n4-(2-2-dimethyl-3-oxo-4h-pyrid(1-4)oxazin-6-yl)-5-fluoro-n2-(3-4-5-trimethoxyphenyl)-2-4-pyrimidinediamine and fostamatinib

Spleen tyrosine kinase (Syk) is a cytoplasmic tyrosine kinase involved in signalling in many of the cells that drive immune inflammation. The development of small molecules that inhibit Syk kinase may change the way we treat disorders such as rheumatoid arthritis (RA), as well as a range of other inflammatory diseases. Fostamatinib (R-788) is an orally bioavailable small molecule. It is the prodrug of R406, which is a potent Syk inhibitor. Fostamatinib was developed because it has more favourable physiochemical properties. It is rapidly converted to R406 by intestinal enterocytes. It has been evaluated in experimental models of RA, such as collagen-induced arthritis. In these models, fostamatinib suppressed clinical arthritis, bone erosions, pannus formation and synovitis. A phase II programme with fostamatinib has largely been completed. Three key trials have been published, lasting 12-26 weeks and each enrolling 189-457 patients (875 in total). All these trials involved placebo therapy and patients continued to receive methotrexate in addition to active treatment with fostamatinib. The first dose-ranging trial evaluated three treatment doses in RA patients who had not fully responded to methotrexate therapy. The second trial compared two treatment doses in patients who had not responded to methotrexate therapy. The third trial compared a single treatment dose with placebo in patients who had not responded to biological therapy. The primary outcome measure was the number of patients achieving American College of Rheumatology (ACR) 20% (ACR20) responses. Placebo ACR20 response rates in all three trials were similar (35-38%). All three trials involved one treatment arm receiving fostamatinib 100 mg twice daily; ACR20 responses with this active treatment ranged from 38% to 67%. A meta-analysis of ACR responses in these trials, using responses to the highest dose in each trial for comparisons with placebo therapy in a random effects model, showed a borderline benefit with ACR20 responses. There were more significant differences with ACR50 and ACR70 responses. The reason that this meta-analysis was not more strongly positive is that the third trial, which evaluated patients who had failed to respond to biological treatments, gave negative results. Individual ACR response components, such as changes in swollen joint counts, showed significant differences in the first two trials, but there were no definite treatment benefits in the third trial. Overall, the dif

Topics: Aminopyridines; Animals; Antirheumatic Agents; Arthritis, Experimental; Arthritis, Rheumatoid; Humans; Intracellular Signaling Peptides and Proteins; Morpholines; Oxazines; Prodrugs; Protein Kinase Inhibitors; Protein-Tyrosine Kinases; Pyridines; Pyrimidines; Syk Kinase

Spleen Tyrosine Kinase (Syk) is widely expressed in the immune system and functions in the transmission of inflammatory signals via ITAM-bearing cell surface receptors. The broad expression pattern and importance of Syk in regulating innate immunity and the inflammatory response have led to significant interest from the pharmaceutical industry to developing anti-Syk therapeutics for the treatment of inflammatory disorders such as allergic rhinitis and rheumatoid arthritis. While the function and regulation of Syk has been well-described in leukocytes, where its primary role is an early transducer of signaling following immunoreceptor engagement, Syk has recently been described in non-immune cells, such as the airway epithelium, that also play an important role in mediating the inflammatory response. This manuscript will focus on the expression and function of Syk in the context of inflammatory lung diseases, and review recent data that have demonstrated novel roles for Syk in airway epithelial cells, particularly its role in mediating the human rhinovirus (HRV) induced inflammatory response and viral cell entry. In addition, data describing the efficacy of novel Syk inhibitors in the management of inflammatory diseases in animal models and early clinical trials are also reviewed.

