Discovery of a Potent and Selective Noncovalent Linear Inhibitor of the Hepatitis C Virus NS3 Protease (BI 201335)

An exploratory in N-doped carbon dots as green fluorescence probes for Hg(II) ions detection

Carbon dots (CDs), as a fascinating carbon nanomaterial, have important applications in various fields due to their unique properties. The physical and chemical properties of CDs can be fine-tuned using heteroatom doping and surface functionalisation. Here, we synthesised N-doped carbon dots (N-CDs) by reacting Citric acid, which serve as the carbon core, with twenty amino acids under microwave irradiation. The fluorescence quenching of each amino acid doped CDs by Hg(II) ions was experimentally measured. Then the effect of the molecular features and chemical properties of amino acids on the fluorescence quenching of N-CDs by Hg(II) ions was investigated by using the quantitative structure-property relationship (QSPR) method. Applying different machine learning techniques including correlation-based and ReliefF algorithm feature selection approaches to choose relevant descriptors, multi-linear regression, and support vector machine to construct QSPR model, some reliable and predictive models were developed. Based on the variables used throughout the final QSPR models, hydrophobic interactions, in addition to hydrogen bonding interactions, can be considered a major factor governing the photoluminescence behaviour of different N-CDs quenched by Hg(II) ions. N-CDs derived from amino acids bearing larger hydrophobic surfaces show greater fluorescence quenching, indicating that a greater capacity to interact with Hg(II) metal ions resulting in further fluorescence quenching.

Cascade reactions with two non-physiological partners for NAD(P)H regeneration via renewable hydrogen

An attractive application of hydrogenases, combined with the availability of cheap and renewable hydrogen (i.e., from solar and wind powered electrolysis or from recycled wastes), is the production of high-value electron-rich intermediates such as reduced nicotinamide adenine dinucleotides. Here, the capability of a very robust and oxygen-resilient [FeFe]-hydrogenase (CbA5H) from Clostridium beijerinckii SM10, previously identified in our group, combined with a reductase (BMR) from Bacillus megaterium (now reclassified as Priestia megaterium) was tested. The system shows a good stability and it was demonstrated to reach up to 28 ± 2 nmol NADPH regenerated s-1 mg of hydrogenase-1 (i.e., 1.68 ± 0.12 U mg-1, TOF: 126 ± 9 min-1) and 0.46 ± 0.04 nmol NADH regenerated s-1 mg of hydrogenase-1 (i.e., 0.028 ± 0.002 U mg-1, TOF: 2.1 ± 0.2 min-1), meaning up to 74 mg of NADPH and 1.23 mg of NADH produced per hour by a system involving 1 mg of CbA5H. The TOF is comparable with similar systems based on hydrogen as regenerating molecule for NADPH, but the system is first of its kind as for the [FeFe]-hydrogenase and the non-physiological partners used. As a proof of concept a cascade reaction involving CbA5H, BMR and a mutant BVMO from Acinetobacter radioresistens able to oxidize indole is presented. The data show how the cascade can be exploited for indigo production and multiple reaction cycles can be sustained using the regenerated NADPH.

Hepatitis C: The Story of a Long Journey through First, Second, and Third Generation NS3/4A Peptidomimetic Inhibitors. What Did We Learn?

Hepatitis C viral (HCV) infection is the leading cause of liver failure and still represents a global health burden. Over the past decade, great advancements made HCV curable, and sustained viral remission significantly improved to more than 98%. Historical treatment with pegylated interferon alpha and ribavirin has been displaced by combinations of direct-acting antivirals. These regimens include drugs targeting different stages of the HCV life cycle. However, the emergence of viral resistance remains a big concern. The design of peptidomimetic inhibitors (PIs) able to fit and fill the conserved substrate envelope region within the active site helped avoid contact with the vulnerable sites of the most common resistance-associated substitutions Arg155, Ala156, and Asp168. Herein, we give an overview of HCV NS3 PIs discovered during the past decade, and we deeply discuss the rationale behind the structural optimization efforts essential to achieve pangenotypic activity.

Exploratory and machine learning analysis of the stability constants of HgII- triazene ligands complexes

Knowing stability constants for the complexes HgII with extracting ligands is very important from environmental and therapeutic standpoints. Since the selectivity of ligands can be stated by the stability constants of cation–ligand complexes, quantitative structure–property relationship (QSPR) investigations on binding constant of HgII complexes were done. Experimental data of the stability constants in ML2 complexation of HgII and synthesized triazene ligands were used to construct and develop QSPR models. Support vector machine (SVM) and multiple linear regression (MLR) have been employed to create the QSPR models. The final model showed squared correlation coefficient of 0.917 and the standard error of calibration (SEC) value of 0.141 log K units. The proposed model presented accurate prediction with the Leave-One-Out cross validation ( Q LOO 2  = 0.756) and validated using Y-randomization and external test set. Statistical results demonstrated that the proposed models had suitable goodness of fit, predictive ability, and robustness. The results revealed the importance of charge effects and topological properties of ligand in HgII - triazene complexation.

