual basis. Each year up to twenty (20) products will be selected by HHS for the Medicare Drug Price Negotiation Program. Products subject to the Medicare Drug Price Negotiation Program are expected to experience a significant reduction in reimbursement from the Medicare program on a per unit basis.

Europe

Since the launch of CHEMOSAT in Europe, there have been over 2,000 commercial treatments and CHEMOSAT is currently available in 22 cancer centers across Europe. Physicians in Europe have used CHEMOSAT to treat patients with a variety of cancers in the liver, primarily uveal melanoma liver metastases, and other tumor types, including hepatocellular carcinoma and cholangiocarcinoma, as well as liver metastases from cutaneous melanoma, colorectal, breast, and pancreatic cancer, as well as neuroendocrine tumors.

For the period of December 2018 through February 2022, medac GmbH was our exclusive distributor for CHEMOSAT in Europe and had the exclusive right to market and sell CHEMOSAT in all member states of the European Union, Norway, Liechtenstein, Switzerland, and the United Kingdom. On March 1, 2022, we assumed direct responsibility for sales, marketing and distribution of CHEMOSAT in Europe.

European Reimbursement

A critical driver of utilization growth for CHEMOSAT in Europe is the expansion of reimbursement mechanisms for the procedure in our priority markets. In most European countries, the government provides healthcare and controls reimbursement levels. Since the European Union has no jurisdiction over patient reimbursement or pricing matters in its member states, the methodologies for determining reimbursement rates and the actual rates vary by country. Reimbursement is administered on a regional and national basis. A medical device is typically reimbursed under a Diagnosis Related Groups (“DRG”) as part of a procedure. Prior to obtaining permanent DRG reimbursement codes, in certain jurisdictions, we are actively seeking interim reimbursement from existing mechanisms that include specific interim reimbursement schemes, new technology payment programs as well as existing DRG codes.

On February 28, 2022, CHEMOSAT received MDR certification under the European Medical Devices Regulation (EU) 2017/745, which may be considered by jurisdictions when evaluating reimbursement.

The release of the clinical study report from the FOCUS Trial has created the opportunity to apply for National Level reimbursement in each European country for treatment of mUM. These applications must be made by us on a country-by-country basis, with priority placed on markets where CHEMOSAT is currently used. Currently, CHEMOSAT has an interim level of reimbursement in Germany. Although Delcath submitted an application for CHEMOSAT reimbursement to the NHS in England in January 2025, the application remains pending. In June 2025, CHEMOSAT was approved for reimbursement for two years in the Vastra Gotaland Region in Sweden.

Government Regulation

Our products are subject to extensive and rigorous government regulation by foreign regulatory agencies and the FDA. Foreign regulatory agencies, the FDA and comparable regulatory agencies in state and local jurisdictions impose extensive requirements upon the clinical development, pre-market clearance and approval, manufacturing, labeling, marketing, advertising and promotion, pricing, storage, and distribution of pharmaceutical and medical device products. Failure to comply with applicable requirements may result in warning letters, fines, civil or criminal penalties, suspensions, delays in clinical development, recall or seizure of products, partial or total suspension of production, or withdrawal of a product from the market.

United States Regulatory Environment

In the United States, the FDA regulates drug and device products under the Food, Drug and Cosmetic Act (“FDCA”), and its implementing regulations. HEPZATO is subject to regulation as a combination product, which means it is composed of both a drug product and a device product. In the case of HEPZATO, the primary mode of action is attributable to the drug component of the product, which means that the Center for Drug Evaluation and Research had primary jurisdiction over its pre-market development and review.

The process required by the FDA before drug product candidates may be marketed in the United States generally involves the following:

•submission to the FDA of an IND application, which must become effective before human clinical trials may begin and must be updated periodically, but at least annually;

•completion of extensive preclinical laboratory tests and preclinical animal studies, all performed in accordance with the FDA’s good laboratory practice, (“GLP”), regulations;

•performance of adequate and well-controlled human clinical trials to establish the safety and efficacy of the product candidate for each proposed indication;

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

•a determination by the FDA within 60 days of its receipt of an NDA to file the NDA for review;

•satisfactory completion of an FDA pre-approval inspection of the manufacturing facilities at which the product is produced and tested to assess compliance with current good manufacturing practice, (“cGMP”), regulations; and

•FDA review and approval of an NDA prior to any commercial marketing or sale of the drug in the United States.

The development and approval process requires substantial time, effort and financial resources, and we cannot be certain that the FDA will approve any of our product candidates on a timely basis, if at all.

The results of preclinical tests (which include laboratory evaluation as well as GLP studies to evaluate toxicity in animals) for a particular product candidate, together with related manufacturing information and analytical data, are submitted as part of an IND to the FDA. The IND automatically becomes effective 30 days after receipt by the FDA, unless the FDA, within the 30-day time period, raises concerns or questions about the conduct of the proposed clinical trial, including concerns that human research subjects will be exposed to unreasonable health risks. In such a case, the IND sponsor and the FDA must resolve any outstanding concerns before the clinical trial can begin. IND submissions may not result in FDA authorization to commence a clinical trial. A separate submission to an existing IND must also be made for each successive clinical trial conducted during product development. Further, an independent institutional review board (“IRB”), for each medical center proposing to conduct the clinical trial must review and approve the plan for any clinical trial before it commences at that center, and it must monitor the study until completed. The FDA, the IRB or the sponsor may suspend a clinical trial at any time on various grounds, including a finding that the subjects or patients are being exposed to an unacceptable health risk. Clinical testing also must satisfy extensive good clinical practice (“GCP”) regulations and regulations for informed consent and privacy of individually identifiable information. Similar requirements to the United States IND are required in the European Union and other jurisdictions in which we may conduct clinical trials.

