Tissue/Site-Agnostic Study of Ribociclib for Tumors With Cyclin D-CDK4/6 Pathway Genomic Alterations: A Phase II, Open-Label, Single-Arm Basket Study.

Purpose: As part of the Novartis Signature Program, this study evaluated the efficacy of ribociclib (selective cyclin-dependent kinase 4/6 [CDK4/6] inhibitor) in patients with cyclin D-CDK4/6 pathway-aberrant tumors.

Methods: This was a phase II, single-arm, signal-seeking study in patients with advanced malignancies that had progressed on or after standard treatment. Prior identification of tumor mutation or amplification, /3 amplification, or mutation or loss was required. Clinical benefit (defined as the proportion of patients with response or stable disease at ≥ 16 weeks) was the primary end point.

Results: From 61 centers in the United States, 106 patients (median age, 62.5 years) were enrolled across multiple malignancies. The patient population was heavily pretreated (median number of prior therapies, three; range, 0 to 19). Median progression-free survival was 1.8 months (95% CI, 1.8 to 1.9). In patients with solid tumors, the clinical benefit rate was 18.1% (n = 19 of 105) and the overall response rate was 2.9% (n = 3 of 105); three partial responses occurred in patients with adenocarcinoma (unknown primary), soft tissue sarcoma, and urothelial carcinoma. No tumor cohort met the prespecified criteria for success. The most common adverse events suspected to be related to treatment were neutropenia (30.2%; decreased neutrophils, 15.1%), fatigue (31.1%), and nausea (29.2%). Fatigue and nausea were typically mild. Only one incident of febrile neutropenia was experienced (grade 3).

Conclusion: No new or unexpected safety signals were observed in this heavily pretreated patient population. Although responses were seen in tumors with - amplifications, the primary end point was not met, suggesting additional evaluation of ribociclib, possibly as combination therapy, is needed.