Discovery of Quinoxaline-Based P1-P3 Macrocyclic NS3/4A Protease Inhibitors with Potent Activity against Drug-Resistant Hepatitis C Virus Variants

The three pan-genotypic HCV NS3/4A protease inhibitors (PIs) currently in clinical use-grazoprevir, glecaprevir, and voxilaprevir-are quinoxaline-based P2-P4 macrocycles and thus exhibit similar resistance profiles. Using our quinoxaline-based P1-P3 macrocyclic lead compounds as an alternative chemical scaffold, we explored structure-activity relationships (SARs) at the P2 and P4 positions to develop pan-genotypic PIs that avoid drug resistance. A structure-guided strategy was used to design and synthesize two series of compounds with different P2 quinoxalines in combination with diverse P4 groups of varying sizes and shapes, with and without fluorine substitutions. Our SAR data and cocrystal structures revealed the interplay between the P2 and P4 groups, which influenced inhibitor binding and the overall resistance profile. Optimizing inhibitor interactions in the S4 pocket led to PIs with excellent antiviral activity against clinically relevant PI-resistant HCV variants and genotype 3, providing potential pan-genotypic inhibitors with improved resistance profiles.

The index of ideality of correlation: QSAR studies of hepatitis C virus NS3/4A protease inhibitors using SMILES descriptors

Robust and reliable QSAR models were developed to predict half-maximal inhibitory concentration (IC₅₀) values of hepatitis C virus NS3/4A protease inhibitors from the Monte Carlo technique. 524 HCV NS3/4A protease inhibitors were extracted from the scientific literature to create a reasonably large set. The models were developed using CORAL software by using two target functions namely target function 1 (TF1) without applying the index of ideality of correlation (IIC) and target function 2 (TF2) that uses IIC. The constructed models based on TF2 were statistically more significant and robust than the models based on TF1. The determination coefficients (r²) of training and test sets were 0.86 and 0.88 for the best split based on TF2. The promoters of the increase/decrease of activity were also extracted and interpreted in detail. The model interpretation results explain the role of different structural attributes in predicting the pIC₅₀ values of hepatitis C virus NS3/4A protease inhibitors. Based on the mechanistic model interpretation results, eight new compounds were designed and their pIC₅₀ values were predicted based on the average prediction of ten models.

Sulfone-Mediated SNAr Reaction as a Powerful Tool for the Synthesis of 4-Quinolinyl Ethers and More-Application to the Synthesis of HCV NS3/4a Protease Inhibitor

An efficient general methodology for the synthesis of 4-quinolinyl ethers is demonstrated via a highly reactive S_NAr reaction of 4-quinolinyl sulfones with a range of structurally diversified 1°, 2°, and 3° alcohols with a wide substrate scope and high yields. By adapting this methodology, a convergent synthesis of a complex target of HCV NS3/4a protease inhibitor BI 201420 was accomplished.

Applications of fluorine-containing amino acids for drug design

Fluorine-containing amino acids are becoming increasingly prominent in new drugs due to two general trends in the modern pharmaceutical industry. Firstly, the growing acceptance of peptides and modified peptides as drugs; and secondly, fluorine editing has become a prevalent protocol in drug-candidate optimization. Accordingly, fluorine-containing amino acids represent one of the more promising and rapidly developing areas of research in organic, bio-organic and medicinal chemistry. The goal of this Review article is to highlight the current state-of-the-art in this area by profiling 42 selected compounds that combine fluorine and amino acid structural elements. The compounds under discussion represent pharmaceutical drugs currently on the market, or in clinical trials as well as examples of drug-candidates that although withdrawn from development had a significant impact on the progress of medicinal chemistry and/or provided a deeper understanding of the nature and mechanism of biological action. For each compound, we present features of biological activity, a brief history of the design principles and the development of the synthetic approach, focusing on the source of tailor-made amino acid structures and fluorination methods. General aspects of the medicinal chemistry of fluorine-containing amino acids and synthetic methodology are briefly discussed.

