Glecaprevir-Pibrentasvir for 8 or 12 Weeks in HCV Genotype 1 or 3 Infection.

BACKGROUND: Glecaprevir and pibrentasvir are direct-acting antiviral agents with pangenotypic activity and a high barrier to resistance. We evaluated the efficacy and safety of 8-week and 12-week courses of treatment with 300 mg of glecaprevir plus 120 mg of pibrentasvir in patients without cirrhosis who had hepatitis C virus (HCV) genotype 1 or 3 infection. METHODS: We conducted two phase 3, randomized, open-label, multicenter trials. Patients with genotype 1 infection were randomly assigned in a 1:1 ratio to receive once-daily glecaprevir-pibrentasvir for either 8 or 12 weeks. Patients with genotype 3 infection were randomly assigned in a 2:1 ratio to receive 12 weeks of treatment with either glecaprevir-pibrentasvir or sofosbuvir-daclatasvir. Additional patients with genotype 3 infection were subsequently enrolled and nonrandomly assigned to receive 8 weeks of treatment with glecaprevir-pibrentasvir. The primary end point was the rate of sustained virologic response 12 weeks after the end of treatment. RESULTS: In total, 1208 patients were treated. The rate of sustained virologic response at 12 weeks among genotype 1-infected patients was 99.1% (95% confidence interval [CI], 98 to 100) in the 8-week group and 99.7% (95% CI, 99 to 100) in the 12-week group. Genotype 3-infected patients who were treated for 12 weeks had a rate of sustained virologic response at 12 weeks of 95% (95% CI, 93 to 98; 222 of 233 patients) with glecaprevir-pibrentasvir and 97% (95% CI, 93 to 99.9; 111 of 115) with sofosbuvir-daclatasvir; 8 weeks of treatment with glecaprevir-pibrentasvir yielded a rate of 95% (95% CI, 91 to 98; 149 of 157 patients). Adverse events led to discontinuation of treatment in no more than 1% of patients in any treatment group. CONCLUSIONS: Once-daily treatment with glecaprevir-pibrentasvir for either 8 weeks or 12 weeks achieved high rates of sustained virologic response among patients with HCV genotype 1 or 3 infection who did not have cirrhosis. (Funded by AbbVie; ENDURANCE-1 and ENDURANCE-3 ClinicalTrials.gov numbers, NCT02604017 and NCT02640157 .).

Pharmacokinetics, Safety, and Efficacy of Glecaprevir/Pibrentasvir in Adolescents With Chronic Hepatitis C Virus: Part 1 of the DORA Study.

The pangenotypic regimen of glecaprevir and pibrentasvir (G/P) is approved to treat adults with chronic hepatitis C virus (HCV) infection and has yielded high cure rates in adults in clinical trials. Approved treatment options for pediatrics may include ribavirin. A pangenotypic regimen for pediatric patients remains an unmet need. DORA is an ongoing phase 2/3, nonrandomized, open-label study evaluating the pharmacokinetics (PK), safety, and efficacy of G/P in pediatric patients with chronic HCV. This analysis includes Part 1 of the study, conducted in adolescent patients 12-17 years of age given the adult regimen of G/P (300 mg/120 mg) once daily for 8-16 weeks according to the indication durations used in adults. Patients were either treatment naïve or experienced with interferon-based regimens. The primary PK endpoint was steady-state exposures for glecaprevir and pibrentasvir; the primary efficacy endpoint was sustained virologic response 12 weeks after treatment (SVR12). The secondary efficacy endpoints were on-treatment virologic failure, relapse, and reinfection. Safety and tolerability were monitored. Part 1 enrolled 48 adolescent patients infected with genotypes 1, 2, 3, or 4, of whom 47 were administered G/P. All 47 patients (100%) achieved SVR12. No on-treatment virologic failures or relapses occurred. PK exposures of glecaprevir and pibrentasvir were comparable to exposures in adults. No adverse events (AEs) led to treatment discontinuation, and no serious AEs occurred. Conclusion: Adolescent patients with chronic HCV infection treated with G/P achieved a comparable exposure to adults, 100% SVR12 rate, and safety profile consistent with that in adults. This pangenotypic regimen demonstrated 100% efficacy within the adolescent population in as little as 8 weeks of treatment.

Glecaprevir/Pibrentasvir in patients with chronic HCV genotype 3 infection: An integrated phase 2/3 analysis.

