Amgen announced an agreement June 1 with Kyowa Kirin, a Japanese pharmaceutical company, to jointly develop and commercialize a human monoclonal antibody that Kyowa Kirin is developing to treat atopic dermatitis and other autoimmune diseases. The deal could be worth $1.25 billion or more.

Amgen will led the development, manufacturing and commercialization for the treatment, known as KHK4083, in all markets except Japan, where Kyowa Kirin will retain the rights. Kyowa Kirin will co-promote KHK4083 with Amgen in the U.S. and other market in Europe and Asia.

Amgen will make a $400 million up-front payment to Kyowa Kirin and future payments worth up to $850 million more, based on meeting certain milestones, along with additional royalty payments on future sales, Amgen said in a June 1 news release.

KHK408 is a fully human monoclonal antibody discovered by Kyowa Kirin. It has been shown to selectively deplete active T cells that are critical in the development of atopic dermatitis. Atopic dermatitis is a skin condition that affects up to 20% of children and 3% of adults worldwide, Amgen said.

This is the latest in a long history of collaborations between the two companies. In 1984, Amgen and Kirin Holdings — the parent company of Kyowa Kirin and Kirin Brewery — established a joint venture to develop and commercialize Epogen. Five years later, it became the first Amgen drug approved in the U.S., and the year after that, it became the first Kirin drug approved in Japan. In 2017, the joint venture became a wholly owned subsidiary of Amgen.