WASHINGTON - A combination of two experimental AIDS drugs can help control the deadly virus in people who are infected with highly resistant forms, an international team of researchers reported on Thursday.

The two drugs -- called etravirine, or TMC125, and darunavir, or TMC114 -- are both made by Tibotec Pharmaceuticals, Ltd., a division of Johnson & Johnson.

The trial of patients in 18 countries offers another weapon for people infected with drug-resistant forms of the AIDS virus -- about 10 percent of those not yet treated, the researchers report in the Lancet medical journal.

"This study is one of the most significant worldwide HIV/AIDS clinical trials in recent years," said Dr. William Towner, of Kaiser Permanente Southern California, who worked on the study. "It showed that when the two drugs are used in combination, there is a good chance HIV can be very effectively controlled in patients who have advanced, multi-drug resistant HIV."

TMC125 is in a class of HIV drugs called non-nucleoside reverse transcriptase inhibitors or NNRTIs. TMC114, which is now approved and sold under the brand name Prezista, is a protease inhibitor.

The drugs do not cure the infection but can control what is known as viral load -- how much virus is circulating in the body. Higher viral load usually means more symptoms.

Different classes of HIV drugs attack the virus at different stages in its cycle of infection and replication.

"Treating a resistant virus with two active agents has been a mantra in HIV care for quite some time," Towner said.

"Adding only one active agent to a patient experiencing drug failure usually results in the rapid, predictable development of resistance to that agent. Very seldom do patients get the chance to receive two potent new investigational agents in one clinical trial."

In the trials, known as DUET 1 and DUET 2, patients who got two drugs instead of one had better control of the human immunodeficency virus that causes AIDS. Close to 40 million people worldwide are infected with HIV.