GSK Mo‑Rez shows 62% confirmed response and 12.2‑month median DoR in platinum‑resistant ovarian cancer
- Confirmed objective response rate (cORR) 62% (28/45) at the 5.8 mg/kg phase III dose.
- Median duration of response (DoR) 12.2 months and median progression‑free survival (PFS) 11.1 months.
- Grade ≥3 treatment‑related adverse events in 71% of patients, predominantly haematologic; 2% discontinued for TRAEs and 2% had ILD/pneumonitis.
- Five pivotal phase III trials now underway across ovarian and endometrial cancers, supported by biomarker analyses showing responses across B7‑H4 expression levels.
BEHOLD‑1 phase Ib efficacy
Updated results from the global BEHOLD‑1 phase I study show mocertatug rezetecan (Mo‑Rez) achieved a confirmed objective response rate of 62% (28/45) and a median duration of response of 12.2 months at the selected phase III dose of 5.8 mg/kg, with median progression‑free survival of 11.1 months. Findings are based on >13 months follow‑up and will be presented at ESMO 2026.
Safety
Safety was consistent with prior reports: grade ≥3 treatment‑related adverse events occurred in 71% (32/45) and were predominantly haematologic. At 5.8 mg/kg, TRAEs led to treatment discontinuation in 2% (1/45) and interstitial lung disease/pneumonitis occurred in 2% (1/45). Across PROC patients in BEHOLD‑1, treatment interruptions occurred in 51% and dose reductions in 47%.
Development programme and biomarkers
Responses were observed across a range of B7‑H4 expression levels in exploratory biomarker analyses, supporting broader potential in gynaecological cancers. GSK has accelerated a large‑scale phase III programme: five pivotal trials are underway covering platinum‑resistant and platinum‑sensitive ovarian cancer, two first‑line maintenance settings, and second‑line advanced/recurrent endometrial cancer.
Drug profile
Mo‑Rez is a B7‑H4‑targeted antibody‑drug conjugate composed of a fully human anti‑B7‑H4 monoclonal antibody linked to a topoisomerase inhibitor payload with a drug‑to‑antibody ratio of 6; GSK holds global rights outside mainland China, Hong Kong, Macau and Taiwan.
Source: GSK