Pfizer has abandoned work on an PD-L1-targeting drug that was being tested in patients with various cancers.
The phase 1 study had been evaluating PF‑08046037—an immunostimulatory drug conjugate (ISAC) with a TLR7 agonist payload—either as a monotherapy or in combination with Pfizer’s investigational PD-1 inhibitor sasanlimab in patients with non-small cell lung cancer, head and neck squamous cell carcinoma, melanoma or pancreatic ductal adenocarcinoma.
The trial kicked off in May 2025, but only eight patients were ever enrolled, according to the federal trials database.
The Big Pharma cited “strategic business reasons” when it confirmed on the database that the study had been terminated. At the time, the company pointed out the decision was not tied to any safety or efficacy concerns.
The end of the trial also marks the end of Pfizer’s plans for PF‑08046037, a spokesperson explained to Fierce. The decision doesn’t have any wider implications on the company’s research into ISACs, they added.
Related
Unlike traditional antibody-drug conjugates, which use a cytotoxic agent as a payload, ISACs use an immunostimulatory payload. In the case of PF‑08046037, the asset was a TLR7 agonist. The hope was that the payload would engage TLR7, a protein found in immune cells, which would in turn activate antigen-presenting cells.
Pfizer’s clinical-stage pipeline doesn’t appear to list any other ISACs, and Fierce has reached out for confirmation on the pharma’s plans in this space.
One company that has been focused on ISACs for some time is Bolt Therapeutics, although that biotech had to halve its workforce last October to fund an ongoing phase 1 study of BDC-4182, an ISAC targeting Claudin 18.2 to treat gastric and gastroesophageal cancers.
