Pfizer is discontinuing the development of an antibody-drug conjugate designed to treat advanced solid tumors, terminating a Phase 1 trial evaluating the drug coded SGN-MesoC2, according to a company spokesperson on July 15.
“We are no longer developing SGN-MesoC2 and the decision was due to business reasons, reflecting a strategic prioritization of resources toward programs we believe will deliver the greatest impact for patients,” a Pfizer spokesperson told BioSpace via email.
The open-label trial, which began in 2024, had enrolled 19 patients as listed on ClinicalTrials.gov. The study's discontinuation was not related to safety concerns. SGN-MesoC2—also known as PF-08052666 or HBM9033—was initially developed by Harbour BioMed (Nona Biosciences) and later licensed to Pfizer for $53 million in upfront and near-term payments at the end of 2023. This licensing occurred shortly after Pfizer completed its $43 billion acquisition of Seagen. The mesothelin-targeted ADC’s clinical trial was conducted by Seagen under Pfizer’s ownership.
As of publication, Pfizer has not responded to inquiries regarding possible workforce changes resulting from this pipeline adjustment.
The discontinuation comes after disappointing results from another Seagen-developed investigational ADC, sigvotatug vedotin, which failed to improve overall survival compared with chemotherapy in a Phase 3 study involving advanced non-squamous non-small cell lung cancer. Despite these results, Pfizer said it would continue testing sigvotatug vedotin in this indication and other solid tumors.
At that time, Leerink Partners said sigvotatug vedotin showed “promising” signals of efficacy in a subgroup of patients who had undergone only one prior line of treatment, and stated they believe the drug “still has a chance to succeed” when combined with Merck’s PD-1 inhibitor Keytruda as a first-line option for non-small cell lung cancer.
