Genmab Receives FDA Breakthrough Therapy Designation for Rinatabart Sesutecan (Rina-S®) in Advanced Endometrial Cancer (EC)

• Breakthrough Therapy Designation granted to Rina-S for the treatment of adult patients with recurrent or progressive endometrial cancer (EC) who have disease progression on or following prior treatment with a platinum-containing regimen and a PD-(L)1 therapy
• Regulatory decision supported by data from the Phase 1/2 RAINFOL™-01 trial showing encouraging responses in heavily pretreated EC patientsⁱ
• Rina-S continues to be evaluated as a single-agent in patients with advanced EC in the Phase 1/2 RAINFOL™-01 trial and will be further evaluated in a planned Phase 3 trial

Genmab A/S (Nasdaq: GMAB) announced today that the U.S. Food and Drug Administration (FDA) has granted Breakthrough Therapy Designation (BTD) to rinatabart sesutecan (Rina-S^®), an investigational folate receptor alpha (FRα)-directed, TOPO1-inhibitor antibody-drug conjugate (ADC), for the treatment of adult patients with recurrent or progressive endometrial cancer (EC) who have disease progression on or following prior treatment with a platinum-containing regimen and a PD-(L)1 therapy. BTD aims to expedite the development and review of investigational medicines by the U.S. FDA for serious or life-threatening diseases in cases where preliminary clinical evidence shows that a therapy may provide substantial improvements over available therapies.

The designation was supported by previously published results from the endometrial cancer monotherapy dose expansion B2 cohort of the multi-part, Phase 1/2 RAINFOL™-01 trial (NCT05579366), evaluating the safety and efficacy of Rina-S in solid tumors. In the B2 cohort, 64 patients with heavily pretreated advanced or recurrent EC whose disease had progressed on or after an anti-PD-(L)1 and platinum-based chemotherapy were enrolled and treated with Rina-S. The results were presented at the 2025 American Society of Clinical Oncology (ASCO) Annual Meeting.

“This Breakthrough Therapy Designation underscores the future potential of Rina-S as a treatment option for women diagnosed with advanced endometrial cancer, who face a poor prognosis after progressing on standard of care treatment,” said Judith Klimovsky, M.D., Executive Vice President and Chief Development Officer of Genmab. “Rina-S reinforces Genmab’s determination to advance wholly owned antibody medicines in areas long overdue for innovation and our commitment to driving a strong clinical development program to help redefine what’s possible to treat gynecologic cancers.”

Rina-S is advancing through late-stage development supported by a growing portfolio of clinical trials, including the ongoing Phase 1/2 RAINFOL-01 trial, the ongoing Phase 3 RAINFOL-02 trial (NCT06619236) in ovarian cancer, and several planned trials to evaluate Rina-S as a potential treatment option for a variety of tumor types, including a Phase 3 trial in endometrial cancer.

About the RAINFOL^TM -01 Trial

RAINFOL™-01 (NCT05579366) is an open-label, multicenter Phase 1/2 study, designed to evaluate the safety and efficacy of rinatabart sesutecan (Rina-S) Q3W at various doses in solid tumors that are known to express FRα. The study consists of multiple parts including Part A dose escalation; Part B tumor-specific monotherapy dose-expansion cohorts; Part C platinum-resistant ovarian cancer (PROC) cohort; Part D combination therapy cohorts; Part F a monotherapy endometrial cancer (EC) cohort; and Part K monotherapy QTc cohort in high-grade ovarian cancer.

About Endometrial Cancer

Endometrial cancer (EC) starts in the lining of the uterus, known as the endometriumⁱⁱ and ranks as the second most prevalent gynecologic cancer globally, with increasing incidence and mortality rates^iii,iv. Patients with advanced or recurrent EC have a relatively poor prognosis and treatment options are limited for those patients who have progressed following treatment with chemotherapy and immune checkpoint inhibitor. FRα is overexpressed on multiple tumors, including EC, making it a promising therapeutic target. Anti-tumor activity with Rina-S was observed across a broad range of FRα expression, and there are currently no approved FRα-directed therapies approved for the treatment of endometrial cancer.

