Summit Therapeutics starts Phase II/III bladder cancer trial for ivonescimab

Summit Therapeutics announced on August 5, 2026 that it is expanding its ivonescimab development program with a new trial in bladder cancer. According to the company's 8-K filing, this marks the first global registrational clinical trial of ivonescimab in a genitourinary cancer, adding to global Phase III studies already underway in non-small cell lung cancer and colorectal cancer.¹

The new study, HARMONi-GU1, is designed as a randomized Phase II/III clinical study evaluating ivonescimab plus the antibody-drug conjugate enfortumab vedotin compared to pembrolizumab plus enfortumab vedotin as first-line therapy in patients with previously untreated locally advanced or metastatic urothelial carcinoma.¹ The company said the comparator regimen is widely considered the global standard of care.¹

Global clinical trial site activations for HARMONi-GU1 will begin later this year, and the multiregional study intends to enroll approximately 800 patients through Phase III.¹ The Phase II portion will identify the recommended Phase III dose of ivonescimab in combination with enfortumab vedotin, and the Phase III primary endpoints are progression-free survival and overall survival.¹

With this addition, ivonescimab is now being evaluated in a total of 16 Phase III clinical trials across multiple tumor types and settings.¹ The filing notes that of these 16 studies, five are Summit-sponsored global studies, one is a multiregional study sponsored by a cooperative group, and 10 are being or have been conducted in China by Akeso.¹

Separately, the filing reiterates that four Phase III ivonescimab trials, including those sponsored by Akeso in China, have read out to date, all with positive data in non-small cell lung cancer.¹ Ivonescimab remains investigational in Summit's territories, though it was initially approved for marketing in China in May 2024.¹