Potency and resistance analysis of hepatitis C virus NS5B polymerase inhibitor BMS-791325 on all major genotypes

Covalent Inhibitors from Saudi Medicinal Plants Target RNA-Dependent RNA Polymerase (RdRp) of SARS-CoV-2

COVID-19, a disease caused by SARS-CoV-2, has caused a huge loss of human life, and the number of deaths is still continuing. Despite the lack of repurposed drugs and vaccines, the search for potential small molecules to inhibit SARS-CoV-2 is in demand. Hence, we relied on the drug-like characters of ten phytochemicals (compounds 1-10) that were previously isolated and purified by our research team from Saudi medicinal plants. We computationally evaluated the inhibition of RNA-dependent RNA polymerase (RdRp) by compounds 1-10. Non-covalent (reversible) docking of compounds 1-10 with RdRp led to the formation of a hydrogen bond with template primer nucleotides (A and U) and key amino acid residues (ASP623, LYS545, ARG555, ASN691, SER682, and ARG553) in its active pocket. Covalent (irreversible) docking revealed that compounds 7, 8, and 9 exhibited their irreversible nature of binding with CYS813, a crucial amino acid in the palm domain of RdRP. Molecular dynamic (MD) simulation analysis by RMSD, RMSF, and Rg parameters affirmed that RdRP complexes with compounds 7, 8, and 9 were stable and showed less deviation. Our data provide novel information on compounds 7, 8, and 9 that demonstrated their non-nucleoside and irreversible interaction capabilities to inhibit RdRp and shed new scaffolds as antivirals against SARS-CoV-2.

Discovery of Novel 3-Hydroxyquinazoline-2,4(1H,3H)-Dione Derivatives: A Series of Metal Ion Chelators with Potent Anti-HCV Activities

Millions of people worldwide suffer from acute or chronic liver inflammation caused by the hepatitis C virus (HCV). Metal ion chelators have achieved widespread success in the development of antiviral drugs. Some inhibitors with metal ion chelating structures have been proven to have good inhibitory activities on non-structural protein 5B (NS5B) polymerase. However, most of the reported metal ion chelators showed poor anti-HCV potency at the cellular level. Hence, we designed and synthesized a series of 3-hydroxyquinazoline-2,4(1H,3H)-dione derivatives with novel metal ion chelating structures. Typical compounds such as 21h, 21k, and 21t showed better anti-HCV activities than ribavirin with EC50 values less than 10 μM. 21t is currently known as one of the metal ion chelators with the best anti-HCV potency (EC50 = 2.0 μM) at the cellular level and has a better therapeutic index (TI > 25) as compared to ribavirin and the reported compound 6. In the thermal shift assay, the representative compounds 21e and 21k increased the melting temperature (Tm) of NS5B protein solution by 1.6 °C and 2.1 °C, respectively, at the test concentration, indicating that these compounds may exert an anti-HCV effect by targeting NS5B. This speculation was also supported by our molecular docking studies and ultraviolet-visible (UV-Vis) spectrophotometry assay, in which the possibility of binding of 3-hydroxyquinazoline-2,4(1H,3H)-diones with Mg2+ in the NS5B catalytic center was observed.

Potent HCV NS3 Protease Inhibition by a Water-Soluble Phyllanthin Congener

NS3/4A protease of hepatitis C virus (HCV) plays an important role in viral RNA replication. A 1,4-diphenylbutanedicarboxylic acid derivative, namely, phyllanthin, extracted from the leaf of a herbal plant, Phyllanthus amarus, inhibits HCV NS3/4A protease and replication activities. However, the reduced aqueous solubility, high toxicity, and poor oral bioavailability are major impediments with phyllanthin. We herein present a design approach to generate phyllanthin congeners in order to potentiate inhibition activity against protease. The phyllanthin congeners were synthesized by chemical methods and subjected to systematic biological studies. One of the congeners, annotated as D8, is identified as a novel and potent inhibitor of the HCV-NS3/4Aprotease activity in vitro and the viral RNA replication in cell culture. Structural analysis using the computational-based docking approach demonstrated important noncovalent interactions between D8 and the catalytic residues of the viral protease. Furthermore, D8 was found to be significantly nontoxic in cell culture. More importantly, oral administration of D8 in BALB/c mice proved its better tolerability and bioavailability, as compared to native phyllanthin. Taken together, this study reveals a promising candidate for developing anti-HCV therapeutics to control HCV-induced liver diseases.

