Positive Mo-Rez Phase Ib data in ovarian cancer
GSK reported updated BEHOLD-1 results for an investigational B7-H4 antibody-drug conjugate in platinum-resistant ovarian cancer.
TL;DR
- GSK reported a 62% confirmed response rate and 12.2-month median response duration for Mo-Rez at the selected dose in the Phase Ib BEHOLD-1 study.
- The results came from 45 patients in a platinum-resistant ovarian cancer cohort and were announced ahead of an ESMO presentation.
- Mo-Rez remains investigational; GSK says five pivotal Phase 3 studies are underway, and the early-phase data do not establish comparative benefit.
GSK announced updated data from BEHOLD-1, a global Phase I study of mocertatug rezetecan, known as Mo-Rez. In the reported platinum-resistant ovarian cancer cohort, the company said the selected Phase III dose produced a confirmed objective response rate of 62% among 45 patients, with a median response duration of 12.2 months. [1]
The treatment is an investigational antibody-drug conjugate targeting B7-H4. GSK said the data had more than 13 months of follow-up and were due for a late-breaking oral presentation at the 2026 ESMO Congress; the figures originate from the company’s study update. [1]
Sharecast independently summarized the update and reported a median progression-free survival of 11.1 months, alongside the response and duration figures. These are Phase Ib results in a selected study population, so they do not establish how Mo-Rez compares with standard treatment in a randomized trial. [2]
GSK said five pivotal Phase III studies are now underway across gynecological cancers. The next open questions include how the data hold up in larger controlled studies, how adverse events compare, and whether any future regulatory filing supports a defined patient population. [1]
Why it matters
The update adds an early clinical signal to GSK’s oncology pipeline, but the development decision depends on larger controlled evidence and remains separate from approval or clinical-use decisions.
Editor's note
Company-reported Phase Ib data are identified as such; efficacy claims are not generalized beyond the reported cohort.