Pfizer’s PD-1 Inhibitor Shows Mixed Results in Bladder Cancer Trial

Pfizer has announced detailed results from its Phase 3 trial evaluating sasanlimab, a subcutaneous PD-1 inhibitor, in combination with Bacillus Calmette-Guérin (BCG) as a first-line treatment for high-risk, non-muscle invasive bladder cancer. The data, presented at the 2025 American Urological Association Annual Meeting, revealed a 32% reduction in the risk of disease-related events. However, the study did not meet all its secondary objectives and showed an increased rate of serious adverse events in the sasanlimab treatment arm.
The primary endpoint of event-free survival (EFS), defined by recurrence of high-grade disease, progression, persistence of carcinoma in situ, or death from any cause, favored the sasanlimab plus BCG induction and maintenance regimen. At 36 months, 82.1% of patients receiving the combination were free from events compared to 74.8% in the control cohort.

Despite achieving the primary EFS endpoint, other findings tempered the overall outcome. In a third cohort where patients received sasanlimab and BCG induction but no maintenance doses, event-free survival outcomes were not superior to the standard of care. This result indicated the necessity of maintaining BCG as a part of the regimen if sasanlimab is incorporated into treatment protocols.
Key secondary endpoints revealed further limitations. Specifically, sasanlimab did not improve overall survival (OS) compared to the standard treatment. These results were collected after a median follow-up period of 40.9 months, with final analysis still pending.
The safety profile of sasanlimab in combination with BCG was reported as generally consistent with previous data. Nonetheless, a notable difference was seen in the incidence of serious treatment-related adverse events. The rate was 17.7% in the sasanlimab plus BCG induction and maintenance group, compared to 1.4% in the control group. Hepatitis and pancreatitis emerged as the most common grade 3 or 4 immune-mediated adverse events among patients treated with sasanlimab, although most cases were managed effectively with thyroid hormone supplementation.

Pfizer has submitted the trial results to health authorities to support potential regulatory filings. If approved, sasanlimab could become the first PD-1 inhibitor authorized for first-line treatment of high-risk, non-muscle invasive bladder cancer. Currently, Merck & Co.’s Keytruda holds approval only for patients unresponsive to BCG. Regulatory approval of sasanlimab could also facilitate Pfizer’s broader plans to integrate the drug with its antibody-drug conjugate therapies.