Pfizer Discontinues Early-Stage STING Trial in Pipeline Restructuring

Pharmaceutical giant Pfizer has terminated a Phase I trial of its investigational STING therapy for advanced solid tumors, marking another step in the company's ongoing efforts to streamline its pipeline and refine its business strategy.

STING Trial Termination

Pfizer's decision to discontinue the trial of PF-07820435, an orally available agonist of the STING (stimulator of interferon genes) protein, was revealed in an update to the study's clinicaltrials.gov page on Thursday. The company cited "strategic business reasons" for the termination, emphasizing that the decision was not based on any safety or efficacy concerns.

The Phase I trial, which began in February 2024, was designed to evaluate PF-07820435 both as a monotherapy and in combination with the PD-1 inhibitor sasanlimab. The study aimed to establish the safety profile of PF-07820435, detect early efficacy signals, and determine the recommended dose for future studies in patients with confirmed diagnoses of solid tumors.

STING agonists, such as PF-07820435, work by activating the STING pathway, which plays a crucial role in anti-cancer immune responses by triggering type I interferons and other inflammatory mediators. Despite the trial's termination, PF-07820435 currently remains listed on Pfizer's pipeline page.

Broader Pipeline Restructuring

The discontinuation of the STING trial is part of a larger trend of pipeline pruning at Pfizer. In recent months, the company has made several significant decisions to reshape its drug development portfolio:

1. In December 2024, Pfizer ended its partnership with Sangamo Therapeutics, abandoning the development of giroctocogene fitelparvovec, a gene therapy candidate for hemophilia A. This decision came despite promising Phase III data showing that 84% of treated patients maintained factor VIII activity above 5%.

2. Last month, Pfizer announced the global withdrawal of Beqvez, its hemophilia B gene therapy. The company attributed this decision to limited interest from patients and healthcare providers in hemophilia gene therapies.

3. In September 2024, Pfizer withdrew Oxbryta, an oral hemoglobin S polymerization inhibitor approved in 2019 for sickle cell disease. This withdrawal followed reports linking the drug to a higher incidence of complications and mortality.

These strategic moves reflect Pfizer's ongoing efforts to optimize its research and development focus, allocating resources to areas with the highest potential for success and market impact. As the pharmaceutical landscape continues to evolve, industry observers will be watching closely to see how Pfizer's pipeline restructuring impacts its future drug development efforts and market position.