Investigation of C-5 alkynyl (alkynyloxy or hydroxymethyl) and/or N-3 propynyl substituted pyrimidine nucleoside analogs as a new class of antimicrobial agents.

The resurgence of mycobacterial infections and the emergence of drug-resistant strains urgently require a new class of agents that are distinct than current therapies. A group of 5-ethynyl (6-10), 5-(2-propynyloxy) (16, 18, 20, 22, 24), 5-(2-propynyloxy)-3-N-(2-propynyl) (17, 19, 21, 23, 25) and 5-hydroxymethyl-3-N-(2-propynyl) (30-33) derivatives of pyrimidine nucleosides were synthesized and evaluated against mycobacteria [Mycobacterium tuberculosis (Mtb), Mycobacterium bovis (BCG) and Mycobacterium avium], gram-positive bacteria (Staphylococcus aureus and Enterococcus faecalis) and gram-negative bacteria (Escherichia coli, Salmonella typhimurium and Pseudomonas aeruginosa) alone and in combination with existing drugs in in vitro assays. Although several compounds exhibited marked inhibitory activity at a higher concentration against Mtb, M. bovis, S. aureus and E. faecalis, they displayed unexpected synergistic and additive interactions at their lower concentrations with antitubercular drugs isoniazid and rifampicin, and antibacterial drug gentamicin. The active analogues were also found to inhibit intracellular Mtb in a human monocytic cell line infected with H37Ra. Oral administration of 5-hydroxymethyl-3-N-(2-propynyl)-3'-azido-2',3'-dideoxyuridine (32) and 5-hydroxymethyl-3-N-(2-propynyl)-2',3'-dideoxyuridine (33) at a dose of 100mg/kg for two weeks showed promising in vivo effects in mice infected with Mtb (H37Ra). No in vitro cytotoxicity of the test compounds was observed up to the highest concentration tested (CC50>300µg/mL).

Discovery of novel 5-(ethyl or hydroxymethyl) analogs of 2'-'up' fluoro (or hydroxyl) pyrimidine nucleosides as a new class of Mycobacterium tuberculosis, Mycobacterium bovis and Mycobacterium avium inhibitors.

Discovery of novel antimycobacterial compounds that work on distinctive targets and by diverse mechanisms of action is urgently required for the treatment of mycobacterial infections due to the emerging global health threat of tuberculosis. We have identified a new class of 5-ethyl or hydroxy (or methoxy) methyl-substituted pyrimidine nucleosides as potent inhibitors of Mycobacterium bovis, Mycobacterium tuberculosis (H37Ra, H37Rv) and Mycobacterium avium. A series of 2'-'up' fluoro (or hydroxy) nucleosides (1, 2, 4-6, 9, 10, 13, 16, 18, 21, 24) was synthesized and evaluated for antimycobacterial activity. Among 2'-fluorinated compounds, 1-(3-bromo-2,3-dideoxy-2-fluoro-ß-d-arabinofuranosyl)-5-ethyluracil (13) exhibited promising activity against M. bovis and Mtb alone, and showed synergism when combined with isoniazid. The most active compound emerging from these studies, 1-(ß-d-arabinofuranosyl)-4-thio-5-hydroxymethyluracil (21) inhibited Mtb (H37Ra) (MIC(50)=0.5 µg/mL) and M. bovis (MIC(50)=0.5 µg/mL) at low concentrations, and was ten times more potent against Mtb (H37Ra) than cycloserine (MIC(50)=5.0 µg/mL), a second line drug. It also showed an additive effect when combined with isoniazid. Compound 21 retained sensitivity against a rifampicin-resistant (H37Rv) strain of Mtb (MIC(50)=1 µg/mL) at concentrations similar to that for a rifampicin-sensitive (H37Rv) strain, suggesting that it has no cross-resistance to a first-line anti-TB drug. In addition, the replication of M. avium was also inhibited by 21 (MIC(50)=10 µg/mL). No cellular toxicity of 13 or 21 was observed up to the highest concentration tested (CC(50)>100 µg/mL). These observations offer promise for a new drug treatment regimen to augment and complement the current chemotherapy of TB.

