CYCLAZOSIN HYDROCHLORIDE is a quinazoline derivative pharmacologically characterized as putative a1B-adrenoceptor antagonist.

Levovirin is a guanosine nucleoside analog and the L-enantiomer of ribavirin. It is an investigational drug for the treatment of hepatitis C virus-mediated diseases. Levovirin has a similar immunomodulatory potency to ribavirin in vitro without accumulating in red blood cells or causing hemolytic anemia, a known side effect of ribavirin. Levovirin has been shown to stimulate host immune responses (enhanced Th1 and reduced Th2 cytokine expression). Significantly improved oral absorption of levovirin was achieved following administration of a valine ester prodrug of levovirin R1518. Levovirin was found more potent to inhibit Tick-borne encephalitis virus (TBEV) on the basis of robust binding affinity between protein-drug interactions. This finding may help to understand the nature of helicase and development of specific anti-TBEV therapies.