Clinical Trials

For purposes of NDA submission and approval, clinical trials are typically conducted in the following sequential phases, which may overlap:

•Phase 1 Clinical Trials. Studies are initially conducted in a limited population to test the product candidate for safety, dose tolerance, absorption, distribution, metabolism, and excretion, typically in healthy humans, but in some cases in patients.

•Phase 2 Clinical Trials. Studies are generally conducted in a limited patient population to identify possible adverse effects and safety risks, explore the initial efficacy of the product for specific targeted indications and to determine dose range or pharmacodynamics. Multiple Phase 2 clinical trials may be conducted by the sponsor to obtain information prior to beginning larger and more expensive Phase 3 clinical trials.

•Phase 3 Clinical Trials. These are commonly referred to as pivotal studies. When Phase 2 evaluations demonstrate that a dose range of the product is effective and has an acceptable safety profile, Phase 3 clinical trials are undertaken in large patient populations to further evaluate dosage, provide substantial evidence of clinical efficacy and further test for safety in an expanded and diverse patient population at multiple, geographically dispersed clinical trial centers.

•Phase 4 Clinical Trials. The FDA may approve an NDA for a product candidate but require that the sponsor conduct additional clinical trials to further assess the drug after NDA approval under a post-approval commitment. In addition, a sponsor may decide to conduct additional clinical trials after the FDA has approved an NDA. Post-approval trials are typically referred to as Phase 4 clinical trials.

New Drug Applications

The results of drug development, preclinical studies and clinical trials are submitted to the FDA as part of an NDA. An NDA must contain extensive chemistry, manufacturing, and control information and be accompanied by a significant user fee, which may be waived in certain circumstances. Once the submission has been accepted for filing, the FDA should review NDAs within ten months of submission or, if the NDA relates to an unmet medical need in a serious or life-threatening indication, six months from submission. The review process is often significantly extended by FDA requests for additional information or clarification. The FDA may refer the NDA to an advisory committee for review, evaluation, and recommendation as to whether the NDA should be approved. For new oncology products, the FDA will often solicit an opinion from an Oncology Drug Advisory Committee (“ODAC”), which is a panel of expert authorities knowledgeable in the fields of general oncology, pediatric oncology, hematologic oncology, immunologic oncology, biostatistics, and other related professions. The ODAC panel reviews and evaluates data concerning the safety and effectiveness of marketed and investigational human drug products for use in the treatment of cancer and makes appropriate recommendations to the Commissioner of the FDA. However, the FDA is not bound by the recommendation of an advisory committee and may deny approval of an NDA by issuing a Complete Response Letter, (“CRL”), if the applicable regulatory criteria are not satisfied. A CRL may require additional clinical data and/or an additional pivotal Phase 3 clinical trial(s), and/or other significant, expensive, and time-consuming requirements related to clinical trials, preclinical studies, or manufacturing.

Approval may be contingent on the implementation and adherence to a REMS that focuses on preventing, monitoring, and/or managing specific risks associated with a product. Once issued, the FDA may withdraw product approval if ongoing regulatory requirements are not met or if safety problems occur after the product reaches the market. In addition, the FDA may require testing, including Phase 4 clinical trials, and surveillance programs to monitor the safety and efficacy of approved products which have been commercialized. The FDA has the power to prevent or limit further marketing of a product based on the results of these post-marketing programs or other information.

There are three primary regulatory pathways for an NDA under Section 505 of the FDCA: Section 505 (b)(1), Section 505 (b)(2) and Section 505(j). A Section 505 (b)(1) NDA is used for approval of a new drug (for clinical use) whose active ingredients have not been previously approved. A Section 505 (b)(2) application is used for a new drug that relies on data not developed by the applicant. Section 505(b)(2) of the FDCA was enacted as part of the Drug Price Competition and Patent Term Restoration Act of 1984, also known as the Hatch-Waxman Act. This statutory provision permits the approval of an NDA where at least some of the information required for approval comes from studies not conducted by or for the applicant and for which the applicant has not obtained a right of reference. The Hatch-Waxman Act permits the applicant to rely, in part, upon the FDA’s findings of safety and effectiveness for previously approved products. A Section 505(j) NDA, also known as an abbreviated NDA, is used for a generic version of a drug that has already been approved.