Resistance outside the substrate envelope: hepatitis C NS3/4A protease inhibitors

Direct acting antivirals have dramatically increased the efficacy and tolerability of hepatitis C treatment, but drug resistance has emerged with some of these inhibitors, including nonstructural protein 3/4 A protease inhibitors (PIs). Although many co-crystal structures of PIs with the NS3/4A protease have been reported, a systematic review of these crystal structures in the context of the rapidly emerging drug resistance especially for early PIs has not been performed. To provide a framework for designing better inhibitors with higher barriers to resistance, we performed a quantitative structural analysis using co-crystal structures and models of HCV NS3/4A protease in complex with natural substrates and inhibitors. By comparing substrate structural motifs and active site interactions with inhibitor recognition, we observed that the selection of drug resistance mutations correlates with how inhibitors deviate from viral substrates in molecular recognition. Based on this observation, we conclude that guiding the design process with native substrate recognition features is likely to lead to more robust small molecule inhibitors with decreased susceptibility to resistance.

Iodide Discrimination by Tetra-Iodotriazole Halogen Bonding Interlocked Hosts

Whilst the exploitation of interlocked host frameworks for anion recognition is widely established, examples incorporating halogen bond donor groups are still relatively rare. Through the integration of a novel tetra(iodotriazole)-pyridinium motif into macrocycle and axle components, a family of halogen bonding catenane and rotaxanes are constructed for anion recognition studies in a competitive aqueous-organic solvent mixture. Importantly, the degree of anion selectivity displayed is dictated by the topological nature and charged state of the respective interlocked host cavity. All the interlocked hosts exhibit iodide anion selectivity over other halides and sulfate, with the level of discrimination being the greatest with the mono-cationic rotaxane. Arising from greater electrostatic interactions working in tandem with halogen bonding and hydrogen bonding, the di-cationic rotaxane displays stronger anion association at the expense of a relatively lower degree of iodide selectivity.

Evolution of efficacious pangenotypic hepatitis C virus therapies

Hepatitis C compromises the quality of life of more than 350 million individuals worldwide. Over the last decade, therapeutic regimens for treating hepatitis C virus (HCV) infections have undergone rapid advancements. Initially, structure-based drug design was used to develop molecules that inhibit viral enzymes. Subsequently, establishment of cell-based replicon systems enabled investigations into various stages of HCV life cycle including its entry, replication, translation, and assembly, as well as role of host proteins. Collectively, these approaches have facilitated identification of important molecules that are deemed essential for HCV life cycle. The expanded set of putative virus and host-encoded targets has brought us one step closer to developing robust strategies for efficacious, pangenotypic, and well-tolerated medicines against HCV. Herein, we provide an overview of the development of various classes of virus and host-directed therapies that are currently in use along with others that are undergoing clinical evaluation.

Proteases and protease inhibitors in infectious diseases

There are numerous proteases of pathogenic organisms that are currently targeted for therapeutic intervention along with many that are seen as potential drug targets. This review discusses the chemical and biological makeup of some key druggable proteases expressed by the five major classes of disease causing agents, namely bacteria, viruses, fungi, eukaryotes, and prions. While a few of these enzymes including HIV protease and HCV NS3-4A protease have been targeted to a clinically useful level, a number are yet to yield any clinical outcomes in terms of antimicrobial therapy. A significant aspect of this review discusses the chemical and pharmacological characteristics of inhibitors of the various proteases discussed. A total of 25 inhibitors have been considered potent and safe enough to be trialed in humans and are at different levels of clinical application. We assess the mechanism of action and clinical performance of the protease inhibitors against infectious agents with their developmental strategies and look to the next frontiers in the use of protease inhibitors as anti-infective agents.

Halogen Bonding in Nucleic Acid Complexes

Halogen bonding (X-bonding) has attracted notable attention among noncovalent interactions. This highly directional attraction between a halogen atom and an electron donor has been exploited in knowledge-based drug design. A great deal of information has been gathered about X-bonds in protein-ligand complexes, as opposed to nucleic acid complexes. Here we provide a thorough analysis of nucleic acid complexes containing either halogenated building blocks or halogenated ligands. We analyzed close contacts between halogens and electron-rich moieties. The phosphate backbone oxygen is clearly the most common halogen acceptor. We identified 21 X-bonds within known structures of nucleic acid complexes. A vast majority of the X-bonds is formed by halogenated nucleobases, such as bromouridine, and feature excellent geometries. Noncovalent ligands have been found to form only interactions with suboptimal interaction geometries. Hence, the first X-bonded nucleic acid binder remains to be discovered.

