Kinase experiment:

Seletalisib is dissolved 1 mM solution in DMSO, and tested in a concentration response (seletalisib), to explore the effects of PI3Kδ-specific inhibition compared with complete inhibition of class I PI3K signaling. In addition, seletalisib is tested in the BioMap BT cell system at concentrations of 1000, 100, 10, and 1 nM. An activity profile is generated based on the effect of the compounds on the levels of cellular readouts, including cytokines, growth factors, adhesion molecules, and proliferation endpoints[1].

Animal experiment:

Rats: Rats are dosed with seletalisib (0.1-10 mg/kg in 500 μL volume) or vehicle via oral gavage 30 min prior to i.v. administration of anti- CD3 antibody administered in a 200 μL dose volume. The vehicle is methylcellulose or saline for oral and i.v. administration, respectively. Seletalisib levels and IL-2 levels are measured[1].

Seletalisib (UCB5857) is potent and selective PI3Kδ inhibitor with an IC50 of 12 nM.

Seletalisib is a potent, ATP-competitive and highly selective PI3Kδ inhibitor able to block AKT phosphorylation following activation of the BCR in a B-cell line. Seletalisib inhibits N-formyl peptides (fMLP)-stimulated but not phorbol myristate acetate (PMA)-stimulated superoxide release from human neutrophils consistent with a PI3Kδ-specific activity. No indications of cytotoxicity are observed in PBMCs or other cell types treated with seletalisib. seletalisib blocks human T-cell production of several cytokines from activated T-cells. Seletalisib inhibits T-cell differentiation to Th1, Th2, and Th17 subtypes. Additionally, seletalisib inhibits B-cell proliferation and cytokine release. In human whole blood assays, seletalisib inhibits CD69 expression upon B-cell activation and anti-IgE-mediated basophil degranulation[1].

Seletalisib significantly inhibits IL-2 release following TCR stimulation in the rat. The inhibition is observed at all tested doses of seletalisib with almost complete inhibition reached at dose levels ≥1 mg/kg. Seletalisib has potent in vivo effects with an estimated IC50 value of<10 nM[1].

[1]. Allen RA, et al. Seletalisib: Characterization of a Novel, Potent, and Selective Inhibitor of PI3Kδ. J Pharmacol Exp Ther. 2017 Apr 25. pii: jpet.116.237347.