Progenics rose 31 percent to $8.49 at the close of New York trading, the biggest gain for the Tarrytown, New York-based company since April 2008. Salix Pharmaceuticals Ltd., which licenses the medication, climbed to its highest price in 11 months.

The drug treats constipation that occurs in people taking opioid analgesics, prescribed for chronic pain during advanced illness, the companies said in a statement today. The injected form of the product is marketed as Relistor. An oral form may generate revenue of $500 million to $800 million a year, said Matthew Weiss, an analyst at Jefferies & Co. in New York

“This is a big success by all measures,” Weiss said in a note to investors.

Salix gained 8.6 percent to $46.94. The shares of the Raleigh, North Carolina-based company are little changed this year. Progenics has gained 55 percent this year.

The trial, the last of the three phases usually needed for U.S. approval, tested a once-daily oral dose of the drug, methylnaltrexone, at doses of 150, 300 and 450 milligrams compared with a placebo for 84 days. The two higher doses improved bowel movement within four hours over 28 days of use.