Pooled analysis of HCV genotype 1 resistance-associated substitutions in NS5A, NS3 and NS5B pre-and post-treatment with 12 weeks of daclatasvir, asunaprevir and beclabuvir

BACKGROUND

Daclatasvir (DCV; non-structural [NS]5A inhibitor) plus asunaprevir (ASV; NS3 inhibitor) plus beclabuvir (BCV; non-nucleoside NS5B inhibitor) is an approved regimen for hepatitis C virus (HCV) genotype (GT)-1 treatment in Japan. A comprehensive analysis of pre-treatment and treatment-emergent HCV resistance to this regimen ± ribavirin (RBV) was performed.

METHODS

Data were pooled from five Phase 2/3 studies of DCV+ASV+BCV±RBV given for 12 weeks to GT-1a- or GT-1b-infected patients. The prevalence and impact of pre-treatment resistance-associated substitutions (RAS) in NS5A, NS3, and NS5B on sustained virological response (SVR) was assessed, as were emergent RAS and their post-treatment persistence.

RESULTS

Baseline NS5A RAS (GT-1a: M28T, Q30H/L/R/S, L31M, Y93C/H; GT-1b: L31I/M, Y93C/H) were present in 5% (26/561) of GT-1a and 16% (85/537) of GT-1b sequences. SVR12 for GT-1b without RBV was 100% (82/82) with RAS and >99% (427/428) without RAS. For GT-1a, SVR12 without RAS was 97% (85/88) with RBV and 92% (410/447) without RBV; SVR12 with RAS was 100% (2/2) with RBV and 54% (13/24) without RBV. Baseline NS3 (at R155 or D168) and NS5B (at P495) RAS were rare (≤1%). Treatment-emergent NS5A RAS (mostly Q30E/H/K/R±Y93H/N) in GT-1a persisted 60 weeks post-treatment, while NS3 RAS (mostly R155K) and NS5B-P495L/S were no longer detected after 48 or 24 weeks, respectively.

CONCLUSIONS

DCV+ASV+BCV±RBV was highly efficacious in HCV GT-1 infection, including HCV GT-1b with NS5A RAS. The fitness of treatment-emergent RAS post-treatment was NS5A > NS3 > NS5B; NS3 and NS5B RAS were generally replaced by wild-type sequence within 48 weeks.

Natural polymorphisms in the resistance associated sites of HCV-G1 NS5B domain and correlation with geographic origin of HCV isolates

BACKGROUND

We evaluated the frequency of naturally occurring resistance associated substitutions (RASs) and their characteristic of polymorphic or non-polymorphic amino acid change to direct acting antivirals (DAAs) in NS5b HCV subtypes 1a and 1b according to different geographic origin of isolates.

METHODS

Using a public database we retrieved 738 worldwide NS5b sequences (for which was available the geographic origin) from HCV genotype (G)1 infected patients naive to DAAs. NS5b sequences clustering with G1a were more conserved in regard of RASs than G1b isolates, (14% vs 57% RASs, P < 0.0001).

RESULTS

In G1a, RASs were differently distributed between isolates from Europe (24%) and USA, (12%) P = 0.0186. In particular, 421 V associated with resistance to non-nucleoside inhibitor beclabuvir was polymorphic in Europe and USA, being detected in 24% and 11% of sequences, respectively, P = 0.0140. In G1b, RASs were found in 45% of sequences from Europe, in 54% of isolates from USA and in 70% of sequences from Asia (P = 0.0051). The 316 N polymorphism was detected in 54% of Asian isolates and at lower frequency, in 28% of isolates from USA and in 20% of European sequences (P < 0.0001).

