About 10% of new HIV patients are infected with a virus resistant to at least one type of AIDS drug, US researchers said today.
Only 5 in 1,000 have a form that evades all three approved therapies, said the US Centers for Disease Control and Prevention at a medical meeting in Los Angeles today. The findings clarify earlier CDC estimates of 5% to 20% for single-drug resistance. About 40,000 new HIV patients are diagnosed a year, the Atlanta-based agency said.
The CDC, the Geneva-based WHO and countries worldwide are strengthening how they monitor resistant HIV to help maintain effectiveness in available drugs. The WHO said on February 24 that Bill and Melinda Gates Foundation will donate $15.2 million to help doctors in poor nations watch for resistance signs. „This is the first time we've had a broad sample of resistance from a variety of care settings,” said Timothy Mastro, who oversees the CDC's resistance testing program.
„The data will help us minimize the emergence of resistance with rational use of antiretroviral therapies.” The study by the Atlanta-based agency was presented today at the 14th Conference on Retroviruses and Opportunistic Infections in Los Angeles. The survey took specimens from more than 3,000 people that ran in 11 states from 2003 through 2006.
The results regarding triple-drug resistance was „consistent with previous estimates,” Mastro said. The findings will help officials determine if existing prevention and treatment regimens curb resistance, he said. „It's important to know if it's increasing over time,” Mastro said. A separate study from Rockefeller University's Aaron Diamond AIDS Research Center found that rates of drug resistance among newly diagnosed patients in New York have also fallen over the past four years.
About 27% of 112 newly diagnosed patients were resistant to at least one drug in 2003-2004, compared with 12% of 108 patients in 2005-2006, said researchers led by clinical scholar Andrea Low. HIV has proven to be a formidable foe for drug designers. The virus's attack begins when it attaches itself to a cell surface molecule, called a receptor, and uses one of its proteins to force its way into the cell.
Once there, HIV makes an enzyme called reverse transcriptase to convert its genetic material into DNA that's integrated into the human cell, tricking it into making new viral proteins. Those proteins are then chopped up by an enzyme called protease into chunks that bud out of the original cell and invade others. The virus is able to evade drugs that target various parts of the infection process through its ability to change its shape and structure through rapid, constant mutation.
About 6.9% of new patients had virus that was resistant to at least one non-nucleoside reverse transcriptase inhibitor, drugs in the same class as Bristol-Myers Squibb Co.'s Sustiva. About half that rate, 3.6%, evaded at least one drug among the nucleoside reverse transcriptase inhibitor class, which includes Gilead Sciences Inc.'s Emtriva drug. The lowest rate of resistance, just 2.4%, was found among drugs such as Abbott Laboratories' protease inhibitor Kaletra. About .5% of patients, or 5 in 1,000, are infected with virus that resists all three classes of HIV drugs. About 1.1 million people in the US are infected with the human immunodeficiency virus, which attacks the immune system.
Infection by the virus leaves the body vulnerable to the infections and tumors that make AIDS, or acquired immune deficiency syndrome, lethal. Last year, the CDC said it was seeking to make testing for HIV universal in clinics, hospitals and emergency rooms as a way to cut back new infections. In December, the CDC said it would begin promoting its plan this month in a series of HIV-testing workshops set for high-volume emergency departments and urgent care centers, then move to hospitals and primary care clinics.
HIV gains resistance to drugs when it is forced to by prolonged treatment, said Donald Sutherland, team leader for WHO's drug resistance monitoring effort. Resistance rates remain low in many developing countries because they have only recently gained access to treatment through WHO programs, or international efforts such as one US. President George W. Bush established to bring treatment to 2 million people internationally by 2009.
Several small studies in selected cities of Tanzania, Thailand and Russia released at the meeting this week suggest that less than 5% of new cases there are caused by drug resistant strains. Drugmakers including Pfizer Inc., Merck & Co., Gilead Sciences Inc., Panacos Pharmaceuticals Inc. and Johnson & Johnson's Tibotec unit are developing new medications to beat resistant HIV strains. The new drugs attack viral targets that have been untouched by available medications. (Bloomberg)