hepatitis C virus/HCV NS5B protein (IC50 < 28 nM)

Beclabuvir exhibits synergistic or additive antiviral effectiveness when combined with pegIFN/RBV and in 2- or 3-drug combinations with other DAAs, including nucleoside NS5B inhibitors, NS5A inhibitors, and HCV NS3 protease inhibitors[2].

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Beclabuvir is a potent, non-nucleoside inhibitor of the HCV NS5B RNA polymerase, with nanomolar activity against HCV genotypes 1, 3, 4, 5 and 6 in vitro. Beclabuvir (formerly BMS-791325) is a potent, non-nucleoside NS5B polymerase inhibitor that binds the NS5B thumb pocket 1 allosteric site and shows nanomolar activity against HCV GTs 1, 3, 4, 5 and 6, with 50% effective concentration (EC50) of 3 and 6 nm, respectively, for GT1a and GT1b 11. In vitro, Beclabuvir demonstrated additive or synergistic antiviral activity with pegIFN/RBV and in 2- or 3-drug combinations with a range of DAAs, such as HCV NS3 protease inhibitors, NS5A inhibitors' and/or nucleoside NS5B inhibitors [2].

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Beclabuvir is an allosteric inhibitor of HCV NS5B RNA-dependent RNA polymerase. The known allosteric inhibitors of HCV NS5B target four distinct sites on the polymerase. The enzyme structure resembles a hand and sites I and II are found in the ‘thumb’ domain, sites III and IV in the ‘palm’ domain. Allosteric inhibitors that target different binding sites are non-cross-resistant each-others. Therefore, these inhibitors might be used with other allosteric inhibitors of NS5B interacting in a synergistic or non-antagonistic way. Beclabuvir is a thumb site 1-NS5B polymerase ligand. In general, such compounds inhibit the initiation step of RNA replication and not the elongation step. Beclabuvir has been shown to equally inhibit de novo and primer dependent synthesis, 5-75 fold more potently than previously studied compounds, thus resulting the most effective thumb site 1 inhibitor of genotype 1 (GT-1) NS5B polymerase to our knowledge. After its binding, beclabuvir inhibits NS5B activity in a time-dependent manner, and thus prevents the formation of active replication complexes[1].

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In vitro, Beclabuvir is able to inhibit recombinant NS5B proteins derived from HCV genotypes 1, 3, 4, and 5 at 50% inhibitory concentrations (IC50) with nanomolar potency. In cell culture, beclabuvir impedes replication of HCV subgenomic replicons from genotypes 1a and 1b at 50% effective concentrations (EC50s) of 3 nM and 6 nM, respectively. Similar values (3 to 18 nM) are observed for genotypes 3a, 4a, and 5a. With regard to genotype 6a, EC50 values shows more variability (9 to 125 nM) while potency was weaker against genotype 2 (EC50, 87 to 925 nM). The absence of activity (EC50s of > 4 μM) against a panel of mammalian viruses (pestivirus, bovine viral diarrhea virus) or human DNA polymerases α,β,γ (IC50 values > 25 µM) is indicative of its specificity, along with cytotoxic concentrations (50%) > 3000-fold above the HCV EC50. Moreover, beclabuvir shows additive synergistic effects on replicon inhibition when in combination with other HCV inhibitors such as daclatasvir, asunaprevir, and human lambda 1 IFN. Moreover, a recent in vitro study has shown that the addition of Beclabuvir and sofosbuvir in a quadruple combination regimen (daclatasvir/asunaprevir/beclabuvir/sofosbuvir) efficiently cleared daclatasvir/asunaprevir-resistant replicons from cells in 5 days of treatment[1].

Researchers analysed the efficacy of DCV/ASV/BCV (Beclabuvir) 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. [3]

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In patients infected with HCV genotype 1, the most prevalent genotype globally, the combination of Beclabuvir, asunaprevir, and daclatasvir provides very high rates of viral eradication (approximately 90%)[1].

