Tyra shares slide after bladder-cancer drug misses investor efficacy bar

Tyra Biosciences shares fell sharply—roughly 30% in premarket trading and about 18% by the close—after initial Phase 2 SURF302 data for oral dabogratinib disappointed investors.

At the 60 mg once-daily dose, dabogratinib produced a 79% overall response rate and a 64% best overall complete-response rate among 14 evaluable patients. Investors had reportedly been looking for a complete-response rate of around 70% or higher.

Results were stronger in patients with a single marker lesion:
a 100% overall response rate and 75% complete-response rate at 60 mg, although this was based on only eight patients.

The 50 mg cohort performed less well, with a 67% overall response rate and a 33% complete-response rate among 12 patients.

Safety appeared manageable:
no Grade 4 or 5 treatment-emergent adverse events were reported, and there were no dose reductions or treatment-related discontinuations in the 60 mg group. Common side effects included fatigue, diarrhea and dry eye.

Tyra plans to advance the 60 mg dose toward a registrational study and may explore a 70 mg dose, but investors are now reassessing the drug’s regulatory and commercial prospects because the headline response rate missed the expected benchmark.