Regeneron Pharmaceuticals, Inc. announced positive clinical data for an investigational regimen of PD-1 inhibitor Libtayo® (cemiplimab) as neoadjuvant monotherapy in stage II to IV resectable cutaneous squamous cell carcinoma (CSCC). The data, from the primary analysis of a confirmatory Phase 2 trial, were presented in an oral session at the European Society for Medical Oncology (ESMO) Congress 2022 in Paris and concurrently published [1] in the New England Journal of Medicine  (NEJM). In the confirmatory, multicenter, single-arm Phase 2 trial, 79 patients received up to four fixed doses of Libtayo every 3 weeks prior to surgery, with 62 receiving all 4 doses and 70 undergoing surgery.

Patients experienced the following efficacy: 63.3% combined pathologic response rate (50 of 79 patients), with 50.6% (40 patients) achieving the primary endpoint of complete pathologic response (0% viable tumor, excluding a null hypothesis of 25%) and 12.7% (10 patients) experiencing a major pathologic response (>0% and =10% viable tumor cells) by independent pathologic review. 68% objective response rate (ORR) (54 of 79 patients; 5 complete responses [CR] and 49 partial responses [PR]) per local imaging review. Adverse events (AE) of any grade occurred in 87% of patients, with 17% considered serious.

The most common AE was fatigue (n=24). AEs that were =grade 3 occurred in 18% of patients. The treatment discontinuation rate due to AEs was 1%, and there was one death due to worsening congestive heart failure considered related to treatment.

There were no new Libtayo safety signals. Patient follow-up in the trial is ongoing to assess disease-free survival. A separate global Phase 3 trial investigating Libtayo in the adjuvant CSCC setting for patients at heightened risk (i.e., due to involvement of multiple lymph nodes, extension of cancer through the lymph node capsule, perineural invasion) for recurrence is enrolling patients.

The potential use of Libtayo described above is investigational, and its safety and efficacy has not been evaluated by any regulatory authority for this indication.