New drug Mo-Rez shows lasting responses in hard-to-treat ovarian cancer

A new antibody-drug conjugate called mocertatug rezetecan (Mo-Rez) is showing impressive staying power in one of oncology's toughest challenges: platinum-resistant ovarian cancer (PROC). Updated results from the phase 1 BEHOLD-1 trial, presented at the 2026 ESMO Congress, confirm that the recommended dose of 5.8 mg/kg every three weeks delivers strong and lasting responses after more than 13 months of follow-up.

At that dose, patients achieved a 62% objective response rate, with tumors shrinking by a median of 45.5%. Responses came quickly — a median of just 42 days — and held up well over time, with 90% of responders still responding at 6 months.

By the Numbers:

• 62% confirmed objective response rate at 5.8 mg/kg
• 11.1 months median progression-free survival at the recommended dose
• 12.2 months median duration of response
• 71% of patients experienced grade 3+ treatment-related adverse effects at 5.8 mg/kg
• 5 global phase 3 trials now underway across ovarian and endometrial cancers

Why it matters: PROC is notoriously difficult to treat, with few effective options after prior therapies. Mo-Rez's durable responses — even in patients previously treated with bevacizumab or PARP inhibitors — signal a potentially meaningful new option for this population, with a broad phase 3 program now underway to confirm its benefit.