Foscarnet Phosphonoformic acid

Foscarnet (phosphonoformic acid) is an inorganic pyrophosphate analog (Figure 49-2) that inhibits viral DNA polymerase, RNA polymerase, and HIVreverse transcriptase directly without requiring activation by phosphorylation. Foscarnet blocks the pyrophosphate binding site of these enzymes and inhibits cleavage of pyrophosphate from deoxynucleotide triphosphates. It has in vitro activity against HSV, VZV, CMV, EBV, HHV-6, HHV-8, and HIV-1. 

Phosphonoformic acid (Foscarnet), an antiviral drug, which consists of carboxylic acid and phosphate linked together, was shown to be absorbed in the small intestine by the phosphate carrier-mediated mechanism [154], The transport of folic acid was investigated in biopsy specimens of intestinal mucosa from healthy volunteers. A pH-dependent, active transport of folic acid was found in the proximal small intestine, whereas in the mucosa of the colon, folic acid uptake was driven by a facilitated diffusion, mediated by a low-affinity carrier [155]. The existence of folate receptors in the human colonic mucosa is logical due to the large amounts of folic acid produced by the colonic flora [145],... 

Acyclovir (nucleoside analogue Foscarnet (phosphate analogue of guanosine) trisodium salt of phosphonoformic acid)... 

The literature on antiviral screening for HHV-6 and HHV-7 is sparse and has been reviewed elsewhere (1,3-5). Cell systems for viral propagation have included primary human peripheral blood and cord blood lymphocytes (CBL), and T-cell lines. Methods for monitoring viral replication have included examining infected cultures for cytopathic effect, immunofluorescence analysis, quantitation of viral DNA, and focus-forming assays. Phosphonoformic acid (foscarnet), phosphonoacetic acid, and ganciclovir inhibit HHV-6 and HHV-7... 

These two compounds may possess some clinical advantage over ara-A due to their low systemic toxicity. The antiviral effects of phosphonoformic acid (PFA, foscarnet sodium), which is presently in Phase III clinical trials in Europe, 3 have been discussed in a recent review.91 The synthesis and structural requirements for antiherpes activity of a series of PFA esters have also been reported.92... 

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