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

Abstract

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 highaffinity IgE receptor-mediated mast cell and basophil degranulation (IC 50 5 115 nM) compared with B-cell receptor-mediated activation of B cells (IC 50 5 810 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 (IC 50 5 323 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 collageninduced 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.

The Novel Oral Syk Inhibitor, Bl1002494, Protects Mice From Arterial Thrombosis and Thromboinflammatory Brain Infarction

“…23 Similar agonist and signaling pathway-dependent differences in Bl1002494 efficacy were observed in various immune cells. 20 Furthermore, GPVI and CLEC-2 signaling differ in the sequential order of Src family kinases and Syk, 6 which could explain the different potencies of BI1002494 for inhibiting GPVI and CLEC-2 signaling and thereby the unaltered tail bleeding times in inhibitor-treated mice compared with the slightly prolonged bleeding times in Syk-deficient mice. However, given previous reports that the concomitant lack of GPVI and CLEC-2 severely compromises hemostasis, 18 this could also point toward signaling-independent functions of the 2 (hem)ITAM receptors in hemostasis.…”

“…Therefore, we capitalized on the novel and highly selective oral ATPcompetitive Syk inhibitor, BI1002494. 20 In vitro, 150 nmol/L BI1002494 abrogated collagen-related peptide responses of wild-type platelets, whereas a concentration of 500 nmol/L was required to completely abolish convulxin and rhodocytin responses ( Figure 4A and 4B). In contrast, no effects on G-protein-coupled receptor signaling were observed with any of the tested inhibitor concentrations ( Figure 4A and 4B).…”

Syk Inhibition in Ischemic Stroke

“…First-generation Syk inhibitors, such as R406/R788 (Rigel), PRT062607 (Portola), and GS-9973 (Gilead), have been used in humans safely; however, small-molecule inhibitors with greater potency and selectivity over other kinases have emerged more recently, including those from Merck, 6 Almirall, 7 and in the current report, Boehringer-Ingelheim. 8 Van Eeuwijk, Nieswandt and colleagues report a comprehensive approach to their proof of concept for the actions of BI1002494 in ischemic stroke (Figure). They combined a genetic approach: mice selectively lacking Syk in platelets (Syk fl/fl,Pf4-cre+/− ), with a pharmacological approach (BI1002494), in platelet function studies ex vivo and in the transient middle cerebral artery occlusion stroke model in vivo.…”

Inhibition of SYK kinase does not confer a pro-proliferative or pro-invasive phenotype in breast epithelium or breast cancer cells

“…In a kinase inhibition assay the IC 50 of BI 1002494 is1nM and in whole blood basophil and B-cell activation assays is 114 nM and 810 nM, respectively. At 1 µM, BI 1002494 inhibits just 22 kinases in the Invitrogen panel of 306 kinases by more than 50%, conferring a favourable potency and selectivity profile over other SYK inhibitors described in the literature [22].…”

“…BI 1002494 is a potent and selective inhibitor of SYK [22]. In a kinase inhibition assay the IC 50 of BI 1002494 is1nM and in whole blood basophil and B-cell activation assays is 114 nM and 810 nM, respectively.…”