QSAR studies of the bioactivity of hepatitis C virus (HCV) NS3/4A protease inhibitors by multiple linear regression (MLR) and support vector machine (SVM)

In this study, quantitative structure-activity relationship (QSAR) models using various descriptor sets and training/test set selection methods were explored to predict the bioactivity of hepatitis C virus (HCV) NS3/4A protease inhibitors by using a multiple linear regression (MLR) and a support vector machine (SVM) method. 512 HCV NS3/4A protease inhibitors and their IC₅₀ values which were determined by the same FRET assay were collected from the reported literature to build a dataset. All the inhibitors were represented with selected nine global and 12 2D property-weighted autocorrelation descriptors calculated from the program CORINA Symphony. The dataset was divided into a training set and a test set by a random and a Kohonen's self-organizing map (SOM) method. The correlation coefficients (r²) of training sets and test sets were 0.75 and 0.72 for the best MLR model, 0.87 and 0.85 for the best SVM model, respectively. In addition, a series of sub-dataset models were also developed. The performances of all the best sub-dataset models were better than those of the whole dataset models. We believe that the combination of the best sub- and whole dataset SVM models can be used as reliable lead designing tools for new NS3/4A protease inhibitors scaffolds in a drug discovery pipeline.

Unusual Amino Acids in Medicinal Chemistry

Unusual amino acids are fundamental building blocks of modern medicinal chemistry. The combination of readily functionalized amine and carboxyl groups attached to a chiral central core along with one or two potentially diverse side chains provides a unique three-dimensional structure with a high degree of functionality. This makes them invaluable as starting materials for syntheses of complex molecules, highly diverse elements for SAR campaigns, integral components of peptidomimetic drugs, and potential drugs on their own. This Perspective highlights the diversity of unnatural amino acid structures found in hit-to-lead and lead optimization campaigns and clinical stage and approved drugs, reflecting their increasingly important role in medicinal chemistry.

Discovery of a Potent Acyclic, Tripeptidic, Acyl Sulfonamide Inhibitor of Hepatitis C Virus NS3 Protease as a Back-up to Asunaprevir with the Potential for Once-Daily Dosing

The discovery of a back-up to the hepatitis C virus NS3 protease inhibitor asunaprevir (2) is described. The objective of this work was the identification of a drug with antiviral properties and toxicology parameters similar to 2, but with a preclinical pharmacokinetic (PK) profile that was predictive of once-daily dosing. Critical to this discovery process was the employment of an ex vivo cardiovascular (CV) model which served to identify compounds that, like 2, were free of the CV liabilities that resulted in the discontinuation of BMS-605339 (1) from clinical trials. Structure-activity relationships (SARs) at each of the structural subsites in 2 were explored with substantial improvement in PK through modifications at the P1 site, while potency gains were found with small, but rationally designed structural changes to P4. Additional modifications at P3 were required to optimize the CV profile, and these combined SARs led to the discovery of BMS-890068 (29).

STARTVerso1: A randomized trial of faldaprevir plus pegylated interferon/ribavirin for chronic HCV genotype-1 infection

BACKGROUND & AIMS

The efficacy and tolerability of faldaprevir, a potent hepatitis C virus (HCV) NS3/4A protease inhibitor, plus peginterferon (PegIFN) and ribavirin (RBV) was assessed in a double-blind, placebo-controlled phase 3 study of treatment-naïve patients with HCV genotype-1 infection.

METHODS

Patients were randomly assigned (1:2:2) to PegIFN/RBV plus: placebo (arm 1, n = 132) for 24 weeks; faldaprevir (120 mg, once daily) for 12 or 24 weeks (arm 2, n = 259); or faldaprevir (240 mg, once daily) for 12 weeks (arm 3, n = 261). In arms 2 and 3, patients with early treatment success (HCV-RNA <25 IU/ml at week 4 and undetectable at week 8) stopped all treatment at week 24. Other patients received PegIFN/RBV until week 48 unless they met futility criteria. The primary endpoint was sustained virologic response 12 weeks post-treatment (SVR12).

RESULTS

SVR12 was achieved by 52%, 79%, and 80% of patients in arms 1, 2, and 3, respectively (estimated difference for arms 2 and 3 vs. arm 1: 27%, 95% confidence interval 17%-36%; and 29%, 95% confidence interval, 19%-38%, respectively; p < 0.0001 for both). Early treatment success was achieved by 87% (arm 2) and 89% (arm 3) of patients, of whom 86% and 89% achieved SVR12. Adverse event rates were similar among groups; few adverse events led to discontinuation of all regimen components.

CONCLUSIONS

Faldaprevir plus PegIFN/RBV significantly increased SVR12, compared with PegIFN/RBV, in treatment-naïve patients with HCV genotype-1 infection. No differences were seen in responses of patients given faldaprevir once daily at 120 or 240 mg.

