Discovery of MK-8742: an HCV NS5A inhibitor with broad genotype activity

Personalized care approaches to hepatitis C therapy: recent advances and future directions

INTRODUCTION

The introduction of direct-acting antivirals (DAAs) has significantly transformed the therapeutic landscape for chronic C hepatitis virus (HCV) infection. However, there is still room for further improvement in optimizing therapy efficacy and minimizing adverse effects.

AREAS COVERED

This review is devoted to the rationale for adopting a personalized approach to HCV therapy. Specifically, we explore the role of host-related factors, such as sex or the presence of comorbidities. We thoroughly examine the implications of commonly encountered comorbidities, including HIV infection, chronic renal disease, liver cirrhosis, and other chronic viral hepatitis infections. Additionally, we discuss the prevalent drug-to-drug interactions between DAAs and other medications, while providing guidance on their management. Finally, we investigate viral-related issues that can influence treatment outcomes, such as viral genotype, quasi-species, and the presence of resistance-associated mutations.

EXPERT OPINION

Despite pivotal trials demonstrating efficacy rates exceeding 90% for currently available DAA regimens, there are still opportunities to optimize therapy outcomes and tailor treatment to each patient. This can be achieved through a meticulous evaluation of the patient's specific clinical conditions and comorbidities, a vigilant approach to manage potential drug interactions, and diligent patient follow-up.

Dinuclear Zn-Catalytic System as Brønsted Base and Lewis Acid for Enantioselectivity in Same Chiral Environment

Zinc (Zn) is a crucial element with remarkable significance in organic transformations. The profusion of harmless zinc salts in the Earth's outer layer qualifies zinc as a noteworthy contender for inexpensive and eco-friendly reagents and catalysts. Recently, widely recognized uses of organo-Zn compounds in the field of organic synthesis have undergone extensive expansion toward asymmetric transformations. The ProPhenol ligand, a member of the chiral nitrogenous-crown family, exhibits the spontaneous formation of a dual-metal complex when reacted with alkyl metal (R-M) reagents, e.g., ZnEt2. The afforded Zn complex possesses two active sites, one Lewis acid and the other Brønsted base, thereby facilitating the activation of nucleophiles and electrophiles simultaneously within the same chiral pocket. In this comprehensive analysis, we provide a thorough account of the advancement and synthetic potential of these diverse catalysts in organic synthesis, while emphasizing the reactivity and selectivities, i.e., dr and ee due to the design/structure of the ligands employed.

Enantioconvergent 6π Electrocyclization Enabled by Photoredox Racemization

This study presents a novel photoredox-enabled enantioconvergent catalytic strategy used to construct chiral 2H-1,3-benzoxazines via an unprecedented oxa-6π electrocyclization utilizing racemic α-substituted glycinates as substrates. The approach leverages a cobalt-based chiral Lewis acid catalyst, which promotes the transformation under thermal or photoredox conditions. While the thermal reaction selectively converts only the (S)-configured glycinates into enantioenriched 2H-1,3-benzoxazines (up to 96:4 e.r.), the addition of 0.5 mol % of a commercially available iridium photocatalyst under visible light irradiation transforms the reaction into an enantioconvergent process. Detailed mechanistic and time course studies of optically pure α-deuterated substrates revealed the presence of an enantiospecific kinetic isotope effect, which helped to clarify the role of both the photo- and chiral Lewis acid catalyst in the reaction sequence. In this dual catalytic system, the photocatalyst promotes a dynamic interconversion between the substrate enantiomers─a process not accessible via ground-state chemistry─while the chiral Lewis acid selectively transforms only the (S)-configured substrates. Further mechanistic evidence for the proposed mechanism is provided by linear free energy relationship analysis, which suggests that the stereodetermining step involves a 6π electrocyclization under both thermal and photoredox conditions.

The rise of degrader drugs

The cancer genomics revolution has served up a plethora of promising and challenging targets for the drug discovery community. The field of targeted protein degradation (TPD) uses small molecules to reprogram the protein homeostasis system to destroy desired target proteins. In the last decade, remarkable progress has enabled the rational development of degraders for a large number of target proteins, with over 20 molecules targeting more than 12 proteins entering clinical development. While TPD has been fully credentialed by the prior development of immunomodulatory drug (IMiD) class for the treatment of multiple myeloma, the field is poised for a "Gleevec moment" in which robust clinical efficacy of a rationally developed novel degrader against a preselected target is firmly established. Here, we endeavor to provide a high-level evaluation of exciting developments in the field and comment on steps that may realize the full potential of this new therapeutic modality.

Synthesis of Indole-Fused Six-, Seven-, or Eight-Membered N,O-Heterocycles via Rhodium-Catalyzed NH-Indole-Directed C-H Acetoxylation/Hydrolysis/Annulation

We report herein the facile synthesis of indole-fused six-, seven-, or eight-membered N,O-heterocycles through rhodium-catalyzed C-H acetoxylation/hydrolysis/annulation. The notable features of this method include C-H acetoxylation using NH-indole as the intrinsic directing group, high functional group compatibility, and construction of indole-fused medium-sized rings.

The Discovery of Conformationally Constrained Bicyclic Peptidomimetics as Potent Hepatitis C NS5A Inhibitors

HCV NS5A inhibitors are the backbone of directly acting antiviral treatments against the hepatitis C virus (HCV). While these therapies are generally highly curative, they are less effective in some specific HCV patient populations. In the search for broader-acting HCV NS5A inhibitors that address these needs, we explored conformational restrictions imposed by the [7,5]-azabicyclic lactam moiety incorporated into daclatasvir (1) and related HCV NS5A inhibitors. Unexpectedly, compound 5 was identified as a potent HCV genotype 1a and 1b inhibitor. Molecular modeling of 5 bound to HCV genotype 1a suggested that the use of the conformationally restricted lactam moiety might have resulted in reorientation of its N-terminal carbamate to expose a new interaction with the NS5A pocket located between amino acids P97 and Y93, which was not easily accessible to 1. The results also suggest new chemistry directions that exploit the interactions with the P97–Y93 site toward new and potentially improved HCV NS5A inhibitors.

Elbasvir/grazoprevir is effective and tolerable for the treatment of HCV GT1-infected patients: A real world multicenter observatory study in Taiwan

BACKGROUND & AIMS

Treatment of hepatitis C virus (HCV) by elbasvir/grazoprevir (EBR/GZR) was found to be efficacious and well tolerated in clinical trials. This study aimed to evaluate the effectiveness and tolerability of EBR/GZR in the treatment of HCV genotype 1-infected Taiwanese patients.

METHODS

Chronic hepatitis C patients infected with GT1b or 1a without resistance-associated substitution, and treated with 12-week EBR/GZR were enrolled from 10 hospitals in Taiwan between August 2017 and December 2018. All clinical and virologic data were collected at each participating center. Primary efficacy endpoint was sustained virologic response at week 12 (SVR12) after end of the EBR/GZR therapy, assessed in the per-protocol population, which excluded patients with important deviations from the protocol. Analysis was also performed based on the modified full analysis set, which included all allocated patients receiving at least 4-week medication. Virologic failure was recorded as breakthrough, nonresponse, or relapse. Safety was assessed through collection of adverse events, physical examination, vital signs, and standard laboratory evaluations.

