Philadelphia, PA, USA, July 27, 2026 - The GOG Foundation, Inc. is proud to announce the enrollment of the first patient in GOG-3132/BEHOLD-Ovarian01 (NCT07286266), a global Phase 3 clinical trial titled A Randomized, Open-label, Multicenter, Phase 3 Study to Investigate Mocertatug Rezetecan Compared With Standard of Care in Participants with Platinum-resistant Ovarian Cancer . The study is sponsored by GSK and conducted in collaboration with The GOG Foundation, Inc.
Dr. Floor Backes, Principal Investigator of GOG-3132/BEHOLD-Ovarian01 and gynecologic oncologist at The Ohio State University Comprehensive Cancer Center, stated, "We are pleased to announce the enrollment of the first patient in BEHOLD-Ovarian01, an important milestone in the clinical development of mocertatug rezetecan. Building on the encouraging activity observed in the phase 1 BEHOLD-1 study, this Phase 3 trial will help determine whether B7-H4–targeted therapy can improve outcomes for patients with platinum-resistant ovarian cancer, an area of significant unmet medical need."
Mocertatug rezetecan (Mo-Rez; GSK5733584;) is an investigational B7-H4–targeted antibody-drug conjugate (ADC) being developed for gynecologic malignancies. 1 B7-H4 is an immune checkpoint that is widely expressed in ovarian cancer (approximately 70–90%) while showing minimal expression in normal adult tissues, creating a favorable therapeutic window for ADC-based delivery. 2 Mocertatug rezetecan combines a B7-H4–directed monoclonal antibody with a topoisomerase I inhibitor payload.
1 Oaknin A, et al. Mocertatug rezetecan (GSK5733584), a B7-H4-targeted antibody-drug conjugate (ADC), in platinum-resistant ovarian cancer (PROC) and endometrial cancer (EC): First results from the global BEHOLD-1 study. Gynecol Oncol. 2026;208(Suppl): S454-S455.
2 Porter JM, et al. Antibody drug conjugate targets are highly differentially expressed across the major types of ovarian cancer. European Journal of Cancer. 2025; 224:115522.
In the phase 1 BEHOLD-1 study (NCT06431594), Mo-Rez demonstrated encouraging clinical activity in patients with platinum-resistant ovarian cancer. At the dose selected for phase 3 development (5.8 mg/kg), the confirmed objective response rate was 62%, with responses observed across a range of B7-H4 expression levels and in clinically relevant subgroups, including patients previously treated with bevacizumab and PARP inhibitors. The median duration of response had not yet been reached at the time of analysis, and the safety profile supported advancement into phase 3 development.
BEHOLD-Ovarian01 is a randomized, open-label, multicenter Phase 3 study designed to determine whether Mo-Rez can improve outcomes compared with investigator's choice chemotherapy in patients with platinum-resistant ovarian cancer. The study brings together investigators and research networks from around the world, including The GOG Foundation, ENGOT, APGOT, and LACOG, in a shared effort to advance innovative treatment options for women with ovarian cancer.
Dr Lucy Gilbert, gynecologic oncologist at McGill University Health Centre and investigator at the first enrolling site, commented, “Enrolling the first patient in BEHOLD-Ovarian01 is a meaningful milestone for both our site and the global gynecologic oncology community. The encouraging activity observed with mocertatug rezetecan in early clinical studies supports further evaluation in this Phase 3 trial and highlights the importance of continuing to develop new treatment options for patients whose disease has progressed following prior therapies”
BEHOLD-Ovarian01 is the first of five planned global Phase 3 studies evaluating mocertatug rezetecan across ovarian and endometrial cancers. These studies comprise the BEHOLD clinical development program, a broad effort designed to evaluate the potential role of B7-H4–targeted therapy across multiple gynecologic cancer settings where substantial unmet medical need remains.
Philipp Harter, MD, PhD gynecologic oncologist at Kliniken Essen-Mitte and ENGOT Clinical Chair-Elect, commented, "Dosing the first patient in BEHOLD-Ovarian01 marks an important step in evaluating mocertatug rezetecan for patients with platinum-resistant ovarian cancer, a setting in which further treatment options are needed. This global Phase 3 trial will assess whether Mo-Rez can improve progression-free and overall survival compared with investigator’s choice of chemotherapy. We are pleased that AGO Study Group and the cooperating ENGOT groups are contributing to this international study led by The GOG Foundation.”
Platinum-resistant ovarian cancer remains one of the greatest unmet needs in gynecologic oncology. Treatment has historically relied on non-platinum chemotherapy, including weekly paclitaxel, pegylated liposomal doxorubicin, or topotecan, with or without bevacizumab. 3 Although more recent advances, including mirvetuximab soravtansine for FRα-positive disease, pembrolizumab-based combinations for PD-L1–positive disease, and relacorilant plus nab-paclitaxel, have expanded treatment options for some patients, many women continue to experience disease progression and require additional therapies. 4,5,6
Mo-Rez is being evaluated in a clinically relevant, previously treated patient population, including patients who may have received prior bevacizumab, PARP inhibitors, and other contemporary therapies used in platinum-resistant ovarian cancer. Given the broad expression of B7-H4 across ovarian cancers and the encouraging activity observed in BEHOLD-1, BEHOLD-Ovarian01 will evaluate whether B7-H4–targeted therapy can provide benefit across a diverse patient population in the phase 3 setting.