Asymmetric synthesis of (1R,2S)-1-amino-2-vinylcyclopropanecarboxylic acid by sequential SN2–SN2′ dialkylation of (R)-N-(benzyl)proline-derived glycine Schiff base Ni(ii) complex

The synthesis of the title compound, a key structural fragment of several hepatitis C virus inhibitors, is described.

Discovery of BI 207524, an indole diamide NS5B thumb pocket 1 inhibitor with improved potency for the potential treatment of chronic hepatitis C virus infection

The development of interferon-free regimens for the treatment of chronic HCV infection constitutes a preferred option that is expected in the future to provide patients with improved efficacy, better tolerability, and reduced risk for emergence of drug-resistant virus. We have pursued non-nucleoside NS5B polymerase allosteric inhibitors as combination partners with other direct acting antivirals (DAAs) having a complementary mechanism of action. Herein, we describe the discovery of a potent follow-up compound (BI 207524, 27) to the first thumb pocket 1 NS5B inhibitor to demonstrate antiviral activity in genotype 1 HCV infected patients, BILB 1941 (1). Cell-based replicon potency was significantly improved through electronic modulation of the pKa of the carboxylic acid function of the lead molecule. Subsequent ADME-PK optimization lead to 27, a predicted low clearance compound in man. The preclinical profile of inhibitor 27 is discussed, as well as the identification of a genotoxic metabolite that led to the discontinuation of the development of this compound.

Development of a high-throughput pyrosequencing assay for monitoring temporal evolution and resistance associated variant emergence in the Hepatitis C virus protease coding-region

A new generation of drugs targeting the non-structural (NS) proteins of the Hepatitis C virus (HCV) will substantially increase treatment success rates, reducing global infections. Amongst the NS proteins, the NS3 protease represents an important drug target, responsible for liberation of mature NS proteins from the nascent HCV polyprotein and suppression of host innate immunity. Despite this, the evolutionary stability of the genomic locus encoding the NS3 protease is poorly characterized in chronic HCV infection. To address this shortfall, we developed a high-throughput amplicon pyrosequencing protocol and utilised it to monitor NS3 protease coding-sequence evolution for over a decade in two patients. Although patient-specific evolutionary trends were apparent, the protease amino acid population consensus remained stable with a massive excess of synonymous mutations observed, confirming this locus is under strong purifying selection during chronic infection within individual patients. No evidence for continuous immune escape was detected. Additionally, both patients failed protease inhibitor (PI) therapy and protease sequence diversity pre- and post-therapy were also assessed. No baseline resistance associated variants (RAVs) contributed to treatment failure. Significant reductions in viral diversity were observed post-PI therapy, indicating a population bottleneck occurred. The genetic vestiges of this bottleneck were still detectable 18months after therapy discontinuation. Although significant enrichment of the Q80L mutation was observed in one patient, genetic and phenotypic data reveal no detectable RAV persistence post-therapy failure. Together this investigation provides a sensitive and reproducible high-throughput framework to interrogate viral sequence diversity at high-resolution, with potential applications for routine monitoring of treatment regimens. This study also reveals novel insights into the evolutionary processes that shape NS3 sequence divergence in both chronic HCV infection and post PI-therapy failure.

Targeting gap junction intercellular communication as a potential therapy for HCV-related carcinogenesis

ABSTRACT: 

Worldwide, at least 170 million people are infected with hepatitis C virus (HCV), which is associated with hepatocellular carcinoma (HCC). With the recent success of Sofosbuvir (and other agents) antiviral therapy may be used as a future early-stage HCC treatment; however, in the short term, a cost-effective solution is needed to treat patients with viral-associated HCC. Here, we emphasize the potential of targeting gap junction intercellular communication (GJIC) as a therapeutic approach for HCC as HCV perturbs GJIC, which is linked to cellular transformation. We review the ROCK inhibitor Y-27632 and structurally related compounds that may inhibit the carcinogenic properties of HCV.

Hepatitis C virus serine protease: synthesis of radioactive and stable isotope-labeled potent inhibitors

Drug candidates labeled with radioactive and stable isotopes are required for absorption, distribution, metabolism, and excretion (ADME) studies, pharmacokinetics, autoradiography, bioanalytical, and other research activities. The findings from these studies are crucial in the development of a drug candidate and its approval for human use. Herein, we report the synthesis of potent and selective hepatitis C virus serine protease inhibitors related to BILN 2061 and BI 201335 labeled with radioactive and stable isotopes. Synthetic efforts were focused on the common substituted thiazole moiety, which is easily accessible via a Hantzsch's reaction of α-bromoketones and mono-substituted thioureas. In the radioactive synthesis, commercially available carbon-14 thiourea was utilized to prepare mono-substituted thioureas, which upon condensation with α-bromoketones in isopropanol followed by ester hydrolysis gave the desired carbon-14-labeled protease inhibitors. The same strategy was used to prepare these inhibitors labeled with stable isotopes. Mono-substituted thioureas were obtained from commercially available deuterium-labeled intermediates and then condensed with α-bromoketones followed by ester hydrolysis to give the deuterium-labeled inhibitors.