CONCLUSIONS

In conclusion, a higher prevalence of RASs in G1b respect to G1a was found and a geographical distribution of RASs and polymorphic aa changes was observed in G1a as well in G1b. The clinical and therapeutic impact of the geographic distribution of RASs to polymerase inhibitors remains to be established, particularly in patients with virologic failure to DAAs and/or advanced liver disease.

Recombinant hepatitis C virus genotype 5a infectious cell culture systems expressing minimal JFH1 NS5B sequences permit polymerase inhibitor studies

The six major epidemiologically important hepatitis C virus (HCV) genotypes differ in global distribution and antiviral responses. Full-length infectious cell-culture adapted clones, the gold standard for HCV studies in vitro, are missing for genotypes 4 and 5. To address this challenge for genotype 5, we constructed a consensus full-length clone of strain SA13 (SA13fl), which was found non-viable in Huh7.5 cells. Step-wise adaptation of SA13fl-based recombinants, beginning with a virus encoding the NS5B-thumb domain and 3´UTR of JFH1 (SA13/JF372-X), resulted in a high-titer SA13 virus with only 41 JFH1-encoded NS5B-thumb residues (SA13/JF470-510cc); this required sixteen cell-culture adaptive substitutions within the SA13fl polyprotein and two 3´UTR-changes. SA13/JF372-X and SA13/JF470-510cc were equally sensitive to nucleoside polymerase inhibitors, including sofosbuvir, but showed differential sensitivity to inhibitors targeting the NS5B palm or thumb. SA13/JF470-510cc represents a model to elucidate the influence of HCV RNA elements on viral replication and map determinants of sensitivity to polymerase inhibitors.

Limitations of daclatasvir/asunaprevir plus beclabuvir treatment in cases of NS5A inhibitor treatment failure

Combined daclatasvir (DCV)/asunaprevir (ASV) plus beclabuvir (BCV) treatment shows a high virological response for genotype 1b chronic hepatitis C patients. However, its efficacy for patients for whom previous direct-acting antiviral (DAA) therapy failed is not known. We analysed the efficacy of DCV/ASV/BCV treatment for HCV-infected mice and chronic hepatitis patients. Human hepatocyte chimaeric mice were injected with serum samples obtained from either a DAA-naïve patient or a DCV/ASV treatment failure and were then treated with DCV/ASV alone or in combination with BCV for 4 weeks. DCV/ASV treatment successfully eliminated the virus in DAA-naïve-patient HCV-infected mice. DCV/ASV treatment failure HCV-infected mice developed viral breakthrough during DCV/ASV treatment, with the emergence of NS5A-L31V/Y93H HCV resistance-associated variants (RAVs) being observed by direct sequencing. DCV/ASV/BCV treatment inhibited viral breakthrough in NS5A-L31V/Y93H-mutated HCV-infected mice, but HCV relapsed with the emergence of NS5B-P495S variants after the cessation of the treatment. The efficacy of the triple therapy was also analysed in HCV-infected patients; one DAA-naïve patient and four prior DAA treatment failures were treated with 12 weeks of DCV/ASV/BCV therapy. Sustained virological response was achieved in a DAA-naïve patient and one of the DCV/ASV treatment failures through DCV/ASV/BCV therapy; however, HCV relapse occurred in the other patients with prior DCV/ASV and/or sofosbuvir/ledipasvir treatment failures. DCV/ASV/BCV therapy seems to have limited efficacy for patients with NS5A RAVs for whom prior DAA treatment has failed.

Daclatasvir/asunaprevir/beclabuvir, all-oral, fixed-dose combination for patients with chronic hepatitis C virus genotype 1

BACKGROUND AND AIM

This multinational (Taiwan, South Korea, Russia) phase 3 study evaluated the all-oral, ribavirin-free, fixed-dose combination (DCV-TRIO) of daclatasvir (NS5A inhibitor) 30 mg, asunaprevir (NS3 inhibitor) 200 mg, and beclabuvir (NS5B inhibitor) 75 mg, in patients with chronic hepatitis C virus genotype-1 infection, with or without compensated cirrhosis.

