The importance of Spleen tyrosine kinase (Syk) as a potential therapeutic target in glomerulonephritis
Lead Research Organisation:
Imperial College London
Department Name: Dept of Medicine
Abstract
Antibody-mediated diseases are those caused by the body?s immune system targeting our own organs. When this occurs in the kidneys it causes inflammation, called glomerulonephritis. This is a common cause of kidney failure. Current treatments for this condition are not always effective and may have severe side-effects. Better and safer treatment is needed.
We have shown that a drug called R788 is extremely effective in treating animals with immune-mediated glomerulonephritis. R788 is also effective in treating humans with other forms of immune-mediated disease, such as rheumatoid arthritis. I would like to investigate whether this drug would be a useful and safe treatment for glomerulonephritis in humans.
I will achieve this by comparing the effects of R788 on white blood cells and kidney cells taken from humans and animals with glomerulonephritis. I aim to establish if the drug?s target molecule is present in human cells, and if so, whether it is active in reducing levels of inflammation and the antibodies responsible for autoimmunity. This information may provide the basis for a future clinical trial of R788 in humans with glomerulonephritis.
I will undertake this research along with other doctors from the Imperial College Kidney and Transplant Institute in London.
We have shown that a drug called R788 is extremely effective in treating animals with immune-mediated glomerulonephritis. R788 is also effective in treating humans with other forms of immune-mediated disease, such as rheumatoid arthritis. I would like to investigate whether this drug would be a useful and safe treatment for glomerulonephritis in humans.
I will achieve this by comparing the effects of R788 on white blood cells and kidney cells taken from humans and animals with glomerulonephritis. I aim to establish if the drug?s target molecule is present in human cells, and if so, whether it is active in reducing levels of inflammation and the antibodies responsible for autoimmunity. This information may provide the basis for a future clinical trial of R788 in humans with glomerulonephritis.
I will undertake this research along with other doctors from the Imperial College Kidney and Transplant Institute in London.
Technical Summary
Antibody-mediated glomerulonephritis (GN) is a major cause of end stage renal disease. Current treatments for GN are non-specific, not always effective, and associated with significant toxicity. More effective treatment is needed.
We have shown that R788, an oral prodrug of R407, a small molecule inhibitor of spleen tyrosine kinase (Syk) is remarkably effective in both preventing and treating established disease in an antibody-dependent animal model of crescentic GN that is characterized by early macrophage infiltration into glomeruli (nephrotoxic nephritis, NTN). Syk is an intracellular tyrosine kinase that has an established role in immunoreceptor signaling. There is also accumulating evidence that Syk is involved in post-receptor signaling of various cytokines including TNFa, IFNa and IL-1a. I wish to establish the precise role of Syk in NTN and the mechanisms by which Syk inhibition acts, with a view to developing a rationale for inhibiting Syk in the treatment of human GN.
The proposed study incorporates a detailed in vitro analysis of the effects of Syk inhibition on cultured rat and human cell lines (macrophages and mesangial cells) and nephritic rat glomeruli ex vivo, using a variety of techniques including standard and cell-based ELISA, western blot and microsphere cytokine assays. siRNA techniques will be employed to determine the specificity of R406 in inhibiting Syk dependent pathways.
I will also examine the effect of Syk inhibition on autoantibody production in vivo, using an animal model of glomerulonephritis that relies on antibody production following immunization with the a3 chain of type IV collagen (experimental autoimmune glomerulonephritis).
The proposal also includes a study of human material. The presence of activated Syk and its downstream targets will be assessed in biopsy specimens from patients with GN using immunohistochemistry (IHC), allowing me to identify those patients in whom Syk inhibition should be a therapeutic target. I will determine the pattern of urinary and tissue cytokine expression in these patients, using microsphere cytokine assays of urine samples and real time PCR of tissue obtained from biopsies by laser capture microdissection. By correlation with the IHC findings, I may be able to identify surrogate markers of Syk activation in tissue or urine that could be used clinically to identify patients who would benefit from Syk inhibition.
I expect that the results of these studies should clarify the potential role of Syk in human GN, and may form the basis of future clinical trials using Syk inhibition as a therapeutic strategy.
We have shown that R788, an oral prodrug of R407, a small molecule inhibitor of spleen tyrosine kinase (Syk) is remarkably effective in both preventing and treating established disease in an antibody-dependent animal model of crescentic GN that is characterized by early macrophage infiltration into glomeruli (nephrotoxic nephritis, NTN). Syk is an intracellular tyrosine kinase that has an established role in immunoreceptor signaling. There is also accumulating evidence that Syk is involved in post-receptor signaling of various cytokines including TNFa, IFNa and IL-1a. I wish to establish the precise role of Syk in NTN and the mechanisms by which Syk inhibition acts, with a view to developing a rationale for inhibiting Syk in the treatment of human GN.
The proposed study incorporates a detailed in vitro analysis of the effects of Syk inhibition on cultured rat and human cell lines (macrophages and mesangial cells) and nephritic rat glomeruli ex vivo, using a variety of techniques including standard and cell-based ELISA, western blot and microsphere cytokine assays. siRNA techniques will be employed to determine the specificity of R406 in inhibiting Syk dependent pathways.
I will also examine the effect of Syk inhibition on autoantibody production in vivo, using an animal model of glomerulonephritis that relies on antibody production following immunization with the a3 chain of type IV collagen (experimental autoimmune glomerulonephritis).
The proposal also includes a study of human material. The presence of activated Syk and its downstream targets will be assessed in biopsy specimens from patients with GN using immunohistochemistry (IHC), allowing me to identify those patients in whom Syk inhibition should be a therapeutic target. I will determine the pattern of urinary and tissue cytokine expression in these patients, using microsphere cytokine assays of urine samples and real time PCR of tissue obtained from biopsies by laser capture microdissection. By correlation with the IHC findings, I may be able to identify surrogate markers of Syk activation in tissue or urine that could be used clinically to identify patients who would benefit from Syk inhibition.
I expect that the results of these studies should clarify the potential role of Syk in human GN, and may form the basis of future clinical trials using Syk inhibition as a therapeutic strategy.