Antimycobacterial activities of 5-alkyl (or halo)-3'-substituted pyrimidine nucleoside analogs.

Several 5-alkyl (or halo)-3'-azido (amino or halo) analogs of pyrimidine nucleosides have been synthesized and evaluated against Mycobacterium bovis, Mycobacterium tuberculosis and Mycobacterium avium. Among these compounds, 3'-azido-5-ethyl-2',3'-dideoxyuridine (3) was found to have significant antimycobacterial activities against M. bovis (MIC(50)=1µg/mL), M. tuberculosis (MIC(50)=10µg/mL) and M. avium (MIC(50)=10µg/mL).

Antiviral activity of various 1-(2'-deoxy-ß-D-lyxofuranosyl), 1-(2'-fluoro-ß-D-xylofuranosyl), 1-(3'-fluoro-ß-D-arabinofuranosyl), and 2'-fluoro-2',3'-didehydro-2',3'-dideoxyribose pyrimidine nucleoside analogues against duck hepatitis B virus (DHBV) and human hepatitis B virus (HBV) replication.

Despite the existence of successful vaccine and antiviral therapies, infection with hepatitis B virus (HBV) continues to be a major global cause of acute and chronic liver disease and high mortality. We synthesized and evaluated several lyxofuranosyl, 2'-fluoroxylofuranosyl, 3'-fluoroarabinofuranosyl, and 2'-fluoro-2',3'-didehydro-2',3'-dideoxyribose pyrimidine nucleoside analogues for antiviral activities against hepatitis B virus. Among the compounds examined, 1-(2-deoxy-ß-d-lyxofuranosyl)thymine (23), 1-(2-deoxy-ß-d-lyxofuranosyl)-5-trifluoromethyluracil (25), 1-(2-deoxy-2-fluoro-ß-d-xylofuranosyl)uracil (38), 1-(2-deoxy-2-fluoro-ß-d-xylofuranosyl)thymine (39), 2',3'-dideoxy-2',3'-didehydro-2'-fluorothymidine (48), and 2',3'-dideoxy-2',3'-didehydro-2'-fluoro-5-ethyluridine (49) were found to possess significant anti-HBV activity against DHBV in primary duck hepatocytes with EC(50) values of 4.1, 3.3, 40.6, 3.8, 0.2, and 39.0 µM, respectively. Compounds 23, 25, 39, 48, and 49 (EC(50) = 41.3, 33.7, 19.2, 2.0-4.1, and 39.0 µM, respectively) exhibited significant activity against wild-type human HBV in 2.2.15 cells. Intriguingly, 25, 39, 48, and 49 retained sensitivity against lamivudine-resistant HBV containing a single mutation (M204I) and 48 emerged as an effective inhibitor of drug-resistant HBV with an EC(50) of 4.1 µM. In contrast, 50% inhibition could not be achieved by lamivudine at 44 µM concentration in the drug-resistant strain. The compounds investigated did not show cytotoxicity to host cells up to the highest concentrations tested.

Antiviral activity of 2,3'-anhydro and related pyrimidine nucleosides against hepatitis B virus.

Various 2,3'-anhydro analogs of 5-substituted 1-(2-deoxy-ß-d-lyxofuranosyl)uracils (10-15) and a related 1-(3-O-mesyl-2-deoxy-ß-d-lyxofuranosyl) pyrimidine nucleoside analog (18) have been synthesized for evaluation as a new class of potential anti-HBV agents. The compounds 10, 12, and 15 demonstrated most potent anti-HBV activities against duck HBV (DHBV) and human HBV with EC(50) values in the range of 2.5-10 and 5-10 µg/mL, respectively, at non-toxic concentrations (CC(50) = > 200 µg/mL). The nucleoside 18 also demonstrated significant anti-HBV activity against DHBV with an EC(50) value of 2.5 µg/mL, however, it was less active against HBV in 2.2.15 cells (EC(50) = > 10 µg/mL).

