IO Biotech’s therapeutic cancer vaccine Cylembio combined with Merck’s Keytruda failed to meet the primary endpoint in a pivotal Phase 3 trial for unresectable or metastatic melanoma, narrowly missing statistical significance (P=0.056). Despite this, progression-free survival was improved, with median PFS of 19.4 months versus 11 months for Keytruda alone. Post-hoc analyses suggest stronger benefits in select subgroups, including patients without prior immunotherapy. IO Biotech intends to engage the FDA this fall to discuss a potential approval path based on totality of data.