RISUG: a potential candidate for the entry inhibitor group of antiretroviral drugs

Entry inhibitors are a group of antiretroviral drug which prevents HIV from entering human immune cells. They include both fusion and attachment inhibitors. A hypothesis is put forward in which a new male contraceptive drug with proven antimicrobial property is proposed as a possible candidate for the entry inhibitor group of antiretroviral drugs. The proposed mechanism of action involves (i) interaction with gp120 and thereby preventing binding to CD4 and (ii) competitive binding with the viral glycoprotein and inhibit the glycoprotein - cell surface glyocosaminoglycan Heparan Sulfate (HS) interaction. A new drug RISUG (Reversible Inhibition of Sperm Under Guidance) presently undergoing Phase III clinical trials throughout India for its contraceptive effect in male has also antimicrobial actions. RISUG is a chemical complex of styrene maleic anhydride (SMA(AN)) and dimethyl sulfoxide. On injection into the vas deferens, it reacts with the components of intravas fluid, the spermatic fluid and gets converted to styrene maleic acid (SMA(AC)) and breakdown products like mandelic acid. An anti HIV activity of RISUG is likely due to its electrical charge and mandelic acid generation. For experimental validation HIV in vitro assays can be performed which will involve infectivity assays, luciferase assay and soluble gp120 assays. A positive result from the studies will validate the hypothesis.