Population Council Research that makes a difference

Laboratory scientists at the Population Council's Center for Biomedical Research (CBR) are developing water-based gels that contain carrageenan (a natural polymer isolated from seaweed) and varying amounts of zinc acetate to block sexually transmitted infections such as herpes and HIV in humans.

Using animal models of infection, the scientists have shown that PC-707, a gel comprising 0.3% zinc acetate and 3% carrageenan, effectively blocks both herpes infection in mice and a modified form of HIV infection in macaques (monkeys).

Zinc salts might represent a useful alternative to antiretroviral drugs (ARVs) currently in use and under investigation. They are unlikely to cause resistant strains of HIV to develop, which is always a concern with ARVs. Moreover, many zinc salts are freely soluble in water, which is not the case with many ARVs. This property makes it easier to prepare stable, water-based gels.

Council scientists also are preparing zinc gels in which carrageenan is replaced with other natural and man-made polymers. These gels might have interesting properties regarding their spectrum of activity and movement within the rectum and vagina. The scientists also are trying to determine how zinc acetate blocks herpes and HIV infection.

Council scientists are now optimizing the gels in terms of efficacy, safety, and stability. Once an optimized formulation is identified, the microbicide product development team will prepare clinical-grade material at CBR to support a Phase 1 clinical trial in humans.