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Trials in monotherapy [1]
In a double-blind, placebo-controlled study, a single ascending daily dose of Beclabuvir (100, 300, 600, or 900 mg) or placebo was administered to 24 patients (randomized 5:1 in each dosing cohort) with chronic HCV genotype 1 infection, both IFN naive and experienced. Peak beclabuvir concentrations were observed between 2 and 4 h, and t1/2 was 6.8 to 9.4 h. Although t1/2 appears to be below 10 h, achievable exposures at 24 h greatly exceeded effective concentrations established in vitro. Maximum antiviral response correlated with plasma drug exposure and was medially achieved 24 h post-dose (range, 12 -48 h) by 12 of the 20 patients who received the drug. At all doses of the drug, a robust reduction of viral RNA (between 1 log10 and over 3 log10 IU/ml) was observed. The highest observed maximum reduction of HCV RNA was reached by two patients, one in the 600-mg cohort (pre-dose baseline, 6.6 log10 IU/ml) and one in the 900-mg cohort (pre-dose baseline, 6.5 log10 IU/ml) whose viral load declined by 3.4 log10 UI/mL 24 h after the dose of the drug.

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IFN-free combination trials [1]
The efficacy and safety of the all-oral fixed-dose combination of 3 DAAs, the NS5A inhibitor daclatasvir (DCV), the NS3/4 protease inhibitor asunaprevir (ASV) and the non-nucleoside NS5B polymerase inhibitor Beclabuvir (BCV), given to patients with chronic HCV infection were evaluated in one Phase II study and in two Phase III studies: i) AI443-014 which was a Phase II study carried out on treatment-naive GT-1 and GT-4 patients, and pegIFN/RBV (ribavirin) prior null-responders GT-1 patients. This study explored safety and efficacy of the DCV TRIO therapy (DCV - ASV - BCV) administered for 12 or 24 weeks; ii) UNITY-1 (AI443-102) which was a Phase III study carried out on treatment-naive and treatment-experienced GT-1 patients without cirrhosis. This study assessed safety and efficacy of DCV TRIO therapy administered for 12 weeks; iii) UNITY-2 (AI443-113) which was a Phase III study conducted on treatment-naive and treatment-experienced GT-1 patients with compensated cirrhosis. This study evaluated the DCV TRIO therapy plus RBV administered for 12 weeks.

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This study evaluated the efficacy and safety of Beclabuvir, in combination with peginterferon alfa-2a (pegIFN) and ribavirin (RBV), in HCV genotype 1. In this randomized (1:1:1), double-blinded, placebo-controlled, dose-ranging phase 2a study, 39 treatment-naive patients chronically infected with HCV genotype 1 were treated for 48 weeks with beclabuvir (75 mg or 150 mg) plus pegIFN (180 μg) and RBV (1000 mg/day [<75 kg] or 1200 mg/day [≥ 75 kg]) vs pegIFN/RBV alone. The primary efficacy endpoint of extended rapid virologic response (undetectable HCV RNA at treatment weeks 4 and 12) was achieved by 76.9% (10/13) of patients receiving beclabuvir 75 mg and 38.5% (5/13) receiving beclabuvir 150 mg vs 0% receiving pegIFN/RBV alone. Higher response rates were observed among patients receiving beclabuvir 75 mg for all secondary efficacy endpoints, including sustained virologic response at follow-up weeks 12 or 24. Three patients experienced virologic breakthrough on treatment, all in the beclabuvir 150-mg treatment group. Beclabuvir was well tolerated at both doses, with the most commonly observed adverse events (headache, fatigue, nausea, decreased appetite, irritability, depression and insomnia) consistent with those observed with pegIFN/RBV. In conclusion, beclabuvir was both effective and well tolerated when administered in combination with pegIFN/RBV for the treatment of chronic HCV GT 1, supporting the study of beclabuvir as part of an all-oral regimen for HCV GT1. [2]

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Overall, 69 patients were screened and 39 randomized; of these, 29 patients completed the study (Fig. S1). Baseline characteristics were generally balanced across the three groups, except for a lower proportion of males, and higher proportions of white patients and patients with IL28B (rs12979860) CC genotypes in the Beclabuvir 75-mg arm compared with the other arms (Table S1).

