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. 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. Mocertatug rezetecan combines a B7-H4–directed monoclonal antibody with a topoisomerase I inhibitor payload.
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. 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.
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.
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