Topics: Aminopyridines; Animals; Anti-Inflammatory Agents; Clinical Trials as Topic; Humans; Intercellular Adhesion Molecule-1; Intracellular Signaling Peptides and Proteins; Leukocytes; Lung Diseases, Obstructive; Morpholines; Oxazines; Picornaviridae Infections; Pneumonia, Viral; Protein Kinase Inhibitors; Protein-Tyrosine Kinases; Pyridines; Pyrimidines; Respiratory Mucosa; Rhinovirus; Signal Transduction; Syk Kinase; Virulence; Virus Internalization

R788 (fostamatinib) is an oral prodrug that is rapidly converted into a relatively selective spleen tyrosine kinase (SYK) inhibitor R406, evaluated for the treatment of rheumatoid arthritis (RA). This analysis aimed at developing a pharmacodynamic model for efficacy using pooled ACR20 data from two phase II studies in patients with rheumatoid arthritis (TASKi1 and TASKi2), describing the effect of fostamatinib as a function of fostamatinib exposure (dose, R406 plasma concentration) and other explanatory variables. The exposure-response relationship of fostamatinib was implemented into a continuous time Markov model describing the time course of transition probabilities between the three possible states of ACR20 non-responder, responder, and dropout at each visit. The probability of transition to the ACR20 response state was linearly (at the rate constant level) related to average R406 plasma concentrations and the onset of this drug effect was fast. Further, increases of fostamatinib dose resulted in increased dropout and subsequent loss of efficacy. This analysis provided an increased understanding of the exposure-response relationship, and provided support for fostamatinib 100 mg BID an appropriate dose regimen for further clinical evaluation.

Topics: Administration, Oral; Aminopyridines; Antirheumatic Agents; Arthritis, Rheumatoid; Biotransformation; Clinical Trials, Phase II as Topic; Drug Dosage Calculations; Europe; Humans; Latin America; Linear Models; Markov Chains; Mexico; Morpholines; Oxazines; Prodrugs; Protein Kinase Inhibitors; Pyridines; Pyrimidines; Randomized Controlled Trials as Topic; Syk Kinase; Treatment Outcome; United States

Fostamatinib is an oral spleen tyrosine kinase (SYK) inhibitor which has been evaluated as a potential treatment for rheumatoid arthritis (RA). Treatment with fostamatinib has been associated with an increase in blood pressure (BP). In this work, we present a pooled analysis of the pharmacokinetic-pharmacodynamic (PKPD) relationship for BP, based on 3 Phase III studies, aiming to increase the knowledge about fostamatinib's effect on BP in the RA population. Fostamatinib is rapidly and extensively converted to R406 after oral administration of fostamatinib, and the PK of R406 could be described by a two-compartment population PK model with first order absorption, with an estimated CL/F of 18.7 L/h. Average steady-state concentrations, predicted based on the individual CL/F estimates, were subsequently used in the PKPD analysis. The population PKPD analysis revealed a concentration dependent increase of BP with increasing R406 concentrations, where a power model and an Emax model best described the increase in SBP and DBP, respectively. The predicted increases were +5.2 mmHg for SBP and +4.2 mmHg for DBP, for a 100 mg bid dose. The impact of covariates on the PKPD relationship was investigated but covariates did only explain a minor part of the overall high variability in BP.

Topics: Adolescent; Adult; Aged; Aged, 80 and over; Aminopyridines; Antirheumatic Agents; Arthritis, Rheumatoid; Blood Pressure; Double-Blind Method; Female; Humans; Intracellular Signaling Peptides and Proteins; Male; Middle Aged; Models, Biological; Morpholines; Oxazines; Protein-Tyrosine Kinases; Pyridines; Pyrimidines; Syk Kinase; Young Adult

Fostamatinib (R788) is an orally dosed prodrug designed to deliver the active metabolite R940406 (R406), a spleen tyrosine kinase (SYK) inhibitor, for the treatment of rheumatoid arthritis. The objectives were to evaluate the human pharmacokinetic properties of fostamatinib and R406.. Three clinical studies were conducted in healthy subjects: (A) A single ascending dose study for R406 with doses ranging from 80-600 mg, (B) a single- and multiple-dose study of fostamatinib in aqueous suspension, with single doses ranging from 80-400 mg and multiple doses at 160 mg twice daily and (C) a study comparing suspension and tablet of fostamatinib, with the latter tested in both fed and fasted states.. These studies demonstrated that when administered as a solution, R406 was rapidly absorbed. Increases in exposure were observed with doses up to 400 mg. A terminal half-life of 12-21 h was observed. Similar R406 exposure could be achieved with fostamatinib suspension and steady-state was achieved after 3-4 days following twice daily administration. Fostamatinib tablet and suspension exhibited similar R406 exposure. Upon co-administration with food, a delay in peak time and lower peak concentrations of R406 were observed but at the same time the overall exposure did not change.. Fostamatinib demonstrates rapid and extensive conversion to R406, an inhibitor of SYK. Solid dosage forms of fostamatinib overcome the challenge of low aqueous solubility of R406. The PK profile of R406 could potentially allow once daily or twice daily oral administration of fostamatinib.

