Regeneron Pharmaceuticals said it will grant exclusive development and commercial rights in 11 Asian countries for its Phase II/III musculoskeletal pain treatment fasinumab (REGN475) to Mitsubishi Tanabe Pharma (MTPC). The deal could generate up to $325 million for Regeneron.

The agreement gives Mitsubishi Tanabe rights in Japan, Korea, and nine other Asian countries—but not China.

Fasinumab is a fully human monoclonal antibody that is highly selective for Nerve Growth Factor (NGF). In a prior clinical study in osteoarthritis, fasinumab showed reduced pain compared to placebo and a safety profile comparable to placebo.

Fasinumab is among drug candidates against NGF placed on partial clinical hold by the FDA, limiting duration of trials in osteoarthritis to 16 weeks. The FDA acted in December 2012, following reports of sympathetic nervous system toxicity in mature animals being treated with other NGF antibodies.

However, a Phase IIb/III study of fasinumab for pain due to osteoarthritis was initiated earlier this year.

Mitsubishi Tanabe has agreed to pay Regeneron up to $55 million in upfront and other near-term payments; and up to $170 million in payments toward R&D reimbursement and achievement of development milestones. Regeneron is also eligible for additional one-time purchase price adjustment payments of up to $100 million total upon achievement of specified annual net sales.

Upon commercialization, Regeneron said it will supply the product at a range of purchase prices depending on net sales, such that Regeneron shares in a “significant” portion of any potential profits.

“MTPC has proven experience marketing biologics for rheumatology and pain management and thus is an ideal partner in Asia,” Regeneron president and CEO Leonard S. Schleifer, M.D., Ph.D., said in a statement. “We look forward to advancing our NGF program in the coming months with the goal of bringing this investigational therapy to patients in serious need.”

Mitsubishi Tanabe includes central nervous system among its priority areas of disease focus, as well as autoimmune diseases, diabetes, and kidney diseases.