Mo-Rez shows 62% response rate in platinum-resistant ovarian cancer

GSK has reported updated Phase Ib results showing that mocertatug rezetecan, also known as Mo-Rez, produced durable responses in patients with platinum-resistant ovarian cancer.

The findings come from the global BEHOLD-1 study and are being presented in a late-breaking oral session at the 2026 European Society for Medical Oncology Congress in Madrid.

Mo-Rez is an investigational antibody drug conjugate targeting B7-H4, an immune checkpoint protein that is widely expressed across several gynaecological cancers but found at relatively low levels in normal tissues.

At the selected Phase III dose of 5.8 mg/kg, Mo-Rez achieved a confirmed objective response rate of 62%.

This represented responses in 28 of 45 patients.

Median duration of response reached 12.2 months after more than 13 months of follow-up.

Median progression-free survival was 11.1 months.

GSK said the updated findings build on earlier BEHOLD-1 data and indicate that the responses observed with Mo-Rez can remain durable over time in patients with platinum-resistant ovarian cancer.

Responses were also seen across a range of B7-H4 expression levels.

The company said this finding supports the potential development of Mo-Rez across a broader population of patients with gynaecological cancers rather than restricting treatment to those with the highest levels of B7-H4 expression.

Hesham Abdullah, Senior Vice President and Global Head of Oncology Research and Development at GSK, said durable disease control remains difficult to achieve in platinum-resistant ovarian cancer.

He said the response durability and progression-free survival observed with Mo-Rez have supported the accelerated expansion of the treatment into a broader Phase III development programme.

The safety findings remained consistent with previously reported results.

Grade 3 or higher treatment-related adverse events occurred in 71% of patients at the selected Phase III dose and were primarily haematological.

Treatment-related adverse events led to discontinuation in 2% of patients.

Interstitial lung disease or pneumonitis was reported in one patient, representing 2% of the treatment group.

Vanda Salutari, Investigator in the BEHOLD-1 study at Fondazione Policlinico Universitario Agostino Gemelli IRCCS in Rome, said the duration of response and progression-free survival were encouraging in a treatment setting where patients often experience limited benefit from available therapies.

The BEHOLD development programme is now expanding across ovarian and endometrial cancers.

Five pivotal Phase III studies are underway across gynaecological malignancies.

Additional ESMO presentations include an exploratory biomarker analysis from BEHOLD-1 as well as study designs for the Phase III BEHOLD-Ovarian01 and BEHOLD-Endometrial01 trials.

The 5.8 mg/kg dose evaluated in BEHOLD-1 has been selected for continued testing in the Phase III programme.

---

---

Related Topics and Keywords

ADC, antibody drug conjugate, B7-H4, BEHOLD-1, BEHOLD-Endometrial01, BEHOLD-Ovarian01, Biopharma, clinical trials, duration of response, ESMO 2026, GSK, gynaecological cancer, Mo-Rez, mocertatug rezetecan, objective response rate, Oncology, Ovarian Cancer, pharma news, Phase Ib, phase III, platinum-resistant ovarian cancer, progression-free survival