Discovery of the Human Immunodeficiency Virus Type 1 (HIV-1) Attachment Inhibitor Temsavir and Its Phosphonooxymethyl Prodrug Fostemsavir.

The optimization of the 4-methoxy-6-azaindole series of HIV-1 attachment inhibitors (AIs) that originated with 1 to deliver temsavir (3, BMS-626529) is described. The most beneficial increases in potency and pharmacokinetic (PK) properties were attained by incorporating N-linked, sp-hybridized heteroaryl rings at the 7-position of the heterocyclic nucleus. Compounds that adhered to a coplanarity model afforded targeted antiviral potency, leading to the identification of 3 with characteristics that provided for targeted exposure and PK properties in three preclinical species.

The discovery of asunaprevir (BMS-650032), an orally efficacious NS3 protease inhibitor for the treatment of hepatitis C virus infection.

The discovery of asunaprevir (BMS-650032, 24) is described. This tripeptidic acylsulfonamide inhibitor of the NS3/4A enzyme is currently in phase III clinical trials for the treatment of hepatitis C virus infection. The discovery of 24 was enabled by employing an isolated rabbit heart model to screen for the cardiovascular (CV) liabilities (changes to HR and SNRT) that were responsible for the discontinuation of an earlier lead from this chemical series, BMS-605339 (1), from clinical trials.

Discovery and early clinical evaluation of BMS-605339, a potent and orally efficacious tripeptidic acylsulfonamide NS3 protease inhibitor for the treatment of hepatitis C virus infection.

The discovery of BMS-605339 (35), a tripeptidic inhibitor of the NS3/4A enzyme, is described. This compound incorporates a cyclopropylacylsulfonamide moiety that was designed to improve the potency of carboxylic acid prototypes through the introduction of favorable nonbonding interactions within the S1' site of the protease. The identification of 35 was enabled through the optimization and balance of critical properties including potency and pharmacokinetics (PK).

Hepatitis C virus NS5A replication complex inhibitors: the discovery of daclatasvir.

The biphenyl derivatives 2 and 3 are prototypes of a novel class of NS5A replication complex inhibitors that demonstrate high inhibitory potency toward a panel of clinically relevant HCV strains encompassing genotypes 1-6. However, these compounds exhibit poor systemic exposure in rat pharmacokinetic studies after oral dosing. The structure-activity relationship investigations that improved the exposure properties of the parent bis-phenylimidazole chemotype, culminating in the identification of the highly potent NS5A replication complex inhibitor daclatasvir (33) are described.

Inhibitors of human immunodeficiency virus type 1 (HIV-1) attachment. 12. Structure-activity relationships associated with 4-fluoro-6-azaindole derivatives leading to the identification of 1-(4-benzoylpiperazin-1-yl)-2-(4-fluoro-7-[1,2,3]triazol-1-yl-1h-pyrrolo[2,3-c]pyridin-3-yl)ethane-1,2-dione (BMS-585248).

A series of highly potent HIV-1 attachment inhibitors with 4-fluoro-6-azaindole core heterocycles that target the viral envelope protein gp120 has been prepared. Substitution in the 7-position of the azaindole core with amides (12a,b), C-linked heterocycles (12c-l), and N-linked heterocycles (12m-u) provided compounds with subnanomolar potency in a pseudotype infectivity assay and good pharmacokinetic profiles in vivo. A predictive model was developed from the initial SAR in which the potency of the analogues correlated with the ability of the substituent in the 7-position of the azaindole to adopt a coplanar conformation by either forming internal hydrogen bonds or avoiding repulsive substitution patterns.

Preclinical Profile and Characterization of the Hepatitis C Virus NS3 Protease Inhibitor Asunaprevir (BMS-650032).

Asunaprevir (ASV; BMS-650032) is a hepatitis C virus (HCV) NS3 protease inhibitor that has demonstrated efficacy in patients chronically infected with HCV genotype 1 when combined with alfa interferon and/or the NS5A replication complex inhibitor daclatasvir. ASV competitively binds to the NS3/4A protease complex, with K(i) values of 0.4 and 0.

