Efficacy and safety of a new vaginal contraceptive antimicrobial formulation containing high molecular weight poly(sodium 4-styrenesulfonate)

Host cell infection by sexually transmitted disease (STD)causing microbes and fertilization by spermatozoa may have some mechanisms in common. if so, certain noncytotoxic agents could inhibit the functional activity of both organisms. High molecular mass poly(sodium 4-styrenesulfonate) (T-PSS) may be one of these compounds. T-PSS alone (1 mg/ml) or in a gel (2% or 5% T-PSS) completely prevented conception in the rabbit. Contraception was not due to sperm cytotoxicity or to an effect on sperm migration. However, T-PSS inhibited sperm hyaluronidase (IC50 = 5.3 mug/ml) and acrosin (IC50 = 0.3 mug/ml) and caused the loss of acrosomes from spermatozoa, (85% maximal loss by 0.5 mug/ml). T-PSS (5% in gel) also reduced sperm penetration into bovine cervical mucus (73% inhibition by 1 mg gel/ml). T-PSS (5% in gel) inhibited human immunodeficiency virus (HIV; IC50 = 16 mug gel/ml) and herpes simplex viruses (HSV-1 and HSV-2; IC50 = 1.3 and 1.0 mug gel/ml, respectively). The drug showed high efficacy against a number of clinical isolates and laboratory strains. T-PSS (5% in gel) also inhibited Neisseria gonorrhea (IC50 < 1.0 gel/ml) and Chlamydia trachomatis (IC50 = 1.2 mug gel/ml) but had no effect on lactobacilli These results imply that T-PSS is an effective functional inhibitor of both spermatozoa and certain STD-causing microbes. The noncytotoxic nature should make T-PSS safe for vaginal use. T-PSS was nonmutagenic in vitro and possessed an acute oral toxicity of >5 g/kg (rat). Gel with 10% T-PSS did not irritate the skin or penile mucosa (rabbit) and caused no dermal sensitization (guinea pig). Vaginal administration of the 5% T-PSS gel to the rabbit for 14 consecutive days caused no systemic toxicity and only mild (acceptable) vaginal irritation. T-PSS in gel form is worthy of clinical evaluation as a vaginal contraceptive HIV/ STD preventative.