The Potential for Selective Cyclin-Dependent Kinase 4/6 Inhibition in the Therapy for Head and Neck Squamous Cell Carcinoma

Preclinical data support investigation of selective CDK4/6 inhibition as a therapeutic strategy for human papillomavirus (HPV)-unrelated head and neck squamous cell carcinoma (HNSCC). Phase 1 clinical trials established the feasibility of combining palbociclib with cetuximab in patients with recurrent or metastatic HNSCC. Nonrandomized phase II trials showed that palbociclib plus cetuximab resulted in efficacy outcomes better than cetuximab in biomarker-unselected, platinum-resistant or cetuximab-resistant, HPV-unrelated HNSCC. A double-blind, randomized phase II trial (PALATINUS) evaluated the efficacy of palbociclib or placebo and cetuximab in patients with biomarker-unselected, platinum-resistant, cetuximab-naive, HPV-unrelated HNSCC. Palbociclib and cetuximab did not significantly prolong overall survival compared with placebo and cetuximab. However, correlative biomarker analyses identified that trends for better overall survival with palbociclib and cetuximab were observed in certain prespecified subsets; the largest reduction in risk of death with palbociclib versus placebo and cetuximab occurred in the subset with CDKN2A mutations. Several phase II-III trials are underway investigating palbociclib in biomarker-selected patients with HPV-unrelated locally advanced or recurrent or metastatic HNSCC.