Inhibitors of the interaction of a thyroid hormone receptor and coactivators: preliminary structure-activity relationships

Abstract

The modulation of gene regulation by blocking the interaction between the thyroid receptor (TR) and obligate coregulators has been reported recently with the discovery of the lead compound 3-(dimethylamino)-1-(4-hexylphenyl)propan-1-one). Herein we report studies aimed at optimization of this initial hit to determine the basic parameters of the structure-activity relationships and clarify the mechanism of action. These studies provided new insights, showing that activity and TRbeta isoform selectivity is highly correlated with the structural composition of these covalent inhibitors.

Figure 1

Summary of screened β-aminophenylketone. Inhibition (%) of the interaction between coactivator peptide SRC2-2 and TRβ in the presence of 30 μM compound is depicted in bold.

Figure 2

Scatter plot of solubility and permeability data for all compounds except acrylates.^{a a}Δ Aminophenylketones (Table 1), □ enones (Table 2), + acrylamides (Table 4), ■ electrophiles (Table 5); n = number of X values, s = slope, F = F-values, r² = square correlation coefficient, () excluded data points.

Figure 3

LCMS-PDA analysis of 3h in water, saline (150 mM NaCl), and human blood plasma (all pH 7).^{a a}Integrated absorption area at 254 nm (PDA); black: ratio between peak area of 3h and peak area of internal standard (salicylic acid) measured in blood plasma (left y-axis); grey: area of 3h measured in water (right axis); white: area of 3h measured in saline (right y-axis).

Figure 4

Scatter plot of LD₅₀ values measured in U2OS and ARO cells for all compounds.^{a a}Δ Aminophenylketones (Table 1), □ enones (Table 2), * acrylates (Table 3), + acrylamides (Table 4), ■ electrophiles (Table 5), () excluded data points.

Figure 5

Pharmacophore elucidation using MOE software.^{a a}Molecules are illustrated in stick form: gray = carbon, red = oxygen, blue = nitrogen; green mesh balls = hydrophobic center (Uns = unsaturated, Aro = aromatic, Ali = aliphatic); blue mesh balls = possible electron acceptor site; A: enones (active in FP assay), B: acrylates (IC₅₀ < 30 μM), C: acrylamides (active in FP assay).

Figure 6

Modeling study of the bonding of compound 1 to the TR coactivator binding pocket.^{a a}Surface gray: hydrophobic; blue: nitrogen; red: oxygen; yellow: sulfur.

Scheme 1

Synthesis of β-aminophenylketones 3a–k.^{a a}Reagents: (i) AlCl₃ (2 equiv), acryloyl chloride, DCM, 0°C, 1 h; (ii) HNR₁R₂, THF, rt, 1 h.

Scheme 2

Synthesis of ketones 1, 4a, and 4g.^{a a}Reagents: (i) AlCl₃ (2 equiv), acid chloride (maleic anhydride to form 4a), DCM, 0°C, 1 h.

Scheme 3

Synthesis of unsaturated ketones 4b–f.^{a a}Reagents: (i) BuLi, THF, −78°C, 20 min; (ii) RCHO, −78°C, 2 h; (iii) tetrapropylammonium perruthenate (0.05 equiv), 4-methylmorpholine N-oxide (1.5 equiv), molecular sieves, CH₃CN, rt, 1–4 h.

Scheme 4

Synthesis of substituted acrylates 6a–l.^{a a}Reagents: (i) acryloyl chloride (1.1 equiv), NEt₃ (1.1 equiv), DCM, rt, 1 h.

Scheme 5

Synthesis of substituted acrylamides 7a–l.^{a a}Reagents: (i) acid chloride or anhydride, NEt₃ (1.1 equiv, when the acid chloride was used), DCM, rt, 1 h.

Scheme 6

Synthesis of 8a and 8b.^{a a}Reagents: (i) propionic acid (1.3 equiv), 4-dimethylaminopyridine (0.001 equiv), N,N′-diisopropylcarbodiimide, DCM, rt, 5 h.

Scheme 7

Synthesis of 8a and 8b.^{a a}Reagents: (i) DBU (1.1 equiv), benzene, rt, 2 h; (ii) H₂O₂ (30%) (5 equiv), NaOH (1M in H₂O), MeOH, 20 min.