IO Biotech shares jump 21.19% intraday after positive Cylembio Phase 3 trial results show improved survival in melanoma.

IO Biotech, Inc. surged 21.19% intraday following the presentation of updated Phase 3 trial results for Cylembio at the Jefferies Global Healthcare Conference on November 18, 2025. The trial demonstrated a 19.4-month median progression-free survival with Cylembio versus 11.0 months with pembrolizumab alone, with no significant added systemic toxicity. The results highlighted a $5.6 billion U.S. market opportunity and plans to align on new Phase 3 designs with the FDA. These developments, underscoring Cylembio’s potential in advanced melanoma treatment and regulatory pathways, drove immediate investor optimism. The second news event, citing financial instability, lacked detailed context and did not contradict the positive price action.