RESULTS

Per protocol SVR12 rates were 99.5% (1169/1175) for all HCV genotype 1 patients. Among patients with stage 4 or 5 chronic kidney diseases, 100% (107/107) achieved SVR12. In univariate analyses, variables associated with SVR12 were treatment termination (P < 0.0001) and treatment adherence (P < 0.0001) in the mFAS population. Overall, 22.3% of the patients experienced adverse events during treatment. Seven patients did not complete the treatment, five due to liver-unrelated deaths, one due to adverse event and one due to epilepsy.

CONCLUSIONS

EBR/GZR treatment was highly effective and well tolerated.

Geminal Diheteroatomic Motifs: Some Applications of Acetals, Ketals, and Their Sulfur and Nitrogen Homologues in Medicinal Chemistry and Drug Design

Acetals and ketals and their nitrogen and sulfur homologues are often considered to be unconventional and potentially problematic scaffolding elements or pharmacophores for the design of orally bioavailable drugs. This opinion is largely a function of the perception that such motifs might be chemically unstable under the acidic conditions of the stomach and upper gastrointestinal tract. However, even simple acetals and ketals, including acyclic molecules, can be sufficiently robust under acidic conditions to be fashioned into orally bioavailable drugs, and these structural elements are embedded in many effective therapeutic agents. The chemical stability of molecules incorporating geminal diheteroatomic motifs can be modulated by physicochemical design principles that include the judicious deployment of proximal electron-withdrawing substituents and conformational restriction. In this Perspective, we exemplify geminal diheteroatomic motifs that have been utilized in the discovery of orally bioavailable drugs or drug candidates against the backdrop of understanding their potential for chemical lability.

Prevention of Hepatitis C Virus Infection and Liver Cancer

Hepatocellular carcinoma (HCC) is the fifth most prevalent cancer and the second leading cause of cancer-related death worldwide.

Elbasvir and grazoprevir for the treatment of hepatitis C

Introduction: Hepatitis C is one of the leading causes of chronic liver disease. The direct-acting-antivirals has revolutionized the chronic hepatitis C treatment. DAAs can achieve a sustained virological response rate >95% in different populations.Area covered: This review summarizes the pharmacokinetics, pharmacodynamics, efficacy, and safety of Elbasvir/Grazoprevir (EBR/GZR).Expert opinion: EBR/GZR is a combination of NS5A and NS3/4A inhibitors. The performance in the EBR/GZR combination's safety and tolerability is appreciated in clinical treatment. EBR/GZR also has a higher barrier to resistance-associated substitutions. Based on clinical trials and real-world experience, elbasvir/grazoprevir is effective in the HCV GT1, 4 infections.

Structure-activity relationship (SAR) studies on the mutagenic properties of 2,7-diaminofluorene and 2,7-diaminocarbazole derivatives

We discovered that 2,7-diaminofluorene or 2,7-diaminocarbazole moiety can be employed as a core structure of highly effective NS5A inhibitors that are connected through amide bonds to proline-valine-carbamate motifs. Amide bonds can be easily cleaved via various metabolic pathways upon administration into the body, and metabolites containing 2,7-diaminofluorene and 2,7-diaminocarbazole core structures have been known to be strong mutagens. To avoid the mutagenesis issue of these core structures, we examined various functional groups at the C9 or N9 position of 2,7-diaminofluorene or 2,7-diaminocarbazole, respectively, through the Ames test in TA98 and TA100 mutants of Salmonella typhimurium LT-2. We discovered that, through proper alkyl substitution at the C9 or N9 position, 2,7-diaminofluorene and 2,7-diaminocarbazole moieties can be successfully employed in drug discovery without necessarily causing mutagenicity problems.

Synthesis, biological evaluation and in silico modeling of novel pan-genotypic NS5A inhibitors

A series of novel small-molecule pan-genotypic hepatitis C virus (HCV) NS5A inhibitors with picomolar activity containing 2-[(2S)-pyrrolidin-2-yl]-5-[4-(4-{2-[(2S)-pyrrolidin-2-yl]-1H-imidazol-5-yl}buta-1,3-diyn-1-yl)phenyl]-1H-imidazole core was designed based on molecular modeling study and SAR analysis. The constructed in silico model and docking study provide a deep insight into the binding mode of this type of NS5A inhibitors. Based on the predicted binding interface we have prioritized the most crucial diversity points responsible for improving antiviral activity. The synthesized molecules were tested in a cell-based assay, and compound 1.12 showed an EC₅₀ value in the range of 2.9-34 pM against six genotypes of NS5A HCV, including gT3a, and demonstrated favorable pharmacokinetic profile in rats. This lead compound can be considered as an attractive candidate for further clinical evaluation.

Elbasvir/Grazoprevir in People With Hepatitis C Genotype 1 Infection and Child-Pugh Class B Cirrhosis: The C-SALT Study

Treatment options are limited for people infected with hepatitis C virus (HCV) with decompensated liver disease. The C-SALT study assessed elbasvir (EBR) plus grazoprevir (GZR) in individuals with HCV genotype 1 infection and Child-Pugh class B (CP-B) cirrhosis.

Molecular characterization of hepatitis C virus for subtype determination and resistance-associated substitutions detection among Chinese voluntary blood donors

BACKGROUND

The high prevalence of hepatitis C virus (HCV) infection and the resulting burden of the disease are significant issues to public health worldwide. Although direct-acting antiviral drugs (DAAs) with good tolerance and bioavailability are available, resistance-associated substitutions (RASs) often jeopardize the successful sustainment of virological responses in HCV treatment. High-frequency baseline RASs in treatment-naïve patients can lead to failures in DAA treatment. Clinical data on HCV RASs in patients from China are limited and require investigations.

METHODS

262 HCV RNA positive plasma from Chinese blood donors were genotyped and amplified with subtype-specific primers for NS3 and NS5A regions. RASs were analyzed using Geno2pheno. The codon usage of each resistance-associated substitution was calculated for genetic barrier analysis.

RESULTS

The two main subtypes in mainland China were 1b and 2a, followed by subtype 6a, 3b, 3a, and 1a. In NS3 region of 1b subtype, substitutions (T54S, V55A, Y56F, Q80 K/L, S122 G/T, R117 H/C, V170I and S174A) were present in 89.7% (96/107) of the samples. Other RASs (M28L, R30Q, P58 L/S and Y93H) were observed in 22.1% (25/113) of the samples in NS5A region. A crucial RAS, Q80K, and two other mutations (S122G + V170I) was identified in the same sequence, which reduced its susceptibility to protease inhibitor ASV and resulted in resistance to SMV. In NS5A, Y93H was detected in 9.7% (11/113) of the 1b samples, leading to medium-to-high level resistance to all six commercialized NS5A inhibitors. S122G-NS3 and Y93H-NS5A occurred simultaneously in 38.1% (7/22) of the samples with mutations in both two regions. Moreover, codon usage of S122G-NS3 and Y93H-NS5A revealed that both variants had the lowest genetic barrier and required only one transition to confer resistance.

