- Mo-Rez (mocertatug rezetecan), a B7-H4 ADC with a topoisomerase payload (DAR 6), is planned for five pivotal global Phase III trials beginning in 2026.
- BEHOLD-1 enrolled 224 patients (phase Ia n=44; phase Ib n=180) and recommends 5.8 mg/kg for BEHOLD-Ovarian01 and BEHOLD-Endometrial01 (NCT07286266, NCT07286331).
- Grade ≥3 treatment-related adverse events occurred in 64% (platinum-resistant ovarian cancer) and 54% (endometrial cancer), mainly hematologic; interstitial lung disease/pneumonitis affected 3% (5/178), all grade 1-2.
- GSK holds exclusive worldwide development and commercialization rights to Mo-Rez, licensed from Hansoh Pharma excluding mainland China, Hong Kong, Macau and Taiwan.
Overview
Mocertatug rezetecan (Mo-Rez) is an investigational antibody‑drug conjugate targeting B7‑H4, composed of a fully human anti‑B7‑H4 antibody linked to a topoisomerase inhibitor payload (DAR 6); data were presented at the SGO Annual Meeting in San Juan, Puerto Rico.
Efficacy
In the phase I BEHOLD‑1 study, Mo‑Rez at the highest doses produced confirmed objective response rates of 62% in platinum‑resistant ovarian cancer (5.8 mg/kg; 21/34; 95% CI 44–78) and 67% in recurrent/advanced endometrial cancer (4.8 mg/kg; 8/12; 95% CI 35–90); median duration of response was not reached at interim analysis.
Safety and tolerability
At the highest evaluated dose, grade ≥3 treatment‑related adverse events occurred in 64% of platinum‑resistant ovarian cancer patients and 54% of endometrial cancer patients, predominantly hematologic; common adverse events included nausea (86% PROC; 79% EC), neutropenia (73% PROC; 58% EC) and anaemia (52% PROC; 54% EC); interstitial lung disease/pneumonitis was reported in 3% (5/178), all grade 1–2; treatment discontinuations for TRAE were 0% in PROC and 4% in EC.
Program and development plans
BEHOLD‑1 enrolled 224 patients (phase Ia n=44; phase Ib n=180) and recommends 5.8 mg/kg for the first Phase III studies; GSK plans five pivotal global Phase III trials starting in 2026 (BEHOLD‑Ovarian01, BEHOLD‑Endometrial01 plus BEHOLD‑Ovarian02, BEHOLD‑Ovarian03 and BEHOLD‑Endometrial02); GSK holds global development/commercial rights outside Greater China under a license from Hansoh Pharma.