Orphan Drug Exclusivity

Some jurisdictions, including the United States, may designate drugs for relatively small patient populations as orphan drugs. Pursuant to the United States Orphan Drug Act (the “ODA”), the FDA grants orphan drug designation to drugs

intended to treat a rare disease or condition, which is generally a disease or condition that affects fewer than 200,000 individuals in the United States. The orphan designation is granted for a combination of a drug entity and an indication and, therefore, it can be granted for an existing drug with a new (orphan) indication. Applications are made to the FDA’s Office of Orphan Products Development and a decision or request for more information is rendered in 60 days. NDAs for designated orphan drugs are exempt from user fees, obtain additional clinical protocol assistance, are eligible for tax credits for up to 50% of research and development costs, and are granted a seven-year period of exclusivity upon approval. The FDA cannot approve the same drug for the same condition during this period of exclusivity, except in certain circumstances where a new product demonstrates superiority to the original treatment. Exclusivity begins on the date that the marketing application is approved by the FDA for the designated orphan drug, and an orphan designation does not limit the use of that drug in other applications outside the approved designation in either a commercial or investigational setting. The FDA has granted us six orphan drug designations that provide us a seven-year period of exclusive marketing beginning on the date that our NDA was approved by the FDA for the designated orphan drug.

Other Regulatory Requirements

Products manufactured or distributed pursuant to FDA approvals are subject to continuing regulation by the FDA, including recordkeeping, annual product quality review and reporting requirements. Adverse event experience with the product must be reported to the FDA in a timely fashion and pharmacovigilance programs to proactively look for these adverse events are mandated by the FDA. Drug manufacturers and their subcontractors must 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 ongoing regulatory requirements, including cGMPs, which impose certain procedural and documentation requirements upon drug manufacturers. Following such inspections, the FDA may issue notices on Form 483 and Untitled Letters or Warning Letters that could require the drug manufacturer to modify certain activities. A Form 483 Notice, if issued at the conclusion of an FDA inspection, can list conditions the FDA investigators believe may have violated cGMP or other FDA regulations or guidelines. In addition to Form 483 Notices and Untitled Letters or Warning Letters, failure to comply with the statutory and regulatory requirements can subject a drug manufacturer to possible legal or regulatory action, such as suspension of manufacturing, seizure of product, injunctive action or possible civil penalties.

If Delcath or its present or future third-party manufacturers or suppliers are not able to comply with these requirements, the FDA may require the recall of our product from distribution or may withdraw approval for that product.

The FDA closely regulates the post-approval marketing and promotion of drugs, including standards and regulations for direct-to-consumer advertising, dissemination of off-label information, industry-sponsored scientific and educational activities. Drugs may be marketed only for the approved indications and in accordance with the provisions of the approved label. Further, any product modifications may require a submission to the FDA for its approval of a new or supplemental NDA, which may require the development of additional data or the conduct of additional preclinical studies and clinical trials. Failure to comply with these requirements can result in adverse publicity, warning letters, corrective advertising, and potential civil and criminal penalties.

Physicians may prescribe legally available products for uses that are not described in the product’s labeling and that differ from those that have been tested by the drug manufacturer and approved by the FDA. Such off-label uses are common across medical specialties, in particular in oncology. 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, impose stringent restrictions on manufacturers’ communications regarding off-label use.

United States Healthcare Laws

In addition to FDA restrictions on marketing of pharmaceutical products, several other types of state and federal healthcare laws apply to certain business practices in the biopharmaceutical industry. These laws include anti-kickback statutes, false claims statutes, data privacy and security laws, as well as transparency laws regarding payments or other items of value provided to healthcare providers.

The federal Anti-Kickback Statute prohibits, among other things, knowingly and willfully offering, paying, soliciting, or receiving remuneration to induce or in return for purchasing, leasing, ordering, or arranging for the purchase, lease, or order of any healthcare item or service reimbursable under Medicare, Medicaid, or other federally financed healthcare programs. The term “remuneration” has been broadly interpreted to include anything of value, including for example, gifts, discounts, the furnishing of supplies or equipment, credit arrangements, payments of cash, waivers of payment, ownership interests and providing anything at less than its fair market value. The Anti-Kickback Statute has been interpreted to apply to arrangements between pharmaceutical manufacturers on one hand and prescribers, purchasers, and formulary managers on the other. Although there are a number of statutory exemptions and regulatory safe harbors protecting certain common

activities from prosecution, the exemptions and safe harbors are drawn narrowly, and our practices may not in all cases meet all of the criteria for statutory exemptions or safe harbor protection. Practices that involve remuneration that may be alleged to be intended to induce prescribing, purchases, or recommendations may be subject to scrutiny if they do not qualify for an exemption or safe harbor.

The federal False Claims Act prohibits any person from knowingly presenting, or causing to be presented, a false claim for payment to the federal government. Recently, several pharmaceutical and other healthcare companies have been prosecuted under these laws for allegedly providing free product to customers with the expectation that the customers would bill federal programs for the product. Other companies have been prosecuted for causing false claims to be submitted because of the companies’ marketing of the product for unapproved, and thus non-reimbursable, uses. Additionally, the statute imposes penalties against any person who is determined to have presented or caused to be presented a claim to a federal health program that the person knows or should know is for an item or service that was not provided as claimed or is false or fraudulent.

The federal Health Insurance Portability and Accountability Act of 1996 (“HIPAA”), created additional federal criminal statutes that prohibit knowingly and willfully executing a scheme to defraud any healthcare benefit program, including private third-party payors and knowingly and willfully falsifying, concealing or covering up a material fact or making any materially false, fictitious or fraudulent statement in connection with the delivery of or payment for healthcare benefits, items or services.