CONCLUSIONS

Low genetic barriers facilitated the generation of resistance mutants and threated the efficacy of DAA regimens. The baseline RASs posed a great challenge to real-world DAA application.

Efficacy and safety of elbasvir/grazoprevir in treatment-naive Chinese adults with hepatitis C virus infection: A randomized trial

Background and Aim

In China, clinical experience with direct‐acting antiviral treatments for hepatitis C virus (HCV) infection is still emerging. C‐CORAL is a phase 3, multinational, placebo‐controlled, double‐blind trial of elbasvir/grazoprevir (EBR/GZR) in participants with HCV infection from the Asia‐Pacific region and Russia. Here, we report the data from participants enrolled in China.

Methods

Treatment‐naive participants with chronic HCV genotype (GT) 1, GT4, or GT6 infection were randomly assigned to receive 50 mg EBR/100 mg GZR for 12 weeks (immediate‐treatment group, ITG) or placebo followed by deferred treatment with EBR/GZR (deferred‐treatment group, DTG). The primary efficacy end‐point was sustained virologic response at 12 weeks after completing treatment (SVR12), and the primary safety end‐point was a comparison of safety between participants receiving EBR/GZR and placebo (NCT02251990; Protocol PN‐5172‐067).

Results

A total of 152 participants in China were randomly assigned (ITG, n = 115; DTG, n = 37). SVR12 was achieved in 96.7% (146/151) participants overall and in 97.3% (142/146) of those with GT1b infection. Four participants relapsed (GT1b, n = 3; GT6a, n = 1). Drug‐related AEs were reported in 25 (21.7%) and 9 (24.3%) participants receiving EBR/GZR and placebo, respectively; no drug‐related serious adverse events (AEs) occurred. Two (1.7%) participants receiving EBR/GZR had late hepatic transaminase elevations. Patient‐reported outcomes indicate improved quality of life at follow‐up week 4 in participants receiving EBR/GZR compared to placebo.

Conclusion

EBR/GZR administered for 12 weeks represents a highly effective and safe treatment option for Chinese individuals with HCV GT1 infection.

HCV Replicon Systems: Workhorses of Drug Discovery and Resistance

The development of direct-acting antivirals (DAAs) has revolutionized the state-of-the art treatment of HCV infections, with sustained virologic response rates above 90%. However, viral variants harboring substitutions referred to as resistance-associated substitutions (RASs) may be present in baseline levels and confer resistance to DAAs, thereby posing a major challenge for HCV treatment. HCV replicons have been the primary tools for discovering and evaluating the inhibitory activity of DAAs against viral replication. Interest in replicon systems has further grown as they have become indispensable for discovering genotype-specific and cross-genotype RASs. Here, we review functional replicon systems for HCV, how these replicon systems have contributed to the development of DAAs, and the characteristics and distribution of RASs for DAAs.

Assessment of drug interaction potential between the HCV direct-acting antiviral agents elbasvir/grazoprevir and the HIV integrase inhibitors raltegravir and dolutegravir

BACKGROUND

Elbasvir/grazoprevir is a once-daily fixed-dose combination therapy for the treatment of chronic HCV infection, including HCV/HIV coinfection.

OBJECTIVES

To evaluate the pharmacokinetic interaction of elbasvir and grazoprevir with raltegravir or dolutegravir.

METHODS

Three open-label trials in healthy adult participants were conducted. In the raltegravir trials, participants received a single dose of raltegravir 400 mg, a single dose of elbasvir 50 mg or grazoprevir 200 mg, and raltegravir with either elbasvir or grazoprevir. In the dolutegravir trial, participants received a single dose of dolutegravir 50 mg alone or co-administered with once-daily elbasvir 50 mg and grazoprevir 200 mg.

RESULTS

The raltegravir AUC0-∞ geometric mean ratio (GMR) (90% CI) was 1.02 (0.81-1.27) with elbasvir and 1.43 (0.89-2.30) with grazoprevir. Dolutegravir AUC0-∞ GMR (90% CI) was 1.16 (1.00-1.34) with elbasvir and grazoprevir. The elbasvir AUC0-∞ GMR (90% CI) was 0.81 (0.57-1.17) with raltegravir and 0.98 (0.93-1.04) with dolutegravir. The grazoprevir AUC0-24 GMR (90% CI) was 0.89 (0.72-1.09) with raltegravir and 0.81 (0.67-0.97) with dolutegravir.

CONCLUSIONS

Elbasvir or grazoprevir co-administered with raltegravir or dolutegravir resulted in no clinically meaningful drug-drug interactions and was generally well tolerated. These results support the assertion that no dose adjustments for elbasvir, grazoprevir, raltegravir or dolutegravir are needed for co-administration in HCV/HIV-coinfected people.

The pharmacogenetics of OATP1B1 variants and their impact on the pharmacokinetics and efficacy of elbasvir/grazoprevir

Aim: To evaluate the effect of SLCO1B1 genetic variants on grazoprevir pharmacokinetics and efficacy. Methods: A retrospective analysis of 1578 hepatitis C virus-infected participants from ten Phase II/III clinical trials. Results: Relative to noncarriers of the risk allele, geometric mean ratios (95% CI) of grazoprevir area under curve (AUC)_0-24 were: rs4149056 (risk allele C), one copy, 1.13 (1.06-1.21), two copies, 1.43 (1.16-1.77); and rs11045819 (risk allele A), one copy, 0.93 (0.87-1.00); two copies, 0.78 (0.61-1.00). The rs2306283 variant was not associated with grazoprevir exposure. None of the SLCO1B1 variants were associated with sustained virologic response. Conclusion: Genetic variants in SLCO1B1 were associated with modest changes in grazoprevir pharmacokinetics, but not with meaningful differences in efficacy.

Elbasvir/Grazoprevir for HCV Infection in Russia: A Randomized Trial

Purpose

Hepatitis C virus (HCV) infection is a major healthcare concern in Russia, where almost 5 million individuals are viremic. Elbasvir/grazoprevir is a fixed-dose combination therapy for the treatment of HCV genotype 1 and genotype 4 infection. The present analysis aimed to assess the safety and efficacy of elbasvir/grazoprevir in individuals with HCV infection enrolled at Russian study sites in the C-CORAL study.

Patients and Methods

C-CORAL (Protocol PN-5172-067; NCT02251990) was a Phase 3, placebo-controlled, double-blind study conducted throughout Asia and Russia. Treatment-naive participants with chronic HCV infection were randomly assigned to receive immediate or deferred treatment with elbasvir 50 mg/grazoprevir 100 mg once daily for 12 weeks. Participants in the immediate-treatment group received elbasvir/grazoprevir for 12 weeks, and those in the deferred-treatment group received placebo for 12 weeks, followed by open-label elbasvir/grazoprevir for 12 weeks. The primary endpoint was sustained virologic response at 12 weeks after completion of therapy (SVR12).

