BioWorld International Correspondent

PARIS - A Phase II trial of depot naltrexone (Naltrel), a treatment for heroine addiction being developed by DrugAbuse Sciences Inc., demonstrated "sustained opiate blockade" over six weeks, the company said.

The study, carried out at Johns Hopkins University School of Medicine, involved subjects who had previously used heroin but were not addicted. It was designed to compare the ability of two doses of depot naltrexone to block the effects of hydromorphone, an opiate that has a similar effect as heroin.

Naltrexone already is on the market in oral tablet form, but for the purposes of the trial a formulation was used entailing once-monthly intramuscular injection. It is designed "to improve naltrexone's clinical usefulness by eliminating the need for patients to take tablets on a daily basis," said Elizabeth Greetham, the CEO of DAS, based in Paris and Los Altos, Calif.

Oral naltrexone tablets were launched in the U.S. in December and are indicated for use in the treatment of alcohol dependence and the blockade of exogenously administered opioids. But DAS said their usefulness for treating heroin addiction is limited because the tablets normally have to be taken every day for a period of months to ensure effective abstinence.

Phase III trials of depot naltrexone are already under way in the U.S. to provide further evidence of its "potential efficacy and safety for the treatment of alcoholics," and Sandra Luneau, corporate communications manager at DAS, told BioWorld International that a Phase III trial would "very probably" be conducted in the indication of opiate blockade as well.

DAS has five drug candidates for treating different forms of substance abuse in its pipeline. They include Buprel, a once-a-month injectable, slow-release formulation of buprenorphine being developed as a potential alternative to methadone for treating heroine addiction, and DAS-431, a dopamine receptor agonist for treating cocaine abuse.