Salix Pharmaceuticals has agreed to buy the rights for a drug that treats constipation in patients taking pain medicines.
The deal with Progenics Pharmaceuticals calls for Morrisville-based Salix to pay $60 million upfront, and payments worth up to $290 million more if the drug meets development and sales milestones in coming years.
Salix is one of the few small drug companies based in the Triangle with actual products and revenue. The company sells drugs to treat various gastrointestinal ailments, and has been adding more products to its portfolio.
Progenics' Relistor is an injected drug used in patients taking opioid painkillers, which often cause severe constipation. Progenics, based in Tarrytown, N.Y., sold $16 million of Relistor worldwide last year.
Salix shares fell 34 cents to $39.92 this morning. The stock is up 46 percent in the past year.

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