MSD has voluntarily withdrawn its US accelerated approval application for ifinatamab deruxtecan, a B7-H3-targeted antibody-drug conjugate (ADC), in extensive-stage small cell lung cancer (SCLC) progressing during or after platinum-based chemotherapy, after local regulators indicated that the supporting data, including the Phase II IDeate-Lung01 study, did not support accelerated approval.

Ifinatamab deruxtecan showed a confirmed objective response rate (ORR) of 48.2%, median duration of response (DOR) of 5.3 months, median progression-free survival (PFS) of 4.9 months and median overall survival (OS) of 10.3 months, but treatment-related interstitial lung disease or pneumonitis occurred in 12.4% of patients including two grade 5 events. The registrational Phase III IDeate-Lung02 study against physician's choice chemotherapy in second-line ES-SCLC continues to recruit.

The withdrawal reshuffles the competitive order in B7-H3 ADC development. Hansoh Pharma's risvutatug rezetecan and MediLink Therapeutics' tambotatug pelitecan have both completed Phase III studies in SCLC and filed for approval in China, with Hansoh's ARTEMIS-008 showing overall survival of 18.5 months versus 10.5 months for topotecan, hazard ratio 0.46, and MediLink's TAISHAN-302 showing 13.3 months versus 9.4 months, hazard ratio 0.46.