LONDON - The biotechnology unit of the French drugmaker Sanofi agreed on Monday to buy a 12 percent stake in Alnylam Pharmaceuticals for $700 million as part of an expanded alliance to develop treatments for rare genetic diseases.
Genzyme, a Sanofi company, and Alnylam, a Cambridge, Mass., biopharmaceutical company, formed an alliance in 2012 to develop and commercialize patisiran, a treatment for a transthyretin familial amyloid polyneuropathy, a rare disease that damages the nervous system.
Under an expanded agreement announced Monday, Genzyme will now have the right to commercialize patisiran in all areas outside of North America and Western Europe, not just parts of the Asia-Pacific region. Alnylam will market the drug in North America and Western Europe. Genzyme also will gain the rights to bring to market additional drugs in Alnylam’s pipeline.  Sanofi acquired Genzyme for $20.1 billion in 2011.
“This collaboration is an important building block for our future,†said David Meeker, Genzyme’s president and chief executive. “It strengthens our pipeline and provides us with the opportunity to meet the needs of patients with rare diseases around the world through our well-established global organization.â€
Genzyme will purchase a 12 percent stake in Alnylam at $80 a share, a 27 percent premium  compared with Alnylam’s average share price over the past 30 days.
The transaction has been approved by the boards of both companies and is subject to regulatory approval.
