A new study has found that when a novel intravaginal ring is implanted with anti-retroviral drug tablets or pods, it demonstrates sustained and controlled drug release and safety over 28 days from HIV.
Marc Baum, corresponding author said that the ring, designed to prevent transmission of HIV, was tested in pig-tailed macaque monkeys, and is engineered to be inexpensive, which makes it useable in developing countries.
One of the two drug combinations tested in the ring had been shown in three clinical trials to prevent HIV—some of the time—when taken orally, and is the only product approved by the US Food and Drug Administration (FDA) for HIV prophylaxis.
The ring's topical drug delivery has critical advantages over oral therapy. People often fail to take their medications as prescribed. That probably accounts for some of the wide variation in risk reduction in the three clinical trials, which ranged from 44 to 75%, said Baum, of the Oak Crest Institute of Science, Pasadena, CA.
He added that the issues such as adherence to a regular dosing schedule are significantly reduced by continuous release of the drugs into the vaginal mucosa independently of coitus and daily dosing.
The ring maintains steady state drug levels in the vaginal tissues, the key anatomic compartment for preventing sexual HIV transmission, and eliminates the concentration troughs encountered with oral medications. This according to Baum, should boost effectiveness and dramatically reduce, or eliminate side effects entirely.
The two drug combinations tested include Truvada, which consists of emtricitabine and tenofovir disoproxil fumarate, and Truvada plus maraviroc, which work by blocking the chemokine receptor, CCR5, which is a target entryway of HIV.
This report was published online in Antimicrobial Agents and Chemotherapy.