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Pembrolizumab Demonstrates Robust, Durable Antitumour Activity and Promising Survival in Advanced Cutaneous Squamous Cell Carcinoma

Results of the second interim analysis of the KEYNOTE-629 study
21 Jul 2021
Basal Cell and Squamous Cell Cancers of the Skin

The results of the second interim analysis of the KEYNOTE-629 study that include initial data for the locally advanced cohort and updated data for the recurrent/metastatic cohort of patients with cutaneous squamous cell carcinoma confirm durable pembrolizumab antitumour activity and promising survival in both settings. Adverse events with pembrolizumab were generally consistent with its established safety profile. Dr. Brett G. M. Hughes of the Royal Brisbane and Women’s Hospital, The Prince Charles Hospital, University of Qeensland in Brisbane, Australia and colleagues wrote on 19 July in the Annals of Oncology that based on their study results pembrolizumab is a promising treatment option for patients with advanced cutaneous squamous cell carcinoma.

Cutaneous squamous cell carcinoma is the second most common non-melanoma skin cancer, representing approximately 20% of all non-melanoma skin cancers and 20% of all skin cancer-related mortalities. It has high tumour mutational burden and may be responsive to immunotherapy. The authors wrote in the study background that targeting the PD-1 pathway seems to be an effective option for recurrent/metastatic or unresectable locally advanced cutaneous squamous cell carcinoma.

The KEYNOTE-629 is a global, open-label, non-randomised, phase II study of patients with locally advanced or recurrent/metastatic cutaneous squamous cell carcinoma conducted at 59 centres. Eligible patients received pembrolizumab 200 mg intravenously every three weeks for up to 35 cycles. Primary endpoint was objective response rate (ORR) by blinded independent central review per RECIST v1.1. Secondary endpoints included duration of response (DoR), disease control rate, progression-free survival, overall survival, and safety and tolerability. Efficacy and safety were analyzed in patients who were treated with at least one dose of pembrolizumab.

Based on the first interim analysis, the KEYNOTE-629 investigators concluded that pembrolizumab demonstrates clinically meaningful and durable antitumour activity with a manageable safety profile in patients with recurrent/metastatic cutaneous squamous cell carcinoma. They are now reporting the results from the second interim analysis, including initial data for the locally advanced cohort and updated data for the recurrent/metastatic cohort.

Between November 2017 and September 2019, 159 patients were enrolled and treated with pembrolizumab, 54 in locally advanced cohort and 105 in recurrent/metastatic cohort. The median time from the first dose to data cut-off on 29 July 2020 was 14.9 months in locally advanced cohort and 27.2 months in recurrent/metastatic cohort.

In locally advanced cohort, the ORR was 50.0% (95% confidence interval [CI] 36.1%-63.9%), 16.7% patients achieved complete response (CR) and 33.3% partial response (PR). In recurrent/metastatic cohort, the ORR was 35.2% (95% CI 26.2%-45.2%), 10.5% patients achieved CR and 24.8% achieved PR.

Median DoR was not reached in either cohort.

Grade 3-5 treatment-related adverse events occurred in 11.9% of patients.

Study limitations include the single-arm design and the small number of patients who received pembrolizumab as first-line treatment in the recurrent/metastatic cohort. 

The authors concluded that robust antitumour activity of pembrolizumab was demonstrated in patients with both, locally advanced and recurrent/metastatic cutaneous squamous cell carcinoma. It was rapid, durable and without unexpected safety signals.

The study was funded by Merck Sharp & Dohme Corp., a subsidiary of Merck & Co., Inc., Kenilworth, NJ, USA.


Hughes BGM, Munoz-Couselo E, Mortier L, et al. Pembrolizumab for locally advanced and recurrent/metastatic cutaneous squamous cell carcinoma (KEYNOTE-629 Study): an open-label, nonrandomized, multicenter, phase 2 trial. Annals of Oncology; Published online 19 July 2021. DOI: https://doi.org/10.1016/j.annonc.2021.07.008

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