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Some of the most exciting news to emerge from the 15th Conference on Retroviruses and Opportunistic Infections (CROI) this week in Boston involved the fruitful discoveries stemming from the fusion of two modern sciences: drug discovery and nanotechnology. As was evident in a handful of presentations at CROI, nanoparticles are being used to develop long-acting antiretrovirals—and possibly other medications used to treat HIV-positive people—that may only need to be administered once every few weeks or months.
Nanoparticles are microscopic polymers that are already being used in the production of various consumer- and health-related products. In cancer research, nanoparticles are being studied for their ability to deliver chemotherapy directly to tumors, thereby targeting the efficacy of the drugs while potentially limiting side effects. And in HIV, nanoparticles have been eyed as a way to administer antiretrovirals that are released slowly into the body and do away with cumbersome daily dosing requirements.
In a Wednesday, February 6, presentation at CROI, researchers at Tibotec discussed their experiences using nanoparticles containing rilpivirine (TMC278), the company’s experimental non-nucleoside reverse transcriptase inhibitor (NNRTI). Tibotec’s Gerben van t’Klooster said that rilpivirine’s already favorable pharmacokinetics—in first-time treatment takers, once-daily 75 mg doses of the drug are all that’s necessary to treat HIV infection—made it an ideal candidate to study as a long-acting agent using nanotechnology.
Tibotec has conducted preliminary research of nanoparticles containing rilpivirine in rats, dogs and humans. In all study subjects, the drug was injected, either subcutaneously (SC) or intramuscularly (IM). Once the drug-containing nanoparticles are deposited under the skin or in the muscle, they are slowly broken down, gradually releasing their pharmaceutical payload.
In animals, SC injections resulted in more stable blood levels of the drug. In humans, stable blood levels were achieved with both injection types. However, the researchers noted that injection-site reactions—redness, swelling and hard lumps—were frequently observed in dogs and humans receiving SC injections. These injection-site reactions were not seen with the use of IM injections.
In dogs, high concentrations of rilpivirine were seen for up to three months. Between the third and sixth month after the injections, the release of rilpivirine from the nanoparticles was complete.
In HIV-negative study volunteers, peak concentrations of rilpivirine were documented approximately three days after injecting doses ranging from 200 mg to 600 mg. Blood concentrations fell off by 60 percent by day 14, after which slow gradual decline was noted.
Dr. van t’Klooster said that his group would continue experimenting with long-lasting rilpivirine formulations—and possibly other long-lasting antiretrovirals to combine with it—as well as nanoparticle formulations of drugs that may be used to prevent HIV transmission.
Tibotec is not alone in its exploration of the potential synergy between nanotechnology and HIV drug development. Researchers at Creighton University in Omaha reported in a poster presentation at CROI that their test tube studies involving nanoparticles containing the NNRTI efavirenz and the protease inhibitors lopinavir and ritonavir were successful.
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comments 1 - 3 (of 3 total)
Karl N., Miami, FL, 2008-02-17 10:22:35
Not sure if that's reason for that much excitment. I still wanna see more advancements in gene therapy and finding a way to erradicate this plague!
johnny d, westfield nj, 2008-02-15 10:28:35
I'm wondering why meds were not developed in patch form(like nitro for heart patients)for hiv long before this. was there any discovery of side effects using nonoparticles? how about the effects of the particles themselves?what are the particles composed of besides meds?
Simon Cooper, London, UK, 2008-02-14 02:56:19
My side-effects are not bad and not apparent. I do, however, WORRY about possible FUTURE side-effects, including kidney or liver damage or build-up, and change of body shape, etc.
