Relapsed small-cell lung cancer may soon gain a new standard after a Phase 3 program reported survival benefit for an investigational B7-H3 antibody-drug conjugate. The randomized data, presented at IASLC 2026, showed a 54% reduction in risk of death versus the control approach in patients whose disease progressed after platinum-based chemotherapy. B7-H3 (CD276) is broadly expressed in small-cell lung cancer, and ADCs are designed to combine targeted delivery with cytotoxic payload effects. The reported magnitude of benefit raises the bar for subsequent-line options in a setting where standard second-line therapies have historically delivered limited control. While full trial details were not included in the supplied brief, the headline result adds a late-stage catalyst for ADC developers targeting immuno-oncology checkpoints in SCLC and sets up what to watch next: durability, safety profile, and subgroup outcomes as additional conference materials and publications emerge.