Results

One hundred and nineteen Russian participants were randomized (immediate-treatment group, n=88; deferred-treatment group, n=31). Most participants were white (99%) with HCV genotype 1b infection (97%) and mild-to-moderate (F0–F2) fibrosis (70%). SVR12 was achieved by 98.9% participants in the immediate-treatment group and by 100% of those receiving deferred elbasvir/grazoprevir in the deferred-treatment group. One participant relapsed with nonstructural protein 5A (NS5A) L28M and Y93H resistance-associated substitutions at baseline and at time of failure. Drug-related adverse events were reported by 19% of participants receiving elbasvir/grazoprevir in the immediate-treatment group and by 16% of those receiving placebo in the deferred-treatment group. No serious adverse event or deaths occurred, and no participant discontinued treatment owing to an adverse event.

Conclusion

Elbasvir/grazoprevir for 12 weeks was highly effective in treatment-naive Russian individuals with HCV genotype 1b infection.

QSAR studies on hepatitis C virus NS5A protein tetracyclic inhibitors in wild type and mutants by CoMFA and CoMSIA

Several 3D-QSAR models were built based on 196 hepatitis C virus (HCV) NS5A protein inhibitors. The bioactivity values EC₉₀ for three types of inhibitors, the wild type (GT1a) and two mutants (GT1a Y93H and GT1a L31V), were collected to build three datasets. The programs OMEGA and ROCS were used for generating conformations and aligning molecules of the dataset, respectively. Each dataset was randomly divided into a training set and a test set three times to reduce the contingency of only one random selection. QSAR models were computed by comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA). For the datasets GT1a, GT1a Y93H, and GT1a L31V, the best models CoMFA-INDX, CoMSIA-SEHA, and CoMSIA-SEHA showed an r² value of 0.682 ± 0.033, 0.779 ± 0.036, and 0.782 ± 0.022 on the test sets, respectively. From the contour maps of the three best models, we summarized the favourable and unfavourable substituents on the tetracyclic core, the Z group, the proline group, and the valine group of inhibitors. We guessed the mutants could change the electrostatic surfaces of the wild type active pocket. In addition, we used ECFP analyses to find important substructures and could intuitively understand the results from QSAR models.

A Single- and Multiple-Dose Study to Evaluate the Pharmacokinetics of Fixed-Dose Grazoprevir/Elbasvir in Healthy Chinese Participants

Purpose

The burden of hepatitis C virus infection is particularly high in Asian countries, and new treatments are urgently needed. The purpose of this study was to characterize the pharmacokinetics (PK) and safety of the fixed-dose combination tablet of elbasvir/grazoprevir in healthy Chinese participants.

Patient and Methods

In this Phase I, single-site, open-label, 3-period study in healthy Chinese adults, participants received a single tablet of elbasvir 50 mg/grazoprevir 100 mg, followed by blood sampling for up to 96 hrs (http://www.chinadrugtrials.org.cn/ CTR20160034; Protocol PN071). Participants then received 1 tablet daily for 10 days, followed by a minimum 10-day washout, after which participants received a single dose of 2 tablets (elbasvir 100 mg/grazoprevir 200 mg). Elbasvir and grazoprevir PK were assessed following single and multiple doses. Safety and tolerability were also evaluated.

Results

Twelve participants (50% male) were enrolled in and completed the study. Following single-dose oral administration of elbasvir 50 mg/grazoprevir 100 mg or elbasvir 100 mg/grazoprevir 200 mg, the median T_max was 3–4 hrs and elimination half-life was 18 hrs (elbasvir) and 30 hrs (grazoprevir). Multiple-dose administration resulted in AUC_0–24 accumulation ratios of 1.58 (elbasvir) and 2.35 (grazoprevir). Both elbasvir 50 mg/grazoprevir 100 mg and 100 mg/200 mg regimens were generally well tolerated.

Conclusion

Single-dose administration of elbasvir 50 mg/grazoprevir 100 mg or 100 mg/200 mg and once-daily administration of elbasvir 50 mg/grazoprevir 100 mg for 10 days has been adequately characterized, with PK values within the expected range, and was generally well tolerated in healthy Chinese male and female participants.

Asymmetric N-aminoalkylation of 3-substituted indoles by N-protected N,O-acetals: an access to chiral propargyl aminals

A direct enantioselective N1 aminoalkylation of 3-substituted indoles is efficiently catalyzed by a phosphoric acid catalyst under mild conditions, which could be applied to the modification of tryptophan containing oligopeptides.

Discovery and Characterization of Potent Pan-Genotypic HCV NS5A Inhibitors Containing Novel Tricyclic Central Core Leading to Clinical Candidate

The identification of a novel class of potent pan-genotypic NS5A inhibitors with good pharmacokinetic profile suitable for potential use in treating HCV infections is disclosed here. The present series of compounds are with less complex tricyclic central core, identified through a systematic SAR study carried out on biphenyl moiety. The SAR outcome has confirmed the requirement of near planar and linear conformation of the molecule to achieve the best pan-genotypic activity. In addition, SAR with substituted imidazoles on improvement of antiviral activity is disclosed. The newly identified compounds 12, 16, 19-21 have shown desirable pharmacokinetic profiles with a favorable uptake of compounds in liver and maintained a significant concentration for up to 8 h in the liver. In addition, compounds 20 and 21 have shown superior pan-genotypic anti-HCV activity compared to ledipasvir and daclatasvir. Additional characterization and preliminary safety assessment resulted in the identification of compound 20 as a potential clinical candidate.

Elbasvir/grazoprevir in women with hepatitis C virus infection taking oral contraceptives or hormone replacement therapy

Introduction

Some direct-acting antiviral regimens for hepatitis C virus (HCV) infection pose safety or efficacy concerns if coadministered with drugs containing ethinyl estradiol. The present analysis was conducted to examine the impact of concomitant oral contraceptive pills (OCP) or hormone replacement therapy (HRT) during treatment with elbasvir (EBR)/grazoprevir (GZR) in women with HCV genotype (GT)1 or GT4 infection.

Methods

This is a post hoc, integrated retrospective analysis of female participants with HCV GT1 or GT4 infection who received EBR 50 mg/GZR 100 mg once daily for 12 weeks in phase 2/3 clinical trials. The primary end point was sustained virologic response at 12 weeks after therapy completion (SVR12). For this analysis, participants were stratified according to whether they received OCP or HRT during the original treatment study.

Results

A total of 1,022 women with HCV GT1 or GT4 infection were included (receiving OCP/HRT, n=81; not receiving OCP/HRT, n=941). Most participants receiving OCP/HRT were treatment-naive (79%), noncirrhotic (91.4%), and aged >35 years (71.6%). SVR12 rates were similar in women receiving OCP/HRT and those not receiving OCP/HRT (95.1% vs 96.3%). SVR12 rates remained high across all subgroups within the population receiving OCP/HRT: SVR12 rates were 94.6%, 100%, and 100% in participants with GT1a, GT1b, and GT4 infection, and all women aged 18-35 years achieved SVR (21/21). Treatment-related adverse events occurred in 40.7% (33/81) and 30.1% (283/941) of women receiving and those not receiving OCP/HRT, respectively.

