About the BEHOLD clinical trial programme
The BEHOLD clinical programme is GSK's global development plan that includes the BEHOLD-1 (NCT06431594) monotherapy study and the ongoing BEHOLD-2 (NCT06796907) combination study.
Five pivotal phase III trials are currently underway:
Platinum-resistant ovarian cancer (BEHOLD-Ovarian01 / NCT07286266)
Platinum-sensitive ovarian cancer (BEHOLD-Ovarian02 / NCT07684612)
First-line maintenance setting for ovarian cancer without homologous recombination deficiency (BEHOLD-Ovarian03 / NCT07694427)
Second-line advanced and recurrent endometrial cancer (BEHOLD-Endometrial01 / NCT07286331)
First-line maintenance setting mismatch repair proficient endometrial cancer (BEHOLD-Endometrial02 / NCT07684599).
About BEHOLD-1
The BEHOLD-1 clinical trial is a two-part, open-label, phase I study evaluating the safety, tolerability and efficacy of Mo-Rez injection in patients with platinum-resistant ovarian cancer (PROC) or advanced/recurrent endometrial cancer (EC). Phase Ia assessed up to four Mo-Rez dose levels in patients with advanced solid tumours, with intravenous administration every three weeks until progression or toxicity. In the phase Ib dose expansion, patients with PROC or EC (1-3 prior lines of therapy) were randomised to three or two Mo-Rez dose levels, respectively.
At data cut-off, a total of 136 PROC patients were enrolled in BEHOLD-1. At the selected phase III dose evaluated in phase Ib, the most common adverse events in PROC were gastrointestinal and haematological, consistent with treatments in this class. Treatment-related adverse events led to dose interruptions in 51% of patients with PROC and dose reductions in 47%. Primary endpoints included: incidence of dose-limiting toxicity in phase Ia and confirmed objective response rate (cORR) by investigator per RECIST 1.1 in phase Ib. Patients with EC treated at the selected phase III dose continue to be followed, with data expected to be presented in the future.
About mocertatug rezetecan
Mo-Rez is a novel investigational B7-H4-targeted antibody-drug conjugate designed to optimise efficacy and tolerability. It is composed of a fully human anti-B7-H4 monoclonal antibody covalently linked to a topoisomerase inhibitor payload and has a drug-to-antibody ratio (DAR) of 6. GSK acquired exclusive worldwide rights (excluding mainland China, Hong Kong, Macau and Taiwan) from Hansoh Pharma to progress clinical development and commercialisation of Mo-Rez globally.
About ovarian cancer
Ovarian cancer affects 843,000 people with 240,000 new cases annually.6 70% of people living with ovarian cancer will present with advanced disease and survival usually declines after recurrence.7 ,8 Patients with platinum-resistant ovarian cancer (PROC), one of the hardest to treat, face limited treatment options and poor outcomes.9 Many will develop resistance to platinum-based chemotherapy, the backbone of first-line treatment, underscoring the need for innovations that can deliver meaningful benefit.9
GSK in oncology
GSK is focused on developing differentiated medicines for cancers where patients continue to face poor outcomes, treatment resistance, limited options or significant treatment burden. We focus where advances in science and technology offer the greatest opportunity to improve outcomes across haematological, lung, gastrointestinal, genitourinary and gynaecological cancers. Across multiple modalities, including targeted small molecules, antibody-drug conjugates (ADCs) and immunotherapies, GSK applies deep expertise in cancer biology and immune system science to develop differentiated medicines designed to deliver durable responses, overcome resistance and reduce treatment burden.
About GSK
GSK is a global biopharma company with a purpose to unite science, technology, and talent to get ahead of disease together. Find out more at www.gsk.com.
Cautionary statement regarding forward-looking statements
GSK cautions investors that any forward-looking statements or projections made by GSK, including those made in this announcement, are subject to risks and uncertainties that may cause actual results to differ materially from those projected. Such factors include, but are not limited to, those described in the "Risk Factors" section in GSK's Annual Report on Form 20-F for 2025, and GSK's Q2 Results for 2026.