For more than five decades, the GOG Foundation has been at the forefront of gynecologic oncology research, advancing practice-changing clinical trials that have helped shape standards of care and improve patient outcomes worldwide. Guided by Dr. Herzog’s leadership, the Foundation continues to strengthen its impact through a commitment to inclusive research, global scientific collaboration, and the mentorship of emerging investigators in gynecologic oncology.
3 Pujade-Lauraine E, et al. Bevacizumab combined with chemotherapy for platinum-resistant recurrent ovarian cancer: The AURELIA open-label randomized phase III trial. J Clin Oncol. 2014 May 1;32(13):1302-8. doi: 10.1200/JCO.2013.51.4489.
4 Moore KN, et al. Mirvetuximab soravtansine in FRα-positive, platinum-resistant ovarian cancer. N Engl J Med. 2023;389(24):2169-2180. doi:10.1056/NEJMoa2309169.
5 Colombo N, et al. Pembrolizumab plus weekly paclitaxel in platinum-resistant recurrent ovarian cancer (ENGOT-ov65/KEYNOTE-B96): a multicentre, randomised, double-blind, phase 3 study. Lancet. 2026;407(10538):1525-1537. doi:10.1016/S0140-6736(26)00602-1.
6 Lorusso D, et al. Overall survival with relacorilant and nab-paclitaxel in patients with platinum-resistant ovarian cancer (ROSELLA): a phase 3 randomised controlled trial. Lancet. 2026;407(10538):1513-1524. doi:10.1016/S0140-6736(26)00462-9.
7 American Cancer Society. Key Statistics for Ovarian Cancer. American Cancer Society; 2025. Available at: https://www.cancer.org/cancer/types/ovarian-cancer/about/key-statistics.html
8 Sung H, et al. Global Cancer Statistics 2020: GLOBOCAN estimates of incidence and mortality worldwide for 36 cancers in 185 countries. CA Cancer J Clin. 2021;71(3):209-249. doi:10.3322/caac.21660.
9 Cortez AJ, et al. Advances in ovarian cancer therapy. Cancer Chemother Pharmacol. 2018;81(1):17-38. doi:10.1007/s00280-017-3501-8.
About Ovarian Cancer
Ovarian cancer remains one of the leading causes of gynecologic cancer-related death worldwide. More than 300,000 women are diagnosed with ovarian cancer each year globally, and over 200,000 die from the disease annually. 7,8 In the United States alone, more than 20,000 women are expected to be diagnosed with ovarian cancer this year, and nearly 13,000 will die from the disease.
Because ovarian cancer often presents with nonspecific symptoms, more than 75% of patients are diagnosed with advanced-stage disease. 9 Although many women initially respond to surgery and platinum-based chemotherapy, recurrence is common, particularly among those with advanced disease. Approximately 80% of patients with advanced ovarian cancer will ultimately experience disease recurrence and require additional therapies.
Platinum-resistant ovarian cancer, defined as disease progression during or within six months of platinum-based chemotherapy, remains one of the most difficult-to-treat settings in gynecologic oncology. Treatment options are limited, response rates are often modest, and long-term outcomes remain poor, underscoring the need for innovative therapeutic approaches and continued clinical research.
About The GOG Foundation, Inc. ( www.gog.org )
The GOG Foundation, Inc. is a not-for-profit organization with the purpose of promoting excellence in the quality and integrity of clinical and translational scientific research in the field of gynecologic oncology. The GOG Foundation is committed to maintaining the highest standards in clinical trial development, execution, analysis, and distribution of results. The GOG Foundation is the only clinical trialist group in the United States that focuses its research on patients with pelvic malignancies, such as cancer of the ovary (including surface peritoneal malignancies), uterus (including endometrium, soft tissue sarcoma, and gestational trophoblastic neoplasia), cervix, and vulva. The GOG Foundation is multi-disciplinary in its approach to clinical trials, and includes gynecologic oncologists, medical oncologists, pathologists, radiation oncologists, oncology nurses, biostatisticians (including those with expertise in bioinformatics), basic scientists, quality of life experts, data managers, and administrative personnel.
About the GOG Partners Program
Supported by industry, GOG Partners program is structured to work directly with pharmaceutical organizations and operate clinical trials outside the National Cancer Institute (NCI) framework. The GOG Partners program promotes the mission of the GOG Foundation dedicated to transforming the care in gynecologic oncology. By providing an alternative venue for patient accrual and site infrastructure support, GOG Partners has helped provide additional trials and opportunities for patients outside the national gynecologic clinical trials network and has led to several FDA approvals.
About ENGOT ( https://engot.esgo.org/ )
The European Network of Gynaecological Oncological Trial groups (ENGOT) is a research network of the European Society of Gynaecological Oncology (ESGO) and was founded in Berlin on 29 October 2007.
Currently, ENGOT consists of 22 trial groups from 34 European countries that perform cooperative clinical trials. The up to date list of members and their contact details are available via our website .
ENGOT is a platform that guarantees that the European spirit and culture is incorporated into the medical progress in gynaecological oncology, and that all European patients and countries can participate in an active way in clinical research and progress.
The ultimate goal is to bring the best treatment to gynaecological cancer patients through the best science, and enabling every patient in every European country to access a clinical trial. As a network of national and regional clinical trial units, ENGOT coordinates and promotes clinical trials within Europe on patients with gynaecological cancer.
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773-750-5753, jcummins@gog.org
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