Glecaprevir coformulated with pibrentasvir (G/P) is approved to treat hepatitis C virus (HCV) infection and was highly efficacious in phase 2 and 3 studies. Treating HCV genotype (GT) 3 infection remains a priority, as these patients are harder to cure and at a greater risk for liver steatosis, fibrosis progression and hepatocellular carcinoma. Data were pooled from five phase 2 or 3 trials that evaluated 8-, 12- and 16-week G/P in patients with chronic HCV GT3 infection. Patients without cirrhosis or with compensated cirrhosis were either treatment-naïve or experienced with interferon- or sofosbuvir-based regimens. Safety and sustained virologic response 12 weeks post-treatment (SVR12) were assessed. The analysis included 693 patients with GT3 infection. SVR12 was achieved by 95% of treatment-naïve patients without cirrhosis receiving 8-week (198/208) and 12-week (280/294) G/P. Treatment-naïve patients with cirrhosis had a 97% (67/69) SVR12 rate with 12-week G/P. Treatment-experienced, noncirrhotic patients had SVR12 rates of 90% (44/49) and 95% (21/22) with 12- and 16-week G/P, respectively; 94% (48/51) of treatment-experienced patients with cirrhosis treated for 16 weeks achieved SVR12. No serious adverse events (AEs) were attributed to G/P; AEs leading to study drug discontinuation were rare (<1%). G/P was well-tolerated and efficacious for patients with chronic HCV GT3 infection, regardless of cirrhosis status or prior treatment experience. Eight- and 12-week durations were efficacious for treatment-naïve patients without cirrhosis and with compensated cirrhosis, respectively; 16-week G/P was efficacious in patients with prior treatment experience irrespective of cirrhosis status.

Glecaprevir/Pibrentasvir in patients with hepatitis C virus genotype 1 or 4 and past direct-acting antiviral treatment failure.

Patients with hepatitis C virus (HCV) who have virological failure (VF) after treatment containing a nonstructural protein 5A (NS5A) inhibitor have limited retreatment options. MAGELLAN-1 Part 2 was a randomized, open-label, phase 3 study to evaluate the efficacy and safety of ribavirin (RBV)-free glecaprevir and pibrentasvir (G/P; 300 mg/120 mg) in patients with chronic HCV and past VF on at least one NS3/4A protease and/or NS5A inhibitor-containing therapy. Patients with compensated liver disease, with or without cirrhosis, and HCV genotype (GT) 1, 4, 5, or 6 were randomized 1:1 to receive 12 or 16 weeks of G/P. The primary endpoint was sustained virological response (SVR) at 12 weeks posttreatment (SVR12). Among 91 patients treated, 87 had GT1 and 4 had GT4 infection. SVR12 was achieved by 89% (39 of 44) and 91% (43 of 47) of patients who received 12 and 16 weeks of G/P, respectively. Virological relapse occurred in 9% (4 of 44) of patients treated with 12 weeks of G/P; there were no relapses with 16 weeks of treatment. Past treatment history with one class of inhibitor (protease or NS5A) had no impact on SVR12, whereas past treatment with both classes of inhibitors was associated with lower SVR12 rate. The most common adverse event (AE) was headache (≥10% of patients), and there were no serious AEs assessed as related to study drugs or AEs leading to discontinuation. CONCLUSION: Sixteen weeks of G/P treatment achieved a high SVR12 rate in patients with HCV GT1 infection and past failure to regimens containing either NS5A inhibitors or NS3 protease inhibitors. (Hepatology 2018;67:1253-1260).

Efficacy and Safety of Glecaprevir/Pibrentasvir in Patients Coinfected With Hepatitis C Virus and Human Immunodeficiency Virus Type 1: The EXPEDITION-2 Study.

Background: Once-daily glecaprevir coformulated with pibrentasvir (glecaprevir/pibrentasvir) demonstrated high rates of sustained virologic response 12 weeks after treatment (SVR12) in patients with hepatitis C virus (HCV) genotype 1-6 infection. This phase 3 study evaluated the efficacy and safety of glecaprevir/pibrentasvir in patients with chronic HCV genotype 1-6 and human immunodeficiency virus type 1 (HIV-1) coinfection, including patients with compensated cirrhosis. Methods: EXPEDITION-2 was a phase 3, multicenter, open-label study evaluating glecaprevir/pibrentasvir (300 mg/120 mg) in HCV genotype 1-6/HIV-1-coinfected adults without and with compensated cirrhosis for 8 and 12 weeks, respectively. Patients were either HCV treatment-naive or experienced with sofosbuvir, ribavirin, or interferon, and antiretroviral therapy (ART) naive or on a stable ART regimen. Treatment-experienced genotype 3-infected patients were excluded. The primary endpoint was the SVR12 rate. Results: In total, 153 patients were enrolled, including 16 (10%) with cirrhosis. The SVR12 rate was 98% (n = 150/153; 95% confidence interval, 95.8-100), with no virologic failures in 137 patients treated for 8 weeks. One genotype 3-infected patient with cirrhosis had on-treatment virologic failure. Most adverse events were mild in severity; 4 patients (2.6%) had serious adverse events, all deemed unrelated to glecaprevir/pibrentasvir. Treatment discontinuation was rare (<1%). All patients treated with ART maintained HIV-1 suppression (<200 copies/mL) during treatment. Conclusions: Glecaprevir/pibrentasvir for 8 weeks in noncirrhotic and 12 weeks in cirrhotic patients is a highly efficacious and well-tolerated treatment for HCV/HIV-1 coinfection, regardless of baseline HCV load or prior treatment with interferon or sofosbuvir. Clinical trial registration: NCT02738138.

