Publications

Twenty antiherpes compounds were compared for their inhibitory activities against five laboratory strains and five clinical isolates of varicella-zoster virus (VZV) in human embryo fibroblast cultures. E-5-(2-bromovinyl)-1-beta-D-arabinofuranosyluracil (BVaraU), E-5-(2-iodovinyl)-2'-deoxyuridine (IVDU), and E-5-(2-bromovinyl)-2'-deoxyuridine (BVDU) were the most effective. The average values of the 50% inhibitory dose (ID50) for VZV replication were 0.0013, 0.0015, and 0.0024 micrograms/ml, respectively. 1-beta-D-Arabinofuranosyladenine and 9-(2-hydroxyethoxymethyl)guanine were 1.2 and 3.4 times less effective than 5-iodo-2'-deoxyuridine (IDU). The selectivity indexes (ratio of ID50 for host-cell DNA synthesis to ID50 for VZV replication) of BVaraU, IVDU, and BVDU were between 41,000 and 67,000, whereas those of cytosine arabinoside, IDU, and 5-bromo-2'-deoxyuridine were less than 1.1. BVaraU, IVDU, and BVDU were the most potent and the most selective inhibitors of VZV activity. A deoxythymidine kinase deficient mutant of VZV was resistant to most of the compounds tested at concentrations up to 36,000 times greater than the average ID50 for strains that were not deficient.

Derivatives of the 2'-deoxynucleoside of furo[2,3-d]pyrimidin-2(3H)-one with long-chain alkyl (or 4-alkylphenyl) substituents at C6 exhibit remarkable anti-VZV (varicella-zoster virus) potency and selectivity, and analogous 2',3'-dideoxynucleoside derivatives show anti-HCMV (human cytomegalovirus) activity. We now report a synthetic approach that enables the preparation of long-chain 6-(alkyn-1-yl)furo[2,3-d]pyrimidin-2(3H)-ones in which the rodlike acetylene spacer replaces the 4-substituted-phenyl ring at C6. Analogues with methyl, beta-d-ribofuranosyl, beta-d-arabinofuranosyl, and 2-deoxy-beta-d-erythro-pentofuranosyl substituents at N3 have been prepared. Long-chain derivatives at C6 in the 2'-deoxynucleoside series showed virus-encoded nucleoside kinase-sensitive anti-VZV activity. Surprisingly, 3-methyl-6-(octyn-1-yl)furo[2,3-d]pyrimidin-2(3H)-one (prepared as a negative anti-VZV test control) exhibited anti-HCMV activity, which supports the possibility of development of non-nucleoside anti-HCMV agents originating from uncomplicated derivatives of such bicyclic ring systems.

A comparative study of three cycloSal-d4TMP 1, 2 and 3 and a variety of bis(benzyl) phosphate triester 4-8 of the antivirally active nucleoside analogue 2',3'-dideoxy-2',3'-didehydrothymidine (d4T) will be described. This study has been initiated by the observation that the introduction of a simple 7-methyl group in the cycloSal-structure (2) led to a completely different hydrolysis pattern as compared to the prototype cycloSal-d4TMP 1. Instead of the selective formation of d4TMP, a phenyl phosphate diester was formed in the case of the 7-methyl-substituted compound 2. The difference in degradation pathway was caused by a change of the reaction mechanism. The phenyl phosphate diester was chemically and enzymatically inert to further cleavage to yield d4TMP. For comparison bis(benzyl)-d4TMP 4, bis(alpha-methylbenzyl)-d4TMP 5, bis(alpha-methoxycarbonylmethyl [MCM]-benzyl)-d4TMP 6 as well as the enzyme-cleavable bis(4-acetoxybenzyl)-d4TMP [bis(AB)-d4TMP(7 and bis(alpha-methoxycarbonylmethyl-4-acetoxybenzyl)-d4TMP [bis(alpha-MCM-AB)-d4TMP] 8 were synthesized. Chemical hydrolysis studies proved that all bis(benzyl) triesters hydrolyze to give the intermediate benzyl phosphate diesters. Moreover, the latter two triesters 7,8 and cycloSal-d4TMPs 1 and 3 led finally to the delivery of d4TMP. The chemical hydrolysis studies allowed a detailed mechanistic interpretation of the degradation pathways of triesters 1-8. Cell extract studies of the bis(benzyl) triesters 4-8 confirmed that only triesters 7 and 8 released d4TMP although with a considerable increase of the reaction rate. Anti-HIV evaluation of the compounds showed that cycloSal-d4TMP 1 and the bis(AB) triesters 7,8 were entirely independent of the presence of cellular thymidine kinase (TK).

Based on the detailed analysis of the binding mode of diarylpyrimidines (DAPYs) with HIV-1 RT, we designed several subseries of novel NNRTIs, with the aim to probe biologically relevant chemical space of solvent-exposed tolerant regions in NNRTIs binding pocket (NNIBP). The most potent compound <b>21a</b> exhibited significant activity against the whole viral panel, being about 1.5-2.6-fold (WT, EC₅₀ = 2.44 nM; L100I, EC₅₀ = 4.24 nM; Y181C, EC₅₀ = 4.80 nM; F227L + V106A, EC₅₀ = 17.8 nM) and 4-5-fold (K103N, EC₅₀ = 1.03 nM; Y188L, EC₅₀ = 7.16 nM; E138K, EC₅₀ = 3.95 nM) more potent than the reference drug ETV. Furthermore, molecular simulation was conducted to understand the binding mode of interactions of these novel NNRTIs and to provide insights for the next optimization studies.

The steroids 3,6,17-trihydroxy-stigmasta-4,7,24(28)-triene (A) and 14,15,18,20-diepoxyturbinarin (B) were isolated from the cyclohexane extract of brown alga, Turbinaria conoides (J. Agardh) Kutzing, and have been reported for their antimicrobial activity by us. In this study, the isolated compounds were evaluated for comprehensive antihistaminic, antiviral and cytotoxicity screening. The antihistaminic study was performed using in vitro standard animal models. Evaluation of the potency (EC(50)), affinity (pA(2)) and the maximal response (E(max)) of the histamine alone and in the presence of the compounds were determined. Antiviral activity and cytotoxicity were performed in Crandell-Rees feline kidney (CRFK) cells by a colorimetric formazan-based MTS assay. No significant antiviral activity or cytotoxicity were observed for the compounds in the CRFK cells. Compound A inhibited the histamine-induced concentration at 20 µg mL(-1)(p < 0.05). The most significant inhibition (97%) was observed for compound B (p < 0.01) at the same concentration, which was comparable to that of the positive control chlorpheniramine maleate (10 µg mL(-1)). This potentiality suggests that 14,15,18,20-diepoxyturbinarin (B) can be developed as a new lead antihistaminic agent.