Summit Therapeutics reports 25% lower death risk in biliary-cancer trial

Median survival rose to 14.9 months from 12.1 months as Summit Therapeutics Inc. NASDAQSMMT reported on Sunday that ivonescimab plus chemotherapy beat durvalumab plus chemotherapy in a Chinese Phase 3 biliary-cancer trial. The Oct. 25 results quantify a 25 per cent reduction in the risk of death against the active comparator.

The randomized, double-blind HARMONi-GI1 study enrolled 682 patients, assigning 340 to ivonescimab plus chemotherapy and 342 to durvalumab plus chemotherapy. Akeso, Inc. HKG9926 exclusively generated, managed and analysed the data in China, with overall survival as the primary endpoint.

Summit is a Miami-based biotechnology developer with a concentrated cancer-drug pipeline built around a licensed antibody. Its exclusive development and commercialization territories include North America, Europe and Japan, while China remains outside those rights.

A separate U.S. Phase 2/3 trial is expected to begin activating sites in the fourth quarter of 2026, according to Summit's Oct. 21 collaboration announcement. The open-label study will combine each antibody with gemcitabine and cisplatin, using overall survival as its primary endpoint. Summit calls the study registration-enabling; the announcement includes no FDA assessment of its design.

The survival hazard ratio was 0.75, with a 95 per cent confidence interval of 0.61 to 0.92. The one-sided p value was 0.0031 at the prespecified interim analysis, after median follow-up of 14.3 months.

Median progression-free survival reached 8.4 months with ivonescimab versus 5.8 months with durvalumab. Objective response rates were 53.8 per cent and 32.5 per cent, respectively, providing a separate measure of tumour response alongside the survival endpoint.

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Treatment-emergent serious adverse events occurred in 43.4 per cent of ivonescimab patients and 43.7 per cent of controls. Blood-cell toxicities were common, while potentially VEGF-related events included protein in urine, hypertension and bleeding; Summit reported no additional safety signals.

"This is the first known Phase III study in advanced biliary tract cancer to demonstrate overall survival superiority over an anti-PD-(L)1 therapy combined with chemotherapy," Summit president and co-chief executive Maky Zanganeh said in the release.

An Approved Regimen Sets The Comparison

The comparator belongs to AstraZeneca PLC LONAZN NYSEAZN, which announced U.S. approval of durvalumab, sold as Imfinzi, with chemotherapy for advanced biliary tract cancer on Sept. 5, 2022. HARMONi-GI1 therefore tested another immunotherapy combination rather than chemotherapy alone.

China-based partner Akeso had already announced the endpoint win in August. Sunday's disclosure supplies the effect size, but a study conducted exclusively in China does not establish the same outcome in U.S. patients.

Ivonescimab combines PD-1 blockade with VEGF inhibition in a single antibody, bringing immune and blood-vessel pathways into the same experimental treatment. It remains investigational in Summit's territories, including the United States.

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U.S. Trial Sites Are Expected To Activate In The Fourth Quarter

Summit reported US$690.7 million in cash and investments at June 30 in its July 23 financial update. That historical balance provides no current runway estimate for the expanded program.

Summit shares closed at US$15.47 on Nasdaq at 4:00 p.m. EDT on Oct. 23, according to Google Finance NASDAQSMMT. That close preceded Sunday's detailed results.

The next fixed regulatory date is Nov. 14, the FDA action target Summit reported for a separate lung-cancer application. For biliary cancer, fourth-quarter U.S. site activation would begin a separate survival trial against pembrolizumab or durvalumab, each with chemotherapy.