Tyra Biosciences Inc. experienced a roughly 30% decline in its share price on Wednesday after releasing initial efficacy and safety data from its Phase 2 SURF302 study of dabogratinib in patients with FGFR3-altered low-grade intermediate-risk non-muscle invasive bladder cancer.
The company reported that, for combined single and multiple marker lesion patients receiving 60 mg once-daily dosing, the best overall response measured a 79% overall response rate and a 64% complete response rate. In the subgroup of single marker lesion patients treated with 60 mg once-daily, the best overall response reached a 100% overall response rate and a 75% complete response rate.
The trial had enrolled 44 participants across the 60 mg once-daily and 50 mg once-daily cohorts as of the August 31, 2026 data cutoff. Of those, 26 patients were evaluable for efficacy at that cutoff, with 14 evaluable patients having received 60 mg once-daily and 12 having received 50 mg once-daily.
On safety, Tyra reported Grade 3 treatment-emergent adverse events in 14% of participants treated at 60 mg once-daily and in 9% of participants treated at 50 mg once-daily. Across both cohorts, Grade 3 treatment-related adverse events occurred in 4.5% of participants, with none reported at the 60 mg once-daily dose level. No Grade 4 or Grade 5 treatment-emergent adverse events were recorded. The company also stated that at the 60 mg once-daily dose there were no dose reductions or treatment-related discontinuations.
The most commonly reported treatment-emergent adverse events at the 60 mg once-daily dose were fatigue, diarrhea and dry eye. Tyra noted the absence of clinically significant hyperphosphatemia, nail toxicity or ocular toxicity, and reported that transaminase treatment-emergent adverse events occurred at a frequency below 10%.
Looking ahead, Tyra said it plans to complete enrollment in the 60 mg once-daily cohort and to open a cohort dosed at 70 mg once-daily. The company also intends to engage with health authorities regarding the design of a Phase 3 study and decisions around dose selection.
Separately, in the SURF303 Phase 2 study evaluating dabogratinib in low-grade upper tract urothelial cancer, the company reported that the first patient treated with 60 mg once-daily achieved a complete response at the three-month assessment.
Key points
- Tyra shares fell about 30% on Wednesday following the release of initial Phase 2 SURF302 data for dabogratinib.
- At 60 mg once-daily, combined patients showed a 79% overall response rate and 64% complete response rate; single marker lesion patients had a 100% overall response rate and 75% complete response rate.
- Safety signals included Grade 3 treatment-emergent adverse events in a minority of patients, no Grade 4 or 5 events, and no dose reductions or treatment-related discontinuations at 60 mg once-daily.
Risks and uncertainties
- Stock market reaction - The steep share price decline reflects market sensitivity in biotech and capital markets to clinical readouts.
- Limited evaluable population - Efficacy assessments were based on 26 evaluable patients as of the data cutoff, which may limit the statistical certainty of the reported response rates.
- Dose escalation and regulatory discussions - Future dose selection and Phase 3 design remain contingent on ongoing enrollment, additional safety data and interactions with health authorities.