**2.1. Cidofovir [(S)-HPMPC; (S)-1-(3-hydroxy-2-phosphonomethoxypropyl)cytosine; VISTID]**

The antiviral effect of cidofovir is based on its transformation in the infected cells in di- and triphosphate and such way becoming an alternative substrate of the AdV DNA polymerase possessing higher affinity compared to cellular DNA polymerases (I, II and III) [15]. Sequence changes in a conserved region of the AdV DNA polymerase were established at cidofovirresistant AdV mutants [16].

Cidofovir IC50 values in cell culture testing versus broad spectrum of AdVs are within 0.8– 17 μg/ml [17]. In in vivo testing in ocular infection with AdV (type C) of New Zealand rabbits and cotton rats the compound treatment is efficacious when administered as 0.5–1% eye drops [18–20]. Romanowski and Gordon [21] found efficacy of topical 0.5% cidofovir on several human adenoviruses (AdV1, AdV5 and AdV6) in the New Zealand rabbit ocular model. AdV type B and type C-induced pneumonia registered in mice and in cotton rats [22] could be used for in vivo treatment with antivirals.
