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Pfizer $PFE announced Monday that its experimental lung cancer drug sigvotatug vedotin failed to extend patient survival in a late-stage clinical trial, falling short of the study's primary endpoint.
Pfizer said the Phase 3 SigVie-002 trial found that patients with locally advanced, unresectable or metastatic non-squamous non-small cell lung cancer who had already undergone one or more prior treatments lived no significantly longer on the drug than those who received docetaxel, a standard chemotherapy. The study enrolled 703 participants.
Pfizer stock fell more than 1% in after-hours trading, according to Reuters.
Despite the result, Pfizer said it remains committed to the drug's development. Among the two-thirds of participants who had undergone just a single prior treatment, survival trends were more favorable, which Pfizer cited as evidence that the drug may retain activity when deployed earlier in the treatment sequence. The trial also found no clear relationship between tumor expression of the drug's target protein, integrin beta-6, and patient response.
"Although the overall study results did not demonstrate superiority over docetaxel, it is encouraging that second-line patients treated with sigvotatug vedotin achieved strong efficacy outcomes compared to an established standard of care," Pfizer Chief Oncology Officer Jeff Legos said in a statement.
The drug came to Pfizer as part of its $43 billion acquisition of Seagen $SGEN, the biotechnology firm it purchased in 2023, according to STAT News. At the time, the acquisition was seen as a way for Pfizer to replenish revenue lost to collapsing COVID-19 product sales and competition from generics, while expanding into antibody-drug conjugates — a class of precision cancer medicines. On an earnings call last year, CEO Albert Bourla told investors the drug had blockbuster potential in the years ahead, according to STAT News.
A separate Phase 3 study is underway that pairs the drug with Merck $MRK's Keytruda for patients who have not yet received prior treatment and whose tumors carry high levels of the immunotherapy-response marker PD-L1, the company said. Pointing to results from earlier-phase work, Pfizer executives argued that the drug's prospects improve when it is paired with immunotherapy agents and administered to patients who have not yet exhausted other options.
The company said integrin beta-6, the protein the drug is designed to attack, is found in roughly nine out of ten non-small cell lung cancer tumors, and patients whose cancer expresses the protein tend to face worse outcomes. Pfizer also said it is developing additional antibody-drug conjugates targeting the same protein with alternate payloads.