Pfizer Halts Development of $1.1B-Licensed ADC SGN-MesoC2 from Harbour BioMed

Jul 16, 2026 18:21 CST Updated 18:21

Harbour BioMed

Antibody Drug Developer

Seagen

Monoclonal Antibody Developer

Innovent

High-end Biologics Developer

PfizerAnother ADC project has been terminated.

Recently,A Pfizer spokesperson told the industry media “BioSpace》：“For commercial considerations, the companyDevelopment of SGN-MesoC2 (aSolid Tumor ADCs）。”

According to ClinicalTrials.gov,As early as January this yearPhase I Clinical Study of SGN-MesoC2patient recruitment has already been halted. ThisResearch and DevelopmentInitiated in 2024, the study originally planned to enroll approximately 365 subjects, but actually enrolled only 19.

SGN-MesoC2 is an antibody-drug conjugate (ADC) targeting human mesothelin (MSLN), composed of a fully human IgG1 monoclonal antibody linked to a potent camptothecin-based TOP1 inhibitor payload via a protease-cleavable linker, with an average drug-to-antibody ratio (DAR) of 8.

This drug is not originally developed by Pfizer; its original code was HBM9033, initially byDeveloped by Harbour BioMed's wholly-owned subsidiary, Nona Biosciences.

December 2023, PfizerWith a total transaction value of $1.13 billion ($53 million upfront payment + $1.05 billion in milestones)Acquire global rights to the drug.

At the 2025 AACR Annual Meeting, Pfizer presented preclinical data for SGN-MesoC2: in vivo study results demonstrated that the drug outperformed DM4-based anti-MSLN benchmark ADCs across a range of tumor cell lines and patient-derived xenograft models, including ovarian cancer, lung cancer, and colorectal cancer.

As of the cutoff date, Pfizer has not released complete efficacy, safety, or pharmacokinetic data for these 19 subjects. What is certain is that thisThe study termination was unrelated to drug safety.

It is worth noting that the current project adjustment coincides withAfter the Phase III clinical trial failure of sigvotatug vedotin.This is the first novel ADC drug to report key data since Pfizer’s $43 billion acquisition of Seagen, carrying broad market expectations.

HoweverResultsDisappointing.In previously treated patients with non-squamous non-small cell lung cancer, the drug failed to significantly improve overall survival and did not meet the primary endpoint.

This is not the first setback for Pfizer’s Seagen assets. Since the acquisition was completed,Pfizer has successively terminated its B7-H4 ADC program, as well as two early-stage ADC trials: PF-08046031 and PF-08046037.

In contrast, ahead of this year’s ASCO meeting, Pfizer announced a collaboration with Innovent valued at up to $10.5 billion,The portfolio covers multiple ADCs with novel, differentiated payloads.

Jeff Legos, Chief Oncology Officer at Pfizer, clearly stated that the collaboration with Innovent is designed to complement Seagen’s existing product portfolio.

This means that the value of SGN-MesoC2 will also be reassessed in the new round of internal review, which may have nothing to do with product quality. As a Pfizer spokesperson stated, "for commercial considerations."

References:

1.https://www.biospace.com/drug-development/pfizer-scraps-seagen-developed-adc-for-solid-tumors

2.https://clinicaltrials.gov/study/NCT06466187?tab=results

3. Other Publicly Available Information

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