Pooled Resistance Analysis in Patients with Hepatitis C Virus Genotype 1 to 6 Infection Treated with Glecaprevir-Pibrentasvir in Phase 2 and 3 Clinical Trials.

Over 2,200 patients infected with hepatitis C virus (HCV) genotypes (GT) 1 to 6, with or without cirrhosis, who were treatment naive or experienced to interferon, ribavirin, and/or sofosbuvir were treated with glecaprevir/pibrentasvir for 8, 12, or 16 weeks in eight registrational phase 2 and 3 clinical studies. High rates of sustained virologic response at 12 weeks postdosing (SVR12) were achieved with a <1% virologic failure (VF) rate. The prevalence of baseline polymorphisms (BPs) in NS3 at amino acid position 155 or 168 was low (<3%) in patients infected with GT1, GT2, GT3, GT4, and GT6, while 41.9% of the GT5-infected patients had NS3-D168E; BPs were not detected at position 156 in NS3. The prevalence of NS5A-BPs was high across genotypes, driven by common polymorphisms at amino acid position 30 or 31 in GT2, 58 in GT4, and 28 in GT6. The prevalence of NS5A T/Y93 polymorphisms was 5.5% in GT1, 4.9% in GT3, and 12.5% in GT6. Consistent with the activity of glecaprevir and pibrentasvir against most amino acid polymorphisms in vitro, BPs in NS3 and/or NS5A did not have an impact on treatment outcome for patients infected with GT1 to GT6, with the exception of treatment-experienced GT3-infected patients treated for 12 weeks, for whom a 16-week regimen of glecaprevir/pibrentasvir was required to achieve SVR12 rates of ≥95%. Among the 22 patients experiencing VF, treatment-emergent substitutions were detected in NS3 in 50% of patients and in NS5A in 82% of patients, frequently as a combination of substitutions that conferred resistance to glecaprevir and/or pibrentasvir. The glecaprevir/pibrentasvir regimen, when the recommended durations are used, allows for a pan-genotypic treatment option without the need for baseline resistance testing.

In Vitro Antiviral Activity and Resistance Profile of the Next-Generation Hepatitis C Virus NS3/4A Protease Inhibitor Glecaprevir.

Glecaprevir (formerly ABT-493) is a novel hepatitis C virus (HCV) NS3/4A protease inhibitor (PI) with pangenotypic activity. It inhibited the enzymatic activity of purified NS3/4A proteases from HCV genotypes 1 to 6 in vitro (half-maximal [50%] inhibitory concentration = 3.5 to 11.3 nM) and the replication of stable HCV subgenomic replicons containing proteases from genotypes 1 to 6 (50% effective concentration [EC50] = 0.21 to 4.6 nM). Glecaprevir had a median EC50 of 0.30 nM (range, 0.05 to 3.8 nM) for HCV replicons containing proteases from 40 samples from patients infected with HCV genotypes 1 to 5. Importantly, glecaprevir was active against the protease from genotype 3, the most-difficult-to-treat HCV genotype, in both enzymatic and replicon assays demonstrating comparable activity against the other HCV genotypes. In drug-resistant colony selection studies, glecaprevir generally selected substitutions at NS3 amino acid position A156 in replicons containing proteases from genotypes 1a, 1b, 2a, 2b, 3a, and 4a and substitutions at position D/Q168 in replicons containing proteases from genotypes 3a, 5a, and 6a. Although the substitutions A156T and A156V in NS3 of genotype 1 reduced susceptibility to glecaprevir, replicons with these substitutions demonstrated a low replication efficiency in vitro Glecaprevir is active against HCV with most of the common NS3 amino acid substitutions that are associated with reduced susceptibility to other currently approved HCV PIs, including those at positions 155 and 168. Combination of glecaprevir with HCV inhibitors with other mechanisms of action resulted in additive or synergistic antiviral activity. In summary, glecaprevir is a next-generation HCV PI with potent pangenotypic activity and a high barrier to the development of resistance.

Efficacy of Glecaprevir/Pibrentasvir for 8 or 12 Weeks in Patients With Hepatitis C Virus Genotype 2, 4, 5, or 6 Infection Without Cirrhosis.

