GS-9973 is a selective inhibitor of Syk with IC50 value of 7.7 nM [1].
Spleen tyrosine kinase (Syk) is a cytoplasmic tyrosine kinase that is expressed mainly in hematopoietic cells and acts as a mediator of immunoreceptor signaling. Syk can be used for therapy of autoimmune, oncology indications and allergy [1].
GS-9973 is an orally bioavailable and selective Syk inhibitor. GS-9973 showed good absorption potential and high bioavailability. In monocytes, GS-9973 inhibited immune-complex-stimulated cytokine production and BCR-mediated proliferation and activation of B-cells [1]. In chronic lymphocytic leukemia (CLL) cells, GS-9973 significantly reduced pAkt and ribosomal S6 phosphorylation. These results suggested that GS-9973 inhibited B-cell receptor (BCR) mediated signaling pathways. In CLL samples, the combination of GS-9973 and idelalisib synergistically reduced CLL cell viability [2].
In chronic lymphocytic leukemia patients, GS-9973 inhibited adenopathy and reduced lymph node [3].
References:
[1]. Currie KS, Kropf JE, Lee T, et al. Discovery of GS-9973, a selective and orally efficacious inhibitor of spleen tyrosine kinase. J Med Chem, 2014, 57(9): 3856-3873.
[2]. Burke RT1, Meadows S, Loriaux MM, et al. A potential therapeutic strategy for chronic lymphocytic leukemia by combining Idelalisib and GS-9973, a novel spleen tyrosine kinase (Syk) inhibitor. Oncotarget, 2014, 5(4): 908-915.
[3]. Sharman J, Hawkins M, Kolibaba K, et al. An open-label phase 2 trial of entospletinib (GS-9973), a selective spleen tyrosine kinase inhibitor, in chronic lymphocytic leukemia. Blood, 2015, 125(15): 2336-2343.
