ONX-0914 (PR-957) is a potent and selective immunoproteasome inhibitor with minimal cross-reactivity for the constitutive proteasome.
in vitro: PR-957 blocked presentation of LMP7-specific, MHC-I-restricted antigens in vitro and in vivo. Selective inhibition of LMP7 by PR-957 blocked production of interleukin-23 (IL-23) by activated monocytes and interferon-gamma and IL-2 by T cells.
in vivo: In mouse models of rheumatoid arthritis and lupus, ONX-0914 treatment reverses signs of disease and results in reductions in cellular infiltration, cytokine production and autoantibody levels at well-tolerated doses. The maximum tolerated dose (MTD) of ONX-0914 in mice to be 30 mg/kg body weight. IFN-g release is inhibited by ~60% at LMP7-selective concentrations of ONX-0914 and by ~90% at higher concentrations. Production of IL-2 is also inhibited by ~50%.
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