IO Biotech announced clinical improvement in progression-free survival (PFS) in its pivotal Phase 3 trial of the cancer vaccine Cylembio® combined with Merck's KEYTRUDA® (Pembrolizumab) for first-line treatment of advanced melanoma. Despite demonstrating a median PFS of 19.4 months and positive results in PD-L1-negative patients, the trial narrowly missed achieving statistical significance on its primary endpoint. The company emphasized the favorable safety profile and the magnitude of clinical benefit observed. Following the trial results, IO Biotech's stock experienced notable volatility, initially rising by 60% before fluctuating. The company plans to pursue FDA approval, with discussions expected later this year, focusing on overall survival (OS) data for a broader label or a PD-L1-negative biomarker pathway for a narrower indication. Market analysts acknowledge the setback but see a path forward for the skin cancer vaccine. Additionally, prediction markets have reflected interest in new drug approvals, accurately anticipating outcomes despite some market fluctuations.