Inhibitors of human immunodeficiency virus type 1 (HIV-1) attachment 6. Preclinical and human pharmacokinetic profiling of BMS-663749, a phosphonooxymethyl prodrug of the HIV-1 attachment inhibitor 2-(4-benzoyl-1-piperazinyl)-1-(4,7-dimethoxy-1H-pyrrolo[2,3-c]pyridin-3-yl)-2-oxoethanone (BMS-488043).

BMS-663749, a phosphonooxymethyl prodrug 4 of the HIV-1 attachment inhibitor 2-(4-benzoyl-1-piperazinyl)-1-(4,7-dimethoxy-1H-pyrrolo[2,3-c]pyridin-3-yl)-2-oxoethanone (BMS-488043) (2) was prepared and profiled in a variety of preclinical in vitro and in vivo models designed to assess its ability to deliver parent drug following oral administration. The data showed that prodrug 4 had excellent potential to significantly reduce dissolution rate-limited absorption following oral dosing in humans. Clinical studies in normal healthy subjects confirmed the potential of 4, revealing that the prodrug significantly increased both the AUC and C(max) of 2 compared to a solid capsule formulation containing the parent drug upon dose escalation.

Chemical genetics strategy identifies an HCV NS5A inhibitor with a potent clinical effect.

The worldwide prevalence of chronic hepatitis C virus (HCV) infection is estimated to be approaching 200 million people. Current therapy relies upon a combination of pegylated interferon-alpha and ribavirin, a poorly tolerated regimen typically associated with less than 50% sustained virological response rate in those infected with genotype 1 virus. The development of direct-acting antiviral agents to treat HCV has focused predominantly on inhibitors of the viral enzymes NS3 protease and the RNA-dependent RNA polymerase NS5B.

Mechanistic characterization and molecular modeling of hepatitis B virus polymerase resistance to entecavir.

Background: Entecavir (ETV) is a deoxyguanosine analog competitive inhibitor of hepatitis B virus (HBV) polymerase that exhibits delayed chain termination of HBV DNA. A high barrier to entecavir-resistance (ETVr) is observed clinically, likely due to its potency and a requirement for multiple resistance changes to overcome suppression. Changes in the HBV polymerase reverse-transcriptase (RT) domain involve lamivudine-resistance (LVDr) substitutions in the conserved YMDD motif (M204V/I +/- L180M), plus an additional ETV-specific change at residues T184, S202 or M250.

Utilization of in vitro Caco-2 permeability and liver microsomal half-life screens in discovering BMS-488043, a novel HIV-1 attachment inhibitor with improved pharmacokinetic properties.

Optimizing pharmacokinetic properties to improve oral exposure is a common theme in modern drug discovery. In the present work, in vitro Caco-2 permeability and microsomal half-life screens were utilized in an effort to guide the structure-activity relationship in order to improve the pharmacokinetic properties of novel HIV-1 attachment inhibitors. The relevance of the in vitro screens to in vivo pharmacokinetic properties was first demonstrated with a number of program compounds at the early stage of lead optimization.

Inhibitors of human immunodeficiency virus type 1 (HIV-1) attachment. 5. An evolution from indole to azaindoles leading to the discovery of 1-(4-benzoylpiperazin-1-yl)-2-(4,7-dimethoxy-1H-pyrrolo[2,3-c]pyridin-3-yl)ethane-1,2-dione (BMS-488043), a drug candidate that demonstrates antiviral activity in HIV-1-infected subjects.

Azaindole derivatives derived from the screening lead 1-(4-benzoylpiperazin-1-yl)-2-(1H-indol-3-yl)ethane-1,2-dione (1) were prepared and characterized to assess their potential as inhibitors of HIV-1 attachment. Systematic replacement of each of the unfused carbon atoms in the phenyl ring of the indole moiety by a nitrogen atom provided four different azaindole derivatives that displayed a clear SAR for antiviral activity and all of which displayed marked improvements in pharmaceutical properties. Optimization of these azaindole leads resulted in the identification of two compounds that were advanced to clinical studies: (R)-1-(4-benzoyl-2-methylpiperazin-1-yl)-2-(4-methoxy-1H-pyrrolo[2,3-b]pyridin-3-yl)ethane-1,2-dione (BMS-377806, 3) and 1-(4-benzoylpiperazin-1-yl)-2-(4,7-dimethoxy-1H-pyrrolo[2,3-c]pyridin-3-yl)ethane-1,2-dione (BMS-488043, 4).