The primary efficacy endpoint of eRVR was achieved by a higher proportion of patients in the Beclabuvir 75-mg (76.9%) and 150-mg (38.5%) groups than in the pegIFN/RBV group (0%) (Fig. 1). Patients in the beclabuvir 75-mg group demonstrated the highest response rates for the secondary efficacy endpoints RVR, cEVR, SVR12 and SVR24 (Fig. 1). Similar results were obtained when patients with missing measurements were excluded from the analysis (on-treatment analysis; Fig. S2). Response rates were also generally higher in the beclabuvir treatment arms compared with placebo for both IL28B CC and non-CC genotypes (Fig. 1), although numbers were small. The higher response rates with beclabuvir 75 mg vs 150 mg may be explained by 2 factors: (i) a lower proportion of patients with IL28B (rs1297860) CC genotypes – known to be associated with higher response rates to pegIFN/RBV-based regimes than non-CC genotypes 14-16 – in the 150-mg group (15%) than in the 75-mg group (46%), and (ii) a higher proportion of patients in the 150-mg arm with missing HCV RNA data at post-treatment week 24. When missing data were accounted for, SVR24 rates in the 150-mg treatment arm improved, with observed values of SVR24 rates in both the beclabuvir 150-mg and the placebo arms of 71% (5/7) and 90% (9/10) in the beclabuvir 75-mg arm.

In the Beclabuvir 75-mg group, no patient experienced virologic breakthrough or relapse post-treatment; among the four patients without SVR24, one had detectable HCV RNA at the end of treatment, whereas the remaining 3 (all with undetectable HCV RNA prior to post-treatment follow-up week 24) had missing week 24 post-treatment data, were lost to follow-up, or discontinued due to other reasons (incarceration) prior to this time point. In the beclabuvir 150-mg group, among the eight patients without SVR24, three had virologic breakthrough and one had detectable HCV RNA at end of treatment; no post-treatment relapse was observed. The remaining four patients (all with undetectable HCV RNA prior to post-treatment week 24) either had missing RNA data at post-treatment week 24 (n = 1) or were lost to follow-up (n = 3). In the placebo group, among the eight patients without SVR24, two had detectable HCV RNA at end of treatment, three experienced post-treatment relapse, whereas the remaining three patients (all with undetectable HCV RNA prior to post-treatment week 24) had missing RNA data or withdrew consent.

Among the three patients with virologic breakthrough (all Beclabuvir 150 mg), all had GT1a infection, were IL28B non-CC genotype and had evidence of the NS5B substitutions A421V and P495A/L/S at breakthrough; one patient also had the NS5B substitution M426L at baseline. The observation that all patients with virologic breakthrough had GT1a and NS5B variants at A421 and P495 is consistent with prior data for beclabuvir and other thumb pocket 1 NS5B inhibitors. Variants at P495 are signature resistance-associated substitutions for thumb pocket-1 inhibitors, and A421V has previously been observed following in vitro passage of GT1a replicon cells in the presence of beclabuvir alone and when combined with the NS3 inhibitor asunaprevir [2].

In in vitro studies, binding assays with NS5B genetic variants (wild type, L30S and P495L) revealed a two-step, slow-binding mechanism of the drug. In detail, resistance substitutions selected by Beclabuvir/BCV in genotype 1-based replicons mostly mapped to the NS5B amino acid 495 (P495A/S/L/T), which therefore can be considered the only clinically relevant resistance variant. For P495, the rate of initial complex formation and dissociation is similar to wild type, but the kinetics of the second step is significantly faster. This is associated with a shortened residence time and finally translates into a decrease in inhibitor potency. In contrast, the potency of BCV on L30S is roughly equal to wild-type polymerase. Therefore the detection of L30S mutation is not considered clinically relevant.
With regard to genotype-specific resistance profiles, GT1a has the highest resistance barrier versus Beclabuvir/BCV while GT6a has the lowest. At least in genotype 3 to 6-based replicon systems, substitutions in the thumb domain of NS5B at residues 494 and 495 conferred different levels of resistance to BCV. However, no cross-resistance to NS5A or NS3 protease inhibitors was observed. Regarding subtype 6a, it is noteworthy that A494 polymorphism, which confers reduced potency to BCV, is present in 21% of sequences in the European HCV database[1].

Patients and Methods [2]
This was a randomized (1:1:1), double-blinded, placebo-controlled, dose-ranging phase 2a study (AI443-012; ClinicalTrials.gov: NCT 01193361) evaluating the safety and efficacy of Beclabuvir combined with pegIFN/RBV in treatment-naive adults chronically infected with HCV GT1. Eligible patients received 48 weeks of twice-daily oral beclabuvir at 75 mg, beclabuvir at 150 mg, or placebo, each administered in combination with once-weekly subcutaneous pegIFN (180 μg) and twice-daily oral RBV (weight-based dosing of 1000 mg/day [<75 kg] or 1200 mg/day [≥75 kg]). The duration of post-treatment follow-up was 24 weeks (in patients with undetectable HCV RNA at end of treatment) or 48 weeks (in patients with detectable HCV RNA at end of treatment or relapse).