METHODS

UNITY-4 (NCT02170727) was an open-label, two-cohort study in which 169 patients, treatment-naive (n = 138) or treatment-experienced (n = 31), received twice-daily DCV-TRIO for 12 weeks with 24 weeks of post-treatment follow-up. The primary efficacy end point was sustained virologic response at post-treatment week 12 (SVR12) in treatment-naive patients.

RESULTS

Eighty-eight (52%) patients were men, 81 (48%) Taiwanese, 78 (46%) Korean, and 10 (6%) Russian; 23 (14%) had compensated cirrhosis, and 52 (31%) were IL28B (rs1297860) non-CC genotype. Baseline resistance-associated NS5A polymorphisms (L31 and/or Y93) were detected in 25/165 (15%) patients with available genotype-1 sequencing data. SVR12 was achieved by 98.6% (136/138; 95% confidence interval: 94.9-99.8%) of treatment-naive and 100% (31/31; 95% confidence interval: 88.8-100%) of treatment-experienced patients. Both virologic failures were found to be infected with hepatitis C virus genotype-6g; 100% SVR12 was observed for genotype-1a (n = 8) and genotype-1b (n = 157). Two patients experienced serious adverse events. Eight (5%) patients experienced reversible grade 3/4 alanine aminotransferase or aspartate aminotransferase elevations, leading to discontinuation in four (2%); all achieved SVR12. There were no grade 3/4 total bilirubin increases and no deaths.

CONCLUSIONS

Twelve weeks of DCV-TRIO was well tolerated and provided 100% SVR12 in treatment-naive and treatment-experienced patients with genotype-1 infection, with or without cirrhosis, including those with baseline NS5A-L31 or NS5A-Y93 resistance-associated substitutions.

Searching for synergy: Identifying optimal antiviral combination therapy using Hepatitis C virus (HCV) agents in a replicon system

Direct acting antiviral agents (DAAs) are potent inhibitors of Hepatitis C virus (HCV) that have revolutionized the treatment landscape for this important viral disease. There are currently four classes of DAAs that inhibit HCV replication via distinct mechanisms of action: nonstructural protein (NS) 3/4a protease inhibitors, NS5A inhibitors, NS5B nucleoside polymerase inhibitors, and NS5B non-nucleoside polymerase inhibitors. Combination therapy with two or more DAAs has great potential to further enhance antiviral potency. The purpose of this study was to identify optimal combinations of DAAs against genotype 1 HCV replicons that maximized the inhibition of replicon replication. All possible two-drug combinations were evaluated against genotype 1a and 1b HCV replicons using a 96-well plate luciferase-based assay in triplicate. The Greco Universal Response Surface Area mathematical model was fit to the luciferase data to identify drug-drug interactions (i.e.: synergy, additivity, and antagonism) for antiviral effect against both genotypes. This information was used to rank-order combinations of DAAs based on their ability to inhibit replicon replication against genotype 1a and 1b HCV. These preclinical findings can provide information as to which antiviral regimens should move on in the development process.

Allosteric mechanism of cyclopropylindolobenzazepine inhibitors for HCV NS5B RdRp via dynamic correlation network analysis

HCV RNA dependent RNA polymerase (RdRp) nonstructural protein 5B (NS5B) is a major target against hepatitis C virus (HCV) for antiviral therapy. Recently discovered cyclopropylindolobenzazepine derivatives have been considered as the most potent for their ability to bind the thumb site 1 domain and allosterically inhibit HCV NS5B RdRp activity. However, the allosteric mechanism for these derivatives has not been clarified at the molecular level. In this study, fluctuation correlation networks were constructed based on all-atom molecular dynamics simulations to elucidate the allosteric mechanism. The fluctuation correlation networks between free and M2 bound NS5B are significantly different. Information can better transfer from the allosteric site to the catalytic site for bound NS5B than for free NS5B. Thus, the hypothesis of "binding induced allosteric regulation" is proposed to link the enzyme activation and inhibitor binding and then confirmed by the mutant network. Finally, one possible allosteric pathway was identified with the shortest path and evaluated by the perturbation of the network. These methods will be helpful to identify the allosteric pathway of other proteins and to design new drugs targeting the pathway.

