Scientists are developing a drug that may be effective in treating two sexually transmitted infections at once – HIV and genital herpes – as well as potentially preventing the spread of HIV from one person to another.

Researchers from the University of Leuven (KU Leuven) in Belgium say the experimental drug, dubbed PMEO-DAPym, can tackle both HIV (human immunodeficiency virus) and HSV (herpes simplex virus). The drug can prevent HIV from multiplying, making the cells targeted by the virus less susceptible to infection.

The researchers say that both HIV, the virus that causes AIDS, and HSV, the virus that causes genital herpes, can together have dangerous effects. People with genital herpes are more likely to become infected with HIV. Additionally, the scientists say, for people who carry both viruses, one infection can worsen the symptoms of the other. These people are also more likely to infect their partners.

There are drugs already on the market that are both anti-HIV and anti-HSV – tenofovir and adefovir. But the researchers say these drugs do not have the ability to stop the spread of the HIV virus as well as targeting particular cells.

PMEO-DAPym can do this by effectively “down-modulating” the CCR5 receptor. This a molecule on the surface of human immune cells that the HIV virus exploits to enter and infect the cells.

Jan Balzarini of KU Leuven says:

We are excited about this finding since the concomitant action of one single drug on two different targets in the HIV infection process makes it a multifunctional drug that might eventually result in more efficient suppression of virus replication and a lesser risk of resistance development.”

In comparing the effectiveness of PMEO-DAPym against other HIV and HSV drugs already on the market, the researchers say that PMEO-DAPym was equal to or better than tenofovir and adefovir in the majority of the tests.

When testing PMEO-DAPym in a panel of clinical HIV and HSV isolates that were resistant to the currently available drugs, the new antiviral was effective against all of them.

The drug was less effective against HSV compared with acyclovir, a popular anti-HSV drug. But the researchers claim that PMAO-DAPym would still prove effective in the higher concentrations that can be achieved in topical preparations.

As well as being tested against the HIV and HSV viruses themselves, the researchers also tested the new antiviral on cells, tissues and animals prior to exposure to the viruses.

A relative of PMEO-DAPym, tenofovir, has been shown in previous clinical trials, the researchers say, to have an effect as a “vaginal microbicide” – a gel that can be applied to the vagina before sex, helping to protect women against infection.

They add that this suggests PMEO-DAPym might also be developed as a prevention tool against HIV and HSV.

Based on results that proved the drug to be effective against infection of cells through the CCR5 receptor, the researchers say that in addition to blocking multiplication of the virus, making the human mucosal tissue harder to infect could also be a route to effective prevention of HIV transmission.

Before a decision is reached on whether the drug will be approved for clinical trials in humans, it must first be tested in a “relevant microbicidal animal model.” The researchers add that its application as a systemic treatment following infection also needs to be investigated.