Gilead Sciences Inc said its elvitegravir, a component of the company's important four-drug Quad HIV treatment currently awaiting an approval decision, demonstrated similar efficacy and tolerability to Isentress in difficult-to-treat patients.
In the two-year late-stage clinical trial, elvitegravir met the primary clinical goal of being "non-inferior" to Merck and Co's Isentress, researchers said.
"As patients are living with HIV longer, there is a continued need for new treatment options -- particularly those that are effective against strains of the virus that have developed resistance to currently available therapies," Dr. Richard Elion, the study's lead investigator, said in a statement.
Both once-daily elvitegravir and twice-a-day Isentress, known chemically as raltegravir, belong to a class of drugs known as integrase inhibitors that are used in combination with other HIV medicines to help fight the virus that causes AIDS.
Integrase inhibitors interfere with replication of HIV by blocking the virus's ability to integrate into the genetic material of human cells.
Results of the study in previously treated HIV patients were being presented on Tuesday at the 19th International AIDS Conference in Washington, the company said.
Elvitegravir is under review for approval by U.S. and European health regulators.
Meanwhile, the U.S. Food and Drug Administration is set to make an approval decision next month on the Quad, which is widely considered to be one of Gilead's most important future growth divers.
Gilead acquired rights to elvitegravir through a 2005 licensing deal with Japan Tobacco. Gilead holds worldwide rights to develop and sell the drug with the exception of Japan, where Japan Tobacco retains the marketing rights.
Rates of adverse side effects, discontinuations from side effects and development of drug resistance in the study were similar in both treatment groups with the exception of diarrhea, which was more frequent in patients taking the Gilead drug -- 13 percent versus 8 percent.
Gilead shares were off 38 cents, or 0.7 percent, at $51.51 on Nasdaq.
(Reporting by Bill Berkrot in New York; editing by Matthew Lewis and M.D. Golan)