Biotransformation and mass balance of faldaprevir, a hepatitis C NS3/NS4 protease inhibitor in rats

1. The metabolism, pharmacokinetics, excretion and tissue distribution of a hepatitis C NS3/NS4 protease inhibitor, faldaprevir, were studied in rats following a single 2 mg/kg intravenous or 10 mg/kg oral administration of [(14)C]-faldaprevir. 2. Following intravenous dosing, the terminal elimination t1/2 of plasma radioactivity was 1.75 h (males) and 1.74 h (females). Corresponding AUC0-∞, CL and Vss were 1920 and 1900 ngEq · h/mL, 18.3 and 17.7 mL/min/kg and 2.32 and 2.12 mL/kg for males and females, respectively. 3. After oral dosing, t1/2 and AUC0-∞ for plasma radioactivity were 1.67 and 1.77 h and 11 300 and 17 900 ngEq · h/mL for males and females, respectively. 4. In intact rats, ≥90.17% dose was recovered in feces and only ≤1.08% dose was recovered in urine for both iv and oral doses. In bile cannulated rats, 54.95, 34.32 and 0.27% dose was recovered in feces, bile and urine, respectively. 5. Glucuronidation plays a major role in the metabolism of faldaprevir with minimal Phase I metabolism. 6. Radioactivity was rapidly distributed into tissues after the oral dose with peak concentrations of radioactivity in most tissues at 6 h post-dose. The highest levels of radioactivity were observed in liver, lung, kidney, small intestine and adrenal gland.

New hepatitis C therapies: the toolbox, strategies, and challenges

Therapy for hepatitis C is undergoing a revolution. Several new drugs against the hepatitis C virus (HCV) have reached the market and many others, including direct-acting antivirals and host-targeted agents, are in phase II or III clinical development. All-oral, interferon-free combinations of drugs are expected to cure more than 90% of infections. A vast amount of data from clinical trials are presented regularly at international conferences or released to the press before peer-review, creating confusion in the viral hepatitis field. The goal of this review is to clarify the current stage of HCV therapy and drug development. This review describes the different classes of drugs and their mechanisms and properties, as well as treatment strategies in development, including those that are interferon-based and interferon-free. HCV treatment options that will be available in 2014-2015 are presented for each genotype. A number of unanswered questions and challenges remain, such as how to treat special populations, the role of ribavirin in interferon-free regimens, the role of HCV resistance in treatment failures, and how to best re-treat patients who failed on treatment. Strategic choices, cost issues, HCV screening, and improving access to care in resource-constrained areas also are discussed.

Thermodynamic and structural characterization of halogen bonding in protein-ligand interactions: a case study of PDE5 and its inhibitors

The significance of halogen bonding in protein-ligand interactions has been recognized recently. We present here the first comprehensive thermodynamic and structural characterization of halogen bonding in PDE5-inhibitor interactions. ITC studies reveal that binding strength of the halogen bonding between chlorine, bromine, and iodine of inhibitor and the protein is -1.57, -3.09, and -5.59 kJ/mol, respectively. The halogens interact with the designed residue Y612 and an unexpected buried water molecule.

Mass balance and metabolite profiling of steady-state faldaprevir, a hepatitis C virus NS3/4 protease inhibitor, in healthy male subjects

The pharmacokinetics, mass balance, and metabolite profiles of faldaprevir, a selective peptide-mimetic hepatitis C virus NS3/NS4 protease inhibitor, were assessed at steady state in 7 healthy male subjects. Subjects received oral doses of 480 mg faldaprevir on day 1, followed by 240 mg faldaprevir on days 2 to 8 and 10 to 15. [14C]faldaprevir (240 mg containing 100 μCi) was administered on day 9. Blood, urine, feces, and saliva samples were collected at intervals throughout the study. Metabolite profiling was performed using radiochromatography, and metabolite identification was conducted using liquid chromatography-tandem mass spectrometry. The overall recovery of radioactivity was high (98.8%), with the majority recovered from feces (98.7%). There was minimal radioactivity in urine (0.113%) and saliva. Circulating radioactivity was predominantly confined to plasma with minimal partitioning into red blood cells. The terminal half-life of radioactivity in plasma was approximately 23 h with no evidence of any long-lasting metabolites. Faldaprevir was the predominant circulating form, accounting for 98 to 100% of plasma radioactivity from each subject. Faldaprevir was the only drug-related component detected in urine. Faldaprevir was also the major drug-related component in feces, representing 49.8% of the radioactive dose. The majority of the remainder of radioactivity in feces (41% of the dose) was accounted for in almost equal quantities by 2 hydroxylated metabolites. The most common adverse events were nausea, diarrhea, and constipation, all of which were related to study drug. In conclusion, faldaprevir is predominantly excreted in feces with negligible urinary excretion.