BACKGROUND & AIMS: Hepatitis C virus (HCV) has high genotypic diversity and global distribution. Agents that are effective against all major HCV genotypes, with shorter treatment duration, are needed to reduce disease burden. Glecaprevir (an NS3/4A protease inhibitor) and pibrentasvir (an NS5A inhibitor) have a high barrier to resistance and synergistic antiviral activity. We evaluated the safety and efficacy of 8 and 12 weeks' treatment with glecaprevir/pibrentasvir in patients with HCV genotype 2, 4, 5, or 6 infection without cirrhosis in 3 separate phase 3 trials. METHODS: We performed 2 open label, single-arm studies (SURVEYOR-II, Part 4 and ENDURANCE-4) and a randomized, double-blind, placebo-controlled study (ENDURANCE-2). In the ENDURANCE-2 study, adult patients with untreated or previously treated HCV genotype 2 infection without cirrhosis were randomly assigned (2:1) to groups given once-daily oral glecaprevir/pibrentasvir (n = 202; 300 mg/120 mg) or placebo (n = 100) for 12 weeks. In the SURVEYOR-II, Part 4 and ENDURANCE-4 studies, adult patients with untreated or previously treated patients with HCV genotype 2, genotype 4, genotype 5, or genotype 6 infection, without cirrhosis, were given once-daily oral glecaprevir/pibrentasvir (n = 121 in ENDURANCE-4 and n = 145 in SURVEYOR-II) for 12 or 8 weeks, respectively. In all studies the primary endpoint was sustained virologic response at 12 weeks after treatment (SVR12) in the intention-to-treat population. RESULTS: Among patients receiving glecaprevir/pibrentasvir for 8 weeks, rates of SVR12 were 98% (95% CI, 94.1-99.3) in those infected with HCV genotype 2 and 93% (95% CI, 83.6-97.3) in those infected with HCV genotypes 4, 5, or 6. Among patients receiving glecaprevir/pibrentasvir for 12 weeks, rates of SVR12 were 99.5% (95% CI, 98.5-100) in those infected with HCV genotype 2 and 99% (95% CI, 97.6-100) in those infected with HCV genotype 4, 5, or 6. No virologic failures occurred in patients with HCV genotype 4, 5, or 6 infections. The frequency and severity of adverse events in patients receiving glecaprevir/pibrentasvir were similar to those of patients who received placebo. CONCLUSION: In 3 Phase 3 studies, 8 weeks' treatment with glecaprevir/pibrentasivr produced an SVR12 in at least 93% of patients with chronic HCV genotype 2, 4, 5, or 6 infection without cirrhosis, with virologic failure in less than 1%. The drug combination had a safety profile comparable to 12 week's treatment with glecaprevir/pibrentasvir. ClinicalTrials.gov numbers: NCT02640482 (ENDURANCE-2), NCT02636595 (ENDURANCE-4), and NCT02243293 (SURVEYOR-II).

Glecaprevir and pibrentasvir for 12 weeks for hepatitis C virus genotype 1 infection and prior direct-acting antiviral treatment.

Although direct-acting antiviral (DAA) therapies for chronic hepatitis C virus (HCV) infection have demonstrated high rates of sustained virologic response, virologic failure may still occur, potentially leading to the emergence of viral resistance, which can decrease the effectiveness of subsequent treatment. Treatment options for patients who failed previous DAA-containing regimens, particularly those with nonstructural protein 5A inhibitors, are limited and remain an area of unmet medical need. This phase 2, open-label study (MAGELLAN-1) evaluated the efficacy and safety of glecaprevir (GLE) + pibrentasvir (PIB) ± ribavirin (RBV) in HCV genotype 1-infected patients with prior virologic failure to HCV DAA-containing therapy. A total of 50 patients without cirrhosis were randomized to three arms: 200 mg GLE + 80 mg PIB (arm A), 300 mg GLE + 120 mg PIB with 800 mg once-daily RBV (arm B), or 300 mg GLE + 120 mg PIB without RBV (arm C). By intent-to-treat analysis, sustained virologic response at posttreatment week 12 was achieved in 100% (6/6, 95% confidence interval 61-100), 95% (21/22, 95% confidence interval 78-99), and 86% (19/22, 95% confidence interval 67-95) of patients in arms A, B, and C, respectively. Virologic failure occurred in no patients in arm A and in 1 patient each in arms B and C (two patients were lost to follow-up in arm C). The majority of adverse events were mild in severity; no serious adverse events related to study drug and no relevant laboratory abnormalities in alanine aminotransferase, total bilirubin, or hemoglobin were observed. CONCLUSION: The combination of GLE and PIB was highly efficacious and well tolerated in patients with HCV genotype 1 infection and prior failure of DAA-containing therapy; RBV coadministration did not improve efficacy. (Hepatology 2017;66:389-397).

