DURBAN, SOUTH AFRICA – For physicians who are leery of prescribing oral daily pre-exposure prophylaxis (PrEP) against HIV infection because of concern that it will promote drug-resistant viral strains, Robert Grant, MD, has a reassuring message.
It’s a message based upon his systematic review of published resistance testing results in all the randomized, placebo-controlled PrEP trials.
“For clinicians who are anxious, I can say based on this excellent work that if your primary concern is drug resistance – and I’m not suggesting that it should be – but if you are very concerned about drug resistance, then you should be a PrEP advocate, because in the end, your population will have less drug resistance,” Dr. Grant said at the 21st International AIDS Conference.
The overall rate of resistance to emtricitabine or tenofovir – the antiretrovirals contained in fixed-dose combination in Truvada, the only FDA-approved agent for HIV PrEP – was five cases in 9,222 trial participants, for a risk of 0.05%. The number needed to treat in order to prevent one HIV infection was 13-60, depending upon the adherence rate in a given trial.
In contrast, the number needed to harm by causing emergence of a drug-resistant strain of HIV was 1,844, reported Dr. Grant, professor of medicine at the University of California, San Francisco.
Drug resistance during PrEP is rare. It occurs mainly when PrEP is started or restarted during an acute HIV infection. Almost all of the resistance is to emtricitabine. Those emtricitabine-resistant HIV infections are treatable.
The randomized trials of PrEP used several methods of screening for acute HIV infection: rapid second- and third-generation antibody assays, highly sensitive HIV nucleic acid genotypic assays capable of detecting resistant viral variants present in very low abundance, and a clinical screen.
The use of one or the other of the laboratory approaches is common practice in the United States and Europe. But these tools are much less frequently available in sub-Saharan Africa and elsewhere the HIV epidemic is hitting hardest. That is a setting where a clinical screening program could be of great value.
“The majority of people with acute HIV infection will have some sort of symptoms of an acute viral syndrome. They’re nonspecific symptoms: a flu-like illness, fever, sore throat, headache, a rash,” he observed.
Dr. Grant was first author of the iPrEx OLE study, the only published trial to examine a strategy of clinical screening for acute viral syndromes and acute HIV infection in PrEP candidates (Lancet Infect Dis. 2014 Sep;14[9]:820-9).
Thirty of 1,603 PrEP candidates (1.9%) who underwent clinical screening had PrEP deferred because of an acute viral syndrome. Two of those 30 patients subsequently proved to have acute HIV infection on laboratory testing, 25 of the HIV-negative patients had a delayed start of PrEP, and 3 of the 30 never started PrEP. Thus, clinical screening had 100% sensitivity, 98% specificity, 100% negative predictive value, and a 6.7% positive predictive value, according to Dr. Grant.
The World Health Organization sponsored his systematic review. Dr. Grant reported having no financial conflicts of interest.