IO Biotech’s off-the-shelf therapeutic cancer vaccine, Cylembio, narrowly missed statistical significance in its Phase 3 melanoma trial when combined with Merck's Keytruda, despite showing a 23% relative risk reduction in progression-free survival. Post-hoc analyses revealed stronger benefits in Keytruda-naïve patients. The company plans to engage the FDA this fall to explore approval pathways based on the totality of data. This development underscores the challenge of advancing cancer vaccines amid competitive immunotherapy landscapes.