Spleen tyrosine kinase (SYK) is a critical regulator of signaling in a variety of immune cell types such as B-cells, monocytes, and macrophages. Accordingly, there have been numerous efforts to identify compounds that selectively inhibit SYK as a means to treat autoimmune and inflammatory diseases. We previously disclosed GS-9973 (entospletinib) as a selective SYK inhibitor that is under clinical evaluation in hematological malignancies. However, a BID dosing regimen and drug interaction with proton pump inhibitors (PPI) prevented development of entospletinib in inflammatory diseases. Herein, we report the discovery of a second-generation SYK inhibitor, GS-9876 (lanraplenib), which has human pharmacokinetic properties suitable for once-daily administration and is devoid of any interactions with PPI. Lanraplenib is currently under clinical evaluation in multiple autoimmune indications.

We describe the discovery of three structurally differentiated potent and selective MTH1 inhibitors and their subsequent use to investigate MTH1 as an oncology target, culminating in target (in)validation. Tetrahydronaphthyridine 5 was rapidly identified as a highly potent MTH1 inhibitor (IC50 = 0.043 nM). Cocrystallization of 5 with MTH1 revealed the ligand in a Φ-cis-N-(pyridin-2-yl)acetamide conformation enabling a key intramolecular hydrogen bond and polar interactions with residues Gly34 and Asp120. Modification of literature compound TH287 with O- and N-linked aryl and alkyl aryl substituents led to the discovery of potent pyrimidine-2,4,6-triamine 25 (IC50 = 0.49 nM). Triazolopyridine 32 emerged as a highly selective lead compound with a suitable in vitro profile and desirable pharmacokinetic properties in rat. Elucidation of the DNA damage response, cell viability, and intracellular concentrations of oxo-NTPs (oxidized nucleoside triphosphates) as a function of MTH1 knockdown and/or small molecule inhibition was studied. Based on our findings, we were unable to provide evidence to further pursue MTH1 as an oncology target.

In our continued effort to discover and develop best-in-class Bruton's tyrosine kinase (Btk) inhibitors for the treatment of B-cell lymphomas, rheumatoid arthritis, and systemic lupus erythematosus, we devised a series of novel tricyclic compounds that improved upon the druglike properties of our previous chemical matter. Compounds exemplified by G-744 are highly potent, selective for Btk, metabolically stable, well tolerated, and efficacious in an animal model of arthritis.

Systemic lupus erythematosus (SLE) is often associated with exaggerated B cell activation promoting plasma cell generation, immune-complex deposition in the kidney, renal infiltration of myeloid cells, and glomerular nephritis. Type-I IFNs amplify these autoimmune processes and promote severe disease. Bruton's tyrosine kinase (Btk) inhibitors are considered novel therapies for SLE. We describe the characterization of a highly selective reversible Btk inhibitor, G-744. G-744 is efficacious, and superior to blocking BAFF and Syk, in ameliorating severe lupus nephritis in both spontaneous and IFNα-accelerated lupus in NZB/W_F1 mice in therapeutic regimens. Selective Btk inhibition ablated plasmablast generation, reduced autoantibodies, and - similar to cyclophosphamide - improved renal pathology in IFNα-accelerated lupus. Employing global transcriptional profiling of spleen and kidney coupled with cross-species human modular repertoire analyses, we identify similarities in the inflammatory process between mice and humans, and we demonstrate that G-744 reduced gene expression signatures essential for splenic B cell terminal differentiation, particularly the secretory pathway, as well as renal transcriptional profiles coupled with myeloid cell-mediated pathology and glomerular plus tubulointerstitial disease in human glomerulonephritis patients. These findings reveal the mechanism through which a selective Btk inhibitor blocks murine autoimmune kidney disease, highlighting pathway activity that may translate to human SLE.