Patients were required to have HCV RNA ≥10–5 IU/mL (COBAS TaqMan HCV Test 2.0; Roche Molecular Diagnostics, Pleasanton, California; lower limit of quantitation [LLOQ] 25 IU/mL) at screening, with no evidence of cirrhosis by liver biopsy within 24 months of randomization. Key exclusion criteria included >4 weeks of prior treatment with interferon or RBV within 6 months prior to randomization; alanine aminotransferase (ALT) ≥5 × upper limit of normal (ULN); total bilirubin ≥34 μmol/L (≥2 mg/dL) or direct bilirubin >ULN; international normalization ratio (INR) ≥1.7; confirmed creatinine clearance ≤50 mL/min; or concurrent diagnosis of chronic hepatitis B infection, HIV infection, hepatocellular carcinoma or other non-HCV liver disease.

The primary safety endpoints were the incidence of serious adverse events (SAEs) and discontinuations of study therapy for AEs. The primary efficacy endpoint was the proportion of patients with extended rapid virologic response (eRVR), defined as undetectable (Beclabuvir and its metabolite BMS-794712, and associations between antiviral activity or safety of beclabuvir and host IL28B genotype or beclabuvir exposure.

Population sequencing of NS5B was performed at baseline, and for all Beclabuvir-treated patients experiencing futility (defined as [i] virologic breakthrough [increase in HCV RNA >1 log10 IU/mL above nadir, or HCV RNA ≥LLOQ following a confirmed undetectable measurement on treatment]; [ii] <1 log10 decrease in HCV RNA at week 4; [iii] failure to achieve EVR [defined as <2 log10 IU/mL decrease in HCV RNA at week 12]; or [iv] detectable HCV RNA at week 12 and ≥LLOQ at week 24) or relapse (undetectable HCV RNA at end of treatment followed by confirmed detectable HCV RNA at any post-treatment visit) and with HCV RNA ≥1000 IU/mL.

Pharmacokinetics and metabolism [1]
Optimization of the properties of an early series of NS5B polymerase inhibitors led to a promising group of alkyl bridged piperazine carboxamide antiviral compounds and the discovery and preclinical characterization of Beclabuvir. In vitro beclabuvir was studied in human, rat, dog, and cynomolgus monkey liver microsomes. In human and monkey microsomes, Beclabuvir half-lives (t1/2) were 53 and 23 min, respectively, while in both the rat and dog assays t1/2 were > 200 min. Based on these data, the compound was evaluated in 24 h rat pharmacokinetic study. In this study, when dosed as a solution in PEG-400, the oral bioavailability was 66%, the volume of distribution of 2.7 liters/kg while following an intra-venous administration, plasma clearance resulted 3.5 ml/min/kg and plasma t1/2 was estimated to be 8.3 h.

Plasma and liver exposures in vivo, following oral dosing, in several animal species (rats, dogs and monkeys) indicated that Beclabuvir has a hepatotropic disposition (liver-to-plasma ratios ranging from 1.6- to 60-fold across species). After twenty-four hours from administration, liver exposures across all species tested were greater than or equal to 10 -fold above the inhibitor EC50s observed with HCV genotype 1, 3, and 5 replicon EC50s; between 6.7- and 40-fold above GT 4 replicon EC50s; and 1.5- to 14-fold above GT 6 replicon EC50s.

