IAC: Drug-Resistant HIV Stable in Europe

TORONTO, Aug. 15 -- The transmission of drug-resistant HIV appears to be stabilizing, at least in Europe.

But still 9.1% of newly infected HIV patients are already carrying a virus that carries resistance mutations to one of the three main classes of anti-retroviral medications, reported Annemarie Wensing, M.D., of the University Medical Center in Utrecht, Holland, at the 16^th International AIDS Conference here.

The so-called SPREAD study, supported by the European Commission, is the first to prospectively analyze how many HIV-positive patients have a drug-resistant HIV infection even before they are treated with any medications, Dr. Wensing said.

An earlier retrospective analysis conducted in Europe, the CATCH study, reported that about one in 10 new infections was resistant, Dr. Wensing said, so the current study shows the rate is roughly stable.

The good news from the SPREAD study, she said, is that for two of the classes - protease inhibitors and nucleoside reverse transcriptase inhibitors - the mutations that were found do not appear to confer resistance to the whole class.

On the other hand, while resistance to non-nucleoside reverse transcriptase inhibitors was relatively rare, Dr. Wensing said, the mutations that were found tended to make the virus resistant to the whole class.

Because the non-nucleoside reverse transcriptase inhibitors - and especially Sustiva (efavirenz)-form the backbone of many highly active anti-retroviral therapy (HAART) regimens, such "patients have already limited options," she said.

The analysis, of 1,083 newly-infected patients in the years 2002 and 2003, showed:

• 5.4% had virus resistant to nucleoside reverse transcriptase inhibitors.
• 3.0% had virus resistant to protease inhibitors.
• 2.6% had virus resistant to non-nucleoside reverse transcriptase inhibitors.
• 0.7% had virus already resistant to two classes of anti-retroviral drugs.

Interestingly, she said, the resistance to nucleoside reverse transcriptase inhibitors appears to have been declining over time, from just under 14% in 1996 and 1997 - as reported by the CATCH investigators - to 5.4% today. The change is probably an effect of changing treatment patterns, she said.

All told, there were 96 cases of virus with mutations associated with resistance, Dr. Wensing said, but 68 - or 71% -- had only one such mutation.

Resistance was more common in people carrying virus of subtype B, the strain most prevalent in Europe and North America, Dr. Wensing said. The prevalence of resistance in those with subtype B virus was 10.4%, compared with 6.3% for non-subtype B, and the difference was statistically significant at P=0.03.

The study shows that resistance is not inevitable, according to Stefano Vella, M.D., of the Italian national health agency and a former president of the International AIDS Society. "All resistant viruses are the sons of our mistakes," he said - mistakes such as monotherapy, the use of poor drugs, and complicated regimens that lead to non-adherence.

Resistance "is stabilizing because now we are treating (patients) well," Dr. Vella said in an interview.