Design, synthesis and biological evaluation of phosphorodiamidate prodrugs of antiviral and anticancer nucleosides

Abstract

We herein report the application of the phosphorodiamidate phosphate prodrug approach to a series of thirteen nucleoside analogs with antiviral or anticancer activity. Twenty-five symmetrical phosphorodiamidates were synthesized, bearing esterified l-Alanine (and in one case d-alanine) in the prodrug moiety, each as single stereoisomer. The presence of an achiral phosphorus represents a potential advantage over the phosphoramidate ProTide approach, where diastereoisomeric mixtures are routinely obtained, and different biological profiles may be expected from the diastereoisomers. Optimization of the synthetic pathway allowed us to identify two general methods depending on the particular nucleoside analogs. All the compounds were biologically evaluated in antiviral and anticancer assays and several showed improvement of activity compared to their parent nucleosides, as in the case of ddA, d4T, abacavir and acyclovir against HIV-1 and/or HIV-2. The biological results were supported by metabolism studies with carboxypeptidase Y monitored by 31P NMR to investigate their bioactivation. This work further validates the phosphorodiamidate approach as a monophosphate prodrug motif with broad application in the antiviral and anticancer fields.

Prodrugs of Phosphonates and Phosphates: Crossing the Membrane Barrier

“…Recently, McGuigan and colleagues have claimed just such advantages for a diamidate strategy [119,120]. When the amide is derived from an amino acid, achieving a neutral species requires esterification of the carboxyl group as well (e.g.…”

“…60 ). After examination of a series of twenty-five diamidates for activity against HCV [120] and HIV replication, and anti-proliferative effects in several cell lines, it was found that this strategy is sufficient to afford good cellular activity with several different nucleoside analogues [119]. Furthermore, preparation of symmetrical bisamidates from the symmetrical diesters has been reported [121].…”

Biocatalytic approaches applied to the synthesis of nucleoside prodrugs

“…The SATE derivative of AZT, bis(tBuSATE)AZT-MP (Scheme 1), showed marked antiviral activity in thymidine kinase-deficient CEM cells in which AZT was virtually inactive, reaffirming the hypothesis that it exerts its activity via intracellular delivery of AZT 5′-monophosphate (Lefebvre et al, 1995). Phosphoramidates and phosphorodiamidates have been also explored as pronucleotides with improved bioavailability (McGuigan et al, 2013;Mehellou et al, 2009).…”

“…Other phosphate and phosphonate derivatives have been also developed (McGuigan et al, 2013); for example, S-acyl-2-thioethyl (SATE) groups are hydrolysed inside cells into the phosphodiester derivative by a nonspecific esterase, which subsequently liberates the nucleoside monophosphate by the action of a phosphodiesterase (Peyrottes et al, 2004). The SATE derivative of AZT, bis(tBuSATE)AZT-MP (Scheme 1), showed marked antiviral activity in thymidine kinase-deficient CEM cells in which AZT was virtually inactive, reaffirming the hypothesis that it exerts its activity via intracellular delivery of AZT 5′-monophosphate (Lefebvre et al, 1995).…”

Symmetrical Diamidates as a Class of Phosphate Prodrugs to Deliver the 5′‐Monophosphate Forms of Anticancer Nucleoside Analogues

“…Although less extensively investigated than the ProTide approach, a second phosphoramidate strategy that has been reported by our group as a promising way to deliver nucleoside monophosphates into a cell, is the use of phosphorodiamidates . In this approach, two identical amino acid esters are introduced onto the monophosphate moiety through a P−N bond in order to mask the negative charges.…”