Photo/Illutration Daiichi Sankyo Co. will begin selling the breast cancer drug Enhertu in Japan. (Provided by Daiichi Sankyo Co.)

A new breast cancer drug developed by a major Japanese drugmaker that will be offered domestically as early as May is expected to generate more than 1 trillion yen ($9.3 billion) in sales.

Daiichi Sankyo Co. said during an April 27 conference call held to disclose its financial results it expects combined sales of its anti-cancer drug Enhertu in Japan and the United States to hit 28.5 billion yen during this fiscal year, which began in April.

Enhertu was approved for use in the United States and Japan after proving effective in clinical trials for some terminal breast cancer patients. 

Daiichi Sankyo President Sunao Manabe called Enhertu "a highly anticipated new drug” during the call. Manabe added that the company is intending to "focus on the area of cancer.”

Enhertu was developed using antibody drug conjugates (ADCs), a combination of an antibody that targets specific cancer tissues and a conventional anti-cancer drug, which is powerful but also attacks normal cells.

The combination gives ADCs a high potency. ADCs have the added benefit of also having fewer side effects.

Daichi Sankyo said it succeeded in stabilizing a "linker," which binds the antibody and drug. That enabled Enhertu to bind twice the amount of the antibody and the drug than before, making them even more potent, the company said.

In March, the drug was approved to treat certain types of breast cancer in Japan and is expected to start being administered to patients in May.

Daiichi Sankyo is aiming to have the drug approved for treating other cancers, such as lung, stomach, and colon cancer.

Though Enhertu’s Japan price has not been determined, sales in the United States, where it is already on the market, hit 3.2 billion yen by the end of March.

Kazuaki Hashiguchi, a senior analyst of Daiwa Securities Co., predicted “sales of the drug can top 1 trillion yen a year at their peak.”

But others are cautious about such high expectations, given that the development of the drug may not proceed as Daiichi Sankyo plans.

“The key (to successful sales) is whether Enhertu will be approved for other cancers and whether the company can develop another new drug using a similar mechanism with Enhertu,” said an analyst of a foreign-affiliated securities firm.