HIV-blocking contraceptive gel in phase II trials.(News)

WASHINGTON -- Cellulose sulfate, a new vaginal gel that is being developed as both a contraceptive and as a means of preventing human immunodeficiency virus and other sexually transmitted infections, is as effective as nonoxynol-9 in preventing pregnancy, and also appears to be safer, researchers wrote in a poster presented at the annual meeting of the American College of Obstetricians and Gynecologists.

The cumulative probability of pregnancy during "typical" and "perfect" use of cellulose sulfate was 13.9% and 3.9%, respectively, in a population of 200 heterosexual, fertile couples who used the gel as their primary method of birth control for 6 months as part of a phase II, non-comparative contraceptive effectiveness trial, wrote Dr. Christine Mauck, of the Contraceptive Research and Development (CONRAD) program at the Eastern Virginia Medical School in Arlington, and her associates.

Cellulose sulfate is an antimicrobial that stimulates acrosomal loss, inhibits hyaluronidase, and impedes sperm penetration into cervical mucus.

Animal studies in rabbits have demonstrated the gel's contraceptive ability. Cellulose sulfate is active against cell-free and cell-associated HIV-1 because it blocks glycoprotein 120-CD4-coreceptor interaction, and thereby inhibits the entry of HIV into cells.

Cellulose sulfate has been studied in multiple safety trials of both HIV-free and HIV-infected men and women in which it has been found to be safe, and is currently being studied in two phase III HIV prevention trials, according to Dr. Mauck and her associates.

In this study, the 200 couples were demographically similar with regard to age (27 years for females; 29 years for males), race, and education.

Clinic visits were scheduled at enrollment, after one menstrual cycle, and after 6 months or six menstrual cycles, whichever occurred later.