Synthesis and in vitro antiviral activities of 3'-fluoro (or chloro) and 2',3'-difluoro 2',3'-dideoxynucleoside analogs against hepatitis B and C viruses.

Chronic infections with hepatitis B virus (HBV) and hepatitis C virus (HCV) lead to serious liver diseases worldwide. Co-infection with HBV and HCV is very common and is associated with increased risk of liver pathogenesis, liver cancer, and liver failure. Several 5-substituted 3'-fluoro (or chloro) (1-4, 6, 7, 17-19) and 2',3'-difluoro 2',3'-dideoxynucleosides (15 and 16) were synthesized and evaluated for in vitro antiviral activities against duck hepatitis B virus (DHBV), human hepatitis B virus, and hepatitis C virus. Of these compounds 4, 7, 17, and 19 demonstrated moderate anti-HBV activity, and 2, 4, 7, 8, and 19 were weak inhibitors of HCV. Although 5-iodo derivative (7) was most inhibitory against HCV, it exhibited a reduction in cellular RNA levels in Huh-7 cells. The 5-hydroxymethyl-3'-fluoro-2',3'-dideoxyuridine (4) and 1-(3-chloro-2,3-dideoxy-ß-d-erythro-pentofuranosyl)-5-fluorouracil (19) provided the most inhibition of both viruses without cytotoxicity.

Inhibition of mycobacterial replication by pyrimidines possessing various C-5 functionalities and related 2'-deoxynucleoside analogues using in vitro and in vivo models.

Tuberculosis (TB) has become an increasing problem since the emergence of human immunodeficiency virus and increasing appearance of drug-resistant strains. There is an urgent need to advance our knowledge and discover a new class of agents that are distinct than current therapies. Antimycobacterial activities of several 5-alkyl, 5-alkynyl, furanopyrimidines and related 2'-deoxynucleosides were investigated against Mycobacterium tuberculosis. Compounds with 5-arylalkynyl substituents (23-26, 33, 35) displayed potent in vitro antitubercular activity against Mycobacterium bovis and Mycobacterium tuberculosis. The in vivo activity of 5-(2-pyridylethynyl)-uracil (26) and its 2'-deoxycytidine analogue, 5-(2-pyridylethynyl)-2'-deoxycytidine (35), was assessed in BALB/c mice infected with M. tuberculosis (H37Ra). Both compounds 26 and 35 given at a dose of 50 mg/kg for 5 weeks showed promising in vivo efficacy in a mouse model, with the 2'-deoxycytidine derivative being more effective than the uracil analogue and a reference drug d-cycloserine. These data indicated that there is a significant potential in this class of compounds.

3'-bromo analogues of pyrimidine nucleosides as a new class of potent inhibitors of Mycobacterium tuberculosis.

Tuberculosis (TB) is a major health problem worldwide. We herein report a new class of pyrimidine nucleosides as potent inhibitors of Mycobacterium tuberculosis (M. tuberculosis). Various 2'- or 3'-halogeno derivatives of pyrimidine nucleosides containing uracil, 5-fluorouracil, and thymine bases were synthesized and evaluated for antimycobacterial activities. Among the compounds tested, 3'-bromo-3'-deoxy-arabinofuranosylthymine (33) was the most effective antituberculosis agent in the in vitro assays against wild-type M. tuberculosis strain (H37Ra) (MIC(50) = 1 microg/mL) as well as drug-resistant (H37Rv) (rifampicin-resistant and isoniazid-resistant) strains of M. tuberculosis (MIC(50) = 1-2 microg/mL). Compound 33 also inhibited intracellular M. tuberculosis in a human monocytic cell line infected with H37Ra, demonstrating higher activity against intramacrophagic mycobacteria (80% reduction at 10 microg/mL concentration) than extracellular mycobacteria (75% reduction at 10 microg/mL concentration). In contrast, pyrimidine nucleosides possessing 5-fluorouracil base were weak inhibitors of M. tuberculosis. No cytotoxicity was found up to the highest concentration of compounds tested (CC(50) > 100-200 microg/mL) against a human cell line. Overall, these encouraging results substantiate the potential of this new class of compounds as promising antituberculosis agents.

