Melanoma vaccine combination shows numerical benefit but misses primary endpoint, shares plummet 34%

IO Biotech’s Phase 3 trial evaluating its IO102/IO103 therapeutic cancer vaccine (Cylembio) combined with Keytruda in advanced melanoma narrowly missed its primary endpoint of progression-free survival.

While the vaccine combination showed numerical improvement over Keytruda monotherapy, the results did not achieve statistical significance, leading to a 34% stock price decline following the announcement.

Mixed Results: The “almost but not quite” outcome presents challenges for IO Biotech’s development path. Although signals of efficacy were observed, the failure to reach statistical significance introduces uncertainty about regulatory approval prospects and future development strategy.

The company may pursue subset analyses or additional data to identify patient populations most likely to benefit from the vaccine approach. However, investor sentiment has been significantly impacted by the primary endpoint miss.