Topics: Administration, Oral; Adolescent; Adult; Aminopyridines; Dose-Response Relationship, Drug; Double-Blind Method; Drug Administration Schedule; Female; Food-Drug Interactions; Half-Life; Humans; Intracellular Signaling Peptides and Proteins; Male; Middle Aged; Morpholines; Oxazines; Pharmaceutical Solutions; Prodrugs; Protein Kinase Inhibitors; Protein-Tyrosine Kinases; Pyridines; Pyrimidines; Suspensions; Syk Kinase; Tablets; Young Adult

Spleen tyrosine kinase (SYK) is a core signalling protein that drives inflammatory responses and is fundamental to the propagation of signals via numerous immune receptors, including the B cell receptor and Fc receptors (FcRs). Fostamatinib, a small molecule SYK inhibitor, has shown evidence of ameliorating inflammation in RA patients. We sought to understand how the active metabolite of fostamatinib, R406, affects the inflammatory response at the cellular level.. Antigen-specific in vivo systems and in vitro fluorescence microscopy were combined to investigate the effects of fostamatinib on antigen-specific interactions between dendritic cells (DCs) and CD4(+) T cells.. Although it has previously been shown that R406 reduces the response of DCs to immune complexes (ICs), we found that fostamatinib failed to reduce specific CD4(+) T cell proliferation in mice after immunization with ICs. However, we observed in vitro that R406 reduces both the area and duration of cellular interactions between IC-activated DCs and specific CD4(+) T cells during the initial phase of cellular crosstalk. This led to diminished proliferation of antigen-specific CD4(+) T cells after R406 treatment compared with vehicle controls. This decreased proliferative capacity of CD4(+) T cells was accompanied by reduced expression of the co-stimulatory molecules, inducible T cell co-stimulator (ICOS) and PD-1, and abrogation of the production of inflammatory cytokines such as IFN-γ and IL-17.. Our findings indicate a potential mechanism by which this compound may be effective in inhibiting FcR-driven CD4(+) T cell responses.

Topics: Administration, Oral; Aminopyridines; Animals; Antigen-Antibody Complex; CD4-Positive T-Lymphocytes; Cell Communication; Cell Proliferation; Cells, Cultured; Chemokines; Cytokines; Dendritic Cells; Enzyme Inhibitors; In Vitro Techniques; Intracellular Signaling Peptides and Proteins; Mice; Mice, Inbred C57BL; Mice, Mutant Strains; Models, Animal; Morpholines; Oxazines; Protein-Tyrosine Kinases; Pyridines; Pyrimidines; Syk Kinase

Topics: Aminopyridines; Autoimmune Diseases; Diabetes Mellitus, Type 2; Glomerulonephritis; Humans; Intracellular Signaling Peptides and Proteins; Morpholines; Oxazines; Protein Kinase Inhibitors; Protein-Tyrosine Kinases; Pyridines; Pyrimidines; Reperfusion Injury; Signal Transduction; Spleen; Syk Kinase

