The Food and Drug Administration recently announced two new types of cancer that can be treated by the anti–PD-1 antibody pembrolizumab.
The new indications expand the use of pembrolizumab (Keytruda) to include treatment of patients with unresectable or metastatic tumor mutational burden–high (TMB-H) solid tumors as well as patients with cutaneous squamous cell carcinoma (cSCC). The FDA announced the new indications just 8 days apart, on June 16 and June 24.
In addition, on June 29, the FDA approved a third new indication for pembrolizumab, this time as first-line treatment for patients with unresectable or metastatic microsatellite instability–high or mismatch repair–deficient colorectal cancer.
The new approvals add tofor which pembrolizumab can be used.
Accelerated approval to treat solid tumors
The FDA grantedfor pembrolizumab to treat children and adults with unresectable or metastatic TMB-H solid tumors that progressed after previous treatment or in instances where there are no satisfactory alternative treatment options.
The tumor mutational burden must be confirmed by an FDA-approved test. To that end, the FDA approved the FoundationOneCDx assay, which is designed to help physicians determine which patients meet the threshold for TMB-H malignancies (10 or more mutations per megabase).
The efficacy of pembrolizumab in TMB-H solid tumors was investigated in 10 cohorts from the multicenter, open-label KEYNOTE-158 trial. Participants received 200 mg of pembrolizumab intravenously every 3 weeks until their disease progressed or they experienced unacceptable toxicity.
Within this population, 102 patients had tumors that met the TMB-H definition. In this group, the overall response rate was 29%, including a 25% partial response rate and a 4% complete response rate.
The median duration of response was not reached, but 57% of participants experienced a response lasting 12 months or longer, and 50% had a response lasting 24 months or longer.
The most common adverse events associated with pembrolizumab in this trial were fatigue, musculoskeletal pain, decreased appetite, pruritus, diarrhea, nausea, rash, pyrexia, cough, dyspnea, constipation, pain, and abdominal pain. Pembrolizumab is associated with immune-mediated side effects, including pneumonitis, colitis, hepatitis, endocrinopathies, nephritis, and skin adverse reactions, the FDA noted.
Safety and efficacy of pembrolizumab in pediatric patients with TMB-H central nervous system cancers have not been established.
New option for recurrent or metastatic cSCC
Physicians treating patients with cSCC that is not curable by surgery or radiation now have pembrolizumab to consider as another treatment option.
Theis based on results of the multicenter, open-label KEYNOTE-629 trial. The dosage regimen was 200 mg of pembrolizumab intravenously every 3 weeks until cancer progressed, unacceptable toxicity arose, or 24 months of treatment were completed.
The objective response rate was 34%, and the median duration of response was not reached.
Adverse events were similar to those occurring in patients who received pembrolizumab as a single agent in other clinical trials, the FDA noted.