2 days ago
Findings give hope for monthly HIV prevention pill
There are several antiretroviral formulations proven to prevent HIV infection: a daily pill, two different jabs that offer protection for two and six months respectively, and a vaginal ring for women that has to be replaced monthly. In a few years, a long-acting pill may join the ranks, if it works.
The pill, for now called MK-8527, has the potential to prevent HIV infection for up to a month in its current formulation.
It is a nucleoside reverse transcriptase translocation inhibitor (NRTTI), which means it disrupts a specific step in the cycle by which the virus makes copies of itself.
The pill is now moving onto pivotal phase-three trials, after promising results from a smaller phase-two study presented at the International Aids Society (IAS) conference held in Kigali, Rwanda.
The phase-two study, conducted in trial sites in South Africa, the US and Israel showed that MK-8527 was well tolerated and had a safety profile similar to a placebo. It also showed the levels of the antiretroviral were at the required levels in the bodies of study participants, though the study was not designed to determine whether it is effective.
Whether MK-8527 actually prevents HIV infection will now be tested in two large phase-three studies across multiple countries, including South Africa.
In these studies, the efficacy of the monthly pill will be compared with a daily HIV prevention pill that is already widely available in South Africa's public sector. The daily pill contains the antiretroviral drugs tenofovir disaproxil fumarate and emtricitabine.
Latest findings
The phase-two study looked at three different doses of the monthly pill — 3mg, 6mg and 12mg — as well as a placebo. The 350 participants, about one third of which were from South Africa, were given one pill (either an active pill or placebo) every month for six months. They were monitored for at least two months afterwards. None of the participants acquired HIV during the study.
The researchers enrolled adults who were at a low risk of being exposed to HIV and excluded pregnant and breastfeeding women, and people who had previously used MK-8527 or a similar antiretroviral drug called Islatravir, said Dr Kenneth Mayer, a professor of medicine at Harvard Medical School, who presented the findings in Kigali earlier this month.
The levels of the antiretroviral in the blood of all the participants were measured on day one and two, on the last day of taking the pill, and again at the first follow-up visit after stopping the pill.
Based on these results, Mayer said there doesn't appear to be a build-up of drugs in the body that might prove toxic over time. This supports evaluating the use of a monthly pill over a longer period (than the six months in the study), he said, 'without concern that increasing drug levels will cause toxicity after a longer period of monthly administration'.