Conclusion

The efficacy and safety of EBR/GZR administered for 12 weeks was similar in women receiving OCP/HRT and those not on OCP/HRT. These data indicate that EBR/GZR can be safely used for the treatment of HCV GT1 or GT4 infection in women receiving concomitant OCP/HRT.

Interplay of Amino Acid Residues at Positions 28 and 31 in NS5A Defines Resistance Pathways in HCV GT2

Hepatitis C virus (HCV) genotype (GT) 2 represents approximately 9% of all viral infections globally. While treatment outcomes for GT2-infected patients have improved substantially with direct-acting antiviral agents (DAAs) compared to interferon-α, the presence of polymorphisms in NS5A can impact efficacy of NS5A inhibitor-containing regimens. Thus, pathways of NS5A resistance were explored in GT2 subtypes using elbasvir, an NS5A inhibitor with broad genotype activity. Resistance selection studies, resistance analysis in NS5A-inhibitor treated virologic failures, antiviral activities in replicons bearing a panel of GT2 subtype sequences and amino acid substitutions introduced by site-directed mutagenesis were performed to define determinants of inhibitor susceptibility. Elbasvir showed differential antiviral activity in replicons bearing GT2 sequences. The EC₅₀ values for replicons bearing reference NS5A sequences for GT2a and GT2b were 0.003 and 3.4 nanomolar (nM) respectively. Studies with recombinant replicons demonstrated crosstalk between amino acid positions 28 and 31. The combination of phenylalanine and methionine at positions 28 and 31 respectively, conferred the highest potency reduction for elbasvir in GT2a and GT2b. This combination was observed in failures from the C-SCAPE trial. Addition of grazoprevir, an NS3/4A protease inhibitor, to elbasvir more effectively suppressed the emergence of resistance in GT2 at modest inhibitor concentrations (3X EC₉₀). Ruzasvir, a potent, pan-genotype NS5A inhibitor successfully inhibited replicons bearing GT2 resistance-associated substitutions (RASs) at positions 28 and 31. The studies demonstrate crosstalk between amino acids at positions 28 and 31 in NS5A modulate inhibitor potency and may impact treatment outcomes in some HCV GT2-infected patients.

Safety and efficacy of elbasvir/grazoprevir in Asian participants with hepatitis C virus genotypes 1 and 4 infection

BACKGROUND AND AIM

Estimates suggest that in Asia, more than 31 million individuals have hepatitis C virus infection. The present analysis was conducted to assess the efficacy and safety of elbasvir/grazoprevir in Asian participants enrolled in the elbasvir/grazoprevir phase 2/3 clinical trials.

METHODS

This is an integrated analysis of data from 12 international phase 2/3 clinical trials. Asian participants with chronic hepatitis C virus genotype 1 or 4 infection who received elbasvir 50 mg/grazoprevir 100 mg once daily for 12 weeks or elbasvir/grazoprevir plus ribavirin for 16 weeks were included in this analysis. The primary end point was sustained virologic response at 12 weeks after completion of therapy (SVR12).

RESULTS

Seven hundred eighty Asian participants from 15 countries were included in this analysis. SVR12 was achieved by 756/780 (96.9%) of all participants, including 748/772 (96.9%) of those who received elbasvir/grazoprevir for 12 weeks and 8/8 (100%) of those who received elbasvir/grazoprevir plus ribavirin for 16 weeks. In the genotype 1b-infected population, the SVR12 rate was 691/709 (97.5%), and there was no impact of age, high baseline viral load, or presence of cirrhosis. The most frequently reported adverse events were nasopharyngitis (8.0%), upper respiratory tract infection (5.4%), and diarrhea (5.2%). Twenty participants receiving elbasvir/grazoprevir for 12 weeks reported a total of 25 serious adverse events, and 7 (0.9%) discontinued treatment because of an adverse event.

CONCLUSION

Elbasvir/grazoprevir administered for 12 weeks is an effective and generally well-tolerated treatment option for Asian individuals with hepatitis C virus genotype 1b infection.

Pharmacokinetic Interactions Between the Fixed-Dose Combinations of Elvitegravir/Cobicistat/Tenofovir Disoproxil Fumarate/Emtricitabine and Elbasvir/Grazoprevir in Healthy Adult Participants

Treatment of individuals coinfected with human immunodeficiency virus (HIV) and hepatitis C virus (HCV) requires careful consideration of potential drug-drug interactions. The pharmacokinetic interaction of the HCV fixed-dose combination treatment of elbasvir/grazoprevir (EBR/GZR) when coadministered with the fixed-dose combination HIV treatment of elvitegravir/cobicistat/tenofovir disoproxil fumarate/emtricitabine (EVG/COB/TDF/FTC) was evaluated in 22 healthy adults. In period 1, oral doses of EVG/COB/TDF/FTC (150 mg/150 mg/300 mg/200 mg) were administered once daily for 7 days. In period 2, oral doses of EBR/GZR (50 mg/100 mg) were administered once daily for 10 days. In period 3, oral doses of EVG/COB/TDF/FTC were coadministered with EBR/GZR once daily for 10 days. The pharmacokinetics of EVG/COB/TDF/FTC were not clinically meaningfully altered by concomitant EBR/GZR administration. Geometric mean ratios (90%CIs) for area under the plasma concentration-time curve from time 0 to 24 hours (AUC_0-24 ) in the presence/absence of EBR/GZR were 1.1 (1.0, 1.2) for elvitegravir; 1.1 (1.0, 1.1) for emtricitabine; 1.2 (1.1, 1.2) for tenofovir; and 1.5 (1.4, 1.6) for cobicistat. In comparison, the AUC_0-24 of elbasvir was ∼2 times higher and the AUC_0-24 of grazoprevir was ∼5 times higher following concomitant administration of EVG/COB/TDF/FTC and EBR/GZR. Geometric mean ratios (90%CI) for AUC_0-24 in the presence/absence of EVG/COB/TDF/FTC were 2.2 (2.0, 2.4) for elbasvir and 5.4 (4.5, 6.4) for grazoprevir. Coadministration of EVG/COB/TDF/FTC and EBR/GZR was generally well tolerated in healthy adults in this study. Nevertheless, because of the increased GZR exposure that occurs with coadministration of EVG/COB/TDF/FTC and EBR/GZR, coadministration of this combination is not recommended in those coinfected with HIV and HCV.

