Study of PLK1 Inhibitor, Onvansertib, in Relapsed Small Cell Lung Cancer

This is a single arm, two stage, phase II study of onvansertib in patients with relapsed SCLC who have received not more than 2 lines of prior therapies. The study will enroll 15 patients in stage I. Enrolment into stage II will occur if two or more patients achieve objective response. Subsequent enrolment into stage II will be by biomarker selection if the stage I accrual supports any of the three preliminarily nominated biomarkers i.e., TP53 mutation type, SCLC-Y or MYC expression. In order to establish the safety and tolerability of onvansertib at the dose of 15 mg/m2 on D1-D14 of a 21-day cycle, the first 6 participants will be closely monitored as a safety a run-in. Full safety evaluation will be conducted after all 6 patients have completed at least 1 cycle of therapy. A lower dose of onvansertib will be considered, and schedule of onvansertib as per the planned dose modification strategy, if during the safety run-in there are any deaths not clearly attributable to the underlying disease or extraneous causes or for Grade 4 hematologic or non-hematologic adverse events (AEs) occurring in 2 or more patients. In the event that a dose de-escalation is necessary following the initial safety run-in cohort, the run-in procedure will be repeated for the reduced dose level as described above. The study will continue to enroll to stage I at the dose established to be safe from the safety run-in cohort. Patients treated at the established dose in the safety run-in phase will count toward the total stage I accrual goal of 15 patients.