The Ministry of Food and Drug Safety said Thursday that it has authorized the sale of MSD Korea's Tukysa Tab (50 mg and 150 mg), a new HER2-positive metastatic breast cancer drug.

Tukysa is a tyrosine kinase inhibitor (TKI) that selectively inhibits the HER2 receptor overexpressed by cancer cells. It works by blocking the HER2 intracellular signaling pathway to inhibit tumor cells' survival, proliferation, and metastasis and induce cancer cell death.

Developed by U.S. biotech Seagen, it won approval from the U.S. Food and Drug Administration in April 2020 and later expanded its indication to treat metastatic colorectal cancer. Tukysa is now approved in over 38 countries, including the United States, the European Union, and the United Kingdom.

The domestic indication is for treating HER2 (human epidermal growth factor receptor)-positive locally advanced or metastatic breast cancer that has recurred after at least two anti-HER2 treatments, in combination with the antibody therapy trastuzumab and the cytotoxic anticancer agent capecitabine.

Tukysa's approval will intensify prescription competition with another HER2 inhibitor, Nerlynx (neratinib), approved earlier in Korea.

Developed by U.S. biotech Puma Biotechnology, Nerlynx was approved by the MFDS in October 2021. Korean biotech Bixink Therapeutics holds the domestic sales right.

The ministry expected the approval to provide new treatment opportunities for HER2-positive patients who are difficult to treat with existing therapies.