CNS-targeted NLRP3 Inhibition by NT-0527 confers therapeutic advantage in a CAPS mouse model.

backgroundThe NACHT, LRR and PYD domains-containing protein 3 (NLRP3) inflammasome is a key mediator of innate immune responses which functions to facilitate production of inflammatory cytokines Interleukin (IL)-1β and IL-18 and pyroptotic cell death; dysregulated NLRP3 activation contributes to a wide range of inflammatory diseases. Gain-of-function (GoF) mutations in the NLRP3 gene underlie cryopyrin-associated periodic syndromes (CAPS), a spectrum of rare autoinflammatory disorders characterized by both systemic and central nervous system (CNS) involvement. The hD305N mutant CAPS mouse model recapitulates these human disease features, including spontaneous peripheral and CNS manifestations, making it a powerful tool for evaluating the effectiveness of NLRP3 inhibitors. Here, we use this model to compare blood-brain barrier-penetrant NT-0527 and non-penetrant CP-456,773 inhibitors for their ability to provide therapeutic benefit within peripheral and central compartments and to address the question of whether CNS anti-inflammatory outcomes are enhanced by access of an NLRP3 inhibitor to the local tissue environment.

resultsThe two inhibitors possess similar in vitro pharmacological profiles and effectively inhibited NLRP3 function in vivo following acute LPS challenge of hD305N mice. Moreover, when administered therapeutically, the individual inhibitors reduced peripheral inflammatory biomarkers attendant to IL-1β output resulting from hyperactivity of the hD305N GoF NLRP3 mutein. Peripheral pharmacological impact included direct evidence of NLRP3 target engagement assessed as a reduction in levels of mature IL-1β recovered in tissue homogenates. In sharp contrast, NT-0527 but not CP-456,773 mitigated CNS inflammation as evidenced by normalized expression of a panel of inflammatory genes and reduced accumulation of myeloid cells in brains of hD305N CAPS mice. In line with this differential impact, NT-0527 treatment reduced levels of mature IL-1β recovered in hD305N brain homogenates demonstrating CNS-centric target engagement while CP-456,773 treatment did not. Notably, CP-456,773 reduced inflammatory cell accumulation in the adjacent dura mater, which lies outside the blood–brain and blood–CSF barriers.

conclusionsThese findings highlight the importance of locally generated IL-1β in driving CNS disease manifestations in a mouse CAPS model, and demonstrate a clear therapeutic advantage for a BBB-penetrant NLRP3 inhibitor in mitigating inflammatory outcomes within the central compartment.