Presenting at ECC 2015, Catherine Pietanza outlined data indicating that a delta-like ligand 3 (DLL3)-directed antibody–drug conjugate, rovalpituzumab tesirine (Rova-T), promises to become the first targeted agent for small-cell lung cancer (SCLC)—a disease with a dismal prognosis. In a phase I trial, 73 patients received Rova-T in the second-line or third-line (no agents are approved in the latter setting). The frequency of DLL3 expression was high (>70%), and among 27 DLL3+ patients treated in the expansion cohorts, 44% had a partial response and 34% stable disease. Importantly, in the third-line setting, the response rate was 45% in the DLL3+ patients. Ongoing reponses approaching 1 year have been observed in some patients, which is remarkable.