Assessment of Drug Interaction Potential Between the Hepatitis C Virus Direct-Acting Antiviral Agents Elbasvir/Grazoprevir and the Nucleotide Analog Reverse-Transcriptase Inhibitor Tenofovir Disoproxil Fumarate

Treatment of individuals coinfected with hepatitis C virus (HCV) and human immunodeficiency virus (HIV) requires careful consideration of potential drug-drug interactions. We evaluated the pharmacokinetic interaction of the direct-acting antiviral agents elbasvir and grazoprevir coadministered with the nucleotide reverse transcriptase inhibitor tenofovir disoproxil fumarate (TDF). Three open-label, multidose studies in healthy adults were conducted. In the first study (N = 10), participants received TDF 300 mg once daily, elbasvir 50 mg once daily, and elbasvir coadministered with TDF. In the second study (N = 12), participants received TDF 300 mg once daily, grazoprevir 200 mg once daily, and grazoprevir coadministered with TDF. In the third study (N = 14), participants received TDF 300 mg once daily and TDF 300 mg coadministered with coformulated elbasvir/grazoprevir 50 mg/100 mg once daily. Pharmacokinetics and safety were evaluated. Following coadministration, the tenofovir area under the plasma concentration-time curve to 24 hours and maximum plasma concentration geometric mean ratios (90% confidence intervals) for tenofovir and coadministered drug(s) versus tenofovir were 1.3 (1.2, 1.5) and 1.5 (1.3, 1.6), respectively, when coadministered with elbasvir; 1.2 (1.1, 1.3) and 1.1 (1.0, 1.2), respectively, when coadministered with grazoprevir; and 1.3 (1.2, 1.4) and 1.1 (1.0, 1.4), respectively, when coadministered with the elbasvir/grazoprevir coformulation. TDF had minimal effect on elbasvir and grazoprevir pharmacokinetics. Elbasvir and/or grazoprevir coadministered with TDF resulted in no clinically meaningful tenofovir exposure increases and was generally well tolerated, with no deaths, serious adverse events (AEs), discontinuations due to AEs, or laboratory AEs reported. No dose adjustments for elbasvir/grazoprevir or TDF are needed for coadministration in HCV/HIV-coinfected people.

Medicinal chemistry of indole derivatives: Current to future therapeutic prospectives

Indole is a versatile pharmacophore, a privileged scaffold and an outstanding heterocyclic compound with wide ranges of pharmacological activities due to different mechanisms of action. It is an superlative moiety in drug discovery with the sole property of resembling different structures of the protein. Plenty of research has been taking place in recent years to synthesize and explore the various therapeutic prospectives of this moiety. This review summarizes some of the recent effective chemical synthesis (2014-2018) for indole ring. This review also emphasized on the structure-activity relationship (SAR) to reveal the active pharmacophores of various indole analogues accountable for anticancer, anticonvulsant, antimicrobial, antitubercular, antimalarial, antiviral, antidiabetic and other miscellaneous activities which have been investigated in the last five years. The precise features with motives and framework of each research topic is introduced for helping the medicinal chemists to understand the perspective of the context in a better way. This review will definitely offer the platform for researchers to strategically design diverse novel indole derivatives having different promising pharmacological activities with reduced toxicity and side effects.

An integrated analysis of elbasvir/grazoprevir in Korean patients with hepatitis C virus genotype 1b infection

BACKGROUND/AIMS

In the Republic of Korea, an estimated 231,000 individuals have chronic hepatitis C virus (HCV) infection. The aim of the present analysis was to evaluate the safety and efficacy of elbasvir/grazoprevir (EBR/GZR) administered for 12 weeks in Korean patients who were enrolled in international clinical trial phase 3 studies.

METHODS

This was a retrospective, integrated analysis of data from patients with HCV genotype (GT) 1b infection enrolled at Korean study sites in four EBR/GZR phase 3 clinical trials. Patients were treatment-naive or had previously failed interferon-based HCV therapy, and included those with human immunodeficiency virus coinfection or ChildPugh class A cirrhosis. All patients received EBR 50 mg/GZR 100 mg once daily for 12 weeks. The primary endpoint was sustained virologic response at 12 weeks after completion of therapy (SVR12, HCV RNA <15 IU/mL).

RESULTS

SVR12 was achieved by 73 of 74 (98.6%) patients. No patients had virologic failure and one discontinued from the study after withdrawing consent. SVR12 rates were uniformly high across all patient subgroups. A total of 16 patients had nonstructural protein 5A resistance-associated substitutions at baseline (16/73, 22%), all of whom achieved SVR12. Adverse events (AEs) reported in >5% of patients were fatigue (6.8%), upper respiratory tract infection (5.4%), headache (5.4%), and nausea (5.4%). Thirteen patients (17.6%) reported drug-related AEs, two serious AEs occurred, and two patients discontinued treatment owing to an AEs.

CONCLUSION

In this retrospective analysis, EBR/GZR administered for 12 weeks was well-tolerated and highly effective in Korean patients with HCV GT1b infection.

Pharmacokinetic Interactions between the Hepatitis C Virus Inhibitors Elbasvir and Grazoprevir and HIV Protease Inhibitors Ritonavir, Atazanavir, Lopinavir, and Darunavir in Healthy Volunteers

The combination of the hepatitis C virus (HCV) nonstructural protein 5A (NS5A) inhibitor elbasvir and the NS3/4A protease inhibitor grazoprevir is a potent, once-daily therapy indicated for the treatment of chronic HCV infection in individuals coinfected with human immunodeficiency virus (HIV). We explored the pharmacokinetic interactions of elbasvir and grazoprevir with ritonavir and ritonavir-boosted HIV protease inhibitors in three phase 1 trials. Drug-drug interaction trials with healthy participants were conducted to evaluate the effect of ritonavir on the pharmacokinetics of grazoprevir (n = 10) and the potential two-way pharmacokinetic interactions of elbasvir (n = 30) or grazoprevir (n = 39) when coadministered with ritonavir-boosted atazanavir, lopinavir, or darunavir. Coadministration of ritonavir with grazoprevir increased grazoprevir exposure; the geometric mean ratio (GMR) for grazoprevir plus ritonavir versus grazoprevir alone area under the concentration-time curve from 0 to 24 h (AUC_0-24) was 1.91 (90% confidence interval [CI]; 1.31 to 2.79). Grazoprevir exposure was markedly increased with coadministration of atazanavir-ritonavir, lopinavir-ritonavir, and darunavir-ritonavir, with GMRs for grazoprevir AUC_0-24 of 10.58 (90% CI, 7.78 to 14.39), 12.86 (90% CI, 10.25 to 16.13), and 7.50 (90% CI, 5.92 to 9.51), respectively. Elbasvir exposure was increased with coadministration of atazanavir-ritonavir, lopinavir-ritonavir, and darunavir-ritonavir, with GMRs for elbasvir AUC_0-24 of 4.76 (90% CI, 4.07 to 5.56), 3.71 (90% CI, 3.05 to 4.53), and 1.66 (90% CI, 1.35 to 2.05), respectively. Grazoprevir and elbasvir had little effect on atazanavir, lopinavir, and darunavir pharmacokinetics. Coadministration of elbasvir-grazoprevir with atazanavir-ritonavir, lopinavir-ritonavir, or darunavir-ritonavir is contraindicated, owing to an increase in grazoprevir exposure. Therefore, HIV treatment regimens without HIV protease inhibitors should be considered for HCV/HIV-coinfected individuals who are being treated with elbasvir-grazoprevir.

