SEZ6 and small cell lung carcinoma: B7 homolog 3 (B7-H3, CD276), uniformly expressed across SCLC subtypes and linked to poor prognosis, is another compelling target: the antibody–drug conjugate ifinatamab deruxtecan achieved a 54.8% response rate and meaningful survival in heavily pretreated patients, earning FDA Breakthrough designation. Together, DLL3- and B7-H3–directed therapies (with additional ADCs against Trop-2 and SEZ6 in development) are redefining second-line and later care.