Exposure to Beclabuvir in terms of maximum drug concentration (Cmax) and area under the plasma concentration-time curve (AUCinf) resulted dose dependent and more than dose proportional, with point estimates and 90% confidence intervals of about of 1.1 (0.99 to 1.22) for Cmax and 1.18 (0.99 to 1.36) for AUCinf, accordingly with the expectation of once- or twice-daily dosing. In replicon cultures, the protein-adjusted EC90 value resulted lower than plasma concentrations at all doses (52 ng/ml) within 1 h of dosing and at 24 h in all patients. Therefore, a satisfying antiviral responses can be expected for repeated administration even at the lowest tested doses (100 mg) while single doses above 300 mg provide little additional antiviral benefit. Moreover, Beclabuvir is metabolized to an equipotent compound (BMS-794712) which shows a similar pharmacokinetic profile, with a plasma exposure corresponding approximately to 22% of the parent value, hence contributing significantly to the total antiviral activity. In several clinical trials (see later), beclabuvir has been administered together with daclatasvir and asunaprevir. As all of these drugs are CYP3A4 substrates, OATP1B1 inhibitors and P-glycoprotein inhibitors, the potential drug to drug interactions of the triple combination have been investigated in a PK substudy of trial AI443014 in which 32 treatment-naive, HCV GT 1-infected, non-cirrhotic patients were treated for 12 or 24 weeks with daclatasvir (60 mg q.d.), asunaprevir (200 mg bis in die [b.i.d.]), and beclabuvir at two doses (75 mg b.i.d. or 150 mg b.i.d.). The addition of beclabuvir to daclatasvir and asunaprevir did not show any clinically meaningful interaction.

Even though DCV, ASV and Beclabuvir/BCV are primarily excreted in feces (renal excretion resulting < 10% of the total elimination) there are concerns that indirect mechanisms resulting from chronic kidney disease can equally modify the non-renal clearance of the drugs. For this reason, the open-label, multiple-dose AI443110 study assessed the pharmacokinetics and safety of DCV, ASN and BCV in 41 HCV-uninfected subjects (33 patients with different stages of renal impairment and 8 healthy controls with normal renal function). In subjects with moderate and severe renal impairment, mean concentrations of DCV, ASV, Beclabuvir/BCV and BMS-794712 were higher than in subjects with normal renal function. With respect to subjects with end stage renal disease (ESRD) on hemodialysis (HD), mean concentrations of DCV, BCV and BMS-794712 were comparable to subjects with normal renal function, while mean concentrations of ASV were lower. In patients with renal impairment, Cmax and AUCtau of the drugs were higher than among patients with normal renal function, particularly in subjects with severe renal impairment. Subjects with ESRD showed exposures generally comparable to the subjects with normal renal function due to HD and, after HD, DCV unbound PK parameters were lower when compared with healthy subjects. Cmax and AUCtau increased with decreasing creatinine clearance for DCV, ASV, BCV and BMS-794712 in primary regression analysis (excluding patients on HD), mainly in subjects with severe renal impairment (ranging from 42 to 105%).

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Median time to maximum plasma concentrations (Tmax) for Beclabuvir and its metabolite BMS-794712 were 2 h at each dose (Fig. S3). Exposure to both Beclabuvir and BMS-794712 at treatment week 12 was greater than dose proportional, with a metabolite:parent AUC ratio of ~0.23–0.25, which is consistent with previous single-dose data (100–900 mg) from a beclabuvir phase 1 study 12. No association was observed between composite trough concentrations of beclabuvir and achievement of a virologic response (eRVR, SVR24, RVR, cEVR, SVR12; Fig. S4a and data not shown), incidence of SAEs, or discontinuations for AEs (Fig. S4a). There was also no continuous association between drug exposure and changes from baseline in select clinical laboratory endpoints, including total bilirubin (Fig. S4b), ALT, haemoglobin or absolute neutrophils (data not shown); however, the caveat exists that trough levels are an indirect indication of peak exposure. [2]

Clinical trials: tolerability [1]
In the single-ascending-dose study of Beclabuvir/BCV in monotherapy, tolerability and safety profile was good. No death, SAE (Serious Adverse Event) or discontinuation due to AEs were reported. Recorded AEs were mild, except for two moderate gastrointestinal events in the 900-mg cohort, maybe due, at least partially, to a high capsule burden (18 capsules). Overall, the most frequent on-treatment observed AEs were nausea, vomiting, and headache (all the three symptoms recorded in 2/29 patients).

In IFN-based regimens, Beclabuvir/BCV was well tolerated at both doses (75 and 150 mg b.i.d.), and the most commonly observed AEs (headache, fatigue, nausea, decreased appetite, irritability, depression and insomnia) were consistent with those observed with pegIFN/RBV alone.

