Summit Therapeutics PLC (NASDAQ:SMMT) shares dropped sharply on Monday following the release of mixed results from its Phase III HARMONi trial of ivonescimab, a potential lung cancer therapy.
The stock fell 23.4% to about $20 in the early afternoon.
The trial evaluated ivonescimab, a bispecific antibody targeting PD-1 and VEGF pathways, in combination with platinum-doublet chemotherapy for patients with EGFR-mutated non-small cell lung cancer (NSCLC) who had progressed after third-generation EGFR tyrosine kinase inhibitor therapy.
Data showed that ivonescimab plus chemotherapy provided a consistent improvement in progression-free survival globally.
Patients in China appeared to benefit most, while results in North America and Europe were less pronounced.
The median overall survival for ivonescimab patients was 17 months compared with 14 months for those receiving placebo, but the improvement in Western patients did not meet the statistical threshold for significance, despite a favorable trend with a hazard ratio of 0.78 and a nominal p-value of 0.0332.
Summit highlighted that the longer-term follow-up showed acceptable safety and tolerability, with manageable adverse events.
“The positive results from the HARMONi study underscore the global applicability of ivonescimab and demonstrates the potential benefit ivonescimab has to bring to patients around the world, including the United States,” Summit co-CEO Robert Duggan said in a statement.