BufferGel is a buffering agent designed to maintain normal vaginal acidity in the presence of ejaculate. Studies have shown that HIV is inactivated below a pH of 4 to 5.8. Carbopol 974, the major nonaqueous component of BufferGel, is commonly used as a gelling or tableting agent and has a well-documented safety record. BufferGel has proven safe and well tolerated in Phase I studies. PRO 2000/5 inhibits viral entry into susceptible cells. PRO 2000/5 has also been evaluated in Phase I studies and was found to be safe and well tolerated.