Combining symmetry elements results in potent naphthyridinone (NTD) HIV-1 integrase inhibitors.

A series of naphthyridinone HIV-1 integrase strand-transfer inhibitors have been designed based on a psdeudo-C2 symmetry element present in the two-metal chelation pharmacophore. A combination of two distinct inhibitor binding modes resulted in potent inhibition of the integrase strand-transfer reaction in the low nM range. Effects of aryl and N1 substitutions are disclosed including the impact on protein binding adjusted antiviral activity.

Late Presentation of Pulmonary Artery-Left Atrial Appendage Fistula Formation After Left Atrial Appendage Device Closure.

Atrial fibrillation is the most common arrhythmia in clinical practice with indication for anticoagulation in those patients whose annual risk for thromboembolism is >2%. Left atrial appendage closure is growing as an alternative to anticoagulation. We present a case of pulmonary artery-left atrial appendage fistula seen after left atrial appendage closure. (Level of Difficulty: Intermediate.).

Pseudoaneurysm as a Late Complication of Chronic Stanford Type A Intramural Hematoma Requiring Endovascular Repair.

Aortic intramural hematoma accounts for 5% to 20% of patients with acute aortic syndrome. Endovascular grafts have evolved as minimally invasive alternatives for treatment in some highly selected patients. We present the case of a patient who had late complications of a chronic Stanford type A intramural hematoma requiring thoracic endovascular aortic repair. (Level of Difficulty: Beginner.).

1,3,4-Oxadiazole substituted naphthyridines as HIV-1 integrase inhibitors. Part 2: SAR of the C5 position.

The use of a 1,3,4-oxadiazole in combination with an 8-hydroxy-1,6-naphthyridine ring system has been shown to deliver potent enzyme and antiviral activity through inhibition of viral DNA integration. This report presents a detailed structure-activity investigation of the C5 position resulting in low nM potency for several analogs with an excellent therapeutic index.

The use of oxadiazole and triazole substituted naphthyridines as HIV-1 integrase inhibitors. Part 1: Establishing the pharmacophore.

A series of HIV-1 integrase inhibitors containing a novel metal binding motif consisting of the 8-hydroxy-1,6-naphthyridine core and either an oxadiazole or triazole has been identified. The design of the key structural components was based on a two-metal coordination pharmacophore. This report presents initial structure-activity data that shows the new chelation architecture delivers potent inhibition in both enzymatic and antiviral assays.

Synthesis and antiviral activity of 7-benzyl-4-hydroxy-1,5-naphthyridin-2(1H)-one HIV integrase inhibitors.

The medicinal chemistry and structure-activity relationships for a novel series of 7-benzyl-4-hydroxy-1,5-naphthyridin-2(1H)-one HIV-integrase inhibitors are disclosed. Substituent effects were evaluated at the N-1, C-3, and 7-benzyl positions of the naphthyridinone ring system. Low nanomolar IC(50) values were achieved in an HIV-integrase strand transfer assay with both carboxylic ester and carboxamide groups at C-3. More importantly, several carboxamide congeners showed potent antiviral activity in cellular assays. A 7-benzyl substituent was found to be critical for potent enzyme inhibition, and an N-(2-methoxyethyl)carboxamide moiety at C-3 significantly reduced plasma protein binding effects in vitro. Pharmacokinetic data in rats for one carboxamide analogue demonstrated oral bioavailability and reasonable in vivo clearance.

The naphthyridinone GSK364735 is a novel, potent human immunodeficiency virus type 1 integrase inhibitor and antiretroviral.

The naphthyridinone GSK364735 potently inhibited recombinant human immunodeficiency virus type 1 (HIV-1) integrase in a strand transfer assay (mean 50% inhibitory concentration +/- standard deviation, 8 +/- 2 nM). As expected based on the structure of the drug, it bound competitively with another two-metal binding inhibitor (Kd [binding constant], 6 +/- 4 nM). In a number of different cellular assays, GSK364735 inhibited HIV replication with potency at nanomolar concentrations (e.g., in peripheral blood mononuclear cells and MT-4 cells, 50% effective concentrations were 1.2 +/- 0.4 and 5 +/- 1 nM, respectively), with selectivity indexes of antiviral activity versus in-assay cytotoxicity of at least 2,200. When human serum was added, the antiviral potency decreased (e.g., a 35-fold decrease in the presence of 100% human serum was calculated by extrapolation from the results of the MT-4 cell assay). In cellular assays, GSK364735 blocked viral DNA integration, with a concomitant increase in two-long-terminal-repeat circles. As expected, this integrase inhibitor was equally active against wild-type viruses and mutant viruses resistant to approved drugs targeting either reverse transcriptase or protease. In contrast, some but not all viruses resistant to other integrase inhibitors were resistant to GSK364735. When virus was passaged in the presence of the inhibitor, we identified resistance mutations within the integrase active site that were the same as or similar to mutations arising in response to other two-metal binding inhibitors. Finally, either additive or synergistic effects were observed when GSK364735 was tested in combination with approved antiretrovirals (i.e., no antagonistic effects were seen). Thus, based on all the data, GSK364735 exerted potent antiviral activity through the inhibition of viral DNA integration by interacting at the two-metal binding site within the catalytic center of HIV integrase.

