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The rights to methylnaltrexone bromide (Relistor)—a treatment for opioid-induced constipation—were licensed by Salix Pharmaceuticals, Ltd (Raleigh, North Carolina), in an exclusive worldwide agreement (with the exception of Japan) with Progenics Pharmaceuticals, Inc (Tarrytown, New York).

The peripherally acting mu-opioid receptor antagonist counteracts the constipating effects of opioid pain medications in the gastrointestinal tract without affecting the ability of those agents to relieve pain. Relistor subcutaneous injection is indicated for persons with advanced illness who are receiving palliative care and have an insufficient response to laxative therapy.

Methylnaltrexone bromide, which was cleared for use in the United States in 2008, is the first approved medication to specifically target the underlying cause of opioid-induced constipation in patients in palliative care who are receiving opioid therapy for pain. (The use of the drug beyond 4 months has not been studied.) Single-use, prefilled syringes were approved in the United States, Canada, and the European Union in 2010. The Salix license includes intellectual property from the University of Chicago, Progenics Pharmaceuticals, and Wyeth Pharmaceuticals (now owned by Pfizer, Inc), including patents and applications with expiration dates ranging from 2017 through 2031.

An oral formulation of the drug to address opioid-induced constipation in patients with chronic, noncancer pain is in phase III development (www.progenics.com/releasedetail.cfm?ReleaseID=547932). ONA