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.