Methylnaltrexone Named Orphan Drug to Block Morphine Side Effects

CHICAGO--Methylnaltrexone, an agent that blocks the side effectsof morphine without interfering with pain relief, has been grantedorphan drug status for use in patients with cancer pain.

"Orphan drug status is a big step toward bringing this importantdrug to a population of patients in need," said Michael Roizen,MD. He and his colleague Joseph Foss, MD, both of the Universityof Chicago, have done the preliminary animal and clinical testingof the drug, which is being developed in collaboration with URLabs.

Methylnaltrexone was invented by the late University of Chicagopharmacologist Leon Goldberg, MD, PhD, to help a friend sufferingfrom cancer. By attaching a methyl group to the naltrexone molecule,an anti-addiction agent, he altered the drug to prevent it fromcrossing the blood-brain barrier. As a result, it did not interferewith morphine's effects on pain, centered in the brain, but didprevent its others effects, such as nausea and constipation. PhaseII/III trials of the orphan drug are planned this year.