Pfizer (PFE.US) announced on Wednesday that the U.S. Food and Drug Administration (FDA) has approved its tyrosine kinase inhibitor Tukysa (tucatinib) as part of a combination regimen for first-line maintenance treatment of a certain type of breast cancer.

The approval allows Tukysa to be used in adult patients with HER2-positive (HER2+) breast cancer who have received induction therapy with trastuzumab and pertuzumab.

Trastuzumab and pertuzumab are two cancer drugs marketed by Roche (RHHBY.US) under the brand names Herceptin and Perjeta, respectively.

The decision was supported by data from Pfizer's Phase III HER2CLIMB-05 trial.

In that trial, Tukysa in combination with trastuzumab and pertuzumab met the primary endpoint of progression-free survival in patients with HER2-positive metastatic breast cancer (MBC), with a favorable safety profile.

The oral drug had previously been approved in the U.S. as a subsequent treatment option for adult patients with advanced HER2-positive unresectable or metastatic breast cancer, in combination with chemotherapy, capecitabine and trastuzumab.

Pfizer shares closed up 1.8% on Wednesday and have gained 18% year to date.