The federal Physician Payments Sunshine Act its implementing regulations, require certain manufacturers of drugs, devices, biologicals and medical supplies for which payment is available under Medicare, Medicaid or the Children’s Health Insurance Program (with certain exceptions) to report annually information related to certain payments or other transfers of value provided to physicians (defined to include doctors, dentists, optometrists, podiatrists and chiropractors), other healthcare professionals (such as physicians assistants and nurse practitioners), and teaching hospitals, as well as certain ownership and investment interests held by physicians and their immediate family members.

In addition to the aforementioned federal fraud and abuse laws, the majority of states also have statutes or regulations similar to these laws, some of which are broader in scope and apply to items and services reimbursed under Medicaid and other state programs, or, in several states, apply regardless of the payor. Further, some state laws require pharmaceutical companies to comply with the pharmaceutical industry’s voluntary compliance guidelines and the relevant compliance guidance promulgated by the federal government in addition to requiring drug manufacturers to report information related to payments or other transfers of value provided to physicians and other healthcare providers and entities, marketing expenditures, and drug pricing. Certain state and local laws also require the registration of pharmaceutical sales representatives.

HIPAA, as amended by the Health Information Technology for Economic and Clinical Health Act (“HITECH”), and its implementing regulations, imposes certain requirements on covered entities, including certain healthcare providers, health plans, and healthcare clearinghouses, and their respective business associates that create, receive, maintain or transmit individually identifiable health information for or on behalf of a covered entity as well as their covered subcontractors relating to the privacy, security and transmission of individually identifiable health information. Among other things, HITECH makes HIPAA’s privacy and security standards directly applicable to “business associates”. HITECH also increased the civil and criminal penalties that may be imposed against covered entities, business associates and possibly other persons, and gave states the authority to file civil actions for damages or injunctions in federal courts to enforce the federal HIPAA laws and to seek attorney’s fees and costs associated with pursuing federal civil actions. In addition, state laws govern the privacy and security of health information in certain circumstances, many of which differ from each other in significant ways and may not have the same effect, thus complicating compliance efforts.

These federal and state laws may impact, among other things, our sales, marketing and education programs. If our operations are found to be in violation of any of the federal and state laws described above or any other governmental regulations that apply to us, we may be subject to significant penalties, including administrative, criminal and civil monetary penalties, damages, fines, imprisonment, exclusion from participation in government healthcare programs, and the curtailment or restructuring of our operations, any of which could adversely affect our ability to operate its business and our results of operations.

Health Reform

In the United States and some foreign jurisdictions, there have been a number of legislative and regulatory changes and proposed changes regarding the healthcare system and efforts to control healthcare costs, including drug prices, that could have a significant negative impact on our business, including preventing, limiting or delaying regulatory approval of our drug candidates and reducing the sales and profits derived from our products once they are approved.

For example, in the United States, the Patient Protection and Affordable Care Act of 2010 (“ACA”), substantially changed the way healthcare is financed by both governmental and private insurers and has had a significant impact on the pharmaceutical industry.

Since its enactment, there have been amendments and judicial and Congressional challenges and amendments to certain aspects of the ACA.

For example, on July 4, 2025, the One Big Beautiful Bill Act (the “OBBBA”) was signed into law which narrowed access to ACA marketplace exchange enrollment and declined to extend the ACA enhanced advanced premium tax credits that expired at the end of 2025, which among other provisions in the law, are anticipated to reduce the number of Americans with health insurance. The OBBBA also is expected to reduce Medicaid spending and enrollment by implementing work requirements for some beneficiaries, capping state-directed payments, reducing federal funding, and limiting provider taxes used to fund the program.

Congress is considering proposed legislation intended to further reduce healthcare costs with alternatives to replace the expired ACA subsidies. We expect that additional U.S. federal healthcare reform measures will be adopted in the future, any of which could limit the amounts that the U.S. federal government will pay for healthcare products and services, which could result in reduced demand for our product candidates or additional pricing pressures. The current administration is pursuing policies to reduce regulations and expenditures across government including at HHS, the FDA, CMS and related agencies. These actions, presently directed by executive orders or memoranda from the Office of Management and Budget, may propose policy changes that create additional uncertainty for our business. For example, the current administration has announced agreements with several pharmaceutical companies that require the drug manufacturers to offer, through a direct to consumer platform, U.S. patients and Medicaid programs prescription drug Most-Favored Nation pricing equal to or lower than those paid in other developed nations, with additional mandates for direct-to-patient discounts and repatriation of foreign revenues. In addition, in December 2025, CMS released two MFN drug pricing proposed rules, which, if adopted would implement mandatory drug rebate schemes for select drugs in Medicare B and Medicare Part D. Other recent actions, for example, include (1) directives to reduce agency workforce and cut programs; (2) directing HHS and other agencies to lower prescription drug costs through a variety of initiatives, including establishing Most-Favored-Nation pricing for pharmaceutical products and launching an online clearinghouse (“TrumpRx”) for patients to purchase certain products from manufacturers on a cash pay basis; (3) imposing tariffs on imported pharmaceutical products; and (4) as part of the Make America Healthy Again (“MAHA”) Commission’s recent Strategy Report, working across government agencies to increase enforcement on direct-to-consumer pharmaceutical advertising. Additionally, the current administration recently called on Congress to enact “The Great Healthcare Plan” to codify and expand Most-Favored Nation pricing, lower government subsidies to private insurance companies, increase healthcare price transparency, expand pharmaceutical drugs available for over-the-counter purchase, and enact restrictions on pharmacy benefit manager (“PBM”) payment methodologies, among other things. These actions and policies may significantly reduce U.S. drug prices, potentially impacting manufacturers’ global pricing strategies and profitability, while increasing their operational costs and compliance risks. In June 2024, the U.S. Supreme Court’s Loper Bright decision greatly reduced judicial deference to regulatory agencies, which could increase successful legal challenges to federal regulations affecting our operations. Congress may introduce and ultimately pass health care related legislation that could impact the drug approval process and make changes to the Medicare Drug Price Negotiation Program created under the Inflation Reduction Act (“IRA”).