Background Spleen Tyrosine Kinase (SYK) mediates signaling in a range of hematopoietic cells involved in the initiation and progression of RA including B cells, monocytes, macrophages, dendritic cells, and osteoclasts. There is strong preclinical validation for SYK as a therapeutic target for RA based on cellular data and animal models of disease. We have identified GS-9876 as a potent and selective SYK inhibitor with pharmaceutical properties compatible with once daily oral dosing in human. Objectives To characterize the cellular activity of GS-9876 on pathologically relevant pathways in RA, and establish target inhibition requireements for efficacy in rat models of arthritis. Methods The potency and selectivity of GS-9876 were characterized in biochemical and cellular assays. Effects in B cells were measured by inhibition of BCR-mediated protein phosphorylation, CD69 and CD86 expression, and in macrophages by inhibition of immune-complex (IC)-stimulated cytokine release. Cellular selectivity was demonstrated by comparing the inhibition of B cell proliferation versus T cell proliferation. GS-9876 potency in human blood was evaluated by inhibition of phosphorylated SYK (pSYK), CD63 expression on basophils, and CD69 expression on B cells. The in vivo efficacy of GS-9876 was tested in rat models of collagen-induced arthritis (CIA). Results GS-9876 is a potent SYK inhibitor (IC50=9.5±4.3 nM) and is highly selective against a panel of 456 other kinases. GS-9876 inhibited anti-IgM stimulated phosphorylation of AKT, BLNK, BTK, ERK, MEK, and PKCδ in human B cells with EC50 values of 24–51 nM. Functionally, GS-9876 inhibited anti-IgM mediated CD69 and CD86 expression on B-cells (EC50=112±10 nM and 164±15 nM, respectively) and anti-IgM /anti-CD40 co-stimulated B cell proliferation (EC50=108±55 nM). In human macrophages, GS-9876 inhibited IC-stimulated TNFα and IL-1β release (EC50=121±77 nM and 9±17 nM, respectively). Anti-CD3/anti-CD28 stimulated T cell proliferation was weakly inhibited (EC50=1291±398 nM), with selectivity >10-fold versus the inhibition of B cell proliferation. In human blood, GS-9876 blocked SYK phosphorylation, CD69 expression on B cells, and CD63 expression in basophils. GS-9876 demonstrated a dose-dependent improvement in clinical score and histopathology parameters with once-daily dosing in short and long term rat CIA models. Significant efficacy could be achieved with GS-9876 doses that produced trough pSYK inhibition of <50%. Conclusions GS-9876 is a novel SYK inhibitor that potently inhibits multiple cellular events implicated in RA pathogenesis and displays excellent in vivo efficacy in rat CIA models after once-daily dosing. GS-9876 has markedly improved selectivity over competitor SYK programs. Our data support the development of GS-9876 in inflammatory diseases, with potential for an improved safety profile. Disclosure of Interest J. Di Paolo Shareholder of: Gilead Sciences, P. Blomgren Shareholder of: Gilead Sciences, M. Dolton Shareholder of: Gilead Sciences, R. Jones Shareholder of: Gilead Sciences, J. Kropf Shareholder of: Gilead Sciences, T. Lee Shareholder of: Gilead Sciences, S. Mitchell Shareholder of: Gilead Sciences, B. Murray Shareholder of: Gilead Sciences, K. Suekawa-Pirrone Shareholder of: Gilead Sciences, S. Wise Shareholder of: Gilead Sciences, J. Xu Shareholder of: Gilead Sciences, Z. Zhao Shareholder of: Gilead Sciences, K. Currie Shareholder of: Gilead Sciences

BTK inhibitor GDC-0834 (1) was found to be rapidly metabolized in human studies, resulting in a suspension of clinical trials. The primary route of metabolism was through cleavage of the acyclic amide bond connecting the terminal tetrahydrobenzothiophene with the central linker aryl ring. SAR studies were focused on reducing metabolic cleavage of this amide, and resulted in the identification of several central aryl linker substituents that conferred improved stability. The most promising substituted aryl linkers were then incorporated into an optimized pyridazinone scaffold, resulting in the identification of lead analog 23, possessing improved potency, metabolic stability and preclinical properties.

SAR studies focused on improving the pharmacokinetic (PK) properties of the previously reported potent and selective Btk inhibitor CGI-1746 (1) resulted in the clinical candidate GDC-0834 (2), which retained the potency and selectivity of CGI-1746, but with much improved PK in preclinical animal models. Structure based design efforts drove this work as modifications to 1 were investigated at both the solvent exposed region as well as ‘H3 binding pocket’. However, in vitro metabolic evaluation of 2 revealed a non CYP-mediated metabolic process that was more prevalent in human than preclinical species (mouse, rat, dog, cyno), leading to a high-level of uncertainly in predicting human pharmacokinetics. Due to its promising potency, selectivity, and preclinical efficacy, a single dose IND was filed and 2 was taken in to a single dose phase I trial in healthy volunteers to quickly evaluate the human pharmacokinetics. In human, 2 was found to be highly labile at the exo-cyclic amide bond that links the tetrahydrobenzothiophene moiety to the central aniline ring, resulting in insufficient parent drug exposure. This information informed the back-up program and discovery of improved inhibitors.