About Rinatabart Sesutecan (Rina-S; GEN1184)

Rinatabart sesutecan (Rina-S; GEN1184) is an investigational ADC. It is composed of a novel human monoclonal antibody directed at folate receptor α (FRα), a novel hydrophilic protease-cleavable linker, and exatecan, a topoisomerase I inhibitor payload. The clinical trial program for Rina-S continues to expand including ovarian, endometrial and other cancers of unmet need.

The safety and efficacy of rinatabart sesutecan has not been established. Please visit www.clinicaltrials.gov for more information.

About Genmab

Genmab is an international biotechnology company with a core purpose of guiding its unstoppable team to strive toward improving the lives of patients with innovative and differentiated antibody therapeutics. For more than 25 years, its passionate, innovative and collaborative team has invented next-generation antibody technology platforms and leveraged translational, quantitative and data sciences, resulting in a proprietary pipeline including bispecific T-cell engagers, antibody-drug conjugates, next-generation immune checkpoint modulators and effector function-enhanced antibodies. By 2030, Genmab’s vision is to transform the lives of people with cancer and other serious diseases with knock-your-socks-off (KYSO) antibody medicines^®.

Established in 1999, Genmab is headquartered in Copenhagen, Denmark, with international presence across North America, Europe and Asia Pacific. For more information, please visit Genmab.com and follow us on LinkedIn and X.

This Media Release contains forward looking statements. The words “believe,” “expect,” “anticipate,” “intend” and “plan” and similar expressions identify forward looking statements. Actual results or performance may differ materially from any future results or performance expressed or implied by such statements. The important factors that could cause our actual results or performance to differ materially include, among others, risks associated with preclinical and clinical development of products, uncertainties related to the outcome and conduct of clinical trials including unforeseen safety issues, uncertainties related to product manufacturing, the lack of market acceptance of our products, our inability to manage growth, the competitive environment in relation to our business area and markets, our inability to attract and retain suitably qualified personnel, the unenforceability or lack of protection of our patents and proprietary rights, our relationships with affiliated entities, changes and developments in technology which may render our products or technologies obsolete, and other factors. For a further discussion of these risks, please refer to the risk management sections in Genmab’s most recent financial reports, which are available on www.genmab.com and the risk factors included in Genmab’s most recent Annual Report on Form 20-F and other filings with the U.S. Securities and Exchange Commission (SEC), which are available at www.sec.gov. Genmab does not undertake any obligation to update or revise forward looking statements in this Media Release nor to confirm such statements to reflect subsequent events or circumstances after the date made or in relation to actual results, unless required by law.

Genmab A/S and/or its subsidiaries own the following trademarks: Genmab^®; the Y-shaped Genmab logo^®; Genmab in combination with the Y-shaped Genmab logo^®; HuMax^®; DuoBody^®; HexaBody^®; DuoHexaBody^®, HexElect^®, KYSO^® and RAINFOL™; Rina-S is a trademark of ProfoundBio, US, Co. and Genmab (Suzhou) Co., Ltd.

ⁱ Rinatabart sesutecan (Rina-S) for patients with advanced endometrial cancer: First disclosure from dose expansion cohort B2 of the GTC1184-01 study. JCO 43, 3039-3039(2025). DOI:10.1200/JCO.2025.43.16_suppl.3039

ⁱⁱ Mayo Clinic. Endometrial Cancer. https://www.mayoclinic.org/diseases-conditions/endometrial-cancer/symptoms-causes/syc-20352461. Accessed May 2025.

ⁱⁱⁱ Ferlay J, Ervik M, Lam F, et al. Global cancer observatory: Cancer today (version 1.1). International Agency for Research on Cancer. 05/28/2024 (https://gco.iarc.who.int/today).

^iv Concin N, Matias-Guiu X, Vergote I, et al. ESGO/ESTRO/ESP guidelines for the management of patients with endometrial carcinoma. International journal of gynecological cancer: official journal of the International Gynecological Cancer Society 2021;31(1):12-39. (In eng). DOI: 10.1136/ijgc-2020-002230.

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