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Merck (MRK - Get Report) announced Wednesday that the U.S. Food and Drug Administration has approved its Keytruda plus Lenvima combination treatment for patients with certain types of endometrial carcinoma, a cancer in the uterus.

Merck shares were relatively flat, trading up 15 cents to $82.66 on Wednesday.

Merck made the announcement with Japanese drugmaker Eisai (ESALY) , which discovered the orally available kinase inhibitor Lenvima.

"This marks the first U.S. approval for the combination of Keytruda plus Lenvima and the first time an anti-PD-1 therapy is approved in combination with a kinase inhibitor for advanced endometrial carcinoma in the U.S.," the companies said in a press release.

Merck said the approval was accelerated under the FDA's real-time oncology review pilot program. "This approval is based on tumor response rate and durability of response," the company stated.

The review was conducted under the FDA's Project Orbis, which supports the concurrent submission and review of oncology drugs among international partners.

"Under this project, the FDA, the Australian Therapeutic Goods Administration (TGA) and Health Canada collaboratively reviewed applications for two oncology drugs, allowing for simultaneous decisions in all three countries," the release states.

Merck said it's the first combination treatment to receive simultaneous review decisions in the U.S., Australia and Canada.