IO Biotech filed for bankruptcy and ceased operations after what it described as an FDA refusal that derailed its cancer vaccine Cylembio. The Danish biotech’s wind-down follows a Phase 3 miss in unresectable or metastatic melanoma, where Cylembio did not outperform Merck’s Keytruda on progression-free survival. According to the bankruptcy filing, IO Biotech also faced unproductive interactions after FDA requested additional disclosures tied to a December meeting—ultimately leading the company to cut staff and explore new trials, but without recovering a path to approval. The company’s shutdown arrives alongside other biotech exits in the same timeframe, reinforcing how regulatory outcomes can rapidly convert into liquidity crises for early and mid-stage developers with limited runway. For the sector, the closure is a reminder that “borderline” statistical outcomes can still lead to non-approval, especially when subsequent engagement and manufacturing or evidence requirements remain unresolved.