Pfizer said its first new antibody-drug conjugate following the $43 billion Seagen acquisition, sigvotatug vedotin, failed a Phase 3 trial in non-small cell lung cancer. The readout marks another high-profile ADC disappointment as the modality faces intense scrutiny over target selection, linker-payload performance, and trial design. The result is notable for Pfizer because it represents early post-merger integration outcomes and an important test of the expanded ADC platform portfolio acquired from Seagen. While the company did not provide detailed outcomes in the brief, the failure of a pivotal endpoint in NSCLC typically triggers protocol reassessment and may affect near-term investment priorities. For the industry, the development highlights the ongoing risk in ADC development despite broad pipeline activity and competitive pressure across oncology subtypes.