HIV drug designed to target resistant strains passes late-stage trial

PHOTO: Shutterstock

*Bacteria in vagina breaks down medicine in gel, making it less effective in preventing virus

A promising Human Immuno-deficiency Virus (HIV)/Acquired Immune Deficiency Syndrome (AIDS) drug has succeeded in a late-stage trial – paving the way to a low intensity treatment that could target drug-resistant strains.


Gilead Sciences Inc, the makers of the current best-selling HIV treatment Truvada, announced that a new drug called bictegravir was successful in four phase three studies.


The drug has proven effective at targeting aggressive types of drug-resistant HIV. It is also less demanding than other medications, taken just once a day with no need for a booster.


In recent years, there has been dramatic progress in the medical field surrounding HIV, with more precise testing, potential vaccines and longer life expectancy. Gilead has plans to submit marketing applications in the United States (US) before the end of June, and in the European Union (EU) in before the end of September, so the product can be eventually approved for use.


The latest trials concluded the single tablet was just as effective treating the virus as other medications on the market, with the possibility of less side effects.


Gilead already has approved treatments for HIV and is pinning its hope on combining bictegravir with emtricitabine/tenofovir alafenamide (FTC/TAF). It comes as British rival GlaxoSmithKline (GSK) works on a two-drug treatment regimen for controlling the virus behind AIDS.


Three of the studies tested Gilead’s combination against a regimen containing GSK’s dolutegravir in previously untreated patients. Data showed the Gilead combination was as effective as GSK’s product.The regimen was also well tolerated and no patients discontinued the study due to kidney issues, a frequent side effect seen with HIV treatments.


Also, bacteria in the vagina affect whether a drug stops an HIV infection or is itself stopped cold.A vaginal gel containing tenofovir, an antiretroviral drug used to treat HIV infection, was three times as effective at preventing HIV in women who had healthy vaginal bacterial communities as it was in women with a less beneficial mix.


The finding may help explain why the effectiveness of these gels has varied in trials, researchers report in the June 2 Science.“The vaginal microbiota is yet another variable that we have to take into account when we are thinking about why one intervention does or doesn’t work,” says clinical scientist Khalil Ghanem of Johns Hopkins University School of Medicine, who coauthored a commentary accompanying the study.


For women, one strategy to prevent HIV infection is to apply medicated vaginal gels before and after sex. But results have been mixed regarding how well the gels work. The hit-or-miss effectiveness can partly be explained by some patients not taking the medication as prescribed. But study coauthor Adam Burgener, a microbiologist at the Public Health Agency of Canada in Winnipeg, wondered if there might also be a biological explanation.


The main residents of a healthy vaginal microbial community, or microbiota, are Lactobacillus species. The bacteria produce lactic acid, making the vaginal tract more acidic and possibly “less hospitable for potential pathogenic organisms,” Ghanem says.


To examine the effect of the vaginal microbiota on tenofovir, Burgener and colleagues turned to a previous trial of South African women, which showed that the drug reduced HIV infections by 39 percent. During that trial, samples of vaginal mucus were taken. In the new study, the researchers measured bacterial proteins in 688 of those samples to determine the bacteria in the women’s vaginas when the samples were collected.


Just over 400 women’s vaginal microbiota mainly had Lactobacillus species; the microbiota of the other 281 women were dominated by non-Lactobacillus species, such as Gardnerella vaginalis. Within those two groups were women who had used tenofovir vaginal gel and those who had used a non-medicated gel as a placebo.


In the Lactobacillus-dominant group, the incidence of HIV was 61 percent lower in women using the medicated gel compared with those using the placebo gel. But in the non-Lactobacillus dominant group, it was only 18 percent lower. There was no appreciable difference in the consistency of the gel’s reported use between the two groups, the researchers note.