On September 30, 2025, IO Biotech announced that the U.S. Food and Drug Administration, following a pre‑BLA meeting, advised the company not to submit a Biologics License Application for its lead vaccine, Cylembio, based on data from the Phase 3 IOB‑013 trial.
The FDA’s recommendation came after the IOB‑013 study showed that Cylembio plus pembrolizumab improved progression‑free survival but narrowly missed statistical significance. The agency’s guidance indicates that the current data set is insufficient for a registrational filing and that a new study design will be required.
In response, IO Biotech said it will continue dialogue with the FDA to align on a potential new registrational study and will also discuss the IOB‑013 data with European regulators to determine a path to submission in the EU. The company is implementing a capital‑conservation plan, including a non‑recurring restructuring charge of $1.0‑$1.5 million in Q3 2025 and a 50% reduction in full‑time employees, to extend its runway into the first quarter of 2026.
This regulatory update is material because it alters the company’s product development timeline, may delay market entry for Cylembio, and impacts the company’s ability to secure additional funding. Investors will closely monitor the company’s next steps and the outcome of the proposed new study design.
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