BI 1002494, a Novel Potent and Selective Oral Spleen Tyrosine Kinase Inhibitor, Displays Differential Potency in Human Basophils and B Cells.

BI 1002494 [(R)-4-{(R)-1-[7-(3,4,5-trimethoxy-phenyl)-[1,6]napthyridin-5-yloxy]-ethyl}pyrrolidin-2-one] is a novel, potent, and selective spleen tyrosine kinase (SYK) inhibitor with sustained plasma exposure after oral administration in rats, which qualifies this molecule as a good in vitro and in vivo tool compound. BI 1002494 exhibits higher potency in inhibiting high-affinity IgE receptor-mediated mast cell and basophil degranulation (IC50 = 115 nM) compared with B-cell receptor-mediated activation of B cells (IC50 = 810 nM). This may be explained by lower kinase potency when the physiologic ligand B-cell linker was used, suggesting that SYK inhibitors may exhibit differential potency depending on the cell type and the respective signal transduction ligand. A 3-fold decrease in potency was observed in rat basophils (IC50 = 323 nM) compared with human basophils, but a similar species potency shift was not observed in B cells. The lower potency in rat basophils was confirmed in both ex vivo inhibition of bronchoconstriction in precision-cut rat lung slices and in reversal of anaphylaxis-driven airway resistance in rats. The different cellular potencies translated into different in vivo efficacy; full efficacy in a rat ovalbumin model (that contains an element of mast cell dependence) was achieved with a trough plasma concentration of 340 nM, whereas full efficacy in a rat collagen-induced arthritis model (that contains an element of B-cell dependence) was achieved with a trough plasma concentration of 1400 nM. Taken together, these data provide a platform from which different estimates of human efficacious exposures can be made according to the relevant cell type for the indication intended to be treated.

Design of inducible expression vectors for improved protein production in Ralstonia eutropha H16 derived host strains.

Ralstonia eutropha H16 (Cupriavidus necator H16) is a Gram-negative, facultative chemolithoautotrophic bacterium which can use H2 and CO2 as sole energy and carbon sources in the absence of organic substrates. The biotechnological use of R. eutropha H16 on an industrial scale has already been established; however, only a small number of tools promoting inducible gene expression is available. Within this study two systems promoting inducible expression were designed on the basis of the strong j5 promoter and the Escherichia coli lacI or the Pseudomonas putida cumate regulatory elements. Both expression vectors display desired regulatory features and further increase the number of suitable inducible expression systems for the production of metabolites and proteins with R. eutropha H16.

A novel model of IgE-mediated passive pulmonary anaphylaxis in rats.

Mast cells are central effector cells in allergic asthma and are augmented in the airways of asthma patients. Attenuating mast cell degranulation and with it the early asthmatic response is an important intervention point to inhibit bronchoconstriction, plasma exudation and tissue oedema formation. To validate the efficacy of novel pharmacological interventions, appropriate and practicable in vivo models reflecting mast cell-dependent mechanisms in the lung, are missing. Thus, we developed a novel model of passive pulmonary anaphylaxis in rats. Rats were passively sensitized by concurrent intratracheal and intradermal (ear) application of an anti-DNP IgE antibody. Intravenous application of the antigen, DNP-BSA in combination with Evans blue dye, led to mast cell degranulation in both tissues. Quantification of mast cell degranulation in the lung was determined by (1) mediator release into bronchoalveolar lavage, (2) extravasation of Evans blue dye into tracheal and bronchial lung tissue and (3) invasive measurement of antigen-induced bronchoconstriction. Quantification of mast cell degranulation in the ear was determined by extravasation of Evans blue dye into ear tissue. We pharmacologically validated our model using the SYK inhibitor Fostamatinib, the H1-receptor antagonist Desloratadine, the mast cell stabilizer disodium cromoglycate (DSCG) and the ß2-adrenergic receptor agonist Formoterol. Fostamatinib was equally efficacious in lung and ear. Desloratadine effectively inhibited bronchoconstriction and ear vascular leakage, but was less effective against pulmonary vascular leakage, perhaps reflecting the differing roles for histamine receptor sub-types. DSCG attenuated both vascular leakage in the lung and bronchoconstriction, but with a very short duration of action. As an inhaled approach, Formoterol was more effective in the lung than in the ear. This model of passive pulmonary anaphylaxis provides a tissue relevant readout of early mast cell activity and pharmacological benchmarking broadly reflects responses observed in patients with asthma.