Synthesis and antiviral evaluation of a-l-2'-deoxythreofuranosyl nucleosides

The synthesis of a series of a-l-2'-deoxythreofuranosyl nucleosides featuring the nucleobases A, T, C and U is described in seven steps from 1,2-O-isopropyledene-a-l-threose, involving a Vorbrüggen coupling and a Barton-McCombie deoxygenation protocol as the key steps. All analogues, including a phosphoramidate nucleoside phosphate prodrug of the T analogue, were evaluated against a broad panel of different viruses but found inactive, while also lacking notable cellular toxicity. The thymidine analogue showed inhibition to mitochondrial thymidine kinase-2 (TK-2), herpes simplex virus type 1 (HSV-1) TK, varicella-zoster virus (VZV) TK and Mycobacterium tuberculosis thymidylate kinase

Phosphoramidate ProTides of the Anticancer Agent FUDR Successfully Deliver the Preformed Bioactive Monophosphate in Cells and Confer Advantage over the Parent Nucleoside

The fluorinated pyrimidine family of nucleosides continues to represent major current chemotherapeutic agents for treating solid tumors. We herein report their phosphate prodrugs, ProTides, as promising new derivatives, which partially bypass the dependence of the current drugs on active transport and nucleoside kinase-mediated activation. They are also resistant to metabolic deactivation by phosphorolytic enzymes. We report 39 ProTides of the fluorinated pyrimidine FUDR with variation in the aryl, ester, and amino acid regions. Notably, only certain ProTide motifs are successful in delivering the nucleoside monophosphate into intact cells. We also find that the ProTides retain activity in mycoplasma infected cells, unlike FUDR. Data suggest these compounds to be worthy of further progression

Application of ProTide Technology to Gemcitabine: A Successful Approach to Overcome the Key Cancer Resistance Mechanisms Leads to a New Agent (NUC-1031) in Clinical Development

Gemcitabine is a nucleoside analogue commonly used in cancer therapy but with limited efficacy due to a high susceptibility to cancer cell resistance. The addition of a phosphoramidate motif to the gemcitabine can protect it against many of the key cancer resistance mechanisms. We have synthesized a series of gemcitabine phosphoramidate prodrugs and screened for cytostatic activity in a range of different tumor cell lines. Among the synthesized compounds, one in particular (NUC-1031, <b>6f</b>) was shown to be potent <i>in vitro</i>. Importantly, compared with gemcitabine, <b>6f</b> activation was significantly less dependent on deoxycytidine kinase and on nucleoside transporters, and it was resistant to cytidine deaminase-mediated degradation. Moreover, <b>6f</b> showed a significant reduction in tumor volumes <i>in vivo</i> in pancreatic cancer xenografts. The ProTide <b>6f</b> is now in clinical development with encouraging efficacy signals in a Phase I/II study, which strongly supports the ProTide approach to generate promising new anticancer agents

Novel Phosphoramidate Prodrugs of <i>N-</i>Acetyl-(d)-Glucosamine with Antidegenerative Activity on Bovine and Human Cartilage Explants

(d)-Glucosamine and other nutritional supplements have emerged as safe alternative therapies for osteoarthritis (OA), a chronic and degenerative articular joint disease. In our preceding paper, a series of novel O-6 phosphate <i>N</i>-acetyl (d)-glucosamine prodrugs aimed at improving the oral bioavailability of <i>N</i>-acetyl-(d)-glucosamine as its putative bioactive phosphate form were shown to have greater chondroprotective activity in vitro when compared to the parent agent. In order to extend the SAR studies, this work focuses on the O-3 and O-4 phosphate prodrugs of <i>N</i>-acetyl-(d)-glucosamine bearing a 4-methoxy phenyl group and different amino acid esters on the phosphate moiety. Among the compounds, the (l)-proline amino acid-containing prodrugs proved to be the most active of the series, more effective than the prior O-6 compounds, and well processed in chondrocytes in vitro. Data on human cartilage support the notion that these novel O-3 and O-4 regioisomers may represent novel promising leads for drug discovery for osteoarthritis

Synthesis of an Apionucleoside Family and Discovery of a Prodrug with Anti-HIV Activity

