Long-term survival is quite uncommon in refractory small cell lung cancer (SCLC) patients, with less than 25% of patients with limited-stage disease and 1%–2% of patients with extensive-stage disease remaining alive at five years. Recent clinical studies have demonstrated the promising efficacy of amrubicin for patients with relapsed SCLC. This review presents the results of clinical studies showing the efficacy and safety of amrubicin for the treatment of relapsed SCLC. Amrubicin is a synthetic anthracycline agent with a similar structure to doxorubicin, in which the hydroxyl group at position 9 in amrubicin is replaced by an amino group to enhance efficacy. It is converted to an active metabolite, amrubicinol, which is 5–54 times more active than amrubicin. Amrubicin and amrubicinol are inhibitors of DNA topoisomerase II, exerting their cytotoxic effects by stabilizing a topoisomerase II-mediated cleavable complex. The toxicity of amrubicin is similar to that of doxorubicin, although amrubicin shows almost no cardiotoxicity. In the relevant trials, amrubicin was administered intravenously at a dose of 35–40 mg/m2 on days 1–3 every three weeks. The response rate was 34%–52% and median survival times were 8.1–12.0 months. Common hematologic toxicities included neutropenia, leucopenia, anemia, thrombocytopenia, and febrile neutropenia. Nonhematologic adverse events included Grade 3–4 anorexia, asthenia, hyponatremia, and nausea. The results of the studies which demonstrated the efficacy of monotherapy for relapsed SCLC involved mainly Japanese patients. Therefore, it is necessary to conduct more clinical studies in non-Japanese patients to confirm the efficacy of amrubicin
