Amgen Inc. on Monday announced that it has filed for market approval for its osteoporosis drug romosozumab in Japan.

The Thousand Oaks biotech along with its partner Brussels-based UCB are looking for Japan’s Pharmaceuticals and Medical Devices Agency to greenlight the drug for the treatment of osteoporosis – a condition where bones become weak and brittle – in patients with a high risk of fracture.

Amgen and UCB are the co-developers of the drug worldwide. However, Amgen has partnered with Tokyo-based Astellas Pharma Inc. for Japanese development.

Japan has one of the longest life-expectancy rates in the world, and as a result, osteoporosis is a major public health issue among the aging population.

“Submitting romosozumab for marketing approval in Japan is an important milestone in our global development program with UCB and our strategic alliance with Astellas Pharma,” Dr. Sean Harper, Amgen’s executive vice president of research and development, said in a statement. “We look forward to working with regulatory authorities in Japan with a goal of filling a great unmet need.”

Amgen shares closed Tuesday down 52 cents, or less than a percent, to $147.22 on the Nasdaq.