Merck (MRK) said Thursday that the US Food and Drug Administration approved Keytruda and Keytruda Qlex in combination with Trodelvy for the first-line treatment of adults with PD-L1-positive unresectable locally advanced or metastatic triple-negative breast cancer.

The approvals mark the first PD-1 inhibitor plus Trop-2-directed antibody-drug conjugate regimen in advanced triple-negative breast cancer, the company said.

Merck said phase 3 data showed the combination reduced the risk of disease progression or death by 35% versus Keytruda plus chemotherapy, with median progression-free survival improving to 11.2 months from 7.8 months.

Merck shares were 0.8% lower in premarket trading.