Progress under way on the microbicide front
Progress under way on the microbicide front
Canadian scientists are now in clinical trials with the "invisible condom," a topical microbicide that may offer women a female-controlled form of protection against HIV and other sexually transmitted diseases (STDs.)
The "invisible condom" consists of an active ingredient, sodium lauryl sulfate, and a carrier, a thermoreversible gel formulation that has the unique property to be fluid at room temperature and a gel at body temperature. The phase transition temperature at which the formulation chan-ges from liquid to gel can be adjusted as necessary. The gel formulation, when applied with a specially designed applicator, covers not only the cervix area, but the vaginal mucosa as well. (For more information, see Contraceptive Technology Update, April 1999, "Get ready: Women to have more options for preventing disease." Past CTU articles are available on the web site: www.contraceptiveupdate.com.)
Researchers at the Infectious Diseases Research Centre of Laval University in Quebec City, led by Michel Bergeron, MD, FRCP, have shown that sodium lauryl sulfate is a potent inactivator of HIV-1 infectivity to cultured cells.1 Previous studies from the Canadian laboratory have demonstrated that sodium lauryl sulfate inactivates different strains of herpes simplex virus type 1 and type 2 (HSV-1, HSV-2) in vitro.2 The team’s most recently published research shows that the gel formulation prevents infection of susceptible cells by HIV-1 and HSV-2.3
The move into clinical testing represents an exciting advance, says Rabeea Omar, PhD, a member of the research team. The Canadian government has provided $350,000 to help fund the Phase 1 clinical testing.
"We hope to have a safe and effective microbicide for all women," says Omar. "We hope that people will think about this as a potential option for women all over the world."
How does it work?
The name "invisible condom" has been trademarked, and the gel formulation and the unique applicator have been patented, says Omar. But how does the "invisible condom" work?
The Canadian scientists theorize that the gel formulation can be inserted into the vagina well in advance of intercourse. When it is delivered through the specially designed applicator, the formulation can cover the smallest vaginal folds and forms a semisolid physical barrier to infective agents. This adhering capability is seen as a potential advantage of the gel formulation over other carriers, such as creams, which may leak from the vagina and prove unpleasant for use, says Omar.
A second layer of protection, a chemical barrier, is afforded through the active agent, sodium lauryl sulfate, which disrupts viral membranes. The sodium lauryl sulfate gel formulation has been shown not to be toxic to the vaginal mucosa of rabbits. In addition to protection against HIV and HSV-2, sodium lauryl sulfate, which has protein denaturant potency, also may prove effective against human papillomavirus, a nonenveloped virus, of which certain types have been causally linked to cervical cancer.4
The "invisible condom" research is just one of the advances being recorded on the microbicide front, says Polly Harrison, PhD, director of the Silver Spring, MD-based Alliance for Microbicide Development.
"Several products are moving into advanced clinical trials, with another half-dozen in Phase One," states Harrison. "And there are whole new categories of compounds that we are seeing for the first time in active development."
Progress on the protection front will be reported at Microbicides 2002, set for May 12-15, 2002, in Belgium. The three-day conference will be divided into three tracks: basic science; clinical science; and behavioral science, public health, and the microbicide marketplace. It will include scientific overviews; workshops to review issues unique to microbicides, such as trial design, outcome measures, and ethical issues in clinical trials; and poster sessions. (Readers can check out the conference’s web site at www.itg.be/micro2002.)
Harrison, who is serving on the conference organizing committee, says that there is increased interest in microbicide development, which may bode well for the actual delivery of a product.
"There are new requests for proposals that the National Institutes of Health has put out for development teams, and we are seeing people who have never been involved in microbicides coming from the first ranks of science to start working in this arena," she states. "It is thrilling!"
References
1. Bestman-Smith J, Piret J, Desormeaux A, et al. Sodium lauryl sulfate abrogates human immunodeficiency virus infectivity by affecting viral attachment. Antimicrob Agents Chemother 2001; 45:2,229-2,237.
2. Piret J, Lamontagne J, Bestman-Smith J, et al. In vitro and in vivo evaluations of sodium lauryl sulfate and dextran sulfate as microbicides against herpes simplex and human immunodeficiency viruses. J Clin Microbiol 2000; 38:110-119.
3. Piret J, Gagne N, Perron S, et al. Thermoreversible gel as a candidate barrier to prevent the transmission of HIV-1 and herpes simplex virus type 2. Sex Transm Dis 2001; 28:484-491.
4. Howett MK, Neely EB, Christensen ND, et al. A broad-spectrum microbicide with virucidal activity against sexually transmitted viruses. Antimicrob Agents Chemother 1999; 43:314-321.
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