In the trials that evaluated the drug in combination with DCV and ASV, AEs led to treatment discontinuations occurred in two patients, three patients and one patient, in AI443-014, UNITY-1 and UNITY-2, respectively.
In AI443-014, there were six SAEs in GT-1 patients and no SAEs in GT-4 patients; there were no deaths. In treatment-naive GT1 patients, there were three SAEs, one in the Beclabuvir/BCV 75-mg arm (esophageal tumor, unrelated to the combination therapy, which led to treatment discontinuation) and two in the Beclabuvir/BCV 150-mg arm (one of which- throat tightness, related to the combination therapy – led to treatment discontinuation). The most frequent on-treatment AEs (≥ 10%) were headache, diarrhea, fatigue and nausea, in order of decreasing frequency. In prior null responders, three SAEs (cervical radiculopathy, syncope and psychotic disorder with onset 7 days posttreatment) and 1 grade 3 AE (syncope) occurred in the study; all four events occurred with 24 weeks of treatment and were considered unrelated to study medications. No grade 4 AEs were observed. The most common (≥ 10%) AEs included headache, fatigue, pruritus, diarrhea and upper respiratory tract infection. With respect to GT-4 patients, no SAE, grade 3/4 AE, or death was reported. The most commonly reported AEs in GT-4 patients (occurring in ≥ 10% of patients in either group) were headache (29% overall), insomnia (19%), nausea (14%) and pain (14%).

In UNITY-1, there were seven SAEs and one death (posttreatment); none were considered related to treatment. Headache, fatigue, diarrhea and nausea were the most commonly reported AEs (reported for > 10% of patients). AEs led to treatment discontinuation in three (< 1%) patients.

In UNITY-2, there were three SAEs considered related to treatment, with no deaths. Fatigue, headache, nausea, diarrhea, insomnia and pruritus were the most commonly reported AEs (reported for ≥ 10% of patients). On-treatment hemoglobin levels of < 9 g/dl occurred in 5% of patients who received the three DAAs plus RBV and in none of the patients in the RBV-free groups. One patient discontinued DAA treatment because of AEs.

With respect to the open-label, multiple-dose AI443110 study carried out in uninfected-HCV patients with normal or impaired renal function, no death or SAE was reported after the administration of DCV TRIO. One patient discontinued the study drugs because of an AE. A moderate increase of blood uric acid related to study drugs was reported in one subject in the moderate renal impairment group. During the study, 29% of patients with renal impairment experienced one or more AEs, mostly mild in intensity and transient, while no AEs were reported in healthy patients. No clinically relevant laboratory abnormalities were graded as AEs. In conclusion, DCV-TRIO resulted to be generally well tolerated both in patients with renal impairment and in subjects with normal renal function. Patients with renal impairment do not require dose adjustment of the drugs, except subjects with severe renal disease not on HD treatment, who should receive DCV-TRIO once daily.

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Beclabuvir was well tolerated at both doses, with no unexpected safety events (Table 1). No deaths were reported. The nature and incidence of on-treatment AEs were similar across the three groups (≥92%), with the most common AEs typically associated with pegIFN/RBV treatment. The most frequent on-treatment grade 3/4 laboratory abnormalities were haematologic and were also events expected with pegIFN/RBV. While on treatment and during post-treatment follow-up, three patients experienced SAEs; of these, two patients had SAEs considered unrelated to study drug. The third patient (beclabuvir 75 mg) had grade 3 anaemia with grade 2 leukopenia at post-treatment follow-up week 4, which were considered related to study drug. Six patients discontinued from study therapy due to AEs (one receiving 75 mg Beclabuvir, two receiving 150 mg beclabuvir, and three receiving placebo). Four discontinuations were protocol-mandated for confirmed conjugated hyperbilirubinemia (bilirubin ≥3 × baseline and >ULN) within the first 2 weeks (days 5–10; one in each beclabuvir arm, two in placebo arm). All four events were mild (grade 1) or moderate (grade 2) in intensity, with direct bilirubin levels ranging from 0.4 to 1.0 mg/dL (normal range, 0–0.2 mg/dL). Bilirubin abnormalities resolved completely or returned to just above baseline in three patients following discontinuation of all study drugs, but persisted in 1 placebo patient who initiated commercial pegIFN/RBV treatment. [2]

[1]. Beclabuvir for the treatment of hepatitis C. Expert Opin Investig Drugs. 2015;24(8):1111-21.

[2]. A randomized, placebo-controlled study of the NS5B inhibitor beclabuvir with peginterferon/ribavirin for HCV genotype 1. J Viral Hepat. 2015 Aug;22(8):658-64.