Discovery of a Hepatitis C Virus NS5B Replicase Palm Site Allosteric Inhibitor (BMS-929075) Advanced to Phase 1 Clinical Studies

The hepatitis C virus (HCV) NS5B replicase is a prime target for the development of direct-acting antiviral drugs for the treatment of chronic HCV infection. Inspired by the overlay of bound structures of three structurally distinct NS5B palm site allosteric inhibitors, the high-throughput screening hit anthranilic acid 4, the known benzofuran analogue 5, and the benzothiadiazine derivative 6, an optimization process utilizing the simple benzofuran template 7 as a starting point for a fragment growing approach was pursued. A delicate balance of molecular properties achieved via disciplined lipophilicity changes was essential to achieve both high affinity binding and a stringent targeted absorption, distribution, metabolism, and excretion profile. These efforts led to the discovery of BMS-929075 (37), which maintained ligand efficiency relative to early leads, demonstrated efficacy in a triple combination regimen in HCV replicon cells, and exhibited consistently high oral bioavailability and pharmacokinetic parameters across preclinical animal species. The human PK properties from the Phase I clinical studies of 37 were better than anticipated and suggest promising potential for QD administration.

Characterization of NS5A polymorphisms and their impact on response rates in patients with HCV genotype 2 treated with daclatasvir-based regimens

OBJECTIVE

Daclatasvir (DCV) is a pan-genotypic non-structural protein 5A (NS5A) inhibitor that is approved for treatment of hepatitis C virus (HCV) genotype (GT)1 and GT3 in the USA and GT1, GT3 and GT4 in Europe. We set out to examine the impact of daclatasvir-based regimens on the sustained virologic response (SVR) in patients with GT2 infection with respect to GT2 subtype and NS5A polymorphisms at amino acid positions associated with daclatasvir resistance.

METHODS

Analyses were performed on 283 GT2 NS5A sequences from five daclatasvir regimen-based clinical trials (ClinicalTrials.gov: NCT-01257204, NCT-01359644, NCT-02032875, NCT-02032888 and NCT-01616524) and 143 NS5A sequences from the Los Alamos HCV database. Susceptibility analyses of substitutions at amino acid positions associated with daclatasvir resistance and patient-derived NS5A sequences were performed using an in vitro HCV replication assay.

RESULTS

Of 13 GT2 subtypes identified from 426 NS5A sequences, the most prevalent were GT2a (32%), GT2b (48%) and GT2c (10%). The most prevalent NS5A polymorphism was L31M (GT2a = 88%; GT2b = 59%; GT2c = 10%). Substitutions identified in 96% of GT2 NS5A sequences exhibited daclatasvir EC₅₀ values ranging from 0.005 to 20 nM when tested in vitro. A similar range in daclatasvir EC₅₀ values was observed for 16 diverse GT2 patient-derived NS5A sequences (EC₅₀ = 0.005-60 nM). Depending on the daclatasvir-based regimen studied (daclatasvir/interferon-based or daclatasvir/sofosbuvir-based), SVR rates ranged from 90% to 100% in GT2 patients with the most prevalent baseline NS5A-L31M polymorphism, compared with from 96% to 100% without this polymorphism.

CONCLUSIONS

High SVR rates were achieved in patients infected with GT2 treated with daclatasvir-based regimens irrespective of GT2 subtype or baseline NS5A polymorphisms.

