Tyra's Oral FGFR3 Inhibitor Dabogratinib Hits 100% ORR in Single-Lesion NMIBC, But Phase 2 Data Miss Street Bar
核心洞察
Tyra Biosciences reported initial Phase 2 SURF302 results for oral dabogratinib (搜索) in FGFR3 (搜索)-altered low-grade intermediate-risk non-muscle invasive bladder cancer (搜索), identifying 60 mg once daily as the dose for its planned adjuvant strategy.
In single marker lesion patients (n=8), dabogratinib (搜索) 60 mg QD achieved 100% overall response rate and a 75% best overall complete response rate, while combined single and multiple lesion patients (n=14) showed 79% ORR and 64% CR.
Safety was favorable with no Grade 4 or 5 events, no clinically significant hyperphosphatemia, nail or ocular toxicity, and no dose reductions or treatment-related discontinuations at 60 mg.
Tyra Biosciences on September 9, 2026 reported initial results from SURF302, its Phase 2 study of oral dabogratinib (搜索) in patients with FGFR3 (搜索)-altered low-grade intermediate-risk non-muscle invasive bladder cancer (搜索) (LG IR NMIBC), saying the data provided clinical proof of concept for selective oral FGFR3 inhibition and identified 60 mg once-daily (QD) as the potential dose supporting a planned registrational adjuvant development strategy. The announcement, made as of an August 31, 2026 data cutoff, was accompanied by a sharp market reaction: Tyra shares fell roughly 20% to 22% on the day, trading near $20.95, as the efficacy results landed below the threshold Wall Street analysts had set for the program.
Efficacy in Single Versus Multiple Marker Lesions
Among 26 participants evaluable for efficacy across the 60 mg QD (n=14) and 50 mg QD (n=12) cohorts — defined as those who received study treatment and had undergone at least the month 3 disease assessment — the 60 mg cohort produced a 79% overall response rate (ORR) (11/14) and a 64% best overall response (BOR) complete response (CR) rate (9/14) in combined single and multiple marker lesion patients. The 50 mg cohort showed 67% ORR (8/12) and 33% CR (4/12).
In the single marker lesion subgroup, which Tyra describes as most closely mirroring the adjuvant setting where no tumor is left behind, the 60 mg QD cohort (n=8) achieved 100% ORR (8/8) and a 75% BOR CR rate (6/8), with a 63% CR rate (5/8) at the three-month assessment. Pooled across both doses in single marker lesion patients (n=16), ORR was 94% (15/16) and BOR CR was 56% (9/16).
"Patients with a single marker lesion — whose minimal disease most closely mirrors the adjuvant setting (where no tumor is left behind) and historical marker lesion studies — achieved a 100% overall response rate (ORR) (8/8) with 60 mg QD, including a 75% complete response (CR) rate as best overall response (BOR), demonstrating the activity of this dose for our planned Phase 3 adjuvant study," said Doug Warner, M.D., Chief Medical Officer of Tyra Biosciences.
Durability data showed that all three-month CRs with six-month assessments remained in response at six months (n=5), and the first participant in the study remained in CR at 12 months and continued on study drug at 14 months. Tyra noted that all responses are subject to change with continued treatment and follow-up.
Safety Profile Supports Chronic Dosing
Across the 60 mg QD (n=22) and 50 mg QD (n=22) safety cohorts, most treatment-emergent adverse events (TEAEs) were Grade 1 or 2. Grade 3 TEAEs occurred in 3 participants (14%) at 60 mg and 2 participants (9%) at 50 mg. Grade 3 treatment-related AEs occurred in 2 of 44 participants (4.5%) across both cohorts, both at 50 mg QD, with none at 60 mg QD. No Grade 4 or 5 TEAEs were reported.
At 60 mg QD, there were no dose reductions or treatment-related discontinuations. No clinically significant hyperphosphatemia, nail toxicity, or ocular toxicity was observed, and transaminase TEAEs occurred at low frequency (under 10%). The most frequently reported TEAEs at 60 mg QD were fatigue, diarrhea and dry eye, with diarrhea generally Grade 1, transient and limited. Tyra stated these results are consistent with the potential for chronic once-daily administration.
Exposure-Response Analysis Drives Dose Strategy
Preliminary exposure-response analyses across the 50 mg and 60 mg cohorts showed an ORR of 86% (12/14) among participants with a target steady-state exposure above an AUC threshold of 2500 ng·hr/mL, compared with 58% (7/12) among those below the threshold. The relationship was most apparent among participants with multiple marker lesions, while responses in single marker lesion patients occurred across the observed exposure range — supporting 60 mg QD in the planned adjuvant setting, where disease burden is minimal, and evaluation of a higher dose in the ablative setting.
Tyra plans to complete enrollment in the 60 mg QD cohort and initiate a 70 mg QD cohort to explore dabogratinib (搜索) in the ablative setting. The company also plans to engage health authorities on Phase 3 study design and dose selection and, subject to that feedback, to continue preparations for a planned registrational adjuvant study.