[3]. Limitations of daclatasvir/asunaprevir plus beclabuvir treatment in cases of NS5A inhibitor treatment failure. J Gen Virol. 2018 Aug;99(8):1058-1065.

Beclabuvir has been used in trials studying the treatment of Hepatitis C, Chronic.
Beclabuvir is a non-nucleoside, polymerase inhibitor of the hepatitis C virus (HCV) nonstructural protein 5B (NS5B), a RNA-dependent RNA polymerase, with potential activity against HCV. Upon administration and after intracellular uptake, beclabuvir allosterically binds to the non-catalytic Thumb 1 site of viral HCV NS5B polymerase and causes a decrease in viral RNA synthesis and replication. The HCV NS5B protein is essential for the replication of the viral HCV RNA genome. HCV is a small, enveloped, single-stranded RNA virus belonging to the Flaviviridae family.

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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.[1]

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The pharmacokinetics of Beclabuvir/BCV allows for two administrations per day. The co-administration of BCV with the protease inhibitor ASV and the NS5A inhibitor DCV for 12 weeks achieves rates of SVR of about 90% in patients with HCV genotype 1 infection. Few but very favorable data concern the efficacy of the same combination in patients with HCV genotype 4 infection. Data on other non-1 genotypes are currently lacking. Tolerability and safety of this drug are satisfactory.
Based on the above, Beclabuvir/BCV represents a powerful weapon against HCV infection and has to be considered an optimal option as a component of tailored IFN-free combinations.

The treatment of HCV infection is living an era of exciting and rapid changes. The availability of several antiviral combinations active in different genotypes and in different phase of the disease makes potentially curable every patient with HCV infection. However, several aspects need to be assessed such as: i) the tolerability and safety of DAAs in the advanced phase of the disease; ii) the real impact of viral clearance on survival and quality of life if the infection is cleared in an advanced stage. In other words, is there a point of no return beyond which the achievement of viral clearance is not associated with a meaningful clinical benefit? iii) the best combination in every situation; iv) the availability of the drug for all patients at a reasonable price; and v) the potential impact of viral clearance for patients with slight hepatic damage but HCV-related extra-hepatic damages.

Regarding the first two points, it is noteworthy that no study on Beclabuvir/BCV has assessed efficacy and safety in decompensated cirrhosis. This is likely due to the use of ASV in combination regimens which is contraindicated in advanced cirrhosis due to the risk of exposing the patient in Child-Pugh B/C class to increased ASV plasma levels because of an altered liver distribution of ASV in these subjects. We advocate clinical trials that would assess the efficacy and safety of Beclabuvir/BCV in association with other drugs to evaluate its real potential in the treatment of patients with HCV infection and advanced liver disease.

With respect to the choice of the best combination at the best price we underline that most patients enrolled in clinical trial were infected with HCV genotype 1. This is the most common genotype worldwide. However, for this genotype, we have several combinations that have similar excellent SVR rates such as sofosbuvir/ledipasvir, sofosbuvir/DCV, sofosbuvir/simeprevir, ombitasvir-paritaprevir-ritonavir and dasabuvir. What this new drug and the different combinations can add is, above all, an increase in the options for the physicians. This, from one side, makes possible a tailored therapy for the single patient due to the possible drug-drug interaction, presence of resistance or contraindications. From the other side, a large armamentarium of different drugs against HCV increases competition among pharmaceutical companies. A basic market role is that a large competition decreases the price of the goods. This can have very important consequences especially for developing countries that cannot afford the current high price of these drugs.

Finally, a frequent finding in common clinical practice is the management of patients with HCV extrahepatic diseases (such as mixed cryoglobulins or non-Hodgkin lymphoma) which can be life threatening and severely impair the quality of life Citation[76-78]. However, in several circumstances extrahepatic damages are not quantifiable. Indeed, HCV infection has been associated with some metabolic-related disorders such as atherosclerosis, diabetes mellitus and overall cardiovascular risk. Therefore, it is not surprising that some data show a reduction of cardiovascular-related mortality in HCV-patients who achieve an SVR Citation[79]. Some aspects of Beclabuvir/BCV use need to be assessed. They include the efficacy in non-1 genotype. In fact, despite an in vitro, pan-genotypic activity, clinical use to non-1 genotypes is limited to 21 patients with genotype 4; the potential drug-drug interaction of BCV which is a substrate of CYP3A4 and an inhibitor of OATP1B1 and P-glycoprotein. For this reason studies that evaluate the pharmacokinetic of BCV when combined with some commonly used drugs are awaited.

