Could one shot every two months eradicate HIV?
Scanning electron micrograph of HIV-1 budding (in green) from cultured lymphocyte. This image has been colored to highlight important features; see PHIL 1197 for original black and white view of this image. Multiple round bumps on cell surface represent sites of assembly and budding of virions. (Photo Credit: C. Goldsmith Content Providers: CDC/ C. Goldsmith, P. Feorino, E. L. Palmer, W. R. McManus)

A two-drug injection may present the future of HIV prevention – a shot given every two months that would reduce a person’s risk of acquiring HIV by more than 90 percent.

In the latest trials, an injection once every eight weeks performed even better than daily pills, which currently are the gold standard of HIV treatment.

The two drugs -- Johnson & Johnson’s rilpivirine and ViiV Healthcare’s cabotegravir – were found in October to reduce the HIV virus in infected patients to undetectable levels in 95 percent of cases when taking a shot every eight weeks. This compared to 91 percent of those taking an oral pill.

Both are packaged as nanoparticles, which slowly dissipate in the blood over time. Cabotegravir has an exceptionally long half-life of 21-50 days, allowing for long dosing periods.

Scientists are now conducting Phase II clinical trials to see whether these two drugs may work individually as PrEP, or pre-exposure prophylaxis, a relatively new concept in which uninfected patients take medication to prevent HIV infection.

Two years ago, with little fanfare, scientists reported that cabotegravir protected monkeys from simian HIV. Eight monkeys were injected with the drug and eight were given a placebo. Challenged with rectal injections of simian HIV, all eight given the drug remained free of the virus, whereas all eight given a placebo became infected.

Currently, only Truvada – a two-drug combination pill – is approved for pre-exposure treatment. Approved in 2012, Truvada was originally found to reduce infection by 92 percent. Two real-world studies, however, recently found it 100 percent effective in preventing HIV in those who took the pill every day.

The trouble with Truvada is that many find it difficult to comply with a daily pill regimen. Many Truvada trials found poor adherence to a daily pill. Truvada only remains fully effective if it’s taken four or more times per week.

Thus, clinicians – and the CDC – are excited about new treatments that don’t require daily adherence. This excitement carries over into treatment for HIV-infected patients as well. According to CDC estimates presented at the National HIV Prevention Conference in Atlanta early this month, only 30 percent of Americans with HIV have fully suppressed the virus. These individuals are considered “undetectable.”

Today, those on daily medication are often able to achieve “undetectable” status, in which the virus is not detectable by standard blood tests. Recent studies have shown those with undetectable viral loads are not able to pass on the HIV virus.

The reason injectables would be valuable for HIV treatment and prevention, then, is that experts believe medication adherence could dramatically improve, preventing those who are infected from passing on the virus. It could also increase adherence among those taking PrEP to prevent infection.

Initially, scientists believed the injectable’s effectiveness period could be stretched to three months. According to Carl Dieffenbach, the Director for the Division of AIDS at the National Institutes of Health, however, trials have found the period of effectiveness is closer to two. Dieffenbach presented on future HIV prevention treatments at the National Conference for HIV Prevention in December.

Those who follow the HIV drug pipeline say the earliest they believe an injectable would come on the market would be 2020. This is because the FDA requires long-term testing of new treatments, and each clinical trial must be longer than the one before. Stage 3 clinical trials typically last several years.

Tim Horn of Treatment Action Group in New York, who monitors the drug pipeline, cautioned Raw Story that it would be unwise for those who are skeptical of the current HIV prevention drug to wait for an injectable treatment.

“Folks who are sort of waiting on the sidelines for long-acting PrEP options will have a long wait before something is on the market and available,” added Jim Pickett of AIDS Foundation of Chicago, speaking to POZ Magazine. “No one should be under the illusion, or delusion, that this method is coming to a pharmacy near you anytime soon.”

Since the beginning of the HIV epidemic, which began in earnest in the early 1980s, nearly 75 million have been infected with the virus.

The World Health Organization estimates about one-half percent of the population of the Americas is infected. In Sub-Saharan Africa, infection rates hover around 4 percent. Sub-Saharan Africa accounts for more than 70 percent of the world’s HIV cases.

Globally, nearly 1 percent of the world’s population lives with HIV.