Glecaprevir and pibrentasvir yield high response rates in patients with HCV genotype 1-6 without cirrhosis.

BACKGROUND & AIMS: Hepatitis C virus (HCV) therapy that is highly efficacious, pangenotypic, with a high barrier to resistance and short treatment duration is desirable. The efficacy and safety of 8- and 12-week treatments with glecaprevir (ABT-493; NS3/4A protease inhibitor) and pibrentasvir (ABT-530; NS5A inhibitor) were evaluated in non-cirrhotic patients with chronic HCV genotype 1-6 infection. METHODS: SURVEYOR-I and SURVEYOR-II were phase II, open-label, multicenter, dose-ranging trials including patients with chronic HCV genotype 1-6 infection who were either previously untreated or treated with pegylated interferon plus ribavirin. Patients received once-daily glecaprevir plus pibrentasvir at varying doses with or without ribavirin for 8 or 12weeks. The primary efficacy endpoint was the percentage of patients with a sustained virologic response at post-treatment week 12 (SVR12). RESULTS: Of the 449 patients who received varying doses of glecaprevir plus pibrentasvir, 25%, 29%, 39%, and 8% had HCV genotype 1, 2, 3, and 4-6 infection, respectively. Twelve-week treatment achieved SVR12 in 97-100%, 96-100%, 83-94%, and 100% in genotypes 1, 2, 3, and 4-6, respectively. Eight-week treatment with 300mg glecaprevir plus 120mg pibrentasvir in genotype 1-, 2-, or 3-infected patients yielded 97-98% SVR12 with no virologic failures. Three (0.7%) patients discontinued treatment due to adverse events; most events were mild (grade 1) in severity. No post-nadir alanine aminotransferase elevations were observed. CONCLUSIONS: Glecaprevir plus pibrentasvir was well tolerated and achieved high sustained virologic response rates in HCV genotypes 1-6-infected patients without cirrhosis following 8- or 12-week treatment durations. LAY SUMMARY: The combination of direct-acting antivirals glecaprevir and pibrentasvir comprise a once-daily, all-oral, pangenotypic treatment for HCV genotype 1-6 infection. This article describes results from two phase II trials investigating a range of doses at treatment durations of 8 or 12weeks in 449 patients without cirrhosis. Efficacy of the optimal dose, as determined by rates of sustained virologic response at post-treatment week 12, ranged from 92%-100%; treatment was well tolerated and significant laboratory abnormalities were rare. CLINICAL TRIAL REGISTRATION: clinicaltrials.gov Identifiers: NCT02243280 and NCT02243293. http://www.clinicaltrials.gov/show/NCT02243280, http://www.clinicaltrials.gov/show/NCT01939197.

In Vitro Antiviral Activity and Resistance Profile of the Next-Generation Hepatitis C Virus NS5A Inhibitor Pibrentasvir.

Pibrentasvir (ABT-530) is a novel and pan-genotypic hepatitis C virus (HCV) NS5A inhibitor with 50% effective concentration (EC50) values ranging from 1.4 to 5.0 pM against HCV replicons containing NS5A from genotypes 1 to 6. Pibrentasvir demonstrated similar activity against a panel of chimeric replicons containing HCV NS5A of genotypes 1 to 6 from clinical samples. Resistance selection studies were conducted using HCV replicon cells with NS5A from genotype 1a, 1b, 2a, 2b, 3a, 4a, 5a, or 6a at a concentration of pibrentasvir that was 10- or 100-fold over its EC50 for the respective replicon. With pibrentasvir at 10-fold over the respective EC50, only a small number of colonies (0.00015 to 0.0065% of input cells) with resistance-associated amino acid substitutions were selected in replicons containing genotype 1a, 2a, or 3a NS5A, and no viable colonies were selected in replicons containing NS5A from other genotypes. With pibrentasvir at 100-fold over the respective EC50, very few colonies (0.0002% of input cells) were selected by pibrentasvir in genotype 1a replicon cells while no colonies were selected in other replicons. Pibrentasvir is active against common resistance-conferring substitutions in HCV genotypes 1 to 6 that were identified for other NS5A inhibitors, including those at key amino acid positions 28, 30, 31, or 93. The combination of pibrentasvir with HCV inhibitors of other classes produced synergistic inhibition of HCV replication. In summary, pibrentasvir is a next-generation HCV NS5A inhibitor with potent and pan-genotypic activity, and it maintains activity against common amino acid substitutions of HCV genotypes 1 to 6 that are known to confer resistance to currently approved NS5A inhibitors.

High Efficacy of ABT-493 and ABT-530 Treatment in Patients With HCV Genotype 1 or 3 Infection and Compensated Cirrhosis.