Synthesis and HIV-integrase strand transfer inhibition activity of 7-hydroxy[1,3]thiazolo[5,4-b]pyridin-5(4H)-ones.

An efficient synthesis of methyl 7-hydroxy[1,3]thiazolo[5,4-b]pyridin-5(4H)-one-6-carboxylates (8-10 and 16) and 6-carboxamides (17-20) is described. Sub-micromolar enzyme inhibition of HIV integrase was achieved with several carboxamide analogs which were superior to their carboxylic ester congeners.

Kinetic analysis of wild-type and YMDD mutant hepatitis B virus polymerases and effects of deoxyribonucleotide concentrations on polymerase activity.

Mutations in the YMDD motif of the hepatitis B virus (HBV) DNA polymerase result in reduced susceptibility of HBV to inhibition by lamivudine, at a cost in replication fitness. The mechanisms underlying the effects of YMDD mutations on replication fitness were investigated using both a cell-based viral replication system and an in vitro enzyme assay to examine wild-type (wt) and YMDD-mutant polymerases. We calculated the affinities of wt and YMDD-mutant polymerases for each natural deoxyribonucleoside triphosphate (dNTP) and determined the intracellular concentrations of each dNTP in HepG2 cells under conditions that support HBV replication. In addition, inhibition constants for lamivudine triphosphate were determined for wt and YMDD-mutant polymerases. Relative to wt HBV polymerase, each of the YMDD-mutant polymerases showed increased apparent K(m) values for the natural dNTP substrates, indicating decreased affinities for these substrates, as well as increased K(i) values for lamivudine triphosphate, indicating decreased affinity for the drug. The effect of the differences in apparent K(m) values between YMDD-mutant polymerase and wt HBV polymerase could be masked by high levels of dNTP substrates (>20 microM). However, assays using dNTP concentrations equivalent to those measured in HepG2 cells under physiological conditions showed decreased enzymatic activity of YMDD-mutant polymerases relative to wt polymerase. Therefore, the decrease in replication fitness of YMDD-mutant HBV strains results from the lower affinities (increased K(m) values) of the YMDD-mutant polymerases for the natural dNTP substrates and physiological intracellular concentrations of dNTPs that are limiting for the replication of YMDD-mutant HBV strains.

Potent and selective inhibition of human cytomegalovirus replication by 1263W94, a benzimidazole L-riboside with a unique mode of action.

Benzimidazole nucleosides have been shown to be potent inhibitors of human cytomegalovirus (HCMV) replication in vitro. As part of the exploration of structure-activity relationships within this series, we synthesized the 2-isopropylamino derivative (3322W93) of 1H-beta-D-ribofuranoside-2-bromo-5,6-dichlorobenzimidazole (BDCRB) and the biologically unnatural L-sugars corresponding to both compounds. One of the L derivatives, 1H-beta-L-ribofuranoside-2-isopropylamino-5,6-dichlorobenzimidazole (1263W94), showed significant antiviral potency in vitro against both laboratory HCMV strains and clinical HCMV isolates, including those resistant to ganciclovir (GCV), foscarnet, and BDCRB. 1263W94 inhibited viral replication in a dose-dependent manner, with a mean 50% inhibitory concentration (IC(50)) of 0.12 +/- 0.01 microM compared to a mean IC(50) for GCV of 0.53 +/- 0.04 microM, as measured by a multicycle DNA hybridization assay. In a single replication cycle, 1263W94 treatment reduced viral DNA synthesis, as well as overall virus yield. HCMV mutants resistant to 1263W94 were isolated, establishing that the target of 1263W94 was a viral gene product. The resistance mutation was mapped to the UL97 open reading frame. The pUL97 protein kinase was strongly inhibited by 1263W94, with 50% inhibition occurring at 3 nM. Although HCMV DNA synthesis was inhibited by 1263W94, the inhibition was not mediated by the inhibition of viral DNA polymerase. The parent benzimidazole D-riboside BDCRB inhibits viral DNA maturation and processing, whereas 1263W94 does not. The mechanism of the antiviral effect of L-riboside 1263W94 is thus distinct from those of GCV and of BDCRB. In summary, 1263W94 inhibits viral replication by a novel mechanism that is not yet completely understood.