By Randall Osborne

West Coast Editor

With a cancer vaccine and an HIV treatment already well along in the pipeline, Progenics Pharmaceuticals Inc. acquired from UR Labs Inc. the rights to the pain-related drug methylnaltrexone, which is entering Phase II trials.

¿We believe it may be the first drug to make it to market for us,¿ said Richard Krawiec, vice president of investor relations and corporate communications for Tarrytown, N.Y.-based Progenics, who declined to disclose financial terms.

Although it doesn¿t treat pain directly, methylnaltrexone is designed to reverse side effects of opioid pain medications, such as morphine.

Progenics¿ most advanced product, the GMK cancer vaccine, is in Phase III trials for melanoma, but ¿that¿s a very long-term trial, with over three years of dosing, and it just started in May,¿ Krawiec said.

Methylnaltrexone, on the other hand, has been much studied already, mainly in ¿more than a dozen¿ trials at the University of Chicago Medical Center, which most recently began a double-blind, randomized Phase II study evaluating subcutaneous doses of the drug in cancer patients with opioid-induced constipation, Krawiec told BioWorld Today.

Progenics plans to start Phase IIb clinical studies in opioid-induced constipation and post-operative bowel dysfunction, and Phase III trials next year.

Phase II clinical trials of its lead HIV product, PRO 542, a viral-entry inhibitor, are under way, and preclinical development continues with PRO 140 and other follow-on product candidates in HIV infection.

Methylnaltrexone targets not only the opioid side effect of constipation, but urine retention and itching that ¿can drive patients crazy,¿ Krawiec said. Constipation is the worst, he added.

¿It¿s continual,¿ he said. ¿They can¿t eat. During the last six months or so of life, patients are on very heavy doses of morphine, and the side effects are dose limiting. Many patients choose to endure the pain [rather than endure the side effects].¿

Naltrexone is a well-known drug, used to reverse the side effects of narcotics, Krawiec said. Its methylated version ¿ subject of the UR Labs deal ¿ with its changed permeability, ¿does the same thing, but doesn¿t get into the spinal cord,¿ he said.

Last year, a study published in the Journal of the American Medical Association showed methylnaltrexone worked almost immediately to reverse constipation in opioid patients.

¿It¿s unusual to find a drug so well studied, that had such a good safety profile, and showed activity in so many dosing forms,¿ Krawiec said, adding that Progenics plans to study it first in subcutaneous form, then possibly in intravenous and oral doses, investigating the drug¿s effects first in cancer patients, then in those with surgical pain, and then in those with chronic pain.

Another company researching the same area is Adolor Corp., of Exton, Pa., which in July began a Phase III trial of ADL 8-2698, its oral, non-absorbed small-molecule opioid receptor antagonist, in patients with opioid bowel dysfunction. A Phase III trial of the same drug, which affects only the receptors in the gastrointestinal tract, began in March in patients with post-operative ileus.

Progenics¿ stock (NASDAQ:PGNX) closed Monday at $14.20, up 30 cents.