In addition, certain foreign activities related to drugs, biologics, and research, especially with regard to China, have come under increased scrutiny in the United States. On December 10, 2025, the National Defense Authorization Act for Fiscal Year 2026 (“NDAA”) passed overwhelmingly in the U.S. House of Representatives (the “House”) and includes the BIOSECURE Act which prohibits the U.S. government from procuring biotechnology equipment or services from “biotechnology companies of concern,” and would prohibit U.S. government contracts, loans and grants to any entity that uses biotechnology equipment or services from a designated “biotechnology company of concern.” “Biotechnology companies of concern” include companies identified on the U.S. Department of Defense’s “Chinese military companies operating in the United States” list (the 1260H List) and also authorizes the U.S. government to identify additional entities for inclusion as “biotechnology companies of concern”. The U.S. Senate passed the NDAA on December 17, 2025 and President Trump subsequently signed the NDAA into law on December 18, 2025. With the BIOSECURE Act, we may be restricted in our ability to work with certain Chinese biotechnology manufacturing companies to the extent we would contract with, or otherwise receive funding from, the U.S. government.

European Regulatory Environment

In the European Union, the CHEMOSAT system is subject to regulation as a medical device. The European Union is composed of the 27 Member States of the European Union plus Norway, Iceland, and Liechtenstein. Under the European Union Medical Device Directive (Directive No 93/42/EEC of 14 June 1993) (“EU MDD”), as last amended, drug delivery

products such as CHEMOSAT are governed by the European Union laws on pharmaceutical products only if they are (i) placed on the market in such a way that the device and the pharmaceutical product form a single integral unit which is intended exclusively for use in the given combination, and (ii) the product is not reusable. In such cases, the drug delivery product is governed by the European Union Code on Medicinal Products for Human Use (Directive 2001/83/EC, as last amended) (“EUCMPHU”), while the essential requirements of the EU MDD apply to the safety and performance-related device features of the product. Because we do not intend to place the CHEMOSAT system on the European Union market as a single integral unit with melphalan, the product has been governed solely by the EU MDD, while the separately marketed drug is governed by the EUCMPHU and other European Union legislation applicable to drugs for human use.

In order to commercialize a medical device in the European Union, we must comply with the essential requirements of the EU MDD and more recently, the EU MDR. Compliance with these requirements entitles a manufacturer to affix a CE conformity mark, without which the products cannot be commercialized in the European Union. To demonstrate compliance with the essential requirements and obtain the right to affix the CE conformity mark, medical device manufacturers must undergo a conformity assessment procedure, which varies according to the type of medical device and its classification. In April 2011, we obtained authorization to affix a CE Mark for the Generation One CHEMOSAT system and began European commercialization with this version of the CHEMOSAT system in early 2012. In April 2012, we obtained authorization to affix a CE Mark for the Generation Two CHEMOSAT system, and since this time all procedures in Europe have been performed with this version of the system.

The EU MDD establishes a classification system placing devices into Class I, IIa, IIb, or III, depending on the risks and characteristics of the medical device. For certain types of low-risk medical devices (i.e., Class I devices which are non-sterile and do not have a measuring function), the manufacturer may issue an EC Declaration of Conformity based on a self-assessment of the conformity of its products with the essential requirements of the EU MDD. Other devices are subject to a conformity assessment procedure requiring the intervention of a Notified Body, which is an organization designated by a Member State of the European Union to conduct conformity assessments.

A manufacturer without a registered place of business in a Member State of the European Union that places a medical device on the market under its own name must designate an authorized representative established in the European Union who can act before, and be addressed by a Competent Authority on the manufacturer’s behalf with regard to the manufacturer’s obligations under the EU MDD and, more recently, the EU MDR. Our wholly-owned subsidiary, Delcath Systems Ltd. located in Galway, Ireland, serves as the authorized representative of the Company.

The European Commission undertook a review of the EU MDD legislative framework and promulgated REGULATION (EU) 2017/745 OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 5 April 2017 on medical devices, amending Directive 2001/83/EC, Regulation (EC) No 178/2002 and Regulation (EC) No 1223/2009 and repealing Council Directives 90/385/EEC and 93/42/EEC. This EU MDR became effective on May 25, 2017, and governs all facets of medical devices.

