Structural optimization of a CXCR2-directed antagonist that indirectly inhibits γ-secretase and reduces Aβ

Amyloid β (Aβ), a key molecule in the pathogenesis of Alzheimer’s disease (AD), is derived from the amyloid precursor protein (APP) by sequential proteolysis via β- and γ-secretases. Because of their role in generation of Aβ, these enzymes have emerged as important therapeutic targets for AD. In the case of γ-secretase, progress has been made towards designing potent inhibitors with suitable pharmacological profiles. Direct γ-secretase inhibitors are being evaluated in clinical trials and new strategies are being explored to block γ-secretase activity indirectly as well. In this regard, we have previously reported an indirect regulation of γ-secretase through antagonism of CXCR2, a G-protein coupled receptor (GPCR). We demonstrated that N-(2-hydroxy-4-nitrophenyl)-N′-(2-bromophenyl)urea (SB225002), a selective inhibitor of CXCR2 also plays a role in an indirect inhibition of γ-secretase. Furthermore, we reported a ∼5-fold difference in the selective inhibition of APP versus Notch processing via γ-secretase following treatment with SB225002. Herein we describe the synthesis and optimization of SB225002. By determination of the structure–activity relationship (SAR), we derived small molecules that inhibit Aβ40 production with IC50 values in the sub-micromolar range in a cell-based assay and also validated the potential of CXCR2 as a new target for therapeutic intervention in AD.

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