Immunotherapy Pembrolizumab Receives FDA Approval for Squamous Cell Skin Cancer Treatment

For patients who cannot be treated with surgery or radiotherapy and who have recurrent or metastatic cutaneous squamous cell carcinoma (kSHK), pembrolizumab (Keytruda), an immunotherapy drug, was approved on 24 June 2020 by the United States Food and Drug Administration (FDA).

Squamous cell skin cancers are non-melanoma skin cancers and rank 2nd after basal cell carcinoma. Their lifetime incidence ranges from 7-11% and increases by 3-8% worldwide each year.

The figure below: The 3 most common types of skin cancer, a normal mole and their characteristics can be seen.

The KEYNOTE-629 study

Efficacy was investigated in KEYNOTE-629, a multicenter, multicohort, nonrandomized, open-label study. The study included patients who had not previously received an anti-PD-1, anti-PD-L1 or anti-CTLA-4 antibody and who had no autoimmune disease or medical condition requiring immunosuppression. Patients received 200 mg pembrolizumab every 3 weeks until disease progression, unacceptable adverse effects or a maximum of 24 months. Tumor status was assessed every 6 weeks during the first year and every 9 weeks during the second year.

The main efficacy outcome measures, assessed by independent central review, were objective response rate and duration of response.

The objective response rate was 34%, and the median duration of response was not reached.

In patients with cutaneous squamous cell carcinoma (kSHK) enrolled in KEYNOTE-629, the adverse effects were similar to those occurring in patients receiving pembrolizumab as a single agent in other clinical trials (see immunotherapy adverse effects). The most common adverse effects of pembrolizumab are fatigue, musculoskeletal pain, decreased appetite, itching, diarrhea, nausea, rash, pyrexia/fever, cough, shortness of breath, constipation, pain and abdominal pain. Pembrolizumab is also associated with serious immune-mediated adverse effects such as pneumonitis, colitis, hepatitis, endocrinopathies, nephritis and adverse skin reactions.

The efficacy and safety of pembrolizumab using a dosage of 400 mg every 6 weeks for kSHK were based primarily on modeling of dose / exposure efficacy and safety relationships and observed pharmacokinetic data in patients with melanoma.

The recommended pembrolizumab doses for kSHK are 200 mg every 3 weeks or 400 mg every 6 weeks. 

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