No abstract

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).

SUMMARY Polyglutamine (polyQ) stretches exceeding a threshold length confer a toxic function on proteins that contain them and cause at least nine neurological disorders. The basis for this toxicity threshold is unclear. Although polyQ expansions render proteins prone to aggregate into inclusion bodies (IBs), IB formation may be a neuronal coping response to more toxic forms of polyQ. The exact structure of these more toxic forms is unknown. Here we show that monoclonal antibody (mAb) 3B5H10 recognizes a species of polyQ protein in situ that strongly predicts neuronal death. The epitope selectively appears among some of the many low-molecular weight conformational states expanded polyQ assumes and disappears in higher molecular-weight aggregated forms, such as IBs. These results suggest that protein monomers and possibly small oligomers containing expanded polyQ stretches can adopt a conformation that is recognized by 3B5H10 and is toxic or closely related to a toxic species.

Well‐tolerated, ribavirin‐free, pangenotypic hepatitis C virus (HCV) treatments for transplant recipients remain a high priority. Once‐daily glecaprevir/pibrentasvir demonstrates high rates of sustained virologic response at 12 weeks posttreatment (SVR12) across all major HCV genotypes (GTs). This trial evaluated the safety and efficacy of glecaprevir/pibrentasvir for patients with chronic HCV GT1‐6 infection who had received a liver or kidney transplant. MAGELLAN‐2 was a phase 3, open‐label trial conducted in patients who were ≥3 months posttransplant. Patients without cirrhosis who were HCV treatment‐naive (GT1‐6) or treatment‐experienced (GT1, 2, 4‐6; with interferon‐based therapy with or without sofosbuvir, or sofosbuvir plus ribavirin) received glecaprevir/pibrentasvir (300/120 mg) once daily for 12 weeks. The primary endpoint compared the percentage of patients receiving glecaprevir/pibrentasvir with SVR12 to a historic SVR12 rate based on the standard of care. Safety of glecaprevir/pibrentasvir was assessed. In total, 80 liver transplant and 20 kidney transplant patients participated in the trial. Most patients had no or minimal fibrosis (80% had fibrosis scores F0‐F1) and were infected with HCV GT1 (57%) or GT3 (24%). The overall SVR12 was 98% (n/N = 98/100; 95% confidence interval, 95.3%–100%), which exceeded the prespecified historic standard‐of‐care SVR12 threshold of 94%. One patient experienced virologic failure. One patient discontinued because of an adverse event considered to be unrelated to treatment; this patient achieved SVR12. Adverse events were mostly mild in severity, and laboratory abnormalities were infrequent. Conclusion: Once‐daily glecaprevir/pibrentasvir for 12 weeks is a well‐tolerated and efficacious, ribavirin‐free treatment for patients with chronic HCV GT1‐6 infection who have received a liver or kidney transplant. (http://ClinicalTrials.gov NCT02692703.) (Hepatology 2018; 00:000‐000).

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.

Ombitasvir (ABT-267) is a hepatitis C virus (HCV) NS5A inhibitor with picomolar potency, pan-genotypic activity, and 50% effective concentrations (EC 50 s) of 0.82 to 19.3 pM against HCV genotypes 1 to 5 and 366 pM against genotype 6a. Ombitasvir retained these levels of potency against a panel of 69 genotype 1 to 6 chimeric replicons containing the NS5A gene derived from HCV-infected patients, despite the existence of natural sequence diversity within NS5A. In vitro resistance selection identified variants that conferred resistance to ombitasvir in the HCV NS5A gene at amino acid positions 28, 30, 31, 58, and 93 in genotypes 1 to 6. Ombitasvir was evaluated in vivo in a 3-day monotherapy study in 12 HCV genotype 1-infected patients at 5, 25, 50, or 200 mg dosed once daily. All patients in the study were HCV genotype 1a infected and were without preexisting resistant variants at baseline as determined by clonal sequencing. Decreases in HCV RNA up to 3.1 log 10 IU/ml were observed. Resistance-associated variants at position 28, 30, or 93 in NS5A were detected in patient samples 48 hours after the first dose. Clonal sequencing analysis indicated that wild-type virus was largely suppressed by ombitasvir during 3-day monotherapy, and at doses higher than 5 mg, resistant variant M28V was also suppressed. Ombitasvir was well tolerated at all doses, and there were no serious or severe adverse events. HCV genotype 1, predominant in North America, Europe, and Japan, accounts for 60% of the global infections (4-6). Genotype 2 infections are most prevalent in North America, Europe, and Japan, while genotype 3, 6, and 7 infections are predominant within various parts of Southeast Asia (3, 7-9). In Egypt, HCV infections are almost exclusively genotype 4, while genotype 5 is common in South Africa (10, 11). The levels of nucleotide sequence diversity between genotypes and between subtypes are 30 to 35% and 20 to 25%, respectively (12). The viral dynamics are rapid for HCV, with 10 12 virions being produced daily with a half-life of 45 min (13). Moreover, the RNA-dependent RNA polymerase of HCV is intrinsically error prone, and its lack of a proofreading function allows for introduction of approximately one nucleotide change per genome per replication cycle, which under drug pressure results in the expansion of preexisting drug resistant variants (13). These factors have created challenges in developing pan-genotypic HCV inhibitors with high genetic barriers to the development of resistance.HCV replication can be inhibited at various points in the replication cycle by targeting viral or host cell functions (14,15). For the treatment of HCV genotype 1, three HCV NS3/4A protease inhibitors (telaprevir, boceprevir, and simeprevir) and one nucleoside NS5B polymerase inhibitor (sofosbuvir), each in combination with pegylated interferon (pegIFN) and ribavirin (RBV), have received marketing approval in the United States and Europe. The sustained virologic response (SVR) rate increased from 40 to 52% with pegIFN and RBV regimens to 67...