Minimum costs for producing hepatitis C direct-acting antivirals for use in large-scale treatment access programs in developing countries

Large-scale manufacture of treatment to cure hepatitis C virus (HCV) is feasible, with target prices of US$100–$250 per 12-week treatment course. These low prices could make widespread access to HCV treatment in low- and middle-income countries a realistic goal.

Background. Several combinations of 2 or 3 direct-acting antivirals (DAAs) can cure hepatitis C virus (HCV) in the majority of treatment-naive patients. DAAs for HCV infection have similar mechanisms of action and chemical structures to antiretrovirals for human immunodeficiency virus (HIV) infection. Generic antiretrovirals are currently manufactured at very low prices, to treat 10 million people with HIV/AIDS in developing countries.

Methods. Four HCV DAAs, currently either in phase 3 development or recent approval (daclatasvir, sofosbuvir, simeprevir, faldaprevir), and ribavirin were classified by chemical structure, molecular weight, total daily dose, and complexity of synthesis. The likely range of manufacturing costs per gram of DAA were then projected as formulated product cost, based upon treating a minimum of 1 million patients annually (to arrive at volume demand) combined with an analysis of the complexity of synthesis and a 40% margin for formulation. Projections were then compared with actual costs of antiretrovirals with similar structures.

Results. Minimum manufacturing costs of antiretrovirals were US$0.2–$2.1 per gram. The complexity of chemical synthesis for HCV DAAs was ranked from lowest to highest: ribavirin, daclatasvir, sofosbuvir, faldaprevir, and simeprevir. Predicted manufacturing costs (US dollars) for 12-week courses of HCV DAAs were $21–$63 for ribavirin, $10–$30 for daclatasvir, $68–$136 for sofosbuvir, $100–$210 for faldaprevir, and $130–$270 for simeprevir.

Conclusions. Within the next 15 years, large-scale manufacture of 2 or 3 drug combinations of HCV DAAs is feasible, with minimum target prices of $100–$250 per 12-week treatment course. These low prices could make widespread access to HCV treatment in low- and middle-income countries a realistic goal.

Safety and efficacy of faldaprevir with pegylated interferon alfa-2a and ribavirin in Japanese patients with chronic genotype-1 hepatitis C infection

BACKGROUND & AIMS

Faldaprevir (BI 201335) is a potent once-daily (QD) NS3/4A protease inhibitor for the treatment of patients with genotype-1 (GT-1) hepatitis C virus (HCV). The aim of this study was to evaluate the safety, pharmacokinetics and efficacy of faldaprevir plus pegylated interferon alfa-2a (PegIFN) and ribavirin (RBV) in Japanese patients infected with chronic GT-1 HCV.

METHODS

Part 1 of this phase II study was a randomized, double-blind, placebo-controlled, dose-ascending study. Treatment-naïve patients received faldaprevir 120 or 240 mg QD, or placebo, plus PegIFN/RBV for 4 weeks, then PegIFN/RBV alone for 44 weeks. In Part 2 (open label), treatment-experienced patients received faldaprevir 240 mg QD plus PegIFN/RBV for 4 weeks, then PegIFN/RBV alone for 44 weeks. Efficacy was assessed using sustained virological response (SVR) 24 weeks after treatment completion. The pharmacokinetics, safety and tolerability of faldaprevir were also assessed.

RESULTS

SVR was achieved by 4/6 (67%) treatment-naïve patients treated with faldaprevir 120 mg QD, 5/6 (83%) patients treated with faldaprevir 240 mg QD and 2/4 (50%) patients who received placebo. Of the treatment-experienced patients, 3/6 (50%) achieved SVR. Faldaprevir was well tolerated. There was one serious adverse event, which was not considered to be treatment related. Rash and hyperbilirubinaemia were more frequently reported with faldaprevir than with placebo in treatment-naïve patients, but no cases were severe or serious and none led to discontinuation. Steady-state plasma concentrations of faldaprevir were reached within 7 days of QD dosing.

