Discovery of Novel 3-Piperidinyl Pyridine Derivatives as Highly Potent and Selective Cholesterol 24-Hydroxylase (CH24H) Inhibitors.

Yuichi Kajita,Hiromi Fukuda,Shuhei Ikeda,Tsuyoshi Ishii,Weston Lane,Maki Miyamoto,Tatsuki Koike,Etsurou Watanabe,Jason Yano,Toshiya Nishi,Masato Yoshikawa

doi:10.1021/acs.jmedchem.1c01898

Yuichi Kajita, Hiromi Fukuda + Show 9 more

Open Access

https://doi.org/10.1021/acs.jmedchem.1c01898

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Abstract

Cholesterol 24-hydroxylase (CH24H or CYP46A1) is a brain-specific cytochrome P450 enzyme that metabolizes cholesterol into 24S-hydroxycholesterol (24HC) for regulating brain cholesterol homeostasis. For the development of a novel and potent CH24H inhibitor, we designed and synthesized 3,4-disubstituted pyridine derivatives using a structure-based drug design approach starting from compounds 1 (soticlestat) and 2 (thioperamide). Optimization of this series by focusing on ligand-lipophilicity efficiency value resulted in the discovery of 4-(4-methyl-1-pyrazolyl)pyridine derivative 17 (IC50 = 8.5 nM) as a potent and highly selective CH24H inhibitor. The X-ray crystal structure of CH24H in complex with compound 17 revealed a unique binding mode. Both blood-brain barrier penetration and reduction of 24HC levels (26% reduction) in the mouse brain were confirmed by oral administration of 17 at 30 mg/kg, indicating that 17 is a promising tool for the novel and selective inhibition of CH24H.

Highlights

Cholesterol homeostasis is independently regulated in the brain, while the liver plays a pivotal role in the peripheral tissues
CH24H is predominantly expressed in the brain,[4] and its activation has been considered therapeutic for several neurological disorders, including Alzheimer’s disease (AD) and Huntington’s disease (HD).[5]
The overlaid crystal structures of compounds 2 and 6 in the CH24H active site demonstrated that these two compounds