Deficient ganglioside synthesis restores responsiveness to leptin and melanocortin signaling in obese KKAy mice.

GM3, a precursor for synthesis of a- and b-series gangliosides, is elevated in adipocytes of obese model animals and in sera of obese human patients with type 2 diabetes and/or dyslipidemia. GM3 synthase (GM3S)-KO C57BL/6 mice display enhanced insulin sensitivity and reduced development of high-fat diet-induced insulin resistance. However, the pathophysiological roles of GM3 and related gangliosides in the central control of feeding and metabolism remain unclear. We found that a mouse model (KKAy GM3S KO) generated by KO of the GM3S gene in the yellow obese strain, KKAy, displayed significant amelioration of obese phenotype. Whereas KKAy mice were hyperphagic and developed severe obesity, KKAy GM3S KO mice had significantly lower body weight and food intake, and greater glucose and insulin tolerance. The hypothalamic response to intraperitoneal administration of leptin was greatly reduced in KKAy mice, but was retained in KKAy GM3S KO mice. In studies of a cultured mouse hypothalamic neuronal cell line, enhanced leptin-dependent phosphorylation of ERK was observed in GM3S-deficient cells. Furthermore, KKAy GM3S KO mice did show altered coat color, suggesting that GM3S is also involved in melanocortin signaling. Our findings, taken together, indicate that GM3-related gangliosides play key roles in leptin and melanocortin signaling.

Evaluation of the immunogenicity of the dabigatran reversal agent idarucizumab during Phase I studies.

AIMS: Idarucizumab, a humanized monoclonal anti-dabigatran antibody fragment, is effective in emergency reversal of dabigatran anticoagulation. Pre-existing and treatment-emergent anti-idarucizumab antibodies (antidrug antibodies; ADA) may affect the safety and efficacy of idarucizumab. This analysis characterized the pre-existing and treatment-emergent ADA and assessed their impact on the pharmacokinetics and pharmacodynamics (PK/PD) of idarucizumab. METHODS: Data were pooled from three Phase I, randomized, double-blind idarucizumab studies in healthy Caucasian subjects; elderly, renally impaired subjects; and healthy Japanese subjects. In plasma sampled before and after idarucizumab dosing, ADA were detected and titrated using a validated electrochemiluminescence method. ADA epitope specificities were examined using idarucizumab and two structurally related molecules. Idarucizumab PK/PD data were compared for subjects with and without pre-existing ADA. RESULTS: Pre-existing ADA were found in 33 out of 283 individuals (11.7%), seven of whom had intermittent ADA. Titres of pre-existing and treatment-emergent ADA were low, estimated equivalent to <0.3% of circulating idarucizumab after a 5 g dose. Pre-existing ADA had no impact on dose-normalized idarucizumab maximum plasma levels and exposure and, although data were limited, no impact on the reversal of dabigatran-induced anticoagulation by idarucizumab. Treatment-emergent ADA were detected in 20 individuals (19 out of 224 treated [8.5%]; 1 out of 59 received placebo [1.7%]) and were transient in ten. The majority had specificity primarily toward the C-terminus of idarucizumab. There were no adverse events indicative of immunogenic reactions. CONCLUSION: Pre-existing and treatment-emergent ADA were present at extremely low levels relative to the idarucizumab dosage under evaluation. The PK/PD of idarucizumab appeared to be unaffected by the presence of pre-existing ADA.

Safety, pharmacokinetics and pharmacodynamics of idarucizumab, a specific dabigatran reversal agent in healthy Japanese volunteers: a randomized study.

BACKGROUND: Idarucizumab is a humanized monoclonal antibody fragment that specifically binds with high affinity to dabigatran. OBJECTIVES: This study investigated the safety, tolerability and pharmacokinetics of idarucizumab alone and with dabigatran at steady state, and the effects of idarucizumab on dabigatran-induced anticoagulation. PATIENTS/METHODS: This was a two-part, phase I, randomized, placebo-controlled, double-blind, rising-dose trial in healthy Japanese males. Part 1: 32 subjects (males) received single idarucizumab doses (1, 2, 4 or 8 g [n=6/dose group]) or placebo (n=2/dose group). Part 2: 48 males received dabigatran (220 mg bid) followed by idarucizumab (n=9/dose group) 1, 2, 4 or 5 g (2×2.5 g), or placebo (n=3/dose group). Anti-idarucizumab antibodies (ADAs) and idarucizumab effect on anticoagulation parameters (diluted thrombin time [dTT], ecarin clotting time [ECT], activated partial thromboplastin time [aPTT] and thrombin time [TT]) were assessed. RESULTS: No adverse events were reported in subjects receiving idarucizumab. After single doses of idarucizumab (alone or at steady state of dabigatran), maximum plasma concentration was achieved around the end of each infusion. Mean all anticoagulation parameters fell below the upper limit of normal immediately after idarucizumab infusion in all dose groups; the effect was sustained at 4 and 2×2.5 g over the entire measurement period until 72 h. At 1- and 2-g doses, partial return of the anticoagulant effect occurred. Idarucizumab alone had no effect on coagulation parameters. Treatment-emergent ADAs occurred in 6/60 males receiving idarucizumab. CONCLUSIONS: Idarucizumab infusion achieved immediate, complete and sustained reversal of dabigatran-induced anticoagulation in Japanese volunteers. Idarucizumab was well tolerated with no procoagulant effects. Trial registration number: ClinicalTrials.gov NCT02028780 (completed).

