First patient enrolled in Phase 3 trial of mocertatug rezetecan for platinum-resistant ovarian cancer

Philadelphia, PA, USA — July 27, 2026 — The GOG Foundation, Inc. announced the enrollment of the first patient in GOG-3132/BEHOLD-Ovarian01 (NCT07286266), a global Phase 3 trial evaluating mocertatug rezetecan against standard-of-care chemotherapy in participants with platinum-resistant ovarian cancer. Sponsored by GSK and conducted in collaboration with The GOG Foundation, the study marks a key translational step for a next-generation targeted antibody-drug conjugate (ADC).

BEHOLD-Ovarian01 is designed to determine whether mocertatug rezetecan can improve clinically meaningful outcomes in a population facing limited therapeutic options. The trial follows encouraging activity reported from the Phase 1 BEHOLD-1 study, where responses were observed across patient subgroups relevant to real-world platinum-resistant disease.

Mocertatug rezetecan (Mo-Rez; GSK5733584) targets B7-H4, an immune checkpoint receptor expressed in approximately 70–90% of ovarian cancers but with minimal expression in most normal adult tissues. This differential expression is intended to create a favorable therapeutic window for selective ADC delivery.

Mechanistically, Mo-Rez pairs a B7-H4–directed monoclonal antibody with a topoisomerase I inhibitor payload. After binding to B7-H4–expressing tumor cells, the ADC is internalized, delivering the cytotoxic payload to disrupt DNA replication and drive tumor cell death.

In BEHOLD-1, the Phase 3 dose selection was 5.8 mg/kg. At that dose, the confirmed objective response rate was 62%, with responses spanning a range of B7-H4 expression levels. Notably, activity was also reported in clinically relevant groups, including patients previously treated with bevacizumab and PARP inhibitors.

The trial population in BEHOLD-Ovarian01 reflects a previously treated setting, where platinum-resistant ovarian cancer remains difficult to manage. Standard approaches often rely on non-platinum chemotherapy such as weekly paclitaxel, pegylated liposomal doxorubicin, or topotecan, with or without bevacizumab.

The Phase 3 design is randomized, open-label, and multicenter, comparing Mo-Rez with investigator’s choice chemotherapy. Study stakeholders include global cooperative groups such as ENGOT, APGOT, and LACOG, with The GOG Foundation contributing trial leadership and operational expertise.

Collectively, BEHOLD-Ovarian01 aims to establish whether B7-H4–targeted ADC therapy can translate early pharmacology and antitumor signals into improved progression-free and overall survival for patients with platinum-resistant ovarian cancer.