Pfizer’s “golden egg” has hatched. The subcutaneous PD-1 inhibitor improved outcomes when added to the standard of care in bladder cancer, positioning the Big Pharma to file for approval of an antibody that could advance the field for the first time in decades.
The phase 3 trial enrolled people with high-risk, non-muscle invasive bladder cancer (NMIBC) who were yet to try Bacillus Calmette-Guérin (BCG), an immunotherapy that has been the standard of care for years. Merck & Co. won FDA approval for Keytruda in NMIBC in 2020, but the authorization limited use to patients who are unresponsive to BCG.
Pfizer’s phase 3 trial assessed the effect of giving a PD-1 inhibitor, sasanlimab, in combination with BCG as a first-line treatment. All patients in the two arms included in the primary analysis later received BCG as a maintenance therapy. A third cohort had no maintenance period and was used in secondary endpoints.
Event-free survival was longer in patients who received sasanlimab than their peers who only took BCG, causing the study to hit its primary endpoint. Pfizer is yet to share the numbers but the long wait for an improvement in the setting, which Pfizer Chief Oncology Officer Roger Dansey, M.D., put at 30 years in a statement, means any advance over BCG is notable.
Pfizer plans to share the results at an upcoming medical congress. Areas of interest beyond the primary analysis include safety, which Pfizer has so far only said was generally consistent with existing data, and key secondary endpoints. One secondary measure is comparing sasanlimab without BCG maintenance to the control arm. A long-running BCG shortage means there are benefits to reducing use of the drug.
The Big Pharma plans to discuss the data with regulators to support potential filings for approval. The antibody would become the first PD-1 drug approved in the indication. Pfizer believes sasanlimab has an edge even if competition arrives later, in part because the antibody is a simpler, lower-volume injection than other subcutaneous checkpoint inhibitors.
Other trials are testing sasanlimab in combination with antibody-drug conjugates (ADCs). That use case led Dansey to coin the term “golden egg” to describe sasanlimab. The former Seagen exec bestowed the moniker on the antibody at Pfizer’s oncology innovation day last year, telling analysts: “I'd like to grab it and use it because it's well configured, it's a real PD-1 inhibitor and it's an obvious partner for the ADCs.”
The antibody could play a role in phase 1 studies to assess whether ADCs combine well with checkpoint inhibitors, freeing Pfizer from the complexity of using other companies’ drugs in signal-finding trials. As an ADC moves deeper into the clinic, Pfizer could decide whether to continue using sasanlimab in the combination or switch to the rival PD-1 drug that is the standard of care in that indication.