Pfizer (NYSE: PFE), through its wholly owned subsidiary Seagen, has discontinued clinical development of PF-08052666 (SGN-MesoC2, HBM9033), a mesothelin (MSLN)-targeted antibody-drug conjugate (ADC), according to an update posted on ClinicalTrials.gov. The Phase I SGN-MesoC2 trial had been evaluating the candidate in patients with advanced non-small cell lung cancer, platinum-resistant ovarian cancer, pancreatic adenocarcinoma, colorectal cancer, mesothelioma and endometrial cancer. The company said the decision reflected strategic portfolio prioritization rather than safety concerns, with the company confirming the molecule has been discontinued, as reported by BioSpace.
The Phase I study enrolled patients with advanced mesothelin-expressing solid tumors to evaluate safety, pharmacokinetics and preliminary antitumor activity. According to ClinicalTrials.gov, 19 patients were enrolled before the trial was terminated.
The discontinuation continues Pfizer's post-Seagen portfolio optimization as the company concentrates resources on selected oncology assets following its USD 43 billion acquisition of the ADC specialist. While PF-08052666 was an early-stage program, it represented one of several Seagen-discovered ADCs inherited through the acquisition.
PF-08052666 combined a mesothelin-targeting antibody with a topoisomerase 1 inhibitor payload delivered via a cleavable linker, placing it in the same broad payload class as approved agents such as trastuzumab deruxtecan and sacituzumab govitecan. NCT06466187 was the drug's only registered clinical trial, and no other studies of PF-08052666 are listed on ClinicalTrials.gov.