Market Reaction and Competitive Context
The selloff reflected investor disappointment that the 64% complete response rate at 60 mg in single-marker patients missed the 70% benchmark that analysts at Piper Sandler and H.C. Wainwright had identified as the bar for success. The stock had dropped as much as 31.1% to $18.42 in premarket trading before recovering some ground at the open. Piper Sandler has maintained an Overweight rating on Tyra with a $56 price target, projecting the bladder cancer application as a market opportunity exceeding $1 billion.
Company leadership framed the single-marker results as a strong predictor of future success in adjuvant studies, which track patients over years to detect cancer recurrence. "A really high predictor of adjuvant success," CEO Todd Harris said on an investor call, describing how a single lesion disappearing under treatment could serve as a shorter-term proxy for adjuvant efficacy.
Tyra designed dabogratinib (搜索) to be more selective for FGFR3 (搜索) over FGFR1, FGFR2, and FGFR4, aiming to avoid the off-target toxicity associated with Johnson & Johnson's pan-FGFR inhibitor Balversa. In J&J's THOR-2 study of single-marker patients, Balversa achieved a 72% complete response rate at three months, rising to 89% over time, according to Harris, who noted that key opinion leaders had criticized Balversa for toxicity despite its strong efficacy.
Jones Trading analyst Boris Peaker cautioned that while the results do not warrant terminating the program, moving to a 70 mg dose "will come at the cost of additional safety concerns." Some analysts had previously questioned whether an oral medication could deliver sufficient drug concentration to bladder tissue to compete with direct instillation via catheter.
The data lifted shares of UroGen Pharma by 5.6%. UroGen's prescription chemotherapy Zusduri (搜索) is administered directly into the bladder via catheter; it was associated with a 78% remission rate in testing. Johnson & Johnson is also competing in this space with Erda-iDRS (搜索), an investigational drug delivery platform designed to release the kinase inhibitor erdafitinib directly into bladder tissue over a three-month period, and with Inlexzo (搜索), a drug-eluting device. Both Zusduri and Inlexzo require patients to undergo invasive procedures in the urinary tract.
Early SURF303 Signal in Upper Tract Disease
In SURF303, Tyra's Phase 2 study evaluating oral dabogratinib (搜索) in patients with low-grade upper tract urothelial cancer (搜索) (LG UTUC), the first patient treated achieved a complete response at the three-month assessment with 60 mg QD, with no observed TEAEs, and remained on study drug as of the August 31, 2026 data cutoff. Tyra cautioned that early clinical observations from SURF303, including those from an individual participant, may not be predictive of future results.
Unmet Need in Intermediate-Risk NMIBC
Bladder cancer is one of the most common cancers in the United States, with more than 760,000 people living with the disease. IR NMIBC is characterized by frequent tumor recurrence that often requires repeated surveillance and surgical intervention over many years. Current treatment typically includes transurethral resection of bladder tumor (TURBT) followed by intravesical chemotherapy administered through repeated bladder catheterization. Despite evidence that adjuvant intravesical therapy can reduce recurrence, approximately 70% of patients with LG IR NMIBC do not receive treatment intended to prevent recurrence, with many choosing surveillance, or "watch and wait."
"As a community-based urologist, one of the greatest challenges isn't identifying patients who could benefit from therapy—it's that many choose surveillance because the burden of repeated catheterization and intravesical treatments outweighs the perceived benefit," said Mark Silva, M.D., Greater Boston Urology. "Too often, those patients are simply waiting to recur. A well-tolerated once-daily oral therapy could fundamentally change that conversation."
SURF302 (NCT06995677) is a Phase 2, multicenter, open-label study evaluating the efficacy and safety of oral dabogratinib (搜索) in adults with FGFR3 (搜索)-altered low-grade IR NMIBC, with key endpoints including best overall response, complete response at three months, time to recurrence, duration of response, recurrence-free survival, progression-free survival, safety and tolerability.
Dabogratinib (搜索) is Tyra's lead precision medicine candidate from its in-house SNÅP platform and is described as the only investigational oral FGFR3 (搜索)-selective therapy currently in clinical development for patients with FGFR3-altered IR NMIBC. It is in Phase 2 development across three trials: SURF303 in LG UTUC, SURF302 in IR NMIBC and BEACH301 in achondroplasia (搜索), and has been studied in more than 200 individuals to date. The FDA has granted Orphan Drug Designation and Rare Pediatric Disease Designation to oral dabogratinib for the treatment of achondroplasia.
Tyra now faces a pivotal stretch as it works to complete the 60 mg cohort and generate data from the 70 mg arm, with the goal of initiating a registrational study next year. The outcome of that higher-dose evaluation will likely determine whether the company can restore investor confidence in dabogratinib (搜索)'s commercial prospects.