Synthesis of Nonretinoid Inhibitors of RPE65 for the Potential Treatment of Dry Age-Related Macular Degeneration and Stargardt Disease
Loading...
Issue Date
2020-07
Authors
Wang, Ivan E. '20
Degree
MS in Pharmaceutical Sciences
Advisor
Cioffi, Christopher L.
Committee Members
Hass, Martha A.
Voigt, Jeffrey M.
Voigt, Jeffrey M.
Journal Title
Journal ISSN
Volume Title
Abstract
Age-related macular degeneration and Stargardt disease involves neurodegeneration of the macula. Accumulation of cytotoxic bisretinoid fluorophores mediate lipofuscin toxicity. Reducing 11-cis-retinaldehyde and all-trans-retinaldehyde in the retina by modulating the visual cycle may potentially delay or halt the progression of dry AMD and Stargardt disease. A critical step in the visual cycle, catalyzed by RPE65 is the isomerohydrolysis of all-trans-retinyl palmitate ester to 11-cis-retinol. Through the identification of (R)-emixustat and subsequent in silico high-throughput screen, CU239, a selective, competitive inhibitor of RPE65 with a KD = 230 nM and an IC50 = 6 \316\274M was identified. When systemically administered, CU239 exhibited target engagement and conferred a partial protection of the retina in the light-induced retinal damage assay. These data suggest that CU239 is a suitable hit molecule for further optimization. Identification of a more potent analogue with improved physiochemical properties was completed using iterative medicinal chemistry by analyzing structure activity and property relationships. Medicinal chemistry approaches included peptide coupling conditions with HBTU and carboxylic acid intermediates. Compounds were purified using normal phase or reversed phase column chromatography. Synthesized and biologically tested compounds were characterized by 1H NMR and LC-MS with purities of >95%. The analogues explored urea and amide appendages which were designed to understand the RPE65 binding pocket. Hydrophobic aryl, cycloalkyl, and alkyl appendages induce significant RPE65 inhibitory activity, whereas polar heteroaromatic analogues were not well tolerated. This trend supported our proposed pharmacophore and binding pose for CU239. Compound 12 exhibited significantly improved ligand lipophilic efficiency (LLE = 2.0) by demonstrating a 3-fold improvement in potency (IC50 = 2.1 \316\274M) relative to CU239 and significant reduction in molecular weight (351.47 g/mol), cLogP (3.70), and topological polar surface area (53.59 \303\205). Unlike (R)-emixustat, compound 12 did not undergo metabolism by LRAT or VAP-1 and was not a potent inhibitor of VAP-1 or CYP2C19. Using compound 12, further optimization can identify compounds with increased potency and more favorable physiochemical properties. The identification of such compounds will lead to their evaluation of efficacy, pharmacokinetics, and in vivo proof-of-concept target engagement testing in mouse models for dry AMD and Stargardt disease upon oral administration.
Citation
Wang IE. Synthesis of nonretinoid inhibitors of RPE65 for the potential treatment of dry age-related macular degeneration and Stargardt Disease [thesis]. Ann Arbor (MI): Proquest LLC; 2020. 137 p.
ACPHS Research Commons URI
Description
Click on the Resource Link to find this item in the ACPHS Library catalog.