On February 28, 2022, CHEMOSAT received medical device certification under the EU MDR, which replaced CHEMOSAT’s prior certification under the EU MDR. Achieving EU MDR certification entailed a detailed evaluation from a designated European Union Notified Body, including an audit of quality systems and a review of documentation supporting safety and performance claims for the device. The EU MDR greatly expands upon existing EU MDD requirements, including the level of clinical evidence supporting claims, post-marketing surveillance, database traceability, unique device identification or UDI and increased supply chain oversight. Under the EU MDR, CHEMOSAT is a Class III medical device.

In the European Union, we must also comply with the Medical Device Vigilance System, which is designed to improve the protection of the health and safety of patients, users, and others by reducing the likelihood of recurrence of incidents related to the use of a medical device. Under this system, incidents are defined as any malfunction or deterioration in the characteristics and/or performance of a device, as well as any inadequacy in the labeling or the instructions for use which, directly or indirectly, might lead to or might have led to the death of a patient, user or other persons or to a serious deterioration in their state of health. When a medical device is suspected to be a contributory cause of an incident, its manufacturer or authorized representative in the European Union must report it to the Competent Authority of the Member State where the incident occurred.

Incidents are generally investigated by the manufacturer. The manufacturer’s investigation is monitored by the Competent Authority, which may intervene, or initiate an independent investigation if considered appropriate. An investigation may conclude in the adoption of a Field Safety Corrective Action, (“FSCA”). An FSCA is an action taken by a manufacturer to reduce a risk of death or serious deterioration in the state of health associated with the use of a medical device that is already placed on the market. An FSCA may include device recall, modification exchange and destruction.

The manufacturer or its authorized representative must notify its customers and/or the end users of the medical device of the FSCA via a Field Safety Notice.

Our product instructions and indication reference the chemotherapeutic agent melphalan hydrochloride. However, no melphalan labels in the European Union reference our product, and the labels vary from country to country with respect to the approved indication of the drug and its mode of administration. In the exercise of their professional judgment in the practice of medicine, physicians are generally allowed, under certain conditions, to use or prescribe a product in ways not approved by regulatory authorities. Physicians intending to use our device must obtain melphalan separately for use with the CHEMOSAT system and must use melphalan independently at their discretion.

In the European Union, the advertising and promotion of our products is also subject to EU Member States laws implementing the EU MDD, Directive 2006/114/EC concerning misleading and comparative advertising and Directive 2005/29/EC on unfair commercial practices, as well as other European Union Member State legislation governing the advertising and promotion of medical devices. These laws may further limit or restrict the advertising and promotion of our products to the general public and may also impose limitations on our promotional activities with healthcare professionals.

Failure to comply with the European Union Member State laws implementing the EU MDD and, more recently, the EU MDR, the European Union and European Union Member State laws on the promotion of medicinal products or with other applicable regulatory requirements can result in enforcement action by the European Union Member State authorities. An enforcement action may result in any of the following: fines, imprisonment, orders forfeiting products or prohibiting or suspending their supply to the market, or requiring the manufacturer to issue public warnings, or to conduct a product recall.

Intellectual Property

Our success depends in part on our ability to obtain patents and trademarks, maintain trade secret and know-how protection, enforce our proprietary rights against infringers, and operate without infringing on the proprietary rights of third parties. Because of the length of time and expense associated with developing new products and bringing them through the regulatory approval process, the healthcare industry places considerable emphasis on obtaining patent protection and maintaining trade secret protection for new technologies, products, processes, know-how, and methods. We hold rights in 13 United States utility patents, one United States design patent, two pending United States utility patent applications, nine issued foreign counterpart utility patents (including the validations of European Patents with claims directed to our filter and frame apparatus in 19 European countries, with claims directed to our filter apparatus and media in 15 European countries, and with claims to a kit of parts, directed to CHEMOSAT®, in 18 European countries), three issued foreign counterpart design patents, and two pending foreign counterpart patent applications.

When appropriate, we actively pursue protection of our proprietary products, technologies, processes, and methods by filing United States and international patent and trademark applications. We seek to pursue additional patent protection for technology invented through research and development, manufacturing, and clinical use of CHEMOSAT® and HEPZATO® that will enable us to expand our patent portfolio around advances to our current systems, technology, and methods for our current applications as well as beyond the treatment of cancers in the liver.

There can be no assurance that the pending patent applications will result in the issuance of patents, that patents issued to or licensed by us will not be challenged or circumvented by competitors, or that these patents will be found to be valid or sufficiently broad to protect our technology or provide us with a competitive advantage.

To maintain our proprietary position, we also rely on trade secrets and proprietary technological experience to protect proprietary manufacturing processes, technology, and know-how relating to our business. We rely, in part, on confidentiality agreements with our marketing partners, employees, advisors, vendors and consultants to protect our trade secrets and proprietary technological expertise. In addition, we also seek to maintain our trade secrets through maintenance of the physical security of the premises where our trade secrets are located. There can be no assurance that these agreements will not be breached, that we will have adequate remedies for any breach, that others will not independently develop equivalent proprietary information or that third parties will not otherwise gain access to our trade secrets and proprietary knowledge.

In certain circumstances, United States patent law allows for the extension of a patent’s duration for a period of up to five years after FDA approval. In October 2023, after receiving FDA approval for the HEPZATO KIT®, we requested an extension of the term for one of our patents. In addition to our proprietary protections, the FDA has granted us six orphan drug designations that provide us a seven-year period of exclusive marketing beginning on the date that our NDA is approved by the FDA for the designated orphan drug. While the exclusivity only applies to the indication for which the drug has been approved, we believe that this exclusivity will provide us with added protection.

