Amgen Inc., the world's largest biotechnology company, will pay Japan's Kyowa Hakko Kogyo Co. as much as $520 million for the rights to a medicine that is being developed for inflammation and cancer, the two firms said Thursday.

Amgen, based in Thousand Oaks, Calif., will pay Kyowa Hakko $100 million initially and as much as $420 million tied to the development of the medicine, a humanized monoclonal antibody known as KW-0761, the companies said.

The exclusive license agreement will allow Amgen to develop and commercialize Kyowa's KW-0761 worldwide, except in Japan, South Korea, China and Taiwan. Kyowa Hakko Kogyo Co., the drugs unit of Kirin Holdings Co., will retain the rights to develop and sell the medicine in these economies.

Kyowa Hakko, based in Tokyo, has completed the first of three stages of patient studies in KW-0761 in healthy volunteers and those suffering allergic rhinitis. It is conducting phase-1 studies of KW-0761 in lymphoma patients.