Search

Background rVIII-SingleChain, a novel recombinant factor VIII ( rFVIII), has been designed as a B-domain truncated construct with covalently bonded heavy and light chains, aiming to increase binding affinity to von Willebrand factor (VWF). Preclinical studies confirmed greater affinity for VWF, giving improved pharmacokinetic and pharmacodynamic properties compared with full-length rFVIII. Aim To investigate the pharmacokinetics of rVIII-SingleChain and compare them against those of full-length rFVIII. Methods This study enrolled 27 patients with severe haemophilia A in the AFFINITY clinical trial programme. After a 4-day washout period, all patients received a single infusion of 50 IU kg−1 octocog alfa (Advate®); after a ≥4-day postinfusion washout period, they received a single infusion of 50 IU kg−1 rVIII-SingleChain. Blood samples for pharmacokinetic assessments of each product were collected before infusion (predose) and at 0.5, 1, 4, 8, 10, 24, 32, 48 and 72 h postinfusion for both products. Results rVIII-SingleChain had a longer mean half-life ( t1/2) (14.5 vs. 13.3 h), lower mean clearance ( CL) (2.64 vs. 3.68 mL h−1 kg−1), higher mean residence time (20.4 vs. 17.1 h) and larger mean AUCinf (2090 vs. 1550 IU?h dL−1) than octocog alfa, respectively. The mean AUCinf after rVIII-SingleChain infusion was ~35% larger than after octocog alfa. A similar pattern was observed for AUC0-last. No serious adverse events or inhibitors were reported. Conclusions rVIII-SingleChain has a favourable pharmacokinetic profile compared with octocog alfa and was well tolerated. The prolonged t1/2, larger AUC and reduced CL of rVIII-SingleChain may permit longer dosing intervals, thereby improving patient adherence to prophylactic treatment. [ABSTRACT FROM AUTHOR]

Recombinant VIII (rVIII)-SingleChain is a novel B-domain-truncated recombinant factor VIII (rFVIII), comprised of covalently bonded factor VIII (FVIII) heavy and light chains. It was designed to have a higher binding affinity for von Willebrand factor (VWF). This phase 1/3 study investigated the efficacy and safety of rVIII-SingleChain in the treatment of bleeding episodes, routine prophylaxis, and surgical prophylaxis. Participants were ≥12 years of age, with severe hemophilia A (endogenous FVIII <1%). The participants were allocated by the investigator to receive rVIII-SingleChain in either an on-demand or prophylaxis regimen. Of the 175 patients meeting study eligibility criteria, 173 were treated with rVIII-SingleChain, prophylactically (N = 146) or on-demand (N = 27). The total cumulative exposure was 14 306 exposure days (EDs), with 120 participants reaching ≥50 EDs and 52 participants having ≥100 EDs. Hemostatic efficacy was rated by the investigator as excellent or good in 93.8% of the 835 bleeds treated and assessed. Across all prophylaxis regimens, the median annualized spontaneous bleeding rate was 0.00 (Q1, Q3: 0.0, 2.4) and the median overall annualized bleeding rate (ABR) was 1.14 (Q1, Q3: 0.0, 4.2). Surgical hemostasis was rated as excellent/good in 100% of major surgeries by the investigator. No participant developed FVIII inhibitors. In conclusion, rVIII-SingleChain is a novel rFVIII molecule showing excellent hemostatic efficacy in surgery and in the control of bleeding events, low ABR in patients on prophylaxis, and a favorable safety profile in this large clinical study. This trial was registered at www.clinicaltrials.gov as #NCT01486927., (© 2016 by The American Society of Hematology.)

IL-13 is a Th2 cytokine that has been shown to be an important mediator of airway inflammation contributing to asthma lesions. Given its proposed role in asthma, measurements of this cytokine in serum may provide insights into disease mechanisms, progression and pharmacodynamic effects of IL-13 targeted therapeutics. However, current commercially available ELISA immunoassays are frequently unable to detect baseline concentrations of IL-13 in serum from healthy individuals, which are below the limit of detection. Here we describe the use of the novel microparticle-based Erenna IL-13 human immunoassay (Singulex, Inc.), which utilizes proprietary antibodies and single molecule counting technology, to quantify IL-13 from 100 microL of serum from apparently healthy subjects and clinically defined symptomatic and asymptomatic asthma subjects. The lower limit of quantification of the Erenna assay was validated at 0.07 pg/mL and the assay detected baseline concentrations of IL-13 in 98% of serum samples tested. The calibration curve showed good precision over the entire linear range of 0.07-50 pg/mL, with inter-assay imprecision <10% CV except at the lowest concentration tested (<15%). The intra- and inter-assay imprecision of spiked serum samples containing three different IL-13 concentrations (2, 8, and 25 pg/mL) ranged from 2.2-2.4% and 6.1-6.8%, respectively. Using the Erenna IL-13 assay, we observe that serum IL-13 concentrations range from <0.07-1.02 pg/mL in apparently healthy subjects (N=60) with similar ranges in asymptomatic (0.07-0.66 pg/mL, N=26) and symptomatic (<0.07-1.26 pg/mL, N=96) asthma subjects. The Erenna immunoassay improved sensitivity by over two full logs compared to previous ELISA methods, while using smaller sample volumes. In addition, the Erenna assay reliably measured IL-13 in endogenous and spiked human serum samples that were not quantifiable using other methods. Taken together, these results show that this novel assay offers a significant improvement over previous methods for high-sensitive quantitative measurement of IL-13 in human serum samples obtained from both apparently healthy and asthmatic subjects, and can be used in future clinical studies to accurately measure concentrations of this cytokine prior to and following drug therapy in human serum.

Unlabelled: Methodological problems, including binding of myostatin to plasma proteins and cross-reactivity of assay reagents with other proteins, have confounded myostatin measurements. Here we describe development of an accurate assay for measuring myostatin concentrations in humans. Monoclonal antibodies that bind to distinct regions of myostatin served as capture and detector antibodies in a sandwich ELISA that used acid treatment to dissociate myostatin from binding proteins. Serum from myostatin-deficient Belgian Blue cattle was used as matrix and recombinant human myostatin as standard. The quantitative range was 0.15-37.50 ng/mL. Intra- and inter-assay CVs in low, mid, and high range were 4.1%, 4.7%, and 7.2%, and 3.9%, 1.6%, and 5.2%, respectively. Myostatin protein was undetectable in sera of Belgian Blue cattle and myostatin knockout mice. Recovery in spiked sera approximated 100%. ActRIIB-Fc or anti-myostatin antibody MYO-029 had no effect on myostatin measurements when assayed at pH 2.5. Myostatin levels were higher in young than older men (mean+/-S.E.M. 8.0+/-0.3 ng/mL vs. 7.0+/-0.4 ng/mL, P=0.03). In men treated with graded doses of testosterone, myostatin levels were significantly higher on day 56 than baseline in both young and older men; changes in myostatin levels were significantly correlated with changes in total and free testosterone in young men. Myostatin levels were not significantly associated with lean body mass in either young or older men., Conclusion: Myostatin ELISA has the characteristics of a valid assay: nearly 100% recovery, excellent precision, accuracy, and sufficient sensitivity to enable measurement of myostatin concentrations in men and women.