CONCLUSIONS

Faldaprevir with PegIFN/RBV was efficacious and well tolerated, supporting further evaluation of this combination in Japanese patients.

Dynamic kinetic resolution of dehydrocoronamic acid

A dynamic kinetic resolution is described employing enzymatic reaction of a readily racemised azlactone with an alcohol which can provide either enantiomer of dehydrocoronamic acid.

Faldaprevir (BI 201335) for the treatment of hepatitis C in patients co-infected with HIV

Chronic HCV infection affects 130-170 million individuals worldwide and there are currently 34 million people living with HIV/AIDS. The aim of treatment of HCV is the elimination of the virus (sustained virological response). With development of drugs that specifically target HCV replication, direct-acting agents, sustained virological response rates have dramatically changed for genotype 1 infections. Challenges in the use of direct-acting agents in patients with HIV/HCV co-infection include the potential for drug-drug interactions between HIV and HCV drugs, additional drug toxicities and the need for therapy with IFN-α. Faldaprevir (FDV), previously known as BI 201335, is a second-wave HCV NS3/4A protease inhibitor with highly potent in vitro activity against HCV GT-1a/1b and improved pharmacokinetics suitable for once-daily dosing. FDV is currently in Phase III development. This article will review the pharmacology and pharmacodynamics of FDV, the efficacy and safety of the drug and explore possible future developments in the management of chronic hepatitis C infection, focusing on HIV/HCV co-infected patients.

Identification of novel small molecules as inhibitors of hepatitis C virus by structure-based virtual screening

Hepatitis C virus (HCV) NS3/NS4A serine protease is essential for viral replication, which is regarded as a promising drug target for developing direct-acting anti-HCV agents. In this study, sixteen novel compounds with cell-based HCV replicon activity ranging from 3.0 to 28.2 μM (IC₅₀) were successfully identified by means of structure-based virtual screening. Compound 5 and compound 11, with an IC₅₀ of 3.0 μM and 5.1 μM, respectively, are the two most potent molecules with low cytotoxicity.

Ligand bioactive conformation plays a critical role in the design of drugs that target the hepatitis C virus NS3 protease

A ligand-focused strategy employed NMR, X-ray, modeling, and medicinal chemistry to expose the critical role that bioactive conformation played in the design of a variety of drugs that target the HCV protease. The bioactive conformation (bound states) were determined for key inhibitors identified along our drug discovery pathway from the hit to clinical compounds. All adopt similar bioactive conformations for the common core derived from the hit peptide DDIVPC. A carefully designed SAR analysis, based on the advanced inhibitor 1 in which the P1 to P3 side chains and the N-terminal Boc were sequentially truncated, revealed a correlation between affinity and the relative predominance of the bioactive conformation in the free state. Interestingly, synergistic conformation effects on potency were also noted. Comparisons with clinical and recently marketed drugs from the pharmaceutical industry showed that all have the same core and similar bioactive conformations. This suggested that the variety of appendages discovered for these compounds also properly satisfy the bioactive conformation requirements and allowed for a large variety of HCV protease drug candidates to be designed.

Viral resistance in hepatitis C virus genotype 1-infected patients receiving the NS3 protease inhibitor Faldaprevir (BI 201335) in a phase 1b multiple-rising-dose study

Faldaprevir (BI 201335) is a selective NS3/4A protease inhibitor under development for the treatment of chronic hepatitis C virus (HCV) infection. NS3/4A genotyping and NS3 protease phenotyping analyses were performed to monitor the emergence of resistance in patients with HCV genotype 1 infection receiving faldaprevir alone or combined with pegylated interferon alfa 2a and ribavirin (PegIFN-RBV) during a phase 1b study. Among all baseline variants, a maximum 7-fold reduction in in vitro sensitivity to faldaprevir was observed for a rare NS3 (V/I)170T polymorphism. During faldaprevir monotherapy in treatment-naive patients, virologic breakthrough was common (77%, 20/26) and was associated with the emergence of resistance mutations predominantly carrying NS3 substitutions R155K in GT1a and D168V in GT1b. D168V conferred a greater reduction in faldaprevir sensitivity (1,800-fold) than R155K (330-fold); however, D168V was generally less fit than R155K in the absence of selective drug pressure. Treatment-experienced patients treated with faldaprevir-PegIFN-RBV triple therapy showed higher viral load reductions, lower rates of breakthrough (8%, 5/62), and less frequent emergence of resistance-associated variants compared with faldaprevir monotherapy. (This study has been registered at ClinicalTrials.gov under registration no. NCT00793793.).