Ultrasensitive genotypic detection of antiviral resistance in hepatitis B virus clinical isolates.

Amino acid substitutions that confer reduced susceptibility to antivirals arise spontaneously through error-prone viral polymerases and are selected as a result of antiviral therapy. Resistance substitutions first emerge in a fraction of the circulating virus population, below the limit of detection by nucleotide sequencing of either the population or limited sets of cloned isolates. These variants can expand under drug pressure to dominate the circulating virus population.

Long-term monitoring shows hepatitis B virus resistance to entecavir in nucleoside-naïve patients is rare through 5 years of therapy.

Unlabelled: Patients with chronic hepatitis B virus (HBV) infection who develop antiviral resistance lose benefits of therapy and may be predisposed to further resistance. Entecavir (ETV) resistance (ETVr) results from HBV reverse transcriptase substitutions at positions T184, S202, or M250, which emerge in the presence of lamivudine (LVD) resistance substitutions M204I/V +/- L180M. Here, we summarize results from comprehensive resistance monitoring of patients with HBV who were continuously treated with ETV for up to 5 years.

Inhibitors of HIV-1 attachment. Part 2: An initial survey of indole substitution patterns.

The effects of introducing simple halogen, alkyl, and alkoxy substituents to the 4, 5, 6 and 7 positions of 1-(4-benzoylpiperazin-1-yl)-2-(1H-indol-3-yl)ethane-1,2-dione, an inhibitor of the interaction between HIV gp120 and host cell CD4 receptors, on activity in an HIV entry assay was examined. Small substituents at C-4 generally resulted in increased potency whilst substitution at C-7 was readily tolerated and uniformly produced more potent HIV entry inhibitors. Substituents deployed at C-6 and, particularly, C-5 generally produced a modest to marked weakening of potency compared to the prototype.

Comprehensive evaluation of hepatitis B virus reverse transcriptase substitutions associated with entecavir resistance.

Unlabelled: Virologic resistance emerging during entecavir (ETV) therapy for hepatitis B virus (HBV) requires three substitutions in the viral reverse transcriptase (RT), signifying a high barrier to resistance. Two of these substitutions are associated with lamivudine resistance (LVDr) in the tyrosine-methionine-aspartate-aspartate (YMDD) motif (rtM204V and rtL180M), whereas the other occurs at one or more positions specifically associated with ETV resistance (ETVr): rtT184, rtS202, or rtM250. Although a variety of substitutions at these primary ETVr positions arise during ETV therapy, only a subset give rise to clinical virologic breakthrough.

Hepatitis B virus quasispecies susceptibility to entecavir confirms the relationship between genotypic resistance and patient virologic response.

Background/aims: The efficacy of anti-viral therapy for chronic hepatitis B virus (HBV) is lost upon the emergence of resistant virus. Using >500 patient HBV isolates from several entecavir clinical trials, we show that phenotypic susceptibility correlates with genotypic resistance and patient virologic responses.

Methods: The full-length HBV or reverse transcriptase gene was amplified from patient sera, sequenced, and cloned into an HBV expression vector.

Entecavir for treatment of hepatitis B virus displays no in vitro mitochondrial toxicity or DNA polymerase gamma inhibition.

Therapy with nucleoside reverse transcriptase inhibitors (NRTIs) can be associated with mitochondrial toxicity. In vitro studies have been used to predict the predisposition for and characterize the mechanisms causing mitochondrial toxicity. Entecavir (ETV) is an approved deoxyguanosine nucleoside for the treatment of chronic hepatitis B virus (HBV) infection that exhibits potent activity against viral reverse transcriptase.

Inhibition of hepatitis B virus polymerase by entecavir.