Antibody-mediated glomerulonephritis, including that resulting from immune complexes, is an important cause of renal failure and is in need of more specific and effective treatment. Binding of antibody or immune complexes to Fc receptors activates intracellular signal transduction pathways, including spleen tyrosine kinase (Syk), leading to the production of inflammatory cytokines. We examined the effect of R788 (fostamatinib disodium), an oral prodrug of the selective Syk inhibitor R406, in nephrotoxic nephritis in Wistar-Kyoto rats. Treatment with R788 reduced proteinuria, tissue injury, glomerular macrophage and CD8+ cell numbers, and renal monocyte chemoattractant protein-1 (MCP-1) and IL-1beta, even when we started treatment after the onset of glomerulonephritis. When we administered R788 from days 4 to 10, glomerular crescents reduced by 100% (P < 0.01) compared with the vehicle group. When we administered R788 treatment from days 7 to 14, established glomerular crescents reversed (reduced by 21%, P < 0.001), and renal function was better than the vehicle group (P < 0.001). In vitro, R406 downregulated MCP-1 production from mesangial cells and macrophages stimulated with aggregated IgG. These results suggest that Syk is an important therapeutic target for the treatment of glomerulonephritis.

Topics: Aminopyridines; Animals; Cells, Cultured; Chemokine CCL2; Disease Models, Animal; Glomerulonephritis; Interleukin-1beta; Intracellular Signaling Peptides and Proteins; Macrophages; Mesangial Cells; Morpholines; Oxazines; Protein-Tyrosine Kinases; Pyridines; Pyrimidines; Rats; Rats, Inbred WKY; Severity of Illness Index; Signal Transduction; Syk Kinase

The metabolism of the spleen tyrosine kinase inhibitor N4-(2,2-dimethyl-3-oxo-4-pyrid[1,4]oxazin-6-yl)-5-fluoro-N2-(3,4,5-trimethyoxyphenyl)-2,4-pyrimidinediamine (R406) and its oral prodrug N4-(2,2-dimethyl-4-[(dihydrogenphosphonoxy)methyl]-3-oxo-5-pyrid[1,4]oxazin-6-yl)-5-fluoro-N2-(3,4,5-trimethyoxyphenyl)-2,4-pyrimidinediamine disodium hexahydrate (R788, fostamatinib) was determined in vitro and in humans. R788 was rapidly converted to R406 by human intestinal microsomes, and only low levels of R788 were observed in plasma of human subjects after oral administration of (14)C-R788. R406 was the major drug-related compound in plasma from human subjects, and only low levels of metabolites were observed in plasma. The plasma metabolites of R406 were identified as a sulfate conjugate and glucuronide conjugate of the para-O-demethylated metabolite of R406 (R529) and a direct N-glucuronide conjugate of R406. Elimination of drug-related material into the urine accounted for 19% of the administered dose, and the major metabolite in urine from all the human subjects was the lactam N-glucuronide of R406. On average, 80% of the total drug was recovered in feces. Two drug-related peaks were observed; one peak was identified as R406, and the other peak was identified as a unique 3,5-benzene diol metabolite of R406. The 3,5-benzene diol metabolite appeared to result from the subsequent O-demethylations and dehydroxylation of R529 by anaerobic gut bacteria because only R529 was converted to this metabolite after the in vitro incubation with human fecal samples. These data indicate that the major fecal metabolite of R406 observed in humans is a product of a hepatic cytochrome P450-mediated O-demethylation and subsequent O-demethylations and dehydroxylation by gut bacteria.

Topics: Adult; Aminopyridines; Bacteria, Anaerobic; Biotransformation; Gastrointestinal Tract; Humans; In Vitro Techniques; Inactivation, Metabolic; Liver; Male; Microsomes; Morpholines; Oxazines; Prodrugs; Pyridines; Pyrimidines

The spleen tyrosine kinase (Syk) inhibitor R406 is orally administered as the prodrug R788. Following administration of R788 (12.5 mg kg(-1), 20 microCi kg(-1 14)C-R788) to intact and bile duct-cannulated cynomolgus monkeys, drug-related radioactivity was rapidly observed in plasma. No R788 was observed in plasma, while R406 was the major radioactive peak observed at all time points. Only low levels of metabolites were observed in plasma. The half-life for plasma radioactivity was 2.0-2.8 h. The majority (68.9%) of drug-related radioactivity was eliminated into bile. No intact R406 was observed in excreta. Biliary and urinary metabolites consisted of glucuronide and sulfate conjugates of the para-O-demethylated metabolite of R406 (R529), and a direct N-glucuronide of R406. The major metabolite in faeces from intact and bile duct-cannulated monkeys was a unique 3,5-benzene diol metabolite of R406. This metabolite was formed following the sequential O-demethylation and para-dehydroxylation of R529 by anaerobic gut bacteria.

