Pfizer's Seagen-Acquired ADC Sigvotatug Vedotin Fails Phase 3 Lung Cancer Trial
On June 22, 2026, Pfizer announced that its investigational antibody-drug conjugate (ADC), sigvotatug vedotin, failed to meet its primary endpoint of overall survival (OS) in the Phase 3 SigVie-002 study (previously SigVie-002 or SGNB6A-002). The trial evaluated the therapy against the standard chemotherapy docetaxel in patients with previously treated metastatic non-squamous non-small cell lung cancer (NSCLC).
Sigvotatug vedotin is a potential first-in-class ADC targeting integrin beta-6, a protein highly expressed on approximately 90% of non-squamous NSCLC tumors. It was a key clinical asset acquired in Pfizer’s massive $43 billion acquisition of ADC pioneer Seagen. The Phase 3 failure represents a significant commercial setback for Pfizer’s post-Seagen oncology growth strategy. Pfizer has already recorded roughly $4.5 billion in write-offs and impairment charges related to Seagen-acquired assets due to development delays, competitive pressures, and lowered commercial expectations, and this failure could trigger further impairments.
Despite missing the primary OS endpoint across the overall trial population, Pfizer reported a "stronger trend" on survival and tumor progression in a subgroup of patients who had previously received only one line of therapy. Pfizer remains optimistic about sigvotatug vedotin's clinical future, pointing to an ongoing first-line NSCLC trial evaluating the ADC in combination with Merck's Keytruda (pembrolizumab), with results expected in 2027.
Verbatim Quotes
- BioPharma Dive: "The readout represents a notable setback for a drug involved in Pfizer’s $43 billion buyout of ADC specialist Seagen. Pfizer has been looking to oncology, and the ADCs it inherited in that deal, as an important source of revenue growth in the years ahead."
- Jeff Legos, Chief Oncology Officer at Pfizer (via BioPharma Dive): In its statement, Pfizer pointed to a “stronger trend” on survival as well as tumor progression in patients who’d previously received only one line of treatment, as opposed to more than one. That apparent benefit “reinforces our confidence” in the sigvotatug vedotin’s potential, including its prospects in that all-important study in first-line lung cancer, said Chief Oncology Officer Jeff Legos, in the statement.