The immunotherapy agent pembrolizumab (Keytruda) was recently approved by the FDA for treating any cancers that exhibit DNA mismatch repair deficiency, marking the first time the agency has approved a cancer treatment based on a biomarker rather than the location in the body where the tumor originated.
Previously, the FDA granted accelerated approval of pembrolizumab to treat locally advanced or metastatic urothelial carcinoma, and one expert says it may play a role in a subset of prostate cancer patients.
Pembrolizumab was first approved for treating melanoma in 2014, and the FDA approved the agent to treat locally advanced or metastatic urothelial carcinoma in May 2017. It works by promoting the ability of the body’s immune system to fight tumors. It blocks the interaction between PD-1 and its ligands—PD-L1 and PD-L2—resulting in activation of T lymphocytes.
Tralisa Colby, MPH, public affairs specialist for FDA’s Center for Drug Evaluation and Research, said pembrolizumab was granted accelerated approval due to the overall response rate of the therapy in clinical trials.
“The evidence of tumor shrinkage in approximately one-third of patients whose tumor was no longer responding to standard therapy, lasting for more than 6 months in the majority of those achieving a response, provides strong evidence that pembrolizumab is active against tumor and is likely to prolong survival,” Colby said.
The therapy is meant to be used as a first-line treatment in patients who have disease progression during or after platinum-containing chemotherapy or within 1 year of neoadjuvant or adjuvant treatment with platinum-containing chemotherapy.
Administration guidelines are for a fixed dose of 200 mg every 3 weeks by 3-minute intravenous infusion until disease progression or toxicity, or up to 24 months without disease progression, according to Merck, the drug’s manufacturer. Pembrolizumab can also be administered in combination with chemotherapy, and should be administered before chemotherapy when given on the same day.