Sasanlimab

The end of the trial also marks the end of Pfizer’s plans for PF‑08046037.\n Pfizer has abandoned work on a 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. 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.

Pfizer has terminated a Phase I clinical trial evaluating PF-08046037 (also known as SGN-PDL1iT), an immunostimulatory antibody conjugate targeting PD-L1, as monotherapy and in combination with the anti-PD-1 antibody sasanlimab in patients with advanced solid tumors. The NCT06974734 clinical trial terminated after enrolling only eight participants across multiple planned cohorts, according to a ClinicalTrials.gov registry update verified in April 2026. No reason for the termination was disclosed. The open-label, non-randomized Phase I study enrolled adults with advanced or metastatic non-small cell lung cancer, head and neck squamous cell carcinoma, melanoma, or pancreatic ductal adenocarcinoma. The trial followed a sequential design moving through dose escalation, optimization, and expansion phases for both monotherapy and combination arms. Primary endpoints centered on safety — specifically dose-limiting toxicities within the first 21 days and adverse event incidence over the treatment period — with secondary objectives including pharmacokinetic characterization and preliminary efficacy signals such as objective response rate, duration of response, and progression-free survival assessed by RECIST v1.1. According to the ClinicalTrials.gov posting for the trial, the study was terminated “for strategic business reasons” with no safety and/or efficacy concerns cited. There has so far been no further public explanation from Pfizer for the termination. The trial ended within approximately ten months of its May 2026 start date. PF-08046037 entered clinical testing as part of Pfizer’s inherited Seagen pipeline following the company’s USD 43 billion acquisition of Seagen in 2023. The molecule’s alternate name, SGN-PDL1iT, reflects its Seagen origins. The molecule is an immune-stimulating antibody conjugate (ISAC) targeting PD-L1, designed to deliver a TLR7 agonist payload selectively to tumor-associated antigen-presenting cells. Following PD-L1 binding and internalization, the conjugate activates innate immune signaling within endosomes, promoting antigen presentation and reprogramming the tumor microenvironment toward an anti-tumor response. Preclinical studies showed targeted immune activation, reduction of suppressive macrophages, and anti-tumor activity with evidence of immune memory, supporting its rationale prior to program termination. The trial assessed PF-08046037 as monotherapy or in combination with sasanlimab, Pfizer’s subcutaneous anti-PD-1 monoclonal antibody developed under the code PF-06801591. Sasanlimab has its own separate clinical trajectory and recently demonstrated efficacy in a Phase III bladder cancer trial, establishing it as a viable standalone asset. Its pairing with PF-08046037 in this study represented an exploratory combination hypothesis — that innate immune activation via the conjugate might synergize with checkpoint blockade. The termination of NCT06974734 fits a broader pattern within Pfizer’s post-acquisition oncology pipeline. The company has discontinued several early-stage Seagen-derived programs since 2023, including assets in the ADC space where early safety or translational data did not meet internal thresholds. Pfizer is simultaneously executing a cost-reduction program targeting approximately USD 7.2 billion in net savings through 2027, with active rationalization of its research portfolio. Under that framework, early-stage programs without compelling early signals face a higher bar for continuation. The ISAC modality itself remains largely unproven in the clinic. The concept of using a tumor-targeting antibody to deliver a TLR agonist payload selectively to the tumor microenvironment is mechanistically appealing — it aims to convert immunologically cold tumors into inflamed ones without the systemic toxicity associated with systemic TLR agonist administration — but the approach carries inherent risks. Systemic immune activation, cytokine release, and off-tumor payload delivery are recognized liabilities, and the eligibility criteria for this trial reflected awareness of those risks through the exclusion of patients with prior immune-mediated toxicities of grade 3 or higher, active autoimmune disease, or significant pulmonary or neurodegenerative conditions. Pfizer has not indicated whether it intends to out-license PF-08046037 or pursue alternative development pathways for the asset. Your email address will not be published. Required fields are marked * Comment * Name * Email * Website