Despite falling short of analyst expectations, Tyra Biosciences is taking its cancer drug to registrational development for non-muscle invasive bladder cancer.
Response rates for Tyra Biosciences’ investigational bladder cancer pill came in below investor expectations, dragging the biotech’s shares down nearly 18%.
Tyra is testing the drug candidate, dubbed dabogratinib, in the Phase 2 SURF302 study, focusing on patients with low-grade intermediate-risk non-muscle invasive bladder cancer. Initial results, presented Wednesday, showed that eight of 14 patients had no detectable signs of cancer at the three-month assessment, yielding a complete response (CR) rate of 57%. This was the primary goal of the study.
Meanwhile, overall response rate was 79%, while partial response was 21%.
Dabogratinib’s 57% CR came below analyst expectations. William Blair, for instance, had been anticipating CR rates between 70% to 80%. Investors appear to have also been looking forward to stronger results: shares of the California company dropped 17.66% to $22.01 at market close Wednesday.
As for safety, Tyra documented two patients who developed grade 3 treatment-related adverse events, resulting in a 9% incidence rate. There were no grade 4 or 5 events reported. William Blair called dabogratinib’s safety profile “highly favorable,” contending that it “continues to support the core differentiation thesis” for the asset.
Despite the underwhelming readout, Tyra has decided to push dabogratinib into registrational development—a move that William Blair is supportive of.
“We continue to believe the dataset supports advancement into adjuvant Phase 3 development and preserves a viable path to generating clinically meaningful disease-free survival benefit,” the firm said in a Wednesday note, however conceding that SURF302’s readout was “more nuanced than anticipated” and will “likely require investors to recalibrate expectations.”
In particular, the analysts pointed out that response rates to dabogratinib “appeared heavily influenced by residual marker lesion burden,” or how much cancer is left behind after initial treatment. Indeed, CR increased to 63% in patients with single marker lesions—a residual burden that according to Tyra Chief Medical Officer Doug Warner “most closely mirrors the adjuvant setting,” where no tumor remains. The biotech plans to design dabogratinib’s late-stage program in the adjuvant setting.
Taken orally, dabogratinib is a precision medicine that targets and inhibits the FGFR3 protein, which plays a crucial role in regulating cell development, growth and division. Unlike currently available FGFR3 inhibitors, dabogratinib is designed to address emerging treatment resistance and to be more selective for FGFR3 than other forms of the FGFR protein, in turn limiting off-target effects, Tyra claims on its website.
Aside from non-muscle invasive bladder cancer, the company is also studying dabogratinib for low-grade upper tract urothelial cancer, for which the Phase 2 SURF303 trial is ongoing. The first patient dosed in the study showed a complete response at three months, Tyra said on Wednesday.
Dabogratinib is also being tested for skeletal dysplasias, including achondroplasia.
