Inhibitory Activity of Alkoxyalkyl and Alkyl Esters of Cidofovir and Cyclic Cidofovir against Orthopoxvirus Replication In Vitro

Abstract

A new series of ether lipid esters of cidofovir (CDV) were evaluated against vaccinia and cowpox viruses. Activity was dependent on number of atoms in the alkyl or alkoxyalkyl chain, the linker moiety, and the presence of a double bond in the alkoxyalkyl chains linked to the phosphonate moiety of CDV.The threat of an intentional or unintentional spread of poxvirus infections to a vulnerable population has led to increased efforts to find safe, rapidly deployable treatments against such infections. Although vaccination is now being offered to some healthcare workers and other "first responders," there are valid concerns about potential vaccine risks (3, 9). Vaccination is not recommended for those with eczema and other exfoliative skin disorders or those with immunodeficiencies or for pregnant women. Therefore, the use of antiviral therapy in the event of a poxvirus outbreak or in the treatment of vaccination complications against smallpox virus (4) points to the continued need to examine available antiviral therapies as well as to develop new and more efficient treatment.Cidofovir (CDV) and cyclic CDV (cCDV) have been shown to be potent inhibitors of poxvirus replication in vitro (1,7,8,13) and in animal model studies (5, 10, 12); however, these compounds are inactive when given orally.Previous in vitro studies have shown that multiple-log increases in antiviral activity against orthopoxvirus replication (8), as well as enhanced inhibition of cytomegalovirus and herpesvirus replication by these esters (2), were observed with hexadecyloxypropyl (HDP) and octadecyloxyethyl (ODE) derivatives of CDV and cCDV (HDP-CDV, HDP-cCDV, ODE-CDV, and ODE-cCDV) compared to the results seen with the parent compounds. HDP-CDV, ODE-CDV, and oleyloxypropyl-CDV (OLP-CDV) have oral bioavailabilities of 88 to 93% in mice (6) and have oral activity against vaccinia virus (VV) and cowpox virus (CV) infections in mice (11).In this study, the unmodified acyclic nucleoside phosphonates CDV and cCDV (along with a new series of analogs synthesized by esterification of these compounds with an alkyl chain with or without the propoxy-or ethoxy-linker moieties) were evaluated (using methodologies described previously) (7) for activity (plaque reduction assay) against VV and CV and for cytotoxicity (neutral red uptake assay) in human foreskin fibroblast (HFF) cells. To determine efficacy, briefly, HFF cells seeded in 6-well plates 2 days prior to use were infected with either VV or CV by the addition of 20 to 30 PFU per well. After a 1-h incubation period, various concentrations of drug were added to triplicate wells and plates were incubated at 37°C for 3 days. Toxicity was evaluated using HFF cells seeded in 96-well plates incubated with various concentrations of drug for 7 days at 37°C. After incubation, cell monolayers were stained with a 0.01% solution of neutral red. The compounds were synthesized as reported previously (8).As presented in Table 1, the most active ether lipid esters of CDV were OLE-CDV, ODBG-CDV, TDP-CDV, OLP-CDV, and ODP-...

Comparative Activities of Lipid Esters of Cidofovir and Cyclic Cidofovir against Replication of Herpesviruses In Vitro

“…Further differences with these viruses may be due to the fact they replicate in lymphocyte-derived cells rather than fibroblasts as do HSV, VZV, and CMV. As was reported previously (13,20,39), the analogs that were the most active were generally the most toxic both in cell killing (CC 50 ) and cell proliferation (IC 50 ) assays. Presumably this is due to the increased uptake of the drug into the cell because of the lipid conjugate and accelerated conversion to CDVdiphosphate (1).…”

“…This increase in selectivity has been documented previously for CMV, adenovirus, and orthopoxviruses. Due to the large number of viruses used in this study, we have not presented selective index values for each virus, as they are similar to those published previously for other viruses (3,13,20,21).…”

“…In previous studies carried out with CMV, adenoviruses, or orthopoxviruses, a structure-activity analysis indicated that the best activity was observed when the alkyoxyalkyl chain length was 18 to 22 atoms and included either an ethanediol or a propanediol linker (13,20,38). Straight alkyl chains were also optimally active if the chain length was 18 to 22 atoms (38).…”

“…We have reported previously that hexadecyloxypropyl cido-fovir (HDP-CDV), octadecyloxypropyl cidofovir (ODE-CDV), oleyloxyethyl cidofovir (OLE-CDV), and oleyloxypropyl cidofovir (OLP-CDV) may be good candidates for new antiviral agents (3,20,21,22,23,31). On the basis of the activities of these compounds, additional analogs of CDV and cyclic CDV (cCDV) were synthesized.…”

Inhibitory Activity of 4-[(1,2-dihydro-2-oxo-3H-indol-3-ylidene)amino]-N-(4,6-dimethylpyrimidin-2-yl) Benzenesulphonamide and its Derivatives against Orthopoxvirus Replication in vitro

“…Our results demonstrated these compounds possessed significant inhibitory effects against HIV-1 replication. In view of the broad spectrum of antiviral activities of isatin derivatives, this study evaluated the antiviral activity of some novel 4-[(1,2-dihydro-2-oxo-3H-indol-3-ylidene)amino]-N-(4,6-dimethylpyrimidin-2-y)benzenesulphonamides (Figure 1) against pox viruses, such as vaccinia virus (VV) and cowpox virus (CV), in human foreskin fibroblast (HFF) cells using previously published methods (Keith et al, 2004).…”