Merck (MRK) Announces First Clinical Outcomes Evaluating Six-Week Dosing Schedule for KEYTRUDA Presented at AACR

Merck (NYSE: MRK), known as MSD outside the United States and Canada, today announced the presentation of interim data from Cohort B of KEYNOTE-555, a Phase 1 trial evaluating a 400 mg every six-week (Q6W) dosing regimen for KEYTRUDA, Merck’s anti-PD-1 therapy, in patients with metastatic melanoma. Results of the study – which represent the first clinical outcomes evaluating Q6W dosing for KEYTRUDA – demonstrated efficacy and safety comparable to findings from previous melanoma trials evaluating KEYTRUDA monotherapy. Interim data showed an overall response rate (ORR) of 38.6% (n=17/44) (95% CI, 24.4-54.5) in patients who received KEYTRUDA 400 mg Q6W, the primary endpoint of the study.

As previously announced, Merck resubmitted supplemental Biologics License Applications (sBLAs) to the U.S. Food and Drug Administration (FDA) to update the dosing frequency for KEYTRUDA to include a 400 mg Q6W option across all approved adult indications. The results of KEYNOTE-555 supported the resubmission. In the EU, 400 mg Q6W dosing for KEYTRUDA monotherapy was approved by the European Commission in March 2019.

“We remain committed to improving cancer care, which includes the ability to offer greater flexibility in administering KEYTRUDA,” said Dr. Scot Ebbinghaus, vice president, clinical research, Merck Research Laboratories. “These data, coupled with extensive model-based assessments, provide strong evidence for a six-week dosing regimen for KEYTRUDA.”

Results from KEYNOTE-555 Cohort B will be presented tomorrow in an online plenary session at the American Association for Cancer Research (AACR) Virtual Annual Meeting I (Abstract #CT042).

Additional Data from KEYNOTE-555 Cohort B (Abstract #CT042)

KEYNOTE-555 (ClinicalTrials.gov, NCT03665597) is a Phase 1 open-label trial evaluating the relative bioavailability of subcutaneous injection versus intravenous infusion in patients with unresectable stage III or IV melanoma. The primary endpoint is ORR; secondary endpoints include pharmacokinetic (PK) exposures, progression-free survival (PFS) and safety. In Cohort B, 100 patients were assigned to receive KEYTRUDA 400 mg Q6W. An analysis was conducted in the first 44 patients who had sufficient follow-up to evaluate for efficacy. The ORR was 38.6% (n=17/44) (95% CI, 24.4-54.5) in patients treated with the KEYTRUDA 400 mg Q6W regimen, with a complete response rate of 9.1% (n=4/44) and partial response rate of 29.5% (n=13/44). Efficacy findings were comparable to findings observed in previous melanoma trials evaluating KEYTRUDA monotherapy. Additionally, PK exposures for KEYTRUDA 400 mg Q6W were within clinical experience with other tested dosing regimens. Trough concentrations at 400 mg Q6W were comparable to the KEYTRUDA 200 mg and 2 mg/kg every three week (Q3W) regimens and peak concentrations were lower than the KEYTRUDA 10 mg/kg every two week (Q2W) regimen.

The safety profile of KEYTRUDA 400 mg Q6W was consistent with the safety profile of KEYTRUDA 200 mg Q3W, which has been demonstrated in more than 12 tumor types. Any grade all-cause adverse events occurred in 97.7% (n=43/44) of patients. Grade 3-4 all-cause adverse events occurred in 25.0% (n=11/44) of patients. Treatment-related adverse events (TRAEs) occurred in 68.2% (n=30/44) of patients. Grade 3-4 TRAEs occurred in 2.3% (n=1/44) of patients. There were no treatment-related deaths.

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