Simple mono-derivatisation of the aryl moiety of D4A and DDA-based phosphoramidate prodrugs significantly enhances their anti-HIV potency in cell culture

Metabolism of Stavudine-5′-[p-Bromophenyl Methoxyalaninyl Phosphate], Stampidine, in Mice, Dogs, and Cats

“…The metabolism of stampidine may involve demethylation first followed by the release of p-bromophenol, a theory consistent with recent reports of other STV aryl phosphoramide derivatives using an in vitro system by Saboulard's group (Saboulard et al, 1999;Siddiqui et al, 1999). Demethylated stampidine (Fig.…”

Enhanced inhibition of the EDHF phenomenon by a phenyl methoxyalaninyl phosphoramidate derivative of dideoxyadenosine

“…It should be noted that the observed increase in the potency of 2 0 ,3 0 -ddA-PMAPh against EDHF-type hyperpolarizations (B7-fold) is substantially less than the 200 times enhanced antiretroviral activity of 2 0 ,3 0 -ddA-PMAPh compared to 2 0 ,3 0 -ddA in CEM cell cultures (Siddiqui et al, 1999). The reasons for this variation in sensitivity are unclear, but could reflect the differences in prodrug hydrolysis by esterases and phophoramidases and subsequent nucleotide phosphorylation by kinases in different cell types.…”

“…Subsequent enzymatic cleavage of the phosphorus-nitrogen bond ( Figure 4, step 2) delivers the nucleotide monophosphate 2 0 ,3 0 -dd-5 0 -AMP directly, thereby bypassing conversion of 2 0 ,3 0 -ddA to 2 0 ,3 0 -dd-5 0 -AMP by adenosine kinase or via dideoxyinosine (2 0 ,3 0 -ddI) (Siddiqui et al, 1999). Since the ability of 2 0 ,3 0 -ddA and 2 0 ,5 0 -ddA nucleosides to inhibit adenylyl cyclase is markedly increased by addition of successive phosphate groups at the 5 0 or 3 0 locations, respectively, inhibition of EDHF-type hyperpolarizations by 2 0 ,3 0 -ddA-PMAPh may not simply involve direct intracellular delivery of 2 0 ,3 0 -dd-5 0 -AMP, but also its subsequent conversion by nucleotide kinases to 2 0 ,3 0 -dd-5 0 -ATP (Figure 4, step 3), a potent inhibitor of rat brain adenylyl cyclase with an IC 50 value of 0.76 mM (Johnson et al, 1997;Desaubry & Johnson, 1998;Shoshani et al, 1999).…”

“…The antiviral activity of such nucleosides can therefore be enhanced by the addition of a phosphate moiety shielded by hydrophobic groups, thereby generating a lipophilic prodrug that readily enters the cell, where it is converted to the free mononucleotide (Siddiqui et al, 1999;Cahard et al, 2004). Since the addition of phosphates to ddA nucleosides is also known to increase their inhibitory activity against adenylyl cyclase (Johnson et al, 1997;Desaubry & Johnson, 1998;Shoshani et al, 1999), in the present study, we have investigated whether a 'masked phosphate' phenyl methoxyalaninyl phosphoramidate derivative of 2 0 ,3 0 -ddA (2 0 ,3 0 -ddAPMAPh) is a more potent inhibitor of the EDHF phenomenon than the parent nucleoside itself.…”

“…ACh was administered at a concentration (3 mM) that evokes maximal hyperpolarization in the rabbit iliac artery Chaytor et al, 2003). In some experiments, 2 0 ,3 0 -ddA, 2 0 ,3 0 -ddA-PMAPh or the corresponding derivative of adenosine (Ado-PMAPh), synthesized as previously described (Siddiqui et al, 1999), were included in the buffer 30 min prior to the addition of ACh. Stock solutions of these agents were prepared in DMSO, which had no effect in control experiments.…”