We report the synthesis of a family of d- and l-furano-d-apionucleosides, their 3′-deoxy, as well as their 2′,3′-dideoxy analogues with thymine and adenine nucleobases. Single carbon homologation of 1,2-<i>O</i>-isopropylidene-d-glycero-tetrafuranos-3-ulose (<b>15</b>) and optimized glycosylation conditions involving microwave irradiation were key to the successful synthesis of the target compounds. While all target nucleosides failed to show significant antiviral activity, we demonstrated that the triphosphate of 2′,3′-deoxy-d-apio-d-furanoadenosine (<b>1</b>), in contrast to that of its d-apio-l-furanose epimer <b>2</b>, was readily incorporated into a DNA template by HIV reverse transcriptase to act as a DNA chain terminator. This led us to convert adenine derivative <b>1</b> into two phosphoramidate prodrugs. ProTide <b>9b</b> was found active against HIV-1 and HIV-2 (EC₅₀ = 0.5–1.5 μM), indicating that the lack of activity of the parent nucleoside, and possibly also other members of the d-apio-d-furanose nucleoside family must be sought in the inefficient cellular conversion to the monophosphate

Dose-related effects of vitamin D on immune responses in patients with clinically isolated syndrome and healthy control participants: study protocol for an exploratory randomized double- blind placebo-controlled trial.

There is increasing evidence linking vitamin D deficiency to both susceptibility to, and severity of, multiple sclerosis (MS). Patients with the clinically isolated syndrome represent the initial presentation of a demyelinating disorder, and those with asymptomatic lesions on magnetic resonance imaging (MRI) are at risk of progression to clinically definite MS. The aims of this study are to examine the immunologic effects of vitamin D in both healthy individuals and in patients with clinically isolated syndrome, and in the latter group the effects on disease progression assessed by MRI and clinical measures

Effects of vitamin D3 in clinically isolated syndrome and healthy control participants: A double-blind randomised controlled trial

Background: Lowserum vitamin D levels are associated with susceptibility to, and severity of, multiple sclerosis. High dose vitamin D has been proposed as a potential immunomodulator in multiple sclerosis. Objectives: We performed a single centre, investigator-led, exploratory, double-blind, randomised, placebo controlled, trial of vitamin D3 in clinically isolated syndrome and healthy control participants to assess its immunological effects. Secondary end-points included clinical and magnetic resonance imaging outcomes and safety. Methods: Clinically isolated syndrome patients and healthy control participants were randomised to: placebo, 5000 IU or 10,000 IU vitamin D3/day (Vigantol oil). Study duration was 24 weeks. Results: The trial did not meet its primary end point, with no difference in the frequency of proinflammatory CD4þ T cells (interleukin (IL)-17þ/interferon (IFN)-gþ) seen. A higher level of disease freedom (67% versus 50%) was seen in those with serum 1,25 (OH) vitamin D levels>100 nmol/l but this did not reach significance. High dose vitamin D3 was well tolerated with no safety signal. Conclusions: High dose vitamin D3 over 24 weeks was well tolerated but without immunological, magnetic resonance imaging or clinical evidence of benefit. The hypothesised therapeutic effects in clinically isolated syndrome or multiple sclerosis patients may require longer periods of administration or may only be seen in patients treated with vitamin D3 as an adjunct to established disease modifying therapies

Phosphorodiamidates as a Promising New Phosphate Prodrug Motif for Antiviral Drug Discovery: Application to Anti-HCV Agents

We herein report phosphorodiamidates as a significant new phosphate prodrug motif. Sixty-seven phosphorodiamidates are reported of two 6-<i>O</i>-alkyl 2′-<i>C</i>-methyl guanosines, with significant variation in the diamidate structure. Both symmetrical and asymmetric phosphorodiamidates are reported, derived from various esterified amino acids, both d and l, and also from various simple amines. All of the compounds were evaluated versus hepatitis C virus in replicon assay, and nanomolar activity levels were observed. Many compounds were noncytotoxic at 100 μM, leading to high antiviral selectivities. The agents are stable in acidic, neutral, and moderately basic media and in selected biological media but show efficient processing by carboxypeptidases and efficiently yield the free nucleoside monophosphate in cells. On the basis of in vitro data, eight leads were selected for additional in vivo evaluation, with the intent of selecting one candidate for progression toward clinical studies. This phosphorodiamidate prodrug method may have broad application outside of HCV and antivirals as it offers many of the advantages of phosphoramidate ProTides but without the chirality issues present in most cases