Phase Ib/II study of the pan-cyclin-dependent kinase inhibitor roniciclib in combination with chemotherapy in patients with extensive-disease small-cell lung cancer

Objectives: This phase Ib/II study evaluated safety, pharmacokinetics, maximum tolerated dose (MTD), and efficacy of the pan-cyclin-dependent kinase inhibitor roniciclib with cisplatin-etoposide (CIS-ETOP) or carboplatin-etoposide (CARBO-ETOP) in patients with extensive-disease small-cell lung cancer (ED-SCLC). Patients and methods: In this open-label, non-randomized study, patients with previously untreated ED-SCLC received roniciclib twice daily (BID) in a 3 days on/4 days off schedule. Cisplatin 75 mg/m² or carboplatin (AUC5) dose was administered on day 1, and etoposide 100 mg/m² on days 1–3, of 21-day cycles. Phase Ib used a dose-escalation design to define the MTD for phase II. Pharmacokinetics were assessed. Results: Forty-three patients received treatment (roniciclib 2.5 mg BID [+ CARBO-ETOP, n = 4; + CIS-ETOP, n = 3] and roniciclib 5 mg BID [+ CARBO-ETOP, n = 24; + CIS-ETOP, n = 12]). The MTD of roniciclib was 5 mg BID with CARBO-ETOP or CIS-ETOP. Common adverse events were nausea (90.7%) and vomiting (69.8%). Roniciclib was readily absorbed following oral administration at the MTD (median t_max 0.5–1 h), with a 30–40% reduction in exposure when co-administered with CARBO-ETOP or CIS-ETOP; administration of roniciclib had no effect on etoposide or platinum pharmacokinetics. The response rate was 81.4% (35/43) overall and 86.1% (31/36) in the pooled roniciclib 5 mg BID population (all partial responses). Conclusion: Roniciclib co-administered with chemotherapy in patients with ED-SCLC demonstrated tolerability, acceptable pharmacokinetics, and promising efficacy. An observed safety signal in a related phase II study resulted in discontinuation of the present study and termination of further roniciclib development.