June 17, 2020
The U.S. FDA has approved a new indication for Keytruda® (pembrolizumab) injection, manufactured by Merck. The drug is now indicated to treat adult and pediatric patients who have no satisfactory alternative treatment options and have unresectable or metastatic tumor mutational burden-high (TMB-H) solid tumors that have progressed following prior treatment. This is Keytruda’s second FDA-approved indication to treat cancer based on a biomarker alone, regardless of the specific tumor type.
Tumor type is determined by where the cancer first begins in the body. For instance, kidney cancer is defined as cancer that begins in the kidneys, regardless of whether the disease spreads to other organs such as the liver. Biomarkers are substances produced either by cancer cells, or by the body in response to the presence of cancer cells. In some cases, these biomarkers are used to help target cancer therapies. Tumor mutational burden refers to the number of different mutations that occur in a cancer cell and is considered a biomarker that can help predict a patient’s response to certain immunotherapies.
A type of immunotherapy, Keytruda produced an overall response rate (ORR) of 29% in a clinical study when administered to patients diagnosed with TMB-H tumors. Four percent of patients with TMB-H tumors had a complete response, while 25% had a partial response. At the follow-up time of 11.1 months, the median duration of response had not yet been reached. Half of patients who responded to treatment with Keytruda had ongoing responses of at least a 24-month duration.
Recommended dosing for adults under the new indication is 200mg administered via intravenous (IV) infusion over the course of thirty minutes once every three weeks or 400mg via 30-minute IV infusion once every six weeks. For children, recommended dosing is 2mg/kg of patient’s body weight, up to a maximum dose of 200mg, once every three weeks. Treatment should continue until disease progression or unacceptable toxicity occur, or for a maximum of 24 months. The safety and effectiveness of KEYTRUDA in pediatric patients with TMB-H central nervous system cancers have not been established.
Originally FDA approved in 2014, Keytruda has more than 20 indications to treat various types of cancers, as well as an indication to treat cancer based on the microsatellite instability-high (MSI-H) biomarker rather than a specific tumor type. Keytruda’s TMB-H indication is approved under accelerated approval based on tumor response rate and durability of response, and continued approval for the indication may be contingent upon verification and description of clinical benefit in confirmatory trials.