Phosphate derivatives of AZT display enhanced selectivity of action against HIV 1 by comparison to the parent nucleoside

Prodrug Therapies for Infectious and Neurodegenerative Diseases

Prodrugs are bioreversible drug derivatives which are metabolized into a pharmacologically active drug following chemical or enzymatic modification. This approach is designed to overcome several obstacles that are faced by the parent drug in physiological conditions that include rapid drug metabolism, poor solubility, permeability, and suboptimal pharmacokinetic and pharmacodynamic profiles. These suboptimal physicochemical features can lead to rapid drug elimination, systemic toxicities, and limited drug-targeting to disease-affected tissue. Improving upon these properties can be accomplished by a prodrug design that includes the careful choosing of the promoiety, the linker, the prodrug synthesis, and targeting decorations. We now provide an overview of recent developments and applications of prodrugs for treating neurodegenerative, inflammatory, and infectious diseases. Disease interplay reflects that microbial infections and consequent inflammation affects neurodegenerative diseases and vice versa, independent of aging. Given the high prevalence, personal, social, and economic burden of both infectious and neurodegenerative disorders, therapeutic improvements are immediately needed. Prodrugs are an important, and might be said a critical tool, in providing an avenue for effective drug therapy.

Mild and Chemoselective Phosphorylation of Alcohols Using a Ψ-Reagent

An operationally simple, scalable, and chemoselective method for the direct phosphorylation of alcohols using a P(V)-approach based on the Ψ-reagent platform is disclosed. The method features a broad substrate scope of utility in both simple and complex settings and provides access to valuable phosphorylated alcohols that would be otherwise difficult to obtain.

An overview of ProTide technology and its implications to drug discovery

Introduction: The ProTide technology is a phosphate (or phosphonate) prodrug method devised to deliver nucleoside monophosphate (or monophosphonate) intracellularly bypassing the key challenges of antiviral and anticancer nucleoside analogs. Three new antiviral drugs, exploiting this technology, have been approved by the FDA while others are in clinical studies as anticancer agents.Areas covered: The authors describe the origin and development of this technology and its incredible success in transforming the drug discovery of antiviral and anticancer nucleoside analogues. As evidence, discussion on the antiviral ProTides on the market, and those currently in clinical development are included. The authors focus on how the proven capacity of this technology to generate new drug candidates has stimulated its application to non-nucleoside-based molecules.Expert opinion: The ProTide approach has been extremely successful in delivering blockbuster antiviral medicines and it seems highly promising in oncology. Its application to non-nucleoside-based small molecules is recently emerging and proving effective in other therapeutic areas. However, investigations to explain the lack of activity of certain ProTide series and comprehensive structure activity relationship studies to identify the appropriate phosphoramidate motifs depending on the parent molecule are in our opinion mandatory for the future development of these compounds.

Phosphoramidates and phosphonamidates (ProTides) with antiviral activity

Following the first report on the nucleoside phosphoramidate (ProTide) prodrug approach in 1990 by Chris McGuigan, the extensive investigation of ProTide technology has begun in many laboratories. Designed with aim to overcome limitations and the key resistance mechanisms associated with nucleoside analogues used in the clinic (poor cellular uptake, poor conversion to the 5'-monophosphate form), the ProTide approach has been successfully applied to a vast number of nucleoside analogues with antiviral and anticancer activity. ProTides consist of a 5'-nucleoside monophosphate in which the two hydroxyl groups are masked with an amino acid ester and an aryloxy component which once in the cell is enzymatically metabolized to deliver free 5'-monophosphate, which is further transformed to the active 5'-triphosphate form of the nucleoside analogue. In this review, the seminal contribution of Chris McGuigan's research to this field is presented. His technology proved to be extremely successful in drug discovery and has led to two Food and Drug Administration-approved antiviral agents.

Haloalkyl Phosphate Derivatives of AZT as Inhibitors of HIV: Studies in the Phosphate Region

Novel haloalkyl phosphate derivatives of the anti-HIV nucleoside analogue AZT were prepared by phosphorochloridate chemistry. These materials were designed to act as labile membrane-soluble prodrugs of the bio-active free nucleotides. In vitro evaluation revealed the compounds to have a pronounced and selective antiviral action, which varied greatly with the structure of the phosphate moiety. By comparison to simple dialkyl phosphates, which are inactive against HIV-1, the introduction of halogen atoms into the alkyl (phosphate) chains led to anti-HIV activity. Although halogen substitution in just one alkyl chain was sufficient for biological activity, substitution in the second alkyl chain further enhanced activity. Conversely, stabilization of the second chain, by conversion to a phosphonate, led to a reduction in activity. In one case, the diastereo-isomers resulting from mixed stereochemistry at the phosphate centre were separated, and found to differ in activity by one order of magnitude. Lastly, the bis(mono- and di-chloroethyl) phosphates were prepared and found to display moderate anti-HIV activity.

Alkyl Hydrogen Phosphonate Derivatives of the anti-HIV Agent AZT may be Less Toxic than the Parent Nucleoside Analogue

Novel alkyl hydrogen phosphonate derivatives of the anti-HIV nucleoside analogue AZT have been prepared by phosphorochloridite chemistry. These materials are designed to act as labile membrane-soluble prodrugs of the bioactive free nucleotides. In vitro evaluation has revealed the compounds to have a pronounced and selective antiviral action. Short-chain (C1-C7) alkyl derivatives are more potent than the parent hydrogen phosphonate, whilst one long-chain (C18) compound is less active. In an assay that demonstrates the toxicity of the parent drug AZT, the alkyl H-phosphonates appear to be less cytotoxic, whilst retaining full antiviral activity. Lastly, the compounds are all poorly active in a cell line (JM) that is poorly responsive to AZT, indicating that they act as depot forms of the nucleoside rather than of the free nucleotide.