Chlorcyclizine is a phenylpiperazine that acts as a histamine H1 receptor antagonist (Ki = 9 nM).1 It has also been shown to be effective against hepatitis C virus (HCV; EC50 = 44 nM in vitro), preventing viral entry into host cells.2 In chimeric mice engrafted with primary human hepatocytes, 10-50 mg/kg chlorcyclizine significantly inhibited infection of HCV genotypes 1b and 2a.2
1.Tran, V.T., Chang, R.S.L., and Snyder, S.H.Histamine H1 receptors identified in mammalian brain membranes with [3H]mepyramineProc. Natl. Acad. Sci. USA75(12)6290-6294(1978) 2.He, S., Xiao, J., Dulcey, A.E., et al.Discovery, optimization, and characterization of novel chlorcyclizine derivatives for the treatment of hepatitis C virus infectionJ. Med. Chem.59(3)841-853(2016)