Topics: Administration, Oral; Aminopyridines; Animals; Bacteria, Anaerobic; Bile; Carbon Radioisotopes; Feces; Intestines; Intracellular Signaling Peptides and Proteins; Macaca fascicularis; Male; Morpholines; Oxazines; Protein-Tyrosine Kinases; Pyridines; Pyrimidines; Syk Kinase

Urogenital abnormalities are among the most common of all human birth defects. In developmental toxicity studies with the Syk kinase inhibitor R788, a spectrum of findings, including renal agenesis, were observed. R788 has also been found to inhibit the receptor tyrosine kinase Ret. Ret kinase is known to be an essential component in the signaling pathway required for renal organogenesis and ureteric duct formation. Previously known is that mutant mice without the c-ret gene, develop urogenital malformations including renal agenesis.. In GLP developmental toxicity studies, gravid rabbits were treated orally with R788 at doses of 0, 10, 22, and 50 mg/kg/day (gestation days 7-19) and gravid rats received 0, 5, 12.5, and 25 mg/kg/day (gestation days 6-17) by the same route. The activity of R406 against Ret kinase was assessed in biochemical and cell-based assays.. A dose-dependent increase in malformations, including renal and ureteric agenesis and a specific major vessel anomaly, retroesophageal right subclavian artery, was observed in both the rat and rabbit. R788 proved to be a potent inhibitor of Ret kinase.. R788 promoted a spectrum of developmental toxicity, including renal and ureteric agenesis and a specific major vessel abnormality, retroesophageal right subclavian artery, in two different species. These effects are likely the result of inhibition of Ret kinase given its importance in the normal ontogeny of the urogenital and cardiovascular systems across species.

Topics: Abnormalities, Drug-Induced; Aminopyridines; Animals; Cells, Cultured; Embryonic Development; Enzyme Inhibitors; Female; Infertility; Male; Morpholines; Oxazines; Pregnancy; Prenatal Exposure Delayed Effects; Proto-Oncogene Proteins c-ret; Pyridines; Pyrimidines; Rabbits; Rats; Reproduction; Toxicity Tests

Spleen tyrosine kinase (Syk), a key mediator of immunoreceptor signaling in inflammatory cells, is essential for immune complex-mediated signal transduction initiated by activated receptors for immunoglobulin G. In collagen-induced arthritis, R788/R406, a novel and potent small molecule Syk inhibitor suppressed clinical arthritis, bone erosions, pannus formation, and synovitis. Serum anti-collagen type II antibody levels were unaltered, while the half-life of exogenous antibody was extended when co-administered with R406. Expression of the targeted kinase (Syk) in synovial tissue correlated with the joint level of inflammatory cell infiltrates and was virtually undetectable in treated rats. Syk inhibition suppressed synovial cytokines and cartilage oligomeric matrix protein (COMP) in serum, suggesting a sensitive and reliable biomarker for R406 activity. These results highlight the role of activating Fcgamma receptors in inflammatory synovitis and suggest that interruption of the signaling cascade with a novel Syk inhibitor may be a useful addition to immunosuppressive disease-modifying anti-rheumatic drugs currently used in the treatment of human autoimmune diseases such as rheumatoid arthritis.

Topics: Aminopyridines; Animals; Arthritis, Rheumatoid; Arthus Reaction; Bone Resorption; Collagen Type II; Disease Models, Animal; Female; Immunoglobulin G; Inflammation; Intracellular Signaling Peptides and Proteins; Morpholines; Oxazines; Prodrugs; Protein-Tyrosine Kinases; Pyridines; Pyrimidines; Rats; Rats, Sprague-Dawley; Receptors, IgG; Signal Transduction; Syk Kinase; Synovial Fluid; Synovitis