BACKGROUND & AIMS: The combination of ABT-493 (NS3/4A protease inhibitor) plus ABT-530 (NS5A inhibitor) has shown high rates of sustained virologic response at post-treatment week 12 (SVR12) in noncirrhotic patients infected with hepatitis C virus (HCV) genotypes (GTs) 1-6. We describe 2 open-label phase 2 studies investigating the efficacy and safety of ABT-493 plus ABT-530 with or without ribavirin (RBV) in GT1- or GT3-infected patients with compensated cirrhosis. METHODS: Patients with GT1 infection received 200 mg ABT-493 plus 120 mg ABT-530 for 12 weeks. Patients with GT3 infection were randomized 1:1 to receive 300 mg ABT-493 plus 120 mg ABT-530 with or without once-daily 800 mg RBV for 12 weeks; treatment-experienced patients who were not treated with RBV received 16 weeks of therapy. Efficacy was measured by SVR12, defined as an HCV-RNA level less than 25 IU/mL. Adverse events and laboratory parameters were evaluated throughout the study. RESULTS: Twenty-seven patients with GT1 infection and 55 patients with GT3 infection were enrolled. The majority were treatment-naive (84%) and male (65%). In patients with GT1 infection, SVR12 was achieved by 96% (26 of 27; 95% confidence interval [CI], 82-99) of patients, with 1 relapse. Among GT3-infected patients, SVR12 was achieved in 96% (27 of 28; 95% CI, 82-99) of patients in the RBV-free arm (1 relapse), and in 100% (27 of 27; 95% CI, 88-100) in the RBV-containing arm. The most common adverse events were headache, fatigue, and nausea. Laboratory abnormalities were rare; no patient discontinued treatment. CONCLUSIONS: In cirrhotic HCV GT1- or GT3-infected patients, ABT-493 plus ABT-530 with or without RBV achieved SVR12 rates of 96%-100% and was well tolerated. ClinicalTrials.gov identifiers NCT02243280 and NCT02243293.

High antiviral activity of NS5A inhibitor ABT-530 with paritaprevir/ritonavir and ribavirin against hepatitis C virus genotype 3 infection.

BACKGROUND & AIMS: ABT-530 is a next-generation hepatitis C virus (HCV) NS5A inhibitor with potent pangenotypic antiviral activity in vitro. Paritaprevir is an NS3/4A protease inhibitor codosed with ritonavir that displays in vitro activity against HCV genotypes 1-4 and 6. METHODS: Efficacy, pharmacokinetics and safety of ABT-530 with paritaprevir/ritonavir and ribavirin were evaluated in this phase 2, open-label, multicentre study in treatment-naïve non-cirrhotic patients with genotype 3 infection. Ten patients, all genotype 3a, received 120 mg ABT-530 and 150/100 mg paritaprevir/ritonavir once daily with ribavirin for 12 weeks. RESULTS: Nine (90%) patients achieved a sustained virological response at post-treatment weeks 12 and 24. One patient experienced virological failure at treatment week 6. Sequence analyses for HCV variants in samples from this patient identified A166S in NS3 at baseline and after breakthrough, as well as A30K at baseline and linked S24F+M28K+A30K variants in NS5A after breakthrough. Neither genotype 3 NS3 A166S nor NS5A A30K variant confers any resistance to paritaprevir or ABT-530 respectively. However, genotype 3 NS5A S24F+M28K+A30K-linked variant confers a >5000-fold increase in ABT-530 EC50 relative to that of the wild-type replicon. This patient's ABT-530 exposure was comparable to the cohort, while paritaprevir and ritonavir exposures were the lowest of all patients. No serious or severe adverse events and adverse events leading to early discontinuation were reported. CONCLUSIONS: Results from this study show that ABT-530 holds promise as part of a direct-acting antiviral treatment regimen for HCV genotype 3 infection.

Potent Antiviral Activities of the Direct-Acting Antivirals ABT-493 and ABT-530 with Three-Day Monotherapy for Hepatitis C Virus Genotype 1 Infection.