There has been and continues to be substantial litigation regarding patent and other intellectual property rights in the pharmaceutical and medical device areas. If a third party asserts a claim against us, we may be forced to expend significant time and money defending such actions and an adverse determination in any patent litigation could subject us to significant liabilities to third parties, require us to redesign our product, require us to seek licenses from third parties and, if licenses are not available, prevent us from manufacturing, selling, or using our product. Additionally, we plan to enforce our intellectual property rights vigorously and may find it necessary to initiate litigation to enforce our patent rights or to protect our trade secrets or know-how. Patent litigation is costly and time consuming and there can be no assurance that the outcome will be favorable to us.

Competition

The healthcare industry is characterized by extensive research, rapid technological progress and significant competition from numerous healthcare companies and academic institutions. Competition in the cancer treatment industry is intense. We believe that the primary competitive factors for products addressing cancer include safety, efficacy, ease of use, reliability, price, and patient’s quality of life. We also believe that physician relationships, especially relationships with leaders in the medical, surgical, and oncology communities, are important competitive factors. We also believe that the current global economic conditions, as well as potential future conditions, which may be impacted by the implementation of tariffs by the United States and other countries, and new healthcare reforms in the jurisdictions in which we and our suppliers and manufacturers operate could put competitive pressure on us, including reduced selling prices and potential reimbursement rates, and overall procedure rates. Certain markets in Europe are experiencing the effects of continued economic weakness, which is affecting healthcare budgets and reimbursement. Moreover, there is great uncertainty with respect to potential changes in trade regulations, tariffs, sanctions and export controls which also increase volatility in the global economy and may have an adverse impact on our commercial efforts.

CHEMOSAT and HEPZATO compete with all forms of liver cancer treatments, including surgery, systemic chemotherapy, focal therapies, and palliative care. In the disease states we are targeting there are also numerous clinical trials sponsored by third parties, which can compete for potential patients in the near term and may ultimately lead to new competitive therapies.

In January 2022, Immunocore Holdings plc announced FDA approval for KIMMTRAK (tebentafusp-tebn) for the treatment of HLA-A *02:01-positive adult patients with unresectable or mUM. This is the first drug approved specifically for patients with mUM. HLA-A *02:01 patients represent approximately 45% of patients with uveal melanoma. HEPZATO is approved to treat all mUM patients and is the only approved drug to treat the remaining 55% of patients. Traditionally, mUM patients have been treated with both systemic and a variety of local regional techniques. There are numerous companies developing and marketing devices for the performance of local regional procedures, including Boston Scientific Corporation, the Covidien Products division of Medtronic plc, Merit Medical Systems, Inc., Varian Medical Systems, Inc., Sirtex Medical Limited, and AngioDynamics, Inc. These procedures include trans-arterial chemoembolization (TACE, DEBTACE) and Radioembolization (SIRT, TARE, or Y90). Neither of these procedures are approved for the treatment of mUM.

IDEAYA Biosciences (“IDEAYA”) and Replimune Group (“Replimune”) are currently developing therapies for the treatment of mUM. IDEAYA is developing darovasertib, an oral protein kinase C PKC inhibitor, in combination with crizotinib, a cMET inhibitor, targeting first-line HLA-A2 negative mUM patients. This combination has received FDA Fast Track designation and is currently being evaluated in a potentially registration-enabling Phase 2/3 trial. In the third quarter of 2025, IDEAYA initiated a global, randomized Phase 3 neoadjuvant registrational trial (designated OptimUM-10) for darovasertib in primary uveal melanoma. Replimune is investigating RP2, an oncolytic immunotherapy, for mUM. Replimune has commenced a randomized Phase 2/3 trial comparing RP2 combined with nivolumab versus the combination of ipilimumab and nivolumab in immune checkpoint inhibitor-naïve adult patients with mUM. Neither of these products have been approved for the treatment of mUM.

Many of our competitors may have substantially greater financial, technological, research and development, marketing, and personnel resources. In addition, some of our competitors may have considerable experience in conducting clinical trials, regulatory, manufacturing and commercialization capabilities. Our competitors may develop alternative treatment methods, or achieve earlier product development, in which case the likelihood of us achieving meaningful revenues or profitability will be substantially reduced.

Manufacturing and Quality Assurance

We manufacture certain critical medical device components, including our proprietary filter media and double balloon catheter and assemble and package CHEMOSAT and HEPZATO at our facility in Queensbury, New York. Our European headquarters and distribution facility in Galway, Ireland conducts final manufacturing, processing, and assembly. We use

third parties to manufacture most of the components of CHEMOSAT and HEPZATO. CHEMOSAT and HEPZATO and their components must be manufactured and sterilized in accordance with approved manufacturing and pre-determined performance specifications. In addition, certain components will require sterilization prior to distribution, and we use third-party vendors to perform the sterilization process.

