GOG Foundation, Inc. is proud to announce that the first patient has been enrolled in a global Phase 3 clinical trial titled GOG-3132/BEHOLD-Ovarian01 (NCT07286266). A randomized, open-label, multicenter, phase III study investigating moseltatug rezetecan compared to standard of care in participants with platinum-resistant ovarian cancer.. This research is sponsored by GSK and conducted in collaboration with GOG Foundation, Inc.
“We are excited to announce this new study,” said Dr. Floor Bax, principal investigator of GOG-3132/BEHOLD-Ovarian01 and a gynecologic oncologist at The Ohio State University Comprehensive Cancer Center. “We are pleased to announce that the first patient has been enrolled in BEHOLD-Ovarian01, an important milestone in the clinical development of mosertatag rezetecan. Building on the encouraging activity observed in the Phase 1 BEHOLD-1 trial, this Phase 3 study 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%) but shows minimal expression in normal adult tissues, creating a favorable therapeutic area 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 enhanced 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. At the time of analysis, the median duration of response had not yet been reached, and the safety profile supported progress toward phase 3 development.
BEHOLD-Ovarian01 is a randomized, open-label, multicenter Phase III trial designed to determine whether Mo-Rez can improve outcomes compared to investigator-selected chemotherapy in patients with platinum-resistant ovarian cancer. The study brings together researchers and research networks from around the world, including the GOG Foundation, ENGOT, APGOT and LACOG, in a collaborative effort to advance innovative treatment options for women with ovarian cancer.
Dr. Lucy Gilbert, a gynecological oncologist at McGill University Health Center and a researcher on the original enrollment site, commented: “Enrolling the first patient in BEHOLD-Ovarian01 is a meaningful milestone for both our institution and the global gynecologic oncology community. The encouraging activity observed with mosertatag 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 after previous therapy.”
BEHOLD-Ovarian01 is the first of five planned global Phase 3 studies evaluating moseltatug rezetecan in ovarian and endometrial cancer. These studies constitute the BEHOLD clinical development program, a broad-based effort designed to evaluate the potential role of B7-H4 targeted therapies in multiple gynecologic cancer settings where substantial unmet medical needs remain.
Philipp Harter, MD, gynecological oncologist at Kliniken Essenmitte and incoming ENGOT Clinical Chair, commented: “The first patient administration of BEHOLD-Ovarian01 marks an important step in the evaluation of mosertatag rezetecan for patients with platinum-resistant ovarian cancer who require additional treatment options. We are pleased that the ENGOT group, in collaboration with the AGO research group, is 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 traditionally relied on non-platinum chemotherapy such as weekly paclitaxel, pegylated liposomal doxorubicin, or topotecan with or without bevacizumab. Although recent advances such as mirvetuximab solafutansine for FRα-positive disease, pembrolizumab-based combination therapy for PD-L1-positive disease, and lilacorilant plus nab-paclitaxel combination therapy have expanded treatment options for some patients, many women still experience disease progression and require additional treatment.
Mo-Rez is being evaluated in clinically relevant, previously treated patient populations, including patients who may have previously received bevacizumab, PARP inhibitors, and other modern therapies used for platinum-resistant ovarian cancer. Given the widespread expression of B7-H4 across ovarian cancer and the promotive activity observed with BEHOLD-1, BEHOLD-Ovarian01 will assess whether B7-H4-targeted therapies can provide benefit across diverse patient populations in a phase 3 setting.
For more than 50 years, the GOG Foundation has been at the forefront of gynecologic oncology research, driving practice-changing clinical trials that shape the standard of care and improve patient outcomes around the world. Guided by Dr. Herzog’s leadership, the Foundation continues to strengthen its impact through comprehensive research, global scientific collaboration, and a commitment to mentoring emerging researchers in gynecologic oncology.
