ABSTRACT
Huntington's disease (HD) is a lethal autosomal dominant neurodegenerative disorder resulting from a CAG repeat expansion in the huntingtin (HTT) gene. The product of translation of this gene is a highly aggregation-prone protein containing a polyglutamine tract >35 repeats (mHTT) that has been shown to colocalize with histone deacetylase 4 (HDAC4) in cytoplasmic inclusions in HD mouse models. Genetic reduction of HDAC4 in an HD mouse model resulted in delayed aggregation of mHTT, along with amelioration of neurological phenotypes and extended lifespan. To further investigate the role of HDAC4 in cellular models of HD, we have developed bifunctional degraders of the protein and report the first potent and selective degraders of HDAC4 that show an effect in multiple cell lines, including HD mouse model-derived cortical neurons. These degraders act via the ubiquitin-proteasomal pathway and selectively degrade HDAC4 over other class IIa HDAC isoforms (HDAC5, HDAC7, and HDAC9).
Subject(s)
Histone Deacetylases , Huntington Disease , Animals , Disease Models, Animal , Drug Development , Histone Deacetylases/metabolism , Huntingtin Protein/genetics , Huntingtin Protein/metabolism , Huntington Disease/genetics , Mice , Neurons/metabolism , Proteolysis , UbiquitinsABSTRACT
Antagonists of retinol-binding protein 4 (RBP4) impede ocular uptake of serum all-trans retinol (1) and have been shown to reduce cytotoxic bisretinoid formation in the retinal pigment epithelium (RPE), which is associated with the pathogenesis of both dry age-related macular degeneration (AMD) and Stargardt disease. Thus, these agents show promise as a potential pharmacotherapy by which to stem further neurodegeneration and concomitant vision loss associated with geographic atrophy of the macula. We previously disclosed the discovery of a novel series of nonretinoid RBP4 antagonists, represented by bicyclic [3.3.0]-octahydrocyclopenta[c]pyrrolo analogue 4. We describe herein the utilization of a pyrimidine-4-carboxylic acid fragment as a suitable isostere for the anthranilic acid appendage of 4, which led to the discovery of standout antagonist 33. Analogue 33 possesses exquisite in vitro RBP4 binding affinity and favorable drug-like characteristics and was found to reduce circulating plasma RBP4 levels in vivo in a robust manner (>90%).
Subject(s)
Bridged Bicyclo Compounds/therapeutic use , Geographic Atrophy/drug therapy , Macular Degeneration/congenital , Pyrroles/therapeutic use , Retinol-Binding Proteins, Plasma/antagonists & inhibitors , Animals , Bridged Bicyclo Compounds/chemistry , Bridged Bicyclo Compounds/pharmacokinetics , Dogs , Humans , Macular Degeneration/drug therapy , Madin Darby Canine Kidney Cells , Pyrroles/chemistry , Pyrroles/pharmacokinetics , Rats , Rats, Sprague-Dawley , Retinol-Binding Proteins, Plasma/metabolism , Stargardt Disease , Structure-Activity RelationshipABSTRACT
Accumulation of lipofuscin in the retina is associated with pathogenesis of atrophic age-related macular degeneration and Stargardt disease. Lipofuscin bisretinoids (exemplified by N-retinylidene-N-retinylethanolamine) seem to mediate lipofuscin toxicity. Synthesis of lipofuscin bisretinoids depends on the influx of retinol from serum to the retina. Compounds antagonizing the retinol-dependent interaction of retinol-binding protein 4 (RBP4) with transthyretin in the serum would reduce serum RBP4 and retinol and inhibit bisretinoid formation. We recently showed that A1120 (3), a potent carboxylic acid based RBP4 antagonist, can significantly reduce lipofuscin bisretinoid formation in the retinas of Abca4(-/-) mice. As part of the NIH Blueprint Neurotherapeutics Network project we undertook the in vitro exploration to identify novel conformationally flexible and constrained RBP4 antagonists with improved potency and metabolic stability. We also demonstrate that upon acute and chronic dosing in rats, 43, a potent cyclopentyl fused pyrrolidine antagonist, reduced circulating plasma RBP4 protein levels by approximately 60%.
Subject(s)
Drug Design , Macular Degeneration/drug therapy , Macular Degeneration/pathology , Piperidines/chemical synthesis , Piperidines/pharmacology , Retinol-Binding Proteins, Plasma/antagonists & inhibitors , Animals , Atrophy , Chemistry Techniques, Synthetic , Ligands , Male , Mice , Molecular Docking Simulation , Piperidines/chemistry , Piperidines/metabolism , Prealbumin/antagonists & inhibitors , Protein Conformation , Rats , Retinol-Binding Proteins, Plasma/chemistry , Retinol-Binding Proteins, Plasma/metabolism , Stargardt Disease , Structure-Activity RelationshipABSTRACT
[chemical reaction: see text]. A direct access to (+/-)-5-epi-10-epi-vibsanin E is described, based on three key cycloaddition steps, a rhodium-catalyzed [4 + 3] cycloaddition, a heteronuclear [4 + 2] cycloaddition, and a photochemically induced [4 + 2] cycloaddition.
