Amgen Inc. on Wednesday said that it is spending $25 million to expand its licensing agreement with Cytokinetics Inc. to cover the Japanese market.

The Thousand Oaks biotech and San Francisco-based Cytokinetics first agreed in 2006 to collaborate on drug development, most notably a heart failure treatment that is still in trials. The initial deal gave Amgen license to market omecamtiv mecarbil overseas, but excluded the Japanese market.

In the expanded deal, Cytokinetics will be paid an upfront $15 million licensing fee and the Thousand Oaks biotech will purchase $10 million of its common stock. Additionally, Cytokinetics could receive up to $50 million in milestone payments as the drug moves toward market and royalties on sales once it is commercially available.

“This expanded collaboration furthers Amgen’s hopes to address the needs of patients with heart failure in Japan,” said Sean Harper, Amgen’s executive vice president of research and development, in a statement.

The deal is the second in less than a month aimed at expanding Amgen’s presence in Japan.

In late May Amgen signed an agreement with Japan’s second-largest biopharmaceutical company, Astellas Pharma Inc. of Tokyo, to develop and commercialize five drugs in Amgen’s pipeline.