We are required to comply with cGMP regulations and quality system regulations relating to our manufacturing of HEPZATO KIT for distribution in the United States. We are also required to comply with the FDA’s cGMP regulations and international quality system regulations, including those established by the International Standards Organization (“ISO”), with respect to products sold in the European Union. We are required to maintain ISO 13485 certification for medical devices to be sold in the European Union, which requires, among other items, an implemented quality system that applies to component quality, supplier control, product design and manufacturing operations. Our facilities are ISO 13485:2016 certified.

Human Capital Management

Our management team is comprised of highly experienced pharmaceutical and biotechnology executives with successful track records in researching, developing, gaining approval for and commercializing novel medicines to treat serious diseases. Each member of our management team has 20 to 30 years of industry experience. Additionally, the team has significant experience in capital raises, mergers/acquisitions, business development, and sales and marketing in the pharmaceutical industry. Our Board also consists of individuals with significant experience in the pharmaceutical and biotechnology industries. As of February 13, 2026, including our management team, we had approximately 156 full time employees, of which 141 are located in the United States and 15 are located in Europe. None of our employees are represented by a labor union or covered by a collective bargaining agreement, nor have we experienced any work stoppages. We believe our relationship with our employees is good. Although we have consolidated our offices to Queensbury, New York, the majority of our employees work remotely outside of the Queensbury area.

As required, we also engage consultants to provide services to us, including those related to marketing, quality assurance, manufacturing, and corporate services.

We are committed to growing our business over the long-term and increasing value to our stockholders. We believe that our future success will depend, in part, on our continued ability to attract, hire and retain qualified personnel and to motivate such individuals to perform to the best of their abilities. As a result of the competitive nature of the industry in which we operate, employees have significant career mobility and competition for experienced employees is great. The existence of this competition, and our need for experienced and talented employees to achieve our business objectives, underlies the design and implementation of our compensation programs. We provide our employees base salaries and leave and benefits programs that we believe are competitive and consistent with industry standards. In addition, we grant stock options to permanent employees, both upon initial hiring and thereafter, and pay cash bonuses to permanent employees based on the achievement of corporate and/or personal performance objectives.

We have developed corporate policies and guidelines to define our expectations regarding professional behavior. Our policies and practices apply to all employees, regardless of title. These guidelines include our Code of Business Conduct and Ethics, policies for corporate disclosure, insider trading and whistle-blowers.

We do not discriminate based on race, religion, creed, color, national origin, ancestry, physical disability, mental disability, medical condition, genetic information, marital status, sex, gender, gender identity, gender expression, age, military and veteran status, sexual orientation or any other protected characteristic as established by federal, state or local laws.

We are committed to the health and safety of our employees, patients and other partners in the healthcare community. We work to promote an environment of awareness and shared responsibility for safety and regulatory compliance throughout our organization, in order to minimize risks of injury, exposure, or business impact.

Available Information

Our website address is www.delcath.com. The information found on, or otherwise accessible through, our website is not incorporated by reference into, and does not form a part of, this Annual Report on Form 10-K or any other report or document we file with or furnish to the SEC. We make available, free of charge, on or through the SEC Filings section of our website, our Annual Reports on Form 10-K, Quarterly Reports on Form 10-Q, Current Reports on Form 8-K and any amendments to such reports filed or furnished pursuant to Section 13(a) or 15(d) of the Exchange Act, as soon as reasonably practicable after we electronically file such material with, or furnish it to, the SEC. We have also posted on our website the Audit Committee Charter, the Compensation and Stock Option Committee Charter, the Nominating and Corporate Governance Committee Charter, the Code of Business Conduct and Ethics and Whistleblower Policy.

DELCATH SYSTEMS, INC. (DCTH) Business

Company Overview

We have sufficient raw material and component constituent parts of the HEPZATO KIT to meet anticipated demand and we intend to manage supply chain risk through stockpiled inventory and contracting with multiple suppliers for critical components.

Cancers in the Liver—A Significant Unmet Medical Need

Table of Contents

Uveal Melanoma

Colorectal Cancer

Breast Cancer

Table of Contents

Neuroendocrine Cancer

Pancreatic Cancer

Cholangiocarcinoma

Hepatocellular Carcinoma

Intrahepatic Cholangiocarcinoma

Table of Contents

Kingdom and the European Union annually could be candidates for treatment with HEPZATO KIT (if it received FDA approval for such treatment) and CHEMOSAT.

About HEPZATO KIT and CHEMOSAT

The FOCUS Trial

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CHOPIN Trial

Clinical Development Program

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Metastatic Colorectal Cancer

Metastatic Breast Cancer

Market Access and Commercial Clinical Adoption

United States

United States Reimbursement

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•cost-effective; and

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Europe

European Reimbursement

On February 28, 2022, CHEMOSAT received MDR certification under the European Medical Devices Regulation (EU) 2017/745, which may be considered by jurisdictions when evaluating reimbursement.

Government Regulation

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United States Regulatory Environment

Clinical Trials

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New Drug Applications

Orphan Drug Exclusivity

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Other Regulatory Requirements

If Delcath or its present or future third-party manufacturers or suppliers are not able to comply with these requirements, the FDA may require the recall of our product from distribution or may withdraw approval for that product.

United States Healthcare Laws

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Health Reform

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European Regulatory Environment

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Intellectual Property

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Competition

Manufacturing and Quality Assurance

Table of Contents

Human Capital Management

Available Information