Neoadjuvant lenvatinib plus pembrolizumab in Merkel cell carcinoma: an investigator-initiated, open-label phase II trial.

BACKGROUND: Given the success of checkpoint inhibitor therapy in the advanced Merkel cell carcinoma (MCC) setting, there is interest in exploring immunotherapy as a neoadjuvant approach. We report the primary results of a neoadjuvant study of lenvatinib plus pembrolizumab in resectable MCC. METHODS: In this single-center, phase II open-label trial, resectable stage II-IV MCC patients received 6 weeks of neoadjuvant therapy with lenvatinib 20 mg orally daily plus pembrolizumab 200 mg intravenous dose every 3 weeks. Following local therapy, patients received continued adjuvant pembrolizumab monotherapy to complete a total treatment duration of 1 year. Pathological complete response (pCR) rate was the primary endpoint of the study. RESULTS: 26 patients were enrolled, including 5 (19.2%) with clinical stage II disease, 20 (76.9%) with stage III, and 1 (3.8%) with stage IV. Following neoadjuvant treatment, 2 patients (7.7%) were unable to undergo planned surgery, one due to progressive disease and one due to toxicity. On intention to treat, 15 of the 26 patients (57.7%) achieved pCR. Among 22 radiographically evaluable patients, 16 (72.7%) achieved an objective response. At a median follow-up of 20.0 months, median progression-free survival (PFS) has not been reached. PFS significantly correlated with radiographic response to neoadjuvant therapy. pCR was associated with superior PFS, though this result was not statistically significant (p=0.22). Grade 3 treatment-related adverse events (TRAEs) occurred in 14 patients (53.8%), most commonly grade 3 hypertension in 11 patients (42.3%). No grade 4-5 TRAEs were observed. CONCLUSIONS: Lenvatinib plus pembrolizumab demonstrated encouraging efficacy with anticipated toxicity when used as neoadjuvant therapy for MCC. Further investigation of these promising findings is warranted. TRIAL REGISTRATION NUMBER: NCT04869137.