Shares of enGene Holdings cratered after updated trial data for its bladder cancer therapy detalimogene showed declining complete response (CR) rates. The investigational treatment, formerly known as EG-70, is being evaluated in patients with high-risk, BCG-unresponsive non-muscle invasive bladder cancer.
As of an April 21 data cutoff, 67 of 124 evaluable patients achieved a 54% CR at any time, which fell to 43% (52 of 121 evaluable patients) at six months. This compares unfavorably with earlier results announced in November 2025, when the first 62 patients assessed showed a 63% CR at any time and a 62% CR at six months.
The drop in durability raises questions about the therapy's long-term efficacy. While the initial cohort suggested robust and sustained responses, the expanded dataset reveals a significant falloff, with the six-month CR rate declining by nearly 20 percentage points.
enGene is now under pressure to explain the discrepancy and outline next steps for detalimogene's regulatory path. The company had previously positioned the therapy as a potential leader in the bladder cancer space, but the latest numbers may force a reassessment of its commercial prospects.
Investors reacted sharply: shares plummeted in the wake of the announcement. The stock's decline reflects growing caution around the asset's risk profile, particularly as competing therapies continue to advance.