An injectable drug could be the key to reducing the rate of HIV transmissions in women, a new study reported.

For this research, the team from the division of infectious diseases at the University of North Carolina School of Medicine wanted to find a more effective way of getting women to use preventive measures for HIV. Currently, there are several forms of pre-exposure prophylaxis (PrEP), such as vaginal rings or gels that can greatly reduce risk of contracting the virus. Despite having these options, the adherence rate is still very low.

The researchers, who worked with Merck, tested out the effectiveness of the oral HIV drug, raltegravir. Instead of using it in pill form, they changed the drug into a long-acting injectable.

"Raltegravir is a well-tolerated drug with a strong track record of use for the treatment of HIV," said Martina Kovarova, an assistant professor of medicine in the division of infectious diseases at the UNC School of Medicine. "Changing its form from an oral pill to a subcutaneous injection produced a long-acting release of the drug that can be used for pre-exposure prophylaxis."

The researchers then compared how long raltegravir can stay in the mice when it was either taken orally twice a day or was injected once. They found that after two weeks, mice from both groups had the same levels of drug.

After determining that the long-acting injectable version of the drug was effective at suppressing viral load, the researchers created a model of vaginal HIV transmission to test how the injectable drug would work in this specific scenario. The researchers found that the injectable drug was capable of protecting the body from several strains of HIV that were introduced in the model.

The researchers hope that if study's findings could be replicated in humans, an injectable PrEP might be able to increase the adherence rate since one shot has the potential to last for weeks. The drug in pill form has to be taken twice a day.

"A single injection of long-acting raltegravir may only be needed every month or every few months to provide protection against HIV infection, which could improve adherence," Kovarova said.

"Effective long-acting formulations for HIV prevention represent the next generation of pre-exposure prophylaxis. This is a very exciting new formulation of raltegravir with great potential," said study co-author Victor Garcia, professor of medicine in the division of infectious diseases at the UNC School of Medicine.

The study was published in the Journal of Antimicrobial Chemotherapy.