Merck’s Keytruda plus chemotherapy meets primary endpoint in mTNBC trial

Merck, known as MSD outside the United States and Canada, announced that the pivotal Phase 3 KEYNOTE-355 trial investigating KEYTRUDA, Merck’s anti-PD-1 therapy, in combination with chemotherapy met one of its dual primary endpoints of progression-free survival (PFS) in patients with metastatic triple-negative breast cancer (mTNBC) whose tumors expressed PD-L1 (Combined Positive Score [CPS] ≥10). Based on an interim analysis conducted by an independent Data Monitoring Committee (DMC), first-line treatment with KEYTRUDA in combination with chemotherapy (nab-paclitaxel, paclitaxel or gemcitabine/carboplatin) demonstrated a statistically significant and clinically meaningful improvement in PFS compared to chemotherapy alone in these patients. Based on the recommendation of the DMC, the trial will continue without changes to evaluate the other dual primary endpoint of overall survival (OS). The safety profile of KEYTRUDA in this trial was consistent with that observed in previously reported studies; no new safety signals were identified.

“Triple-negative breast cancer is an aggressive malignancy. It is very encouraging that KEYTRUDA in combination with chemotherapy has now demonstrated positive results as both a first-line treatment in the metastatic setting with this trial, and as neoadjuvant therapy in the KEYNOTE-522 trial,” said Dr. Roger M. Perlmutter, president, Merck Research Laboratories. “We look forward to sharing these findings with the medical community at an upcoming congress and discussing them with the FDA and other regulatory authorities.”

The KEYTRUDA breast cancer clinical development program encompasses several internal and external collaborative studies. In addition to KEYNOTE-355, in TNBC these include the ongoing registration-enabling studies KEYNOTE-242 and KEYNOTE-522.