Treatment News

Compiled by Gus Cairns

One shot a month – the next stage in HIV therapy?

With a good choice of HIV therapy now available, and resistance rates going down rather than up, what’s the next stage in creating HIV treatment that’s easier to take?

The answer may lie in nanoparticles – tiny grains of plastic or metal which can be infused with HIV drugs and then injected into the body, where they slowly release the drugs over a time scale of as long as a month.

However, this idea is still at a very early stage and not all HIV drugs would be suitable for such an injectable formulation, the Retrovirus Conference heard.

Scientists from the company Tibotec have managed to do this trick with their as-yet unlicensed new non-nucleoside (NNRTI) drug rilpivirine (TMC278), a drug with similar properties to efavirenz (Sustiva®).

They infused the drug into tiny particles scarcely bigger than the HIV virus itself and gave HIV-negative volunteers a single injection of them.

Drug levels fell below the therapeutic level after a few days. However similar experiments in rats and dogs showed that if injections were repeated, drug levels built up till a once-a-month injection should be sufficient.

Gerben van t’Klooster of Tibotec commented that rilpivirine is suitable for this idea because the dose needed to stop HIV replicating is very small; it would not be suitable for drugs like the protease inhibitors, which need larger doses. However, other scientists have managed to perform the same trick with the protease inhibitor drug lopinavir (the active ingredient in Kaletra®) by inducing human cells to take up the nanoparticles. The cells then transport them to areas where HIV is actively reproducing.

Many safety experiments need to be done before a large study of this idea is possible. Van t’Klooster commented that one of the problems was that if someone had a bad reaction to the drug, they were stuck with it for a month as there was no way to remove it once it was injected.

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