Pfizer has linked its PD-1 inhibitor to a 32% reduction in the risk of disease-related events in a phase 3 bladder cancer trial. But the study fell short of a clean sweep of positive outcomes, with the Big Pharma finding no effect on overall survival (OS) and seeing a higher rate of serious adverse events in the PD-1 arm.
The New York drugmaker reported the headline findings from the trial in January. Back then, Pfizer said giving its subcutaneous PD-1 inhibitor sasanlimab and Bacillus Calmette-Guérin (BCG) as a first-line treatment for high-risk, non-muscle invasive bladder cancer increased event-free survival (EFS). BCG has been the standard of care in the indication for decades.
Saturday, April 26 Pfizer shared a closer look at the results. The EFS primary endpoint looked at recurrence of high-grade disease, progression of disease, persistence of carcinoma in situ or death due to any cause. The probability of being free from any of those events at 36 months was 82.1% in patients who received sasanlimab plus induction and maintenance doses of BCG, compared to 74.8% in the control cohort.
The success of the primary EFS endpoint was, however, offset by failures elsewhere. A third cohort of patients took sasanlimab and BCG induction. However, Pfizer found removing the BCG maintenance doses negatively affected outcomes. EFS in the third cohort was no better than in the standard-of-care arm, showing that BCG maintenance will remain a part of the regimen, even if sasanlimab becomes an established therapy.
Another key secondary endpoint found OS was no better on sasanlimab than the standard of care. Pfizer reported the survival data after a median follow-up of 40.9 months and is continuing to track the outcome through the final analysis of the trial.
The company said the overall safety profile of sasanlimab plus BCG was generally consistent with existing evidence on the two treatments. Researchers shared details of the data at the 2025 American Urological Association Annual Meeting Saturday. The rate of serious treatment-related adverse events was 17.7% in the sasanlimab plus BCG induction and maintenance arm, versus just 1.4% in the control group.
Hepatitis and pancreatitis were the most common grade 3 or 4 immune-mediated adverse events in the two arms that received sasanlimab. Most of the cases resolved with thyroid hormone supplementation.
Pfizer has shared the results with health authorities to support potential regulatory filings. Sasanlimab could become the first PD-1 drug approved in the indication. Merck & Co.’s oncology blockbuster Keytruda is approved for use in people who are unresponsive to BCG. Winning approval could further Pfizer’s plans to use sasanlimab in combination with its antibody-drug conjugates.