Targeting B Cells and Bruton's Tyrosine Kinase for SCI Therapeutics

Following spinal cord injury (SCI), there is an urgent need for therapeutics to minimize motor deficits. Inflammatory/B cell autoimmune mechanisms are strongly implicated in the secondary injury cascade. The NLRP3 inflammasome, expressed in myeloid cells, mediates activation of caspase 1 and in turn results in production of the cytokines IL-1â and IL-18, which contributes to inflammation and locomotor deficits after SCI. B cell autoimmunity causes axon and myelin damage, glial cell activation, and resultant locomotor deficits in humans and in animal models. There are few therapies designed to target these mechanisms. B cell-depleting monoclonal antibodies have been developed for use in autoimmune diseases. However, these therapies are associated with severe toxicity/side effects. Classic microtubule-inhibiting agents, such as colchicine, have anti-inflammatory/immune effects but also exhibit significant toxicity. Bruton’s tyrosine kinase (BTK) is a key player in B cell autoimmunity and myeloid cell NLRP3 inflammasome activation and inflammation. Ibrutinib (PCI 32765, an FDA-approved selective inhibitor of BTK) is highly efficacious and safe for attenuating B cell malignancy in humans. However, little is known about the roles of BTK in SCI. This proposal builds upon on our discovery that fenbendazole (FBZ) reduces B cell response and locomotor deficits following SCI in mice. FBZ and related compound (flubendazole, FluBZ) are benzimidazole anthelmintics. FluBZ is approved for human use, while FBZ is only used in veterinary medicine. FluBZ can be administered long term at therapeutic doses with minimal side effects. Preliminary data demonstrated that SCI results in BTK upregulation and activation in lesion site of spinal cord 4 weeks post-injury that are reduced by FluBZ intraperitoneal administration. The purpose of the proposal is to determine if FluBZ and Ibrutinib inhibit BTK activation, B cell autoimmunity, myeloid cell NLRP3 inflammasome activation, and improve functional outcomes following SCI in rats. The experiments outlined in Aim 1 of this proposal will evaluate the hypothesis that FluBZ and Ibrutinib administration post-injury will attenuate pathology and functional deficits after SCI in rats. Aim 2 is to examine the hypothesis that FluBZ and Ibrutinib will inhibit the BTK activation, B cell proliferation and activation, and autoimmunity, following SCI. Support of our hypothesis would suggest FluBZ and Ibrutinib as novel potential therapeutics for protecting in SCI. These compounds are-approved for human use, are safe at therapeutic doses, and could easily be translated to human clinical trials.