Therefore, Beclabuvir/BCV represents a valid drug that has a good tolerability and safety profile and, together with other antivirals is associated with an optimal efficacy against HCV in compensated phases of the diseases. [1]

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Median time to maximum plasma concentrations (Tmax) for Beclabuvir and its metabolite BMS-794712 were 2 h at each dose (Fig. S3). Exposure to both beclabuvir and BMS-794712 at treatment week 12 was greater than dose proportional, with a metabolite:parent AUC ratio of ~0.23–0.25, which is consistent with previous single-dose data (100–900 mg) from a Beclabuvir phase 1 study. No association was observed between composite trough concentrations of beclabuvir and achievement of a virologic response (eRVR, SVR24, RVR, cEVR, SVR12; Fig. S4a and data not shown), incidence of SAEs, or discontinuations for AEs (Fig. S4a). There was also no continuous association between drug exposure and changes from baseline in select clinical laboratory endpoints, including total bilirubin (Fig. S4b), ALT, haemoglobin or absolute neutrophils (data not shown); however, the caveat exists that trough levels are an indirect indication of peak exposure.

Together, these data show that Beclabuvir is effective and well tolerated in combination with pegIFN/RBV for the treatment of chronic HCV GT1, and support the use of beclabuvir in all-oral regimens. Based on these results and similar data involving the DAAs daclatasvir (DCV; NS5A inhibitor) and asunaprevir (ASV), a phase 2b study in GT1 was initiated with the triple DAA combination Beclabuvir (75 mg or 150 mg), DCV (60 mg) and ASV (200 mg). In a pilot cohort (N = 66), this all-oral combination achieved SVR12 in 92% of patients after 12 or 24 weeks of treatment, with response rates apparently independent of either IL28B genotype and treatment duration. Similar efficacy and safety findings with this three-DAA regimen, using either the 75-mg or 150-mg beclabuvir dose, were subsequently reported for a larger (N = 166) cohort of patients treated for 12 weeks. Further phase 3 studies of the triple regimen of beclabuvir (75-mg dose) plus DCV and ASV as a fixed-dose combination pill are being conducted, targeting treatment-naive as well as -experienced patient populations.[2]

C36H45N5O5S

659.84

659.314

C, 65.53; H, 6.87; N, 10.61; O, 12.12; S, 4.86

958002-33-0

958002-36-3 (HCl);958002-33-0;

49773361

White to off-white solid powder

1.5±0.1 g/cm3

1.722

4.71

1

7

6

47

1320

2

CN1CC2CCC(C1)N2C(=O)[C@]34C[C@H]3C5=C(C=CC(=C5)OC)C6=C(C7=C(N6C4)C=C(C=C7)C(=O)NS(=O)(=O)N(C)C)C8CCCCC8

ZTTKEBYSXUCBSE-VSBZUFFNSA-N

InChI=1S/C36H45N5O5S/c1-38(2)47(44,45)37-34(42)23-10-14-28-31(16-23)40-21-36(35(43)41-24-11-12-25(41)20-39(3)19-24)18-30(36)29-17-26(46-4)13-15-27(29)33(40)32(28)22-8-6-5-7-9-22/h10,13-17,22,24-25,30H,5-9,11-12,18-21H2,1-4H3,(H,37,42)/t24?,25?,30-,36-/m0/s1

(8S,10R)-19-cyclohexyl-N-(dimethylsulfamoyl)-5-methoxy-10-(3-methyl-3,8-diazabicyclo[3.2.1]octane-8-carbonyl)-12-azapentacyclo[10.7.0.02,7.08,10.013,18]nonadeca-1(19),2(7),3,5,13(18),14,16-heptaene-15-carboxamide

Beclabuvir; Beclabuvir [USAN:INN]; MYW1X5CO9S; Beclabuvir [USAN]; BMS-791325; BECLABUVIR [MI]; BECLABUVIR [INN]; ...; 958002-33-0;

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO : ≥ 30 mg/mL (45.47 mM)

Solubility in Formulation 1: ≥ 2.5 mg/mL (3.79 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.5 mg/mL (3.79 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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Solubility in Formulation 3: ≥ 2.5 mg/mL (3.79 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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 (Please use freshly prepared in vivo formulations for optimal results.)