Idarucizumab does not have procoagulant effects: Assessment of thrombosis biomarkers in healthy volunteers.

Idarucizumab, a humanised monoclonal antibody fragment, binds dabigatran with high affinity and immediately, completely and sustainably reverses dabigatran-induced changes on blood coagulation. The present analysis focuses on the evaluation of potential procoagulant properties of idarucizumab when administered in the absence of dabigatran. As part of two Phase I studies conducted in healthy Caucasian and Japanese male volunteers, the effect of idarucizumab (8 g as a 1-hour [h] infusion and 4 g as a 5-minute [min] infusion) and placebo on calibrated automated thrombography (CAT) was assessed using platelet-poor plasma samples. Measures were made before and 15 min after the end of infusion in Caucasian subjects, as well as pre-dose, 15 min, 4 h and 8 h in Japanese subjects. The levels of the thrombosis markers D-dimer and prothrombin fragment 1 + 2 (F1.2) were assessed over time in plasma samples up to 72 h after the end of infusion of idarucizumab and placebo. Idarucizumab had no apparent effect on endogenous thrombin formation as measured by CAT. D-dimer and F1.2 levels were highly variable in all dose groups but did not increase when compared with placebo or pre-dose levels. In conclusion, idarucizumab had no effect on endogenous thrombin generation. Additional markers of thrombosis, F1.2 and D-dimer, did not differ between placebo and idarucizumab, indicating a lack of procoagulant properties of idarucizumab.

Non-methylated CpG motif packaged into fusogenic liposomes enhance antigen-specific immunity in mice.

DNA rich in non-methylated CG motifs (CpGs) enhances induction of immune responses against co-administered antigen encoding genes. CpGs are therefore among the promising adjuvants known to date. However, naked plasmid DNA, even which contains CpG motifs, are taken up by antigen presenting cells via the endocytosis pathway. Endocytosed DNAs are thus degraded and their gene expression levels are inefficient. In this context, an effective plasmid delivery carrier is required for DNA vaccine development. We show in the present study that packaging plasmids containing CpGs into fusogenic liposomes (FL) derived from conventional liposomes and Sendai virus-derived active accessory proteins is an attractive method for enhancing the efficacy of a DNA vaccine. These CpG-enhanced plasmids (possessing 16 CpG repeats) that were packaged into FL, enhanced ovalbumin (OVA)-specific T cell proliferation and cytotoxic T cell activity after immunization. In fact, vaccination with CpG enhanced plasmid-loaded FL induced effective prophylactic effects compared with 13 repeats CpG containing plasmid in a tumor challenge experiment. Thus, the development of a CpG-enhanced DNA-FL genetic immunization system represents a promising tool for developing candidate vaccines against some of the more difficult infectious, parasitic, and oncologic disease targets.

Augmentation of antigen-specific immune responses using DNA-fusogenic liposome vaccine.

In an attempt to enhance the immunological efficacy of genetic immunization, we investigated a new biological means for delivering antigen gene directly to the cytoplasm via membrane fusion. In this context, we investigated fusogenic liposome (FL) encapsulating DNA as a possible genetic immunization vehicle. RT-PCR analysis indicated that a FL could introduce and express encapsulating OVA gene efficiently and rapidly in vitro. Consistent with this observation, an in vitro assay showed that FL-mediated antigen-gene delivery can induce potent presentation of antigen via the MHC class I-dependent pathway. Accordingly, immunization with FL containing the OVA-gene induced potent OVA-specific Th1 and Th2 cytokine production. Additionally, OVA-specific CTL responses and antibody production were also observed in systemic compartments including the spleen, upon immunization with the OVA-gene encapsulating FL. These findings suggest that FL is an effective genetic immunization carrier system for the stimulation of antigen-specific immune responses against its encoding antigen.

A novel T7 system utilizing mRNA coding for T7 RNA polymerase.

The T7 system dose not require the relocation of a reporter gene to the nucleus for its gene expression in the cytoplasm, but relies on the co-localization of T7 RNA polymerase (T7 RNAP) enzyme and reporter gene DNA that is controlled by the T7 promoter. In the present study, we developed a new T7 system in that gene expression can occur at a higher level than those using conventional systems. Insertion of 5'- and 3'-untranslated regions (UTR) of beta-globin gene into a reporter gene enhanced the reporter gene expression, presumably due to the stability and efficient translation of the mRNA. Instead of the T7 RNAP protein used in conventional methods, moreover, transfection of cells with T7 RNAP mRNA, which has been modified by inserting beta-globin 5'- and 3'-UTR sequences as well as the cap and poly(A) tail structures, further enhanced the reporter gene expression. Thus, this novel T7 system using T7 RNAP mRNA may be powerful for the efficient gene expression of DNA exogenously provided in the cytoplasm.