The Z-Profile Study: a multicenter, retrospective cohort study to assess the real-world use and effectiveness of elbasvir/grazoprevir in Canadian adult patients with chronic hepatitis C.

Background: Canada was the first country to approve elbasvir/grazoprevir (EBR/GZR) for the treatment of chronic HCV infection for genotypes 1 and 4 with or without ribavirin and genotype 3 with sofosbuvir, with no recommendation for baseline resistance testing. The aim of this study was to describe the effectiveness of EBR/GZR and the profile of patients selected for treatment in a Canadian real-world setting. Methods: This multicenter retrospective study of HCV-infected patients treated with EBR/GZR took place among selected Canadian health care providers, with no exclusion criteria. Primary outcome measures included parameters associated with patient profile and sustained virologic response at 12 weeks (SVR12) and 24 weeks after treatment. Results: A total of 408 patients were included; 244 had available SVR12 information (per-protocol population [PP]). Genotype distribution included 1a (54.7%), 1b (17.2%), 3 (11.8%), 4 (10.0%), and other (6.4%). The majority (88.7%) of participants were treated for 12 weeks without ribavirin. Fifty-nine (14.5%) participants, predominantly with genotype 1a (49/59) infection, were tested for baseline resistance-associated substitutions (bRAS). SVR12 was achieved by 95.9% of the PP. In an exploratory analysis assessing potential predictors of SVR12, participants who had undergone bRAS testing (OR 0.14, 95% CI 0.03-0.64) and participants who had undergone liver transplant (OR 0.05, 95% CI 0.00-0.68) had significantly lower odds of achieving SVR12. Conclusions: This study supports the real-world effectiveness of EBR/GZR-including a broad range of genotypes and diverse fibrosis stages-in the absence of bRAS testing and in special populations.

Retractile mesenteritis presenting as protein-losing gastroenteropathy.

Retractile mesenteritis is a rare, idiopathic condition characterized by nonspecific inflammation of the mesenteric adipose tissue. The majority of patients present with abdominal pain and/or a palpable mass. In the present report, a 68-year-old man with peripheral edema and mild hypoalbuminemia is presented. Protein-losing gastro-enteropathy was confirmed with an abnormal stool alpha1-antitrypsin clearance test and retractile mesenteritis was diagnosed at laparoscopy. This rare condition may respond to therapy with corticosteroids, azathioprine, cyclophosphamide, colchicine, progesterone, tamoxifen or thalidomide. Gastroenterologists should consider the diagnosis of protein-losing enteropathy in patients who present with unexplained peripheral edema or hypoalbuminemia. The test of choice to confirm this diagnosis is the stool alpha1-antitrypsin clearance test.

Fluorescence based structural analysis of tryptophan analogue-AMP formation in single tryptophan mutants of Bacillus stearothermophilus tryptophanyl-tRNA synthetase.

The symmetrical dimer structure of tryptophanyl-tRNA synthetase is similar to that of tyrosyl-tRNA synthetase whose binding behavior and structural details have been elucidated in detail. The structure of both subunits after forming the intermediate tryptophanyl-AMP has important implications for the binding of the cognate tRNA(Trp). Single tryptophan mutants of Bacillus stearothermophilus tryptophanyl-tRNA synthetase have been constructed and expressed and used to probe structural changes in different domains of the enzyme in both subunits. Substrate titrations using the Trp analogues 4-fluorotryptophan and 7-azatryptophan in the presence of ATP to form the corresponding aminoacyl-adenylate reveal significant structural changes occurring throughout the active subunit in regions not confined to the active site. Changes in environment around the specific Trp residues were monitored using UV absorbance and steady-state fluorescence measurements. When titrated with 4-fluorotryptophan, both Trp 91 and Trp 290 fluorescence is quenched (49 and 22%, respectively) when one subunit has formed Trp-AMP. The fluorescence of Trp 48 is enhanced 19%. No further change in signal was observed after a 1:1 dimer/L-4FW-AMP complex ratio had been established. Using an anion-exchange filter binding assay with radiolabeled l-Trp as a substrate, binding to only one subunit was observed under nonsaturating conditions. This agrees with the results of the assay using 7-azatryptophan as a substrate. The observed changes extend to the unfilled subunit where a similar structure is believed to form after one subunit has formed tryptophan-AMP. Movement in the regions of the enzyme containing Trp 290 and Trp 91 suggests a mechanism for cross-subunit communication involving the helical backbone and dimer interface containing these two residues.