Two presentations at the 17th Conference on Retroviruses and Opportunistic Infections (CROI) investigated the use of the CCR5 inhibitor maraviroc (licensed as Celsentri or Selzentry for HIV treatment) as a possible vaginal and rectal microbicide.

In one, maraviroc, introduced vaginally before challenge, protected five out of five rhesus macaques against a high-dose single injected challenge of the human/monkey chimeric virus SHIV-162p3.

In another, measures of maraviroc in the semen of male volunteers were found to be somewhat lower than in blood plasma – contrary to levels seen in vaginal fluid, which were 3.3 times higher – but levels in rectal tissue biopsies were very much higher than in blood, suggesting that maraviroc might be a promising rectal microbicide candidate.

In the first study, the monkeys were fully protected with a 6mg/ml dose of maraviroc and four out of five were protected with a 2mg/ml dose.

Protection tailed off rapidly as the interval between microbicide dose and challenge lengthened, with protection reduced to 50% after a four-hour delay. This was simply due to microbicide leakage.

Some microbicide experiments with tenofovir have shown that animals infected despite microbicide use develop lower viral loads, but this was not the case with maraviroc.

[Details of second reported study are in the full article, under the sub-heading, "Maraviroc concentrates at very high levels in rectal tissue".]

Read the full article on aidsmap.com/en/news.