IO Biotech's pivotal Phase 3 trial of its cancer vaccine Cylembio in combination with Merck's pembrolizumab (KEYTRUDA) demonstrated a significant median progression-free survival benefit of over 8 months in patients with advanced melanoma, but narrowly missed statistical significance for the primary endpoint. The results triggered a sharp 34.25% decline in the company's stock price to $1.19 on Monday, August 10, 2025.
The Phase 3 trial (IOB-013/KN-D18; NCT05155254) evaluated Cylembio in combination with pembrolizumab versus pembrolizumab alone as a first-line treatment for unresectable or metastatic melanoma. Despite the mixed outcome, CEO Mai-Britt Zocca characterized the miss as being "by a hair," suggesting the results were very close to reaching statistical significance.
Market Response and Trading Activity
IO Biotech shares opened at $1.88 and traded in a range between $1.18 and $2.04, with trading volume surging to 70.37 million shares—significantly above the average of 0.32 million shares on the Nasdaq. The company's 52-week trading range spans from $0.66 to $2.48.
Analyst Maintains Optimistic Outlook
Despite the primary endpoint miss, H.C. Wainwright analyst Emily Bodnar has maintained a Buy rating for IO Biotech with a $14.00 price target. Bodnar cited the significant median progression-free survival benefit of over 8 months with a comparable safety profile as key factors supporting her positive outlook. She views these clinical outcomes and the company's regulatory engagement plans as important drivers for the stock.
FDA Engagement Strategy
IO Biotech is planning strategic discussions with the U.S. FDA this fall to review the complete data package from the trial. This regulatory engagement could potentially lead to further discussions about approval pathways despite the narrow miss on the primary endpoint.
Institutional Activity and Market Sentiment
Recent institutional trading activity shows mixed sentiment, with 5 institutional investors adding shares while 13 decreased their positions in the most recent quarter. Notable moves included Citadel Advisors LLC removing 224,949 shares (83.2% reduction) and Bridgeway Capital Management reducing their position by 99,000 shares (56.9% decrease).
The company is scheduled to hold a conference call and webcast on Monday, August 11, 2025, at 8:30 AM ET to discuss the topline results from the Phase 3 trial in detail.