BackgroundOnce-daily, orally administered, co-formulated glecaprevir (NS3/4A protease inhibitor) and pibrentasvir (NS5A inhibitor) (G/P) demonstrated pangenotypic activity and high sustained virologic response (SVR) rates in studies outside Japan. Here we report safety and efficacy in a subset of Japanese patients with chronic HCV infection who received G/P 300/120 mg in a phase 3, open-label, multicenter study (CERTAIN-1).MethodsThis analysis focuses on three difficult-to-treat subgroups: HCV GT1/2-infected patients who failed to achieve SVR after treatment with a direct acting antiviral (DAA)-containing regimen; GT1/2-infected patients with severe renal impairment (estimated glomerular filtration rate < 30 mL/min/1.73 m2); and GT3-infected patients. Patients in the renal impairment and GT3 cohorts were treatment-naive or interferon treatment-experienced. Noncirrhotic GT1/2-infected, DAA-naïve patients in the renal impairment cohort received G/P for 8 weeks; all other patients were treated for 12 weeks. Primary outcome was SVR (HCV RNA < 15 IU/mL) 12 weeks post-treatment (SVR12).ResultsThe study enrolled 33 GT1/2-infected patients who failed previous DAA treatment (four with cirrhosis); 12 GT1/2-infected patients with severe renal impairment (two with cirrhosis); and 12 GT3-infected patients (two with cirrhosis). SVR12 was achieved by 31/33 (93.9%), 12/12 (100%), and 10/12 (83.3%) patients, respectively. One serious adverse event (fluid overload, not related to G/P) occurred in a patient on chronic intermittent hemodialysis.ConclusionsG/P achieved high SVR12 rates and was well tolerated in three difficult-to-treat patient subgroups with limited treatment options in Japan (DAA-experienced patients, patients with severe renal impairment, and GT3-infected patients). These results support the potential suitability of this regimen for these special populations in Japan.Electronic supplementary materialThe online version of this article (doi:10.1007/s00535-017-1396-0) contains supplementary material, which is available to authorized users.

This study assessed the efficacy and safety of ribavirin‐free coformulated glecaprevir/pibrentasvir (G/P) in patients with hepatitis C virus genotype 3 infection with prior treatment experience and/or compensated cirrhosis, a patient population with limited treatment options. SURVEYOR‐II, Part 3 was a partially randomized, open‐label, multicenter, phase 3 study. Treatment‐experienced (prior interferon or pegylated interferon ± ribavirin or sofosbuvir plus ribavirin ± pegylated interferon therapy) patients without cirrhosis were randomized 1:1 to receive 12 or 16 weeks of G/P (300 mg/120 mg) once daily. Treatment‐naive or treatment‐experienced patients with compensated cirrhosis were treated with G/P for 12 or 16 weeks, respectively. The primary efficacy endpoint was the percentage of patients with sustained virologic response at posttreatment week 12 (SVR12). Safety was evaluated throughout the study. There were 131 patients enrolled and treated. Among treatment‐experienced patients without cirrhosis, SVR12 was achieved by 91% (20/22; 95% confidence interval [CI], 72‐97) and 95% (21/22; 95% CI, 78‐99) of patients treated with G/P for 12 or 16 weeks, respectively. Among those with cirrhosis, SVR12 was achieved by 98% (39/40; 95% CI, 87‐99) of treatment‐naive patients treated for 12 weeks and 96% (45/47; 95% CI, 86‐99) of patients with prior treatment experience treated for 16 weeks. No adverse events led to discontinuation of study drug, and no serious adverse events were related to study drug. Conclusion: Patients with hepatitis C virus genotype 3 infection with prior treatment experience and/or compensated cirrhosis achieved high SVR12 rates following 12 or 16 weeks of treatment with G/P. The regimen was well tolerated. (Hepatology 2018;67:514‐523).