At least one chemical entity chosen from compounds of Formula (I): ** ** Formula and pharmaceutically acceptable salts thereof, wherein R1 is selected from (1-hydroxycyclobutyl) phenyl, (1,1,1-trifluoro -2-hydroxypropane-2-yl) phenyl, (2,2,2-trifluoro-1- hydroxyethyl) phenyl, (1,1,1,3,3,3-hexafluoro-2-hydroxypropan-2-yl) phenyl (2-hydroxy-2-methylpropoxy) -3-methoxyphenyl, (2- hydroxyethyl) (methyl) amino) -3-methoxyphenyl, (2-methoxyethyl) (methyl) amino) -3-methoxyphenyl, (1-hydroxyethyl) phenyl, 3,4- dimethoxyphenyl, 3-methoxyphenyl, 4-ethoxy-3-methoxyphenyl, 4-hydroxymethyl-3-methoxyphenyl, 3-hydroxymethyl-4-methoxyphenyl, 2-fluoro-4-methoxyphenyl, 4- (dimethylamino) propoxy -3-methoxyphenyl, 4-hydroxypropoxy-3-methoxyphenyl, 4- (2-hydroxy-1,1- dimethylethyl) phenyl, 4- (1-hydroxy-1-methylethyl) phenyl, 4-methoxy-3- (pyrrolidin- 1-yl) phenyl, 3-methoxy-4- (pyrrolidin-1-yl) phenyl, 3- methoxy-4- (propan-2-yloxy) phenyl, 3-methoxy-4- (morpholin-4-yl) phenyl , 4- (pyrrolidin-1-yl) phenyl, 4- (3-hydroxypyrrolidinyl) phenyl, 4- (4-hydroxypiperid ynyl) -3-methoxyphenyl, 4- (3-hidroxiacetidinil) -3-methoxyphenyl, 4- (3-hydroxypyrrolidinyl) -3-methoxyphenyl, 4- (2-methoxypropan-2-yl) phenyl, 4- (4-ethylpiperazin -1-yl) -3-methoxyphenyl, 4- (4-ethyl-piperazin-1-yl) phenyl, 4- (3-hydroxy-3- methylpiperidinyl) phenyl, 3-hydroxymethylphenyl, 3,4-dihydro-2H-benzo [ b] [1,4] oxazin-6-yl, 4-methyl-3,4-dihydro-2H-benzo [b] [1,4] oxazin-6-yl, 2,3,4,5-tetrahydrobenzo [b] [1,4] oxazepine-7-yl, 5-methyl-2,3,4,5-tetrahydrobenzo [b] [1,4] oxazepine-7-yl, 2,3-dihydro-1H-indol-2- one-6-yl and 2,3-dihydro-1H-indol-yl 2-one-5-; R2 is selected from 2-fluoropyridin-4-yl, 5-methylpyridin-3-yl, 5-chloropyridin-3-yl and 2-aminopyridin-5-yl; R3 is chosen from hydrogen, halo and C1-C4 alkyl; R4 is chosen from hydrogen and C1-C4 alkyl; and R5 is hydrogen.

Inhibition of receptor tyrosine kinases (RTKs) such as vascular endothelial growth factor receptors (VEGFRs) and platelet-derived growth factor receptors (PDGFRs) has been validated by recently launched small molecules Sutent(R) and Nexavar(R), both of which display activities against several angiogenesis-related RTKs. EphB4, a receptor tyrosine kinase (RTK) involved in the processes of embryogenesis and angiogenesis, has been shown to be aberrantly up regulated in many cancer types such as breast, lung, bladder and prostate. We propose that inhibition of EphB4 in addition to other validated RTKs would enhance the anti-angiogenic effect and ultimately result in more pronounced anti-cancer efficacy. Herein we report the discovery and SAR of a novel series of imidazo[1,2-a]pyrazine diarylureas that show nano-molar potency for the EphB4 receptor, in addition to potent activity against several other RTKs. (C) 2009 Elsevier Ltd. All rights reserved.