The accuracy of baseline viral load for predicting the efficacy of elbasvir/grazoprevir in participants with hepatitis C virus genotype 1a infection: An integrated analysis

European treatment guidelines for hepatitis C virus (HCV) infection recommend that people with genotype (GT) 1a infection and baseline viral load ≤800 000 IU/mL receive elbasvir/grazoprevir (EBR/GZR) for 12 weeks, and those with baseline viral load >800 000 IU/mL receive EBR/GZR plus ribavirin for 16 weeks. This analysis was conducted to clarify whether baseline viral load can serve as an accurate, sensitive or specific stratification factor for defining EBR/GZR regimens. In this post hoc, integrated analysis, participants with GT1a infection who received EBR 50 mg/GZR 100 mg for 12 weeks were stratified according to baseline viral load. Sustained virologic response at 12 weeks post-treatment was achieved by 95.2% (911/957) of participants and was higher among participants with baseline viral load ≤800 000 IU/mL vs >800 000 IU/mL (98.5% vs 93.9%). The 800 000 IU/mL threshold had a positive predictive value of 98.5%, a negative predictive value of 6.1%, a specificity of 91.3%, a sensitivity of 28.4% and an overall accuracy of 31.5%. A baseline viral load cutpoint of 800 000 IU/mL had high positive predictive value and specificity but poor negative predictive value, sensitivity and accuracy in predicting treatment outcomes in this population. Baseline NS5A resistance-associated substitutions (RASs) were detected in 25% (1/4) of virologic failures with baseline viral load ≤800 000 IU/mL and 59.5% (25/42) of those with baseline viral load >800 000 IU/mL. Overall, these data suggest that, compared with the use of a baseline viral load cutpoint, baseline testing for NS5A RASs enables more individuals to receive the 12-week EBR/GZR regimen without compromising the opportunity for SVR.

Pharmacokinetics of elbasvir and grazoprevir in subjects with end-stage renal disease or severe renal impairment

PURPOSE

To describe the phase 1 and population pharmacokinetic investigations that support dosing recommendations for elbasvir/grazoprevir (EBR/GZR) in hepatitis C virus-infected people with advanced chronic kidney disease.

METHODS

This was an open-label, two-part, multiple-dose trial (MK-5172 PN050; NCT01937975) in 24 non-HCV-infected participants with end-stage renal disease (ESRD) or severe renal impairment who received once-daily EBR 50 mg and GZR 100 mg for 10 days. Population pharmacokinetic analyses from the phase 3 C-SURFER study (PN052, NCT02092350) were also conducted.

RESULTS

When comparing haemodialysis (HD) and non-HD days in participants with ESRD, geometric mean ratios (GMRs) (90% confidence intervals [CIs]) for EBR and GZR AUC_0-24 were 1.14 (1.08-1.21) and 0.97 (0.87-1.09). When comparing ESRD and healthy participants, GMRs (90% CIs) for EBR and GZR AUC_0-24 were 0.99 (0.75-1.30) and 0.83 (0.56-1.22) on HD days, and 0.86 (0.65-1.14) and 0.85 (0.58-1.25) on non-HD days. GMRs (90% CIs) for AUC_0-24 in participants with severe renal impairment relative to healthy controls were 1.65 (1.09-2.49) for GZR and 1.86 (1.38-2.51) for EBR. In population modelling of data from C-SURFER, absolute geometric means of steady-state EBR AUC_0-24 were 2.78 and 3.07 μM*h (HD and non-HD recipients) and GZR AUC_0-24 were 1.80 and 2.34 μM*h (HD and non-HD recipients).

CONCLUSIONS

EBR/GZR represents an important treatment option for HCV infection in people with severe renal impairment and those with ESRD. No dosage adjustment of EBR/GZR is required in people with any degree of renal impairment, including those receiving dialysis.

Overview of HCV Life Cycle with a Special Focus on Current and Possible Future Antiviral Targets

Hepatitis C infection is the leading cause of liver diseases worldwide and a major health concern that affects an estimated 3% of the global population. Novel therapies available since 2014 and 2017 are very efficient and the WHO considers HCV eradication possible by the year 2030. These treatments are based on the so-called direct acting antivirals (DAAs) that have been developed through research efforts by academia and industry since the 1990s. After a brief overview of the HCV life cycle, we describe here the functions of the different targets of current DAAs, the mode of action of these DAAs and potential future inhibitors.

Efficacy and Safety of Elbasvir/Grazoprevir in Hepatitis C Virus GT1- and GT4-Infected People Aged 65 Years or Older

Background: In elderly individuals aged ≥65 years with hepatitis C virus (HCV) infection, efficacious and safe HCV therapy is complicated by frequent comorbidities and concomitant medications. The aim of this analysis was to evaluate the efficacy and safety of elbasvir/grazoprevir (EBR/GZR) in people aged ≥65 years. Methods: This is an integrated retrospective analysis of EBR/GZR administered for 12 weeks in participants with HCV genotype 1 or 4 infection enrolled in 12 Phase 2/3 clinical trials. The primary end point was sustained virologic response 12 weeks after completing therapy (SVR12; HCV RNA below the lower limit of quantification). Results: Most participants aged ≥65 years were receiving ≥1 concomitant medication (322/339; 95.0%) and had ≥1 comorbidity (334/339; 99%). SVR12 rates were 95.3% (323/339) in participants aged ≥65 years and 95.4% (2,041/2,139) in those aged <65 years. Rates of adverse events, drug-related adverse events, serious adverse events, and discontinuations were similar in participants aged ≥65 years and those aged <65 years. In participants aged ≥65 years, median estimated glomerular filtration rate was similar at baseline and at the end of treatment. Conclusion: The efficacy and safety of EBR/GZR were similar in participants with HCV infection aged ≥65 years and those aged <65 years.

Efficacy and safety of elbasvir/grazoprevir in participants with hepatitis C virus genotype 1, 4, or 6 infection from the Asia-Pacific region and Russia: Final results from the randomized C-CORAL study

BACKGROUND AND AIM

Although treatment with direct-acting antivirals has dramatically improved morbidity and mortality attributable to chronic hepatitis C virus infection, universal access to these medicines has been slow in the Asia-Pacific region and Russia. This study evaluated efficacy and safety of elbasvir/grazoprevir in participants with hepatitis C virus infection from Asia-Pacific countries and Russia (C-CORAL).

METHODS

C-CORAL was a phase 3, randomized, placebo-controlled study (NCT02251990). Treatment-naive, HIV-negative, cirrhotic and non-cirrhotic participants with chronic hepatitis C genotype 1, 4, or 6 infection were randomized to elbasvir 50 mg/grazoprevir 100 mg once daily for 12 weeks (immediate-treatment group) or placebo followed by deferred treatment with elbasvir/grazoprevir (deferred-treatment group). The primary efficacy outcome was sustained virologic response at 12 weeks, and the primary safety outcome was a comparison between the immediate-treatment group and placebo phase of the deferred-treatment group.