Inhibition of Mycobacterium tuberculosis, Mycobacterium bovis, and Mycobacterium avium by novel dideoxy nucleosides.

The prevalence of tuberculosis (TB) and mutidrug-resistant tuberculosis (MDR-TB) has been increasing, leading to serious infections, high mortality, and a global health threat. Here, we report the identification of a novel class of dideoxy nucleosides as potent and selective inhibitors of Mycobacterium bovis, Mycobacterium tuberculosis, and drug-resistant Mycobacterium tuberculosis. A series of 5-acetylenic derivatives of 2',3'-dideoxyuridine (3-8) and 3'-fluoro-2',3'-dideoxyuridine (22-27) were synthesized and tested for their antimycobacterial activity against M. bovis, M. tuberculosis, and M. avium. 2',3'-Dideoxyuridine possessing 5-decynyl, 5-dodecynyl, 5-tridecynyl, and 5-tetradecynyl substituents (4-7) exhibited the highest antimycobacterial activity against all three mycobacteria. In contrast, in the 3'-fluoro-2',3'-dideoxyuridine series, a 5-tetradecynyl analogue (26) displayed the most potent activity against these mycobacteria. Among other derivatives, 5-bromo-2',3'-dideoxycytidine (11), 5-methyl-2',3'-dideoxycytidine (12), and 5-chloro-4-thio-2',3'-dideoxyuridine (19) exhibited modest inhibition of M. bovis and M. tuberculosis. In the series of dideoxy derivatives of adenosine, guanosine, and purines, 2-amino-6-mercaptoethyl-9-(2,3-dideoxy-beta-d-glyceropentofuranosyl)purine (32) and 2-amino-4-fluoro-7-(2,3-dideoxy-beta-d-glyceropentofuranosyl)pyrrolo[2,3-d]pyrimidine (35) were the most efficacious against M. bovis and M. tuberculosis, and M. avium, respectively.

Studies on acyclic pyrimidines as inhibitors of mycobacteria.

In vitro anti-mycobacterial activities of several 5-substituted acyclic pyrimidine nucleosides containing 1-(2-hydroxyethoxy)methyl and 1-[(2-hydroxy-1-(hydroxymethyl) ethoxy)methyl] acyclic moieties are investigated against three mycobacteria viz. Mycobacterium tuberculosis, Mycobacterium bovis, and Mycobacterium avium, which cause serious infections and mortality in healthy people as well as patients with AIDS. 1-(2-Hydroxyethoxy)methyl-5-(1-azido-2-haloethyl or 1-azidovinyl) analogs (4-7), 1-[(2-hydroxy-1-(hydroxymethyl)ethoxy)methyl]-5-decynyluracil (37), and 1-[(2-hydroxy-1-(hydroxymethyl)ethoxy)methyl]-5-dodecynyluracil (38) exhibited significant in vitro anti-tubercular activity against these mycobacteria.

In vitro anti-mycobacterial activities of various 2'-deoxyuridine, 2'-arabinouridine and 2'-arabinofluoro-2'-deoxyuridine analogues: synthesis and biological studies.

M. tuberculosis, M. bovis and M. avium infections cause the most important mycobacterioses leading to increased mortality in patients with AIDS. Various 5-substituted 2'-deoxyuridines, arabinouridines, arabinocytidines and 2'-arabinofluoro-2'-deoxyuridines were synthesized and evaluated for their in vitro inhibitory activity against M. bovis, M. tuberculosis and M. avium. 5-(C-1 Substituted)-2'-deoxyuridine derivatives emerged as potent inhibitors of M. avium (MIC50 = 1-10 microg/mL range); 5-(1-azidovinyl)-2'-deoxyuridine being the most active (MIC50 = 1-5 microg/mL range). The nature of C-5 substituents appeared to be a determinant of anti-mycobacterial activity.