ABT-493 is a hepatitis C virus (HCV) nonstructural (NS) protein 3/4A protease inhibitor, and ABT-530 is an HCV NS5A inhibitor. These direct-acting antivirals (DAAs) demonstrated potent antiviral activity against major HCV genotypes and high barriers to resistance in vitro. In this open-label dose-ranging trial, antiviral activity and safety were assessed during 3 days of monotherapy with ABT-493 or ABT-530 in treatment-naive adults with HCV genotype 1 infection, with or without compensated cirrhosis. The presence of baseline resistance-associated variants (RAVs) was also evaluated. The mean maximal decreases in HCV RNA levels from baseline were approximately 4 log10 IU/ml for all ABT-493 doses ranging from 100 mg to 700 mg and for ABT-530 doses of ≥ 40 mg. There were no meaningful differences in viral load declines for patients with versus without compensated cirrhosis. Twenty-four (50%) of the baseline samples from patients treated with ABT-493 had RAVs to NS3/4A protease inhibitors. Among 40 patients treated with ABT-530, 6 (15%) carried baseline RAVs to NS5A inhibitors. Viral load declines in patients with single baseline NS5A RAVs were similar to those in patients without RAVs. One patient harbored baseline RAVs at 3 NS5A positions and appeared to have a slightly less robust viral load decline on day 3 of monotherapy. No serious or grade 3 (severe) or higher adverse events and no clinically relevant laboratory abnormalities were observed with either compound. ABT-493 and ABT-530 demonstrated potent antiviral activity and acceptable safety during 3-day monotherapy in patients with HCV genotype 1 infection, with or without compensated cirrhosis. Based on these results, phase II studies assessing the combination of these DAAs for the treatment of chronic HCV infection in patients with or without compensated cirrhosis have been initiated. (This study has been registered at ClinicalTrials.gov under registration no. NCT01995071.).

Development of a sensitive high-throughput enzymatic assay capable of measuring sub-nanomolar inhibitors of SARS-CoV2 Mpro.

The SARS-CoV-2 main protease (Mpro) is essential for viral replication because it is responsible for the processing of most of the non-structural proteins encoded by the virus. Inhibition of Mpro prevents viral replication and therefore constitutes an attractive antiviral strategy. We set out to develop a high-throughput Mpro enzymatic activity assay using fluorescently labeled peptide substrates. A library of fluorogenic substrates of various lengths, sequences and dye/quencher positions was prepared and tested against full length SARS-CoV-2 Mpro enzyme for optimal activity. The addition of buffers containing strongly hydrated kosmotropic anion salts, such as citrate, from the Hofmeister series significantly boosted the enzyme activity and enhanced the assay detection limit, enabling the ranking of sub-nanomolar inhibitors without relying on the low-throughput Morrison equation method. By comparing cooperativity in citrate or non-citrate buffer while titrating the Mpro enzyme concentration, we found full positive cooperativity of Mpro with citrate buffer at less than one nanomolar (nM), but at a much higher enzyme concentration (∼320 nM) with non-citrate buffer. In addition, using a tight binding Mpro inhibitor, we confirmed there was only one active catalytical site in each Mpro monomer. Since cooperativity requires at least two binding sites, we hypothesized that citrate facilitates dimerization of Mpro at sub-nanomolar concentration as one of the mechanisms enhances Mpro catalytic efficiency. This assay has been used in high-throughput screening and structure activity relationship (SAR) studies to support medicinal chemistry efforts. IC50 values determined in this assay correlates well with EC50 values generated by a SARS-CoV-2 antiviral assay after adjusted for cell penetration.

Antiviral Drug Discovery for the Treatment of COVID-19 Infections.

The coronavirus disease 2019 (COVID-19) pandemic is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a recently emerged human coronavirus. COVID-19 vaccines have proven to be successful in protecting the vaccinated from infection, reducing the severity of disease, and deterring the transmission of infection. However, COVID-19 vaccination faces many challenges, such as the decline in vaccine-induced immunity over time, and the decrease in potency against some SARS-CoV-2 variants including the recently emerged Omicron variant, resulting in breakthrough infections. The challenges that COVID-19 vaccination is facing highlight the importance of the discovery of antivirals to serve as another means to tackle the pandemic. To date, neutralizing antibodies that block viral entry by targeting the viral spike protein make up the largest class of antivirals that has received US FDA emergency use authorization (EUA) for COVID-19 treatment. In addition to the spike protein, other key targets for the discovery of direct-acting antivirals include viral enzymes that are essential for SARS-CoV-2 replication, such as RNA-dependent RNA polymerase and proteases, as judged by US FDA approval for remdesivir, and EUA for Paxlovid (nirmatrelvir + ritonavir) for treating COVID-19 infections. This review presents an overview of the current status and future direction of antiviral drug discovery for treating SARS-CoV-2 infections, covering important antiviral targets such as the viral spike protein, non-structural protein (nsp) 3 papain-like protease, nsp5 main protease, and the nsp12/nsp7/nsp8 RNA-dependent RNA polymerase complex.

Biomarkers for the clinical development of antiviral therapies.