2015 Philip S. Portoghese Medicinal Chemistry Lectureship. Curing Hepatitis C Virus Infection with Direct-Acting Antiviral Agents: The Arc of a Medicinal Chemistry Triumph

The development of direct-acting antiviral agents that can cure a chronic hepatitis C virus (HCV) infection after 8-12 weeks of daily, well-tolerated therapy has revolutionized the treatment of this insidious disease. In this article, three of Bristol-Myers Squibb's HCV programs are summarized, each of which produced a clinical candidate: the NS3 protease inhibitor asunaprevir (64), marketed as Sunvepra, the NS5A replication complex inhibitor daclatasvir (117), marketed as Daklinza, and the allosteric NS5B polymerase inhibitor beclabuvir (142), which is in late stage clinical studies. A clinical study with 64 and 117 established for the first time that a chronic HCV infection could be cured by treatment with direct-acting antiviral agents alone in the absence of interferon. The development of small molecule HCV therapeutics, designed by medicinal chemists, has been hailed as "the arc of a medical triumph" but may equally well be described as "the arc of a medicinal chemistry triumph".

Interferon-Free Treatments for Chronic Hepatitis C Genotype 1 Infection

Hepatitis C virus (HCV) infection affects as many as 185 million people globally, many of whom are chronically infected and progress over time to cirrhosis, decompensated liver disease, hepatocellular carcinoma, and eventually death without a liver transplant. In the United States, HCV genotype 1 constitutes about 75% of all infections. While interferon and ribavirin therapy was the cornerstone of treatment for many years, interferon-free treatments have become the standard of care with the emergence of new direct-acting agents, resulting in more effective treatment, shorter duration of therapy, better tolerability, lower pill burden, and ultimately better adherence. This review will summarize the evidence for the currently available combination therapies as well as emerging therapies in phase 3 trials for treatment of HCV genotype 1.

Resistance to direct-acting antiviral agents: clinical utility and significance

PURPOSE OF REVIEW

This article examines the dynamics and factors underlying hepatitis C virus (HCV) resistance, along with their impact on daily clinical management of HCV-infected patients.

RECENT FINDINGS

Across available treatment-regimens, GT-3 is the most difficult-to-cure genotype, but also genotype-1a may show lower success-rates compared with genotype-1b. Natural resistance to NS3, NS5A and NS5B inhibitors may contribute to treatment failures. The Q80K NS3-protease mutation affects sensibility to simeprevir + peg-interferon/ribavirin combinations. It reaches up to 48% prevalence in genotype-1a in some studies (but it is lower in other). Resistant variants (particularly in NS5A) developed at failure can persist, in a substantial proportion of patients, even 3 years after treatment-discontinuation, potentially affecting readministration of the same direct-acting antiviral agent (DAA)-class. This will become an issue for those patients failing all-oral regimens with multiple-resistant viruses.

SUMMARY

Recent data support the importance of an accurate genotype and genotype-1 subtype (1a/1b) assignment prior therapy. Resistance testing at baseline has no clear indication so far in clinical practice for all-DAA regimens selection, while it remains a valuable option at the retreatment of patients who failed DAA-containing regimens, provided that data are generated to inform treatment decisions based on the results of resistance testing. In this context, long-term RAVs persistence after failure should be taken into account.

Beclabuvir for the treatment of hepatitis C

INTRODUCTION

About 185,000,000 people worldwide are chronically infected with hepatitis C virus (HCV). Currently, the most successful HCV infection antiviral therapies reduce the chance of progression towards the advanced phases of the hepatopathy (liver cirrhosis, hepatocellular carcinoma and death). Recently, however, several new direct-acting antivirals against HCV are available or are in an advanced phase of clinical development.

AREAS COVERED

This review focuses on beclabuvir , an allosteric non-nucleotide inhibitor of HCV polymerase. The article covers its pharmacokinetics, mechanism of action, in addition to its tolerability and safety profile as well as its resistance pattern.

EXPERT OPINION

The pharmacokinetic, efficacy and tolerability profile of beclabuvir, as well as its barrier to resistance, are very favorable. In particular, the combination of beclabuvir with asunaprevir and daclatasvir achieves very high rates of viral eradication (about 90%) in patients infected with HCV genotype 1, which is the most common genotype worldwide. Therefore, beclabuvir represents a powerful weapon against HCV infection and has to be considered an optimal option in tailored IFN-free combinations.