South Korean biotechnology company Celltrion said Wednesday that the company‘s breast cancer drug Herzuma reached a market share of 44 percent in Japan last year.

Herzuma is a biosimilar of Roche’s blockbuster breast cancer drug Herceptin (trastuzumab), used in treating patients with certain breast and gastric cancers.

In the third quarter of 2019, the market share of Herzuma in Japan was just 2 percent, but the figure jumped to 12 percent in the following quarter.

Herzuma’s market share in Japan continued to report fast growth in 2020. The drug’s market share soared to 25 percent in the first quarter in 2020, 35 percent in the second quarter and 39 percent in the third quarter.

The rapid growth started in 2019 when the Ministry of Health, Labor and Welfare of Japan approved patients with HER2 positive breast cancer taking trastuzumab to use the drug on a three-week cycle method, a Celltrion official explained.

There are two methods of using trastuzumab when treating breast cancer patients: a one-week cycle method with 52 doses and a three-week cycle with 18 doses.

In Japan, around 90 percent of breast cancer patients receiving trastuzumab are treated with a three-week cycle method.

Celltrion’s Japan-based distribution partner Nippon Kayaku first received approval for Herzuma from the authority in March 2018 to use the drug when treating patients with HER2-positive gastric cancers.

In November 2018, the company received another permission from the authority to use the drug to treat patients with HER2-positive breast cancer with the one-week cycle method after resolving patent issues with Roche.

Meanwhile, Celltrion’s infliximab biosimilar Remsima, used to treat rheumatoid arthritis, has also reported an increased market share in Japan. According to health care consulting firm IQVIA, the market share of Remsima in Japan went up to 18 percent by the end of last year, from 11 percent in the fourth quarter of 2019.

By Shim Woo-hyun (ws@heraldcorp.com)