The Development of the Combination Drug Leukovir® Tablets for the Treatment of Multiple Sclerosis: A Comprehensive Review.

The review is devoted to the development and study of the drug Leukovir® (cladribine+ ribavirin) and its use in the treatment of relapsing-remitting and secondary progressive forms of multiple sclerosis, a chronic neurodegenerative disease aiming the risk reduction of relapse and progression of a disability. In clinical trials Leukovir® has proved to be efficient by up to 56 weeks for the treatment of relapsing-remitting and secondary progressive forms of multiple sclerosis. The drug is registered in the Republic of Belarus. The efficacy, safety and tolerability profile of the drug Leukovir® suggests that it is well suited for disease-modifying therapy of multiple sclerosis. Patients require four 35-day courses of treatment, each consisting of seven days of treatment followed by a break of 28 days. The use of Leukovir® has contributed to the suppression of inflammatory process activity according to MRI data and stabilization of the clinical condition. It has reduced the number of relapses in patients with relapsing-remitting and secondary-progressive forms of multiple sclerosis.

A comparison of enzymatic phosphorylation and phosphatidylation of beta-L- and beta-D-nucleosides.

Enzymatic 5'-monophosphorylation and 5'-phosphatidylation of a number of beta-L- and beta-D-nucleosides was investigated. The first reaction, catalyzed by nucleoside phosphotransferase (NPT) from Erwinia herbicola, consisted of the transfer of the phosphate residue from p-nitrophenylphosphate (p-NPP) to the 5'-hydroxyl group of nucleoside; the second was the phospholipase D (PLD)-catalyzed transphosphatidylation of L-alpha-lecithin with a series of beta-L- and beta-D-nucleosides as the phosphatidyl acceptor resulted in the formation of the respective phospholipid-nucleoside conjugates. Some beta-L-nucleosides displayed similar or even higher substrate activity compared to the beta-D-enantiomers.

Synthesis of 9-(2,3-dideoxy-2,3-difluoro-beta-D-arabinofuranosyl)adenine.

Convergent synthesis of 9-(2,3-dideoxy-2,3-difluoro-beta-D-arabinofuranosyl)adenine is described starting from methyl 5-O-benzyl-2-deoxy-2-fluoro-alpha-D-arabinofuranoside.

Striking ability of adenosine-2'(3')-deoxy-3'(2')-triphosphates and related analogues to replace ATP as phosphate donor for all four human, and the Drosophila melanogaster, deoxyribonucleoside kinases.

In extension of an earlier report, six non-conventional analogues of ATP, three adenosine-2'-triphosphates (3'-deoxy, 3'-deoxy-3'-fluoro- and 3'-deoxy-3'-fluoroxylo-), and three adenosine-3'-triphosphates (2'-deoxy-, 2'-deoxy-2'-fluoro- and 2'-deoxy-2'-fluoroara-), were compared with ATP as potential phosphate donors for human deoxycytidine kinase (dCK), cytosolic thymidine kinase (TK1), mitochondrial TK2, deoxyguanosine kinase (dGK), and the deoxyribonucleoside kinase (dNK) from Drosophila melanogaster. With one group of enzymes, comprising TK1, TK2, dNK and dCK (with dAdo as acceptor), only 3'-deoxyadenosine-2'-triphosphate was an effective donor (5-60% that for ATP), and the other five analogues much less so, or inactive. With a second set, including dCK (dCyd, but not dAdo, as acceptor) and dGK (dGuo as acceptor), known to share high sequence similarity (approximately 45% sequence identity), all six analogues were good to excellent donors (13-119% that for ATP). With dCK and ATP1, products were shown to be 5'-phosphates. With dCK, donor properties of the analogues were dependent on the nature of the acceptor, as with natural 5'-triphosphate donors. With dCK (dCyd as acceptor), Km and Vmax for the two 2'(3')-deoxyadenosine-3'(2')-triphosphates are similar to those for ATP. With dGK, Km values are higher than for ATP, while Vmax values are comparable. Kinetic studies further demonstrated Michaelis-Menten (non-cooperative) or cooperative kinetics, dependent on the enzyme employed and the nature of the donor. The physiological significance, if any, of the foregoing remains to be elucidated. The overall results are, on the other hand, highly relevant to studies on the modes of interaction of nucleoside kinases with donors and acceptors; and, in particular, to interpretations of the recently reported crystal structures of dGK with bound ATP, of dNK with bound dCyd, and associated modeling studies.

