RecruitingPhase 2Drug trialStudy of PLK1 Inhibitor, Onvansertib, in Relapsed Small Cell Lung CancerThis phase II clinical trial will study the safety and efficacy of onvansertib to treat patients with small cell lung cancer (SCLC) who have either not responded to or are unable to tolerate chemotherapy. Onvansertib is a drug that inhibits polo-like kinase 1 (PLK-1), an enzyme that is over-expressed in many cancer cells and is involved in cellular repair.