An experimental AIDS drug taken in combination with a recently approved medication drastically reduced the amount of virus in the blood of patients with a history of drug resistance, according to two international studies published today.
The studies reported that up to 18 percent more drug-resistant patients saw the amount of virus in their blood drop to undetectable levels after 24 weeks compared with those taking a standard drug regimen.
The results with the experimental drug etravirine give a much-needed boost in the fight against drug resistance among HIV patients, particularly those resistant to the workhorse class of drugs known as non-nucleoside reverse transcriptase inhibitors, or NNRTIs.
"There are a lot of patients out there who need salvage therapy with a new NNRTI, and it looks like we'll have one," said Dr. Mark Wainberg, director of the McGill University AIDS Center in Montreal, who was not involved in the study.
Almost 50 percent to 60 percent of patients on antiretroviral medications develop resistance to a drug in this class, said Wainberg, who has consulted for the maker of etravirine, Tibotec Pharmaceuticals of Yardley, Pa.
Tibotec plans to seek Food and Drug Administration approval for etravirine in the next few months.
The drug, previously known as TMC125, blocks one of the enzymes needed for replication by the human immunodeficiency virus, which causes AIDS.
The two studies, funded by Tibotec, followed 1,203 HIV patients in 18 countries. The patients had severely compromised immune systems and were resistant to NNRTIs and another commonly used class of drugs known as protease inhibitors.
Roughly half the patients were given etravirine and a protease inhibitor from Tibotec called Prezista, which was approved by the FDA last year. The remainder were given Prezista and a placebo.
Patients in both groups were also given other AIDS drugs depending on the recommendation of their doctors.
Dr. William Towner, one of the study authors and medical director for Kaiser Permanente's HIV/AIDS Research Trials Program in Southern California, said using several drugs at once has proven to be an effective strategy against the quickly mutating AIDS virus.
"Adding only one active agent to a patient experiencing drug failure usually results in the rapid, predictable development of resistance to that agent," he said.
One of the studies found that 62 percent of patients on the etravirine regimen suppressed the virus to undetectable levels compared with 44 percent in the placebo group. The other study reported successful viral suppression in 56% of the etravirine group compared to 39 percent in the placebo group.
Most side effects were mild or moderate and occurred at about the same rate in the experimental and control groups. Rash, however, occurred slightly more often in the etravirine groups.
Results from this study suggest that etravirine is best used in combination with other drugs that retain a strong ability to control the virus, said Dr. W. David Hardy, director of infectious diseases at Cedars-Sinai Medical Center. "It will not perform by itself," said Hardy, who was not involved in this study, but has consulted for Tibotec and other pharmaceutical companies.
But according to an editorial accompanying the studies, etravirine did not help a group of patients who were taking for the first time the drug Fuzeon, which is part of a relatively new class of drugs known as fusion inhibitors.
Jia-Rui Chong writes for the Los Angeles Times.