Developing a Rat Analogue of a Human Transglutaminase 2 Inhibitory Antibody to Facilitate Preclinical Testing in Treating Kidney Fibrosis

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Fibrosis, or scarring, is a frequent feature of a number of relatively common, usually chronic, diseases. These include many types of lung, liver and heart disease and essentially all forms of chronic kidney disease. Studies of the mechanisms underlying the scarring process is an area of intense activity given that currently there is no recognized anti-scarring / anti-fibrotic therapy available for a condition that is ultimately fatal for millions of people each year. Subsequently the potential therapeutic benefits offered by the development of agents able to block or reduce the impact of scarring are considerable. Cumulative data from a range of different groups and experimental designs have highlighted tissue transglutaminase (transglutaminase type 2 ,TG2) as a key effector of the scarring process. Transglutaminases are a family of closely related enzymes that all catalyze the crosslinking of peptide chains via covalent epsilon (gamma-glutamyl) lysine bonds. It is this peptide crosslinking activity of TG2 that acts to produce the increased deposition and stabilization of extracellular matrix observed in chronic scarring. Knockdown of TG2, either genetically, or through the use of small molecule inhibitors, has been shown to have clear beneficial effects in animal models of chronic kidney disease (CKD). Scarring & fibrosis is reduced and kidney function preserved by up to 80% over the timescale of the experiments. Translation of these results into the patient setting would have profound therapeutic application in the area of CKD, and possibly other diseases that feature chronic scarring. Prolonging kidney function and delaying the requirement for dialysis or renal transplantation would offer a substantial increase in the quality of life of CKD patients and have major cost implications for the health service. Given the clear case for the development of TG2 inhibitors, there is much interest in this area of research. Development of inhibitors have been hampered by the degree of structural conservation between the 8 different members of the TG family. The catalytic site, or 'core', is highly conserved and all existing small molecule candidates have exhibited prohibitive levels of cross reactivity with other related enzymes. This is particularly important in the case of TG1 and TG3, which are critical to maintaining integrity of the dermis, and factor XIIIa, a major component of the clotting process. Inhibition of these related TG molecules produces serious side effects that would preclude a therapeutic role for existing small molecule inhibitors. A monoclonal antibody approach to this problem offers the potential to overcome these specificity issues due to the very precise nature of antibody targeting.Using an innovative immunization approach we have successfully generated a series of TG2-specific inhibitory monoclonal antibodies. All are specific for human TG2 and show no cross reactivity to other members of the enzyme family. We have established the inhibitory potential of these mAbs in different in vitro systems and derived IC50 data. The most effective of these antibodies has been humanised, with the affinity and inhibitory activity being preserved. The next stage in the development of this potential therapeutic is to generate preclinical data in FDA approved animal models of chronic fibrosis. The most effective monoclonal, AB1, and the other candidates, are all specific for human TG2, and lack significant inhibitory action against mouse or rat TG2. Accordingly, the aim of this project is to allow us to generate orthologous inhibitory antibodies against rat and mouse TG2, in order that we can gather this crucial preclinical data, attract downstream commercial partners, and accelerate the development of this potentially new class of therapeutic agents.