Ability of adenosine-2'(3')-deoxy-3'(2')-triphosphates and related analogues to replace ATP as phosphate donor for all human and Drosphila melanogaster deoxyribonucleoside kinases.

Six non-conventional adenosine-2'- and 3'-triphosphate analogues of ATP were tested as potential phosphate donors for all four human, and D. melanogaster, deoxyribonucleoside kinases. With dCK (only dAdo as acceptor), TK1, TK2 and dNK only 3'-deoxyadenosine-2'-triphosphate was an effective donor (5-60% that for ATP). With dCK (dCyd as acceptor) and dGK (dGuo as acceptor), sharing 45% sequence identity, donor activities ranged from 13 to 119% that for ATP. Products were 5'-phosphates. In some instances, kinetics are dependent on the nature of the acceptor, and donor and acceptors properties are mutually interdependent. Results are highly relevant to studies on the modes of interaction with the enzymes, and to interpretations of reported crystal structures of dCK and dNK with bound ligands.

Synthesis and antiviral activity of purine 2',3'-dideoxy-2',3'-difluoro-D-arabinofuranosyl nucleosides.

9-(2',3'-Dideoxy-2',3'-difluoro-beta-D-arabinofuranosyl)adenine (20), 2-chloro-9-(2',3'-dideoxy-2,3-difluoro-beta-D-arabinofuranosyl)adenine (22), as well as their respective alpha-anomers 21 and 23, were synthesized by the nucleobase anion glycosylation of intermediate 5-O-benzoyl-2,3-dideoxy-2,3-difluoro-alpha-D-arabinofuranosyl bromide (13) starting from methyl 5-O-benzyl-3-deoxy-3-fluoro-alpha-D-ribofuranoside (3) and methyl 5-O-benzoyl-alpha-D-xylofuranoside (10). These compounds were evaluated as potential inhibitors of HIV-1 and hepatitis C virus in human PBM and Huh-7 Replicon cells, respectively. The adenosine analog 20 demonstrated potent activity against HIV-1 in primary human lymphocytes with no apparent cytotoxicity. Conformation of pentofuranose ring of nucleoside 20 in solution was studied by PSEUROT calculations.

3-Deazaadenosine analogues of p5'A2'p5'A2'p5'A: synthesis, stereochemistry, and the roles of adenine ring nitrogen-3 in the interaction with RNase L.

Sequence-specific 3-deazaadenosine (c(3)A)-substituted analogues of trimeric 2',5'-oligoadenylate, p5'A2'p5'A2'p5'A, were synthesized and evaluated for their ability to activate human RNase L (EC 3.1.2.6) aiming at the elucidation of the nitrogen-3 role in this biochemical process. Substitution of either 5'-terminal or 2'-terminal adenosine with c(3)A afforded the respective analogues p5'(c(3)A)2'p5'A2'p5'A and p5'A2'p5'A2'p5'(c(3)A) that were as effective as the natural tetramer itself as activators of RNase L (EC(50)=1nM). In contrast, p5'A2'p5'(c(3)A)2'p5'A showed diminished RNase L activation ability (EC(50)=10nM). The extensive conformational analysis of the c(3)A-substituted core trimers versus the parent natural core trimer by the (1)H and (13)C NMR, and CD spectroscopy displayed close stereochemical similarity between the natural core trimer and (c(3)A)2'p5'A2'p5'A and A2'p5'A2'p5'(c(3)A) analogues, thereby strong evidences for the syn base orientation about the glycosyl bond of the c(3)A residue of the latter were found. On the contrary, an analogue A2'p5'(c(3)A)2'p5'A displayed rather essential deviations from the spatial arrangement of the parent natural core trimer.