Entecavir (ETV; Baraclude) is a novel deoxyguanosine analog with activity against hepatitis B virus (HBV). ETV differs from the other nucleoside/tide reverse transcriptase inhibitors approved for HBV therapy, lamivudine (LVD) and adefovir (ADV), in several ways: ETV is >100-fold more potent against HBV in culture and, at concentrations below 1 microM, displays no significant activity against human immunodeficiency virus (HIV). Additionally, while LVD and ADV are obligate DNA chain terminators, ETV halts HBV DNA elongation after incorporating a few additional bases.

Two-year assessment of entecavir resistance in Lamivudine-refractory hepatitis B virus patients reveals different clinical outcomes depending on the resistance substitutions present.

Entecavir (ETV) is a deoxyguanosine analog approved for use for the treatment of chronic infection with wild-type and lamivudine-resistant (LVDr) hepatitis B virus (HBV). In LVD-refractory patients, 1.0 mg ETV suppressed HBV DNA levels to below the level of detection by PCR (<300 copies/ml) in 21% and 34% of patients by Weeks 48 and 96, respectively.

Respiratory syncytial virus fusion inhibitors. Part 4: optimization for oral bioavailability.

A series of benzimidazole-based inhibitors of respiratory syncytial virus (RSV) fusion were optimized for antiviral potency, membrane permeability and metabolic stability in human liver microsomes. 1-Cyclopropyl-1,3-dihydro-3-[[1-(4-hydroxybutyl)-1H-benzimidazol-2-yl]methyl]-2H-imidazo[4,5-c]pyridin-2-one (6m, BMS-433771) was identified as a potent RSV inhibitor demonstrating good bioavailability in the mouse, rat, dog and cynomolgus monkey that demonstrated antiviral activity in the BALB/c and cotton rat models of infection following oral administration.

Entecavir resistance is rare in nucleoside naïve patients with hepatitis B.

Comprehensive monitoring of genotypic and phenotypic antiviral resistance was performed on 673 entecavir (ETV)-treated nucleoside naïve hepatitis B virus (HBV) patients. ETV reduced HBV DNA levels to undetectable by PCR (<300 copies/mL, <57 IU/mL) in 91% of hepatitis B e antigen (HBeAg)-positive and -negative patients by Week 96. Thirteen percent (n = 88) of the comparator lamivudine (LVD)-treated patients experienced a virologic rebound (> or =1 log increase from nadir by PCR) in the first year, with 74% of these having LVD resistance (LVDr) substitutions evident.

The effects of the Roche AMPLICOR HIV-1 MONITOR UltraSensitive Test versions 1.0 and 1.5 viral load assays and plasma collection tube type on determination of response to antiretroviral therapy and the inappropriateness of cross-study comparisons.

Background: Because there are limited head-to-head data comparing antiretroviral combinations, physicians are tempted to rely on cross-trial comparisons to evaluate the relative efficacy of HIV drugs. However, a variety of factors can confound these comparisons, resulting in misleading or invalid conclusions.

Objectives: To compare and evaluate the use of: (i) versions 1.

Protection of macaques from vaginal SHIV challenge by vaginally delivered inhibitors of virus-cell fusion.

Human immunodeficiency virus type 1 (HIV-1) continues to spread, principally by heterosexual sex, but no vaccine is available. Hence, alternative prevention methods are needed to supplement educational and behavioural-modification programmes. One such approach is a vaginal microbicide: the application of inhibitory compounds before intercourse.

A dose-ranging study of the efficacy and tolerability of entecavir in Lamivudine-refractory chronic hepatitis B patients.

Background & Aims: Entecavir is a nucleoside analogue with potent in vitro activity against lamivudine-resistant hepatitis B virus (HBV). This randomized, dose-ranging, phase 2 study compared the efficacy and safety of entecavir with lamivudine in lamivudine-refractory patients.

Methods: Hepatitis B e antigen (HBeAg)-positive and -negative patients (n = 182), viremic despite lamivudine treatment for > or =24 weeks or having documented lamivudine resistance substitutions, were switched directly to entecavir (1.