RESULTS

A total of 489 participants were randomized (immediate-treatment group, n = 366; deferred-treatment group, n = 123). Sustained virologic response at 12 weeks in the combined immediate/deferred-treatment groups was 94.4% (459/486; 95% confidence interval = 92.4-96.5%). Sustained virologic response at 12 weeks was 98.2% in participants with genotype 1b, 91.9% with genotype 1a, and 66.7% with genotype 6 infection. Similar rates of adverse events and drug-related adverse events were seen in the immediate-treatment group versus placebo phase of the deferred-treatment group (51.0% vs 50.4% and 21.4% vs 21.1%).

CONCLUSIONS

Elbasvir/grazoprevir for 12 weeks represents an effective and well-tolerated treatment option for treatment-naive people with genotype 1 infection from Asia-Pacific countries and Russia.

In Vitro Antiviral Profile of Ruzasvir, a Potent and Pangenotype Inhibitor of Hepatitis C Virus NS5A

Inhibition of NS5A has emerged as an attractive strategy to intervene in hepatitis C virus (HCV) replication. Ruzasvir (formerly MK-8408) was developed as a novel NS5A inhibitor to improve upon the potency and barrier to resistance of early compounds. Ruzasvir inhibited HCV RNA replication with 50% effective concentrations (EC50s) of 1 to 4 pM in Huh7 or Huh7.5 cells bearing replicons for HCV genotype 1 (GT1) to GT7. The antiviral activity was modestly (10-fold) reduced in the presence of 40% normal human serum. The picomolar potency in replicon cells extended to sequences of clinical isolates available in public databases that were synthesized and tested as replicons. In GT1a, ruzasvir inhibited common NS5A resistance-associated substitutions (RASs), with the exception of M28G. De novo resistance selection studies identified pathways with certain amino acid substitutions at residues 28, 30, 31, and 93 across genotypes. Substitutions at position 93 were more common in GT1 to -4, while changes at position 31 emerged frequently in GT5 and -6. With the exception of GT4, the reintroduction of selected RASs conferred a ≥100-fold potency reduction in the antiviral activity of ruzasvir. Common RASs from other classes of direct-acting antiviral agents (DAAs) did not confer cross-resistance to ruzasvir. The interaction of ruzasvir with an NS3/4A protease inhibitor (grazoprevir) and an NS5B polymerase prodrug (uprifosbuvir) was additive to synergistic, with no evidence of antagonism or cytotoxicity. The antiviral profile of ruzasvir supported its further evaluation in human trials in combination with grazoprevir and uprifosbuvir.

No Pharmacokinetic Interactions Between Elbasvir or Grazoprevir and Buprenorphine/Naloxone in Healthy Participants and Participants Receiving Stable Opioid Agonist Therapy

The aims of these phase I trials were to evaluate the pharmacokinetic interaction between elbasvir (EBR) or grazoprevir (GZR) and buprenorphine/naloxone (BUP/NAL). Trial 1 was a single-dose trial in healthy participants. Trial 2 was a multiple-dose trial in participants on BUP/NAL maintenance therapy. Coadministration of EBR or GZR with BUP/NAL had minimal effect on the pharmacokinetics of BUP/NAL, EBR, and GZR. The geometric mean ratios (GMRs (90% CI)) for BUP, norbuprenorphine, and NAL AUC0-∞ were 0.98 (0.89-1.08), 0.97 (0.86-1.09), and 0.88 (0.78-1.00) in the presence/absence of EBR; 0.98 (0.81-1.19), 1.13 (0.97-1.32), and 1.10 (0.82-1.47) in the presence/absence of GZR. The GMRs (90% CI) for EBR and GZR AUC0-∞ in the absence/presence of BUP/NAL were 1.22 (0.98-1.52) and 0.86 (0.63-1.18). In conclusion, no dose adjustment for BUP/NAL, EBR, or GZR is required for patients with HCV infection receiving EBR/GZR and BUP/NAL maintenance therapy.

Convergent Synthesis of the NS5B Inhibitor GSK8175 Enabled by Transition Metal Catalysis

A convergent eight-stage synthesis of the boron-containing NS5B inhibitor GSK8175 is described. The previous route involves 13 steps in a completely linear sequence, with an overall 10% yield. Key issues include a multiday S_NAr arylation of a secondary sulfonamide using HMPA as solvent, multiple functional group interconversions after all of the carbon atoms are installed (including a Sandmeyer halogenation), use of carcinogenic chloromethyl methyl ether to install a protecting group late in the synthesis, and an unreliable Pd-catalyzed Miyaura borylation as the penultimate step. We have devised an orthogonal approach using a Chan-Lam coupling between a halogenated aryl pinacol boronate ester and an aryl methanesulfonamide. This reaction is performed using a cationic Cu(I) precatalyst, which can be easily generated in situ using KPF₆ as a halide abstractor. High-throughput screening revealed a new Pd catalyst system to effect the penultimate borylation chemistry using simple monodentate phosphine ligands, with PCyPh₂ identified as optimal. Reaction progress analysis of this borylation indicated likely mass-transfer rate limitations under standard conditions using KOAc as the base. We have devised a K₂CO₃/pivalic acid system as an alternative, which dramatically outperforms the standard conditions. This new synthesis proceeds in eight stages with a 20% overall yield.

Pharmacokinetics, Safety, and Tolerability of Single-Dose Elbasvir in Participants with Hepatic Impairment

BACKGROUND

The combination of elbasvir and grazoprevir is approved for the treatment of hepatitis C virus genotype 1 or 4 infection.

OBJECTIVE

To evaluate the pharmacokinetics and safety of single-dose elbasvir 50 mg in participants with hepatic impairment.

METHODS

Participants with mild, moderate, or severe hepatic impairment and age-, sex-, and weight-matched healthy controls were enrolled in a 3-part, open-label, sequential-panel, single-dose pharmacokinetic study. Blood samples were collected to assess pharmacokinetics. Safety and tolerability were assessed throughout the study.

RESULTS

Thirty-four participants were enrolled: eight with mild hepatic impairment, 11 with moderate hepatic impairment, seven with severe hepatic impairment, and eight healthy matched controls. Participants with mild, moderate, and severe hepatic impairment demonstrated a numeric, but not statistically significant, decrease in elbasvir exposure compared with controls, with a mean 39, 28, and 12% decrease in area under the concentration-time curve from time 0 extrapolated to infinity, as well as a 42, 31, and 42% decrease in maximum plasma concentration (C _max), respectively. The observed median time to C _max was similar in participants with hepatic impairment and controls. Single-dose administration of elbasvir was well tolerated.

CONCLUSIONS

The pharmacokinetics of elbasvir after a single, oral 50-mg dose were not clinically meaningfully altered in non-HCV-infected participants with mild, moderate, or severe hepatic dysfunction. However, since elbasvir is currently available only as part of a fixed-dose combination with grazoprevir, the fixed-dose combination should not be administered to patients with moderate or severe hepatic impairment, due to the significantly increased plasma grazoprevir exposures in those populations.