Pfizer was studying PF-07820435, an orally available agonist of the STING protein, for solid tumors.
Pfizer has terminated a Phase I trial of its investigational STING therapy in advanced solid tumors, according to an update to the study’s clinicaltrials.gov page on Thursday.
The move to discontinue the trial of PF-07820435 was based on “strategic business reasons,” according to the webpage. “The decision was not based on any safety and/or efficacy concerns.”
BioSpace has reached out to Pfizer to confirm the discontinuation and will update this space accordingly.
The Phase I trial was testing PF-07820435, with or without the PD-1 inhibitor sasanlimab, in nine patients with confirmed diagnoses of solid tumors. The main objective of the study was to establish the safety of PF-07820435 and detect early signals of efficacy, as well as determine the drug’s recommended dose for further studies. The study was initiated in February last year.
STING, which stands for “stimulator interferon genes,” is a protein that plays a central role in a patient’s anti-cancer immune response by activating type I interferons and other inflammatory players. An orally available drug, PF-07820435 belongs to a class of drugs called STING agonists, which work by triggering the STING pathway and promoting immune activity against cancer cells.
As of this writing, PF-07820435 remains on the pharma’s pipeline page.
If Pfizer does eventually decide to completely drop PF-07820435, it will be the latest casualty in the pharma’s push to trim its pipeline and refine its business strategy.
In December 2024, Pfizer turned its back on Sangamo Therapeutics and its gene therapy candidate giroctocogene fitelparvovec, which the companies were previously developing for hemophilia A. Phase III data released in July 2024 showed that 84% of patients treated with giroctocogene fitelparvovec maintained factor VIII activity above 5%, and majority achieved factor VIII levels greater than 15% of normal.
Pfizer and Sangamo were supposed to file a Biologics License Application for giroctocogene fitelparvovec this year. The termination of the companies’ partnership will take effect on April 21, after which the pharma will transition the hemophilia A program back to Sangamo.
Last month, Pfizer announced it was pulling its hemophilia B gene therapy Beqvez from markets worldwide—a decision the company pinned on “the limited interest patients and their doctors have demonstrated in hemophilia gene therapies.”
Pfizer, in September 2024, likewise withdrew Oxbryta, an oral hemoglobin S polymerization inhibitor that won the FDA’s approval in 2019 for sickle cell disease. The drug has since been linked to a higher occurrence of complications and death.