With the morbidity and mortality associated with the COVID-19 pandemic that we are witnessing this year, the risks posed by emerging viral diseases to global health are all too obvious. This pandemic highlights the importance of antiviral drug discovery, which targets emerging viral pathogens, as well as existing pathogenic viruses that undergo continuous evolution. Drug discovery and development is a long and resource intensive process; however, the use of biomarkers can accelerate clinical development of antivirals by providing information regarding diagnosis of specific viral infections, status of infection, potential safety parameters, and antiviral responses. In clinical practice, many of the biomarkers initially utilized to support clinical development are also used for patient care. While viral load is a standard and essential biomarker used to detect the desired viral suppression induced by an antiviral agent, it has become apparent that additional biomarkers, whether related to the virus, the host or as a consequence of the drug's mechanistic effects, are also important for monitoring clinical outcomes associated with an antiviral therapy. This review summarizes the biomarkers used in the clinical development (as well as in clinical practice, where appropriate) of antiviral therapies for hepatitis C virus, hepatitis B virus, human immunodeficiency virus, and severe acute respiratory syndrome coronavirus 2.

Non-peptide entry inhibitors of HIV-1 that target the gp41 coiled coil pocket.

The ectodomain of HIV-1 gp41 mediates the fusion of viral and host cellular membranes. The peptide-based drug Enfuvirtide(1) is precedent that antagonists of this fusion activity may act as anti HIV-agents. Here, NMR screening was used to discover non-peptide leads against this target and resulted in the discovery of a new benzamide 1 series. This series is non-peptide, low molecular weight, and analogs have activity in a cell fusion assay with EC50 values ranging 3-41microM. Structural work on the gp41/benzamide 1 complex was determined by NMR spectroscopy using a designed model peptide system that mimics an open pocket of the fusogenic form of the protein.

Sequence Analysis of the Fusion Protein Gene of Human Respiratory Syncytial Virus Circulating in China from 2003 to 2014.

The human respiratory syncytial virus (HRSV) fusion (F) protein is important for HRSV infection, but few studies have examined the genetic diversity of the F gene from Chinese samples. In this study, a total of 330 HRSV F sequences collected from different regions of China between 2003 and 2014 were analyzed to understand their genetic characteristics. In addition, these sequences were compared with 1150 HRSV F sequences in Genbank from 18 other countries. In phylogenetic analysis, Chinese HRSV F sequences sorted into a number of clusters containing sequences from China as well as other countries. F sequences from different genotypes (as determined based on the G gene sequences) within a HRSV subgroup could be found in the same clusters in phylogenetic trees generated based on F gene sequences. Amino acid analysis showed that HRSV F sequences from China and other countries were highly conserved. Of interest, F protein sequences from all Chinese samples were completely conserved at the palivizumab binding site, thus predicting the susceptibility of these strains to this neutralizing antibody. In conclusion, HRSV F sequences from China between 2003 and 2014, similar to those from other countries, were highly conserved.

Hepatitis C virus genetic diversity by geographic region within genotype 1-6 subtypes among patients treated with glecaprevir and pibrentasvir.

Hepatitis C virus (HCV) is genetically diverse and includes 7 genotypes and 67 confirmed subtypes, and the global distribution of each HCV genotype (GT) varies by geographic region. In this report, we utilized a large dataset of NS3/4A and NS5A sequences isolated from 2348 HCV GT1-6-infected patients treated with the regimen containing glecaprevir/pibrentasvir (GLE/PIB) to assess genetic diversity within HCV subtypes by geographic region using phylogenetic analyses, and evaluated the prevalence of baseline amino acid polymorphisms in NS3 and NS5A by region/country and phylogenetic cluster. Among 2348 NS3/4A and NS5A sequences, phylogenetic analysis identified 6 genotypes and 44 subtypes, including 3 GT1, 8 GT2, 3 GT3, 13 GT4, 1 GT5, and 16 GT6 subtypes. Phylogenetic analysis of HCV subtype 1a confirmed the presence of two clades, which differed by geographic region distribution and NS3 Q80K prevalence. We detected phylogenetic clustering by country in HCV subtypes 1a, 1b, 2a, 2b, and 5a, suggesting that genetically distinct virus lineages are circulating in different countries. In addition, two clades were detected in HCV GT4a and GT6e, and NS5A amino acid polymorphisms were differentially distributed between the 2 clades in each subtype. The prevalence of NS3 and NS5A baseline polymorphisms varied substantially by genotype and subtype; therefore, we also determined the activity of GLE or PIB against replicons containing NS3/4A or NS5A from HCV GT1-6 clinical samples representing 6 genotypes and 21 subtypes overall. GLE and PIB retained activity against the majority of HCV replicons containing NS3/4A or NS5A from HCV GT1-6 clinical samples, with a median EC50 of 0.29 nM for GLE and 1.1 pM for PIB in a transient replicon assay. The data presented in this report expands the available data on HCV epidemiology, subtype diversity by geographic region, and NS3 and NS5A baseline polymorphism prevalence.