Nearly Half of Patients With Metastatic CSCC Have Responses to Cemiplimab

Danny Rischen, MBBS, FRACP, MD

Results from a phase II trial demonstrated that cemiplimab, a PD-1 inhibitor, induced an overall response rate (ORR) of 47.5% in patients with metastatic cutaneous squamous cell carcinoma (CSCC). These findings were presented at the 2018 ASCO Annual Meeting and published in the New England Journal of Medicine.^1,2

Responses were observed irrespective of prior systemic therapy and at a median follow-up of 7.9 months, 28 of the 59 patients had a response. Addionally, 4 (6.8%) of these patients had partial responses and 24 (40.7%) had complete responses. Overall, 57% had responses >6 months and 82% had an ongoing response and continued to receive the PD-1 inhibitor.

“In the largest prospective study reported in patients with metastatic CSCC, cemiplimab…showed substantial activity and durable responses with an acceptable safety profile,” Danny Rischin, MBBS, FRACP, MD, director, division of Cancer Medicine, head, department of medical oncology, Peter MacCallum Cancer Centre, Melbourne, Australia, and coauthors, wrote in their ASCO poster.

“Cemiplimab showed an acceptable risk/benefit profile in this metastatic CSCC population, which tends to be elderly and associated with medical comorbidities,” added Rischin, et al.

The phase II trial included patients with either metastatic or locally advanced CSCC. The data presented at ASCO were only for the cohort of 59 patients with metastatic disease. These patients received cemiplimab intravenously at 3 mg/kg every 2 weeks. The median age of the 59 patients was 71 (range, 38-93), with 43 (73%) patients aged ≥65 years.

Ninety-two percent of patients were male, 39% had and ECOG performance score of 0 and 61% had a score of 1. The primary site of CSCC included head or neck (64%), arm or leg (20%), and trunk (15%). Forty-four percent of patients were treatment naive, 37% had 1 prior regimen for CSCC, and 19% had ≥2 prior regimens. Three-fourths (76%) of patients had distant metastasis and 24% had regional metastasis only.

The median time to response was 1.9 months (range 1.7-6.0). The median duration of response had not been reached at the data cutoff. Beyond the 47.4% (95% CI, 34-61) ORR, the stable disease rate was 15% (n = 9) and the progressive disease rate was 19% (n = 11). Twelve percent (n = 7) of patients could not be evaluated and 7% (n = 4) had nontarget lesions only. The durable disease control rate (DCR) was 61.0% (95% CI, 47.4-73.5). 

The ORR in treatment-naive patients was 57.7% (15/26; 95% CI, 36-9-76.6), including 3 complete responses and 12 partial responses. The durable DCR was 69.2% (95% CI, 48.2-85.7). Among previously treated patients, the ORR was 39.4% (13/33; 95% CI, 22.9-57.9), including 1 CR and 12 PRs. The durable DCR was 54.5% (95% CI, 36.4-71.9).

Grade ≥3 adverse events (AEs) occurred in 42% of patients, leading to treatment discontinuation in 3 patients, and were linked to 3 patient deaths. Grade ≥3 AEs included diarrhea (n = 1), fatigue (n = 1), constipation (n = 1), anemia (n = 1), and pneumonitis (n = 2). Serious AEs occurred in 29% of patients. There were also 8 patient deaths due to disease progression.

The article published in NEJM also included phase I study data from expansion cohorts of patients with locally advanced or metastatic CSCC. The findings were for 26 patients treated with the same cemiplimab dose as in the phase II study. The ORR was 50% (95% CI, 30-70) among these patients, comprising all partial responses (n = 13). Six patients had stable disease, 3 had progressive disease, 3 could not be evaluated, and 1 had nontarget lesions only. The durable DCR was 65% (95% CI, 44-83) and the median time to response was 2.3 months (95% CI, 1.7-7.3).

Based on the phase I and II data, the FDA granted a priority review in April 2018 to a biologics license application (BLA) for cemiplimab for the treatment of patients with metastatic CSCC or patients with locally advanced CSCC who are not eligible for surgery. The FDA is scheduled to make its decision on the BLA by October 28, 2018.

References:

1. Rischin CD, Migden MR, Chang A, et al. Primary analysis of phase 2 results for cemiplimab, a human monoclonal anti-PD-1, in patients with metastatic cutaneous squamous cell carcinoma (mCSCC).J Clin Oncol. 2018;36 (suppl; abstr 9519).
2. Migden MR, Rischin CD, Schmults A, et al. PD-1 blockade with cemiplimab in advanced cutaneous squamous-cell carcinoma [published online June 4, 2018].N Engl J Med.doi: 10.1056/NEJMoa1805131.