Summit Therapeutics said updated overall survival data from its global phase III HARMONI trial showed the benefit for ivonescimab plus chemotherapy widened with longer follow-up.
In the April 2025 primary analysis, the combination posted median overall survival of 16.8 months versus 14.0 months for placebo plus chemotherapy, with a hazard ratio of 0.79 and p=0.057. By the June 2026 data cut, the hazard ratio improved to 0.76 with nominal p=0.0151, while the median overall survival figures remained 16.8 months versus 14.0 months.
The western subgroup also improved as follow-up lengthened. At the April 2025 analysis, western patients had a hazard ratio of 0.98, essentially flat versus placebo. By September 2025, that moved to 0.84, and by June 2026 it improved further to 0.76. Median follow-up for western patients increased from 9.2 months at the primary analysis to 23.2 months in the latest update.
In the western subgroup, median overall survival was not reached for ivonescimab plus chemotherapy at the first look, then stood at 17.0 months in September 2025 and 17.5 months in June 2026, versus 14.0 months for placebo plus chemotherapy at the first analysis and 14.0 months again in the later updates.
Summit said the safety profile remained manageable, with no new safety signals in the latest HARMONI data cut.
The company also disclosed detailed overall survival data from HARMONI-2, a China-only phase III study. In that trial, ivonescimab monotherapy produced median overall survival of 30.8 months versus 22.6 months for pembrolizumab, with a hazard ratio of 0.73 and p=0.009. The 24-month overall survival rate was 57.9% versus 48.0%, and the 36-month rate was 45.0% versus 33.1%.
Subgroup results in HARMONI-2 showed a hazard ratio of 0.58 in PD-L1 high patients, 0.65 in squamous histology, 0.79 in non-squamous histology, 0.75 in patients younger than 65, 0.72 in patients 65 and older, 0.74 in men and 0.69 in women.
Safety in HARMONI-2 also held up with longer treatment exposure. Serious treatment-related adverse events were reported in 29.9% of ivonescimab patients versus 21.6% of pembrolizumab patients. Treatment-related discontinuations were 4.1% versus 5.0%, and treatment-related deaths were 0.5% versus 1.5%.
Summit said its U.S. filing is based on HARMONI and that the FDA action date is Nov. 14, 2026. The market has reacted to these announcements by moving the company's shares -3.64% to a price of $17.75. For the full picture, make sure to review Summit Therapeutics's 8-K report.
