FDA approves second biomarker-based indication for Merck & Co.'s Keytruda

Merck & Co. said Wednesday that the FDA approved Keytruda (pembrolizumab) for the treatment of patients with unresectable or metastatic tumour mutational burden-high (TMB-H) solid tumours that have progressed following prior treatment and who have no satisfactory alternative options. The company noted that the anti-PD-1 therapy is the first checkpoint inhibitor authorised in this indication.

According to Merck, the accelerated approval is based on tumour response rate and durability of response data from the KEYNOTE-158 study. Results showed that in 102 patients whose tumours were TMB-H, defined as at least 10 mutations per megabase, Keytruda demonstrated an objective response rate (ORR) of 29%, with a complete response rate of 4% and a partial response rate of 25%. After a median follow-up time of 11.1 months, the median duration of response (DOR) had not been reached. The company indicated that among the 30 responding patients, 57% had ongoing responses of 12 months or longer, and 50% had ongoing responses of 24 months or longer.

Meanwhile, in a pre-specified analysis of 70 patients with TMB of at least 13 mutations per megabase, Keytruda demonstrated an ORR of 37%, with complete and partial response rates of 3% and 34%, respectively. After a median follow-up time of 11.1 months, the median DOR had not been reached, while among the 26 responding patients, 58% had ongoing responses of 12 months or longer, and 50% had ongoing responses of 24 months or longer.

"For the second time, Keytruda monotherapy is now approved based on a biomarker rather than the location in the body where the tumour originated," remarked Scot Ebbinghaus, vice president of clinical research at Merck Research Laboratories. The therapy was previously awarded accelerated approval by the FDA for the treatment of any metastatic microsatellite instability-high or mismatch repair deficient solid tumour.

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