Entospletinib (GS-9973) is an orally bioavailable, selective Syk inhibitor with IC50 of 7.7 nM in a cell-free assay and showed 13-to >1000-fold cellular selectivity for Syk over other kinases(including Jak2, ckit, Flt3, Ret, KDR) as assessed by target protein phosphorylation or functional response.
Orally bioavailable Syk-selective inhibitor that has been tested in Phase II clinical trials for treatment of Haematological Malignancies.
GS-9973 shows good bidirectional permeability across Caco-2 cell monolayers in vitro. In cells, GS-9973 also shows excellent selectivity for Syk, and potently inhibits BCR-mediated activation and proliferation of B-cells as well as immune-complex-stimulated cytokine production in monocytes. The combination of idelalisib and GS-9973 synergistically inhibits CLL cell viability and further disrupts chemokine signaling.
GS-9973 (1 mg/kg p.o.) shows moderate to high bioavailability in rat and dog. In a rat collagen-induced arthritis model, GS-9973 (1-10 mg/kg p.o.) significantly inhibits ankle inflammation. Moreover, GS-9973 also shows disease-modifying activity in multiple histological measurements, including inhibition of pannus formation, cartilage damage, bone resorption, and peritosteal bone formation with ED50 ranging from 1.2 to 3.9 mg/kg .
Spleen tyrosine kinase (Syk) is a non-receptor tyrosine kinase that upon phosphorylation binds to immunoreceptor tyrosine-based activation motifs of FcRγ chains and mediates downstream signaling related to platelet function and inflammation. GS-9973 is a potent Syk inhibitor (IC50 = 7.7 nM) that demonstrates 10-35-fold selectivity for Syk over a panel of 359 nonmutant kinases. In conjunction with the PI3Kδ inhibitor CAL-101 , it has been used to reduce chronic lymphocytic leukemia cell survival and to disrupt chemokine signaling at nanomolar concentrations.
GS 9973 is a selective and orally bioavailable inhibitor of spleen tyrosine kinase (Syk).
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