April 21, 2009

Isentress’s Prevention Potential

The integrase inhibitor Isentress (raltegravir), when taken by either HIV-negative or HIV-positive people, might be able to prevent HIV transmission, according to a presentation at the International Clinical Pharmacology Workshop in Amsterdam.

Though Viread (tenofovir) and Truvada (tenofovir plus emtricitabine) are the leading antiretroviral (ARV) treatments being tested for use in HIV-negative people to prevent HIV infection, other ARVs are being considered for pre-exposure prophylaxis (PrEP). Researchers have also begun studying whether treating HIV-positive people, regardless of their CD4 count or medical need for ARV therapy, might help them reduce the risk of transmitting HIV to their HIV-negative partners.

One of the primary questions with using a specific ARV with either strategy is how well the drug reaches and accumulates in the genital tract compared with the blood stream. Researchers speculate that if an HIV medication does not easily penetrate the genital tract—the initial site of infection for many exposed to the virus and a reservoir for HIV among those living with the virus—it may not be the best choice for prevention purposes.

To determine genital tract distribution with Isentress, Amanda Jones, PharmD, from the University of North Carolina in Chapel Hill, and her colleagues studied blood and genital levels of Isentress in seven HIV-negative women. All of the women took Isentress twice daily for six days and once in the morning on the seventh day. They began taking their first dose between five and seven days after completing their last menstrual period.

Jones’s team found that Isentress levels took longer to build up in the genital tract following the first dose than in the blood, but after multiple doses Isentress levels stayed 93 percent higher in the genital tract than in the blood. This is lower than a few drugs such as Selzentry (maraviroc), which reaches genital levels more than 400 percent higher than in blood, but roughly comparable with Viread. What’s more, Isentress levels lasted nearly two and a half times longer in the genital tract than in blood.

The authors suggest that Isentress might be a promising candidate for PrEP. They also state that HIV-positive people who take Isentress might be less likely to pass HIV on to others through sexual contact due to high concentrations of the drug in the genital tract.

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