Atigadda VR, Xia G, Desphande A, Boerma LJ, Lobo-Ruppert S, Grubbs CJ, Smith CD, Brouillette WJ, Muccio DD. Methyl substitution of a rexinoid agonist improves potency and reveals site of lipid toxicity.
J Med Chem 2014;
57:5370-80. [PMID:
24801499 PMCID:
PMC4216212 DOI:
10.1021/jm5004792]
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Abstract
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(2E,4E,6Z,8E)-8-(3′,4′-Dihydro-1′(2′H)-naphthalen-1′-ylidene)-3,7-dimethyl-2,4,6-octatrienoic
acid, 9cUAB30, is a selective rexinoid that displays substantial chemopreventive
capacity with little toxicity. 4-Methyl-UAB30, an analogue of 9cUAB30,
is a potent RXR agonist but caused increased lipid biosynthesis unlike
9cUAB30. To evaluate how methyl substitution influenced potency and
lipid biosynthesis, we synthesized four 9cUAB30 homologues with methyl
substitutions at the 5-, 6-, 7-, or 8-position of the tetralone ring.
The syntheses and biological evaluations of these new analogues are
reported here along with the X-ray crystal structures of each homologue
bound to the ligand binding domain of hRXRα. We demonstrate
that each homologue of 9cUAB30 is a more potent agonist, but only
the 7-methyl-9cUAB30 caused severe hyperlipidemia in rats. On the
basis of the X-ray crystal structures of these new rexinoids and bexarotene
(Targretin) bound to hRXRα-LBD, we reveal that each rexinoid,
which induced hyperlipidemia, had methyl groups that interacted with
helix 7 residues of the LBD.
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