Progenics Pharmaceuticals announced that it will hand over commercial duties on Relistor, a subcutaneous injection for opioid-induced constipation, to Salix Pharmaceuticals, beginning in April. Financial terms include a $60 million upfront payment to Progenics, and another potential $290 million in development and sales-based milestone payments, the companies said.

Wyeth (now Pfizer) was the original marketing partner for Relistor, which was first approved in 2008, but Progenics announced in late 2009 that it would end that deal after a transition period, with Wyeth paying $10 million in “costs associated with the transition,” according to a statement. After two extensions, the Wyeth deal will come to an end on March 31, with Salix taking over on April 1. Pfizer/Wyeth will retain certain intellectual property assets on the drug, and agreed to license them to Progenics for free as part of the breakup. Salix’s global (except Japan) licensing rights also include intellectual property from the University of Chicago. Ono Pharmaceuticals has commercial rights to Relistor in Japan.

Salix will market Relistor (methylnaltrexone bromide) with a specialty sales force of 160 reps in the US, according to Michael Freeman, a Salix spokesperson. Reps will target 18,000 gastroenterologists in the US, and the company will not use e-detailing or other digital detailing programs, Freeman said. Physicians interested in a Relistor e-detail, or online physician testimonials and reprints, can visit before March 31, after that, all digital assets will be handed back to Progenics, said Victoria Davis, a Pfizer spokesperson. Pfizer will continue to supply product to countries outside of the US and Japan after March 31, while Salix “effects a country-by-country transition of commercialization rights,” according to a statement. Freeman declined to name the ad agencies involved in promoting the drug.

On a conference call yesterday morning, Paul Maddon, CEO, founder and chief science officer at Progenics, said the company will submit a supplemental New Drug Application (sNDA) during “the first half of this year” which, if approved, would expand Relistor’s indication to include chronic non-cancer pain patients with opioid-induced constipation (OIC). Progenics is also developing a multi-dose pen, and expects to submit an sNDA for that product “by year’s end,” Maddon said on the call. An oral formulation of Relistor is currently in phase 3 development, for OIC patients with chronic, non-cancer pain.

Maddon called the Salix deal a “signal event” for Progenics, and expressed admiration for Salix’s gastroenterology specialty sales force, which also markets Xifaxan, Colazal and Pepsid. Relistor is approved in “over 50 countries,” and had global net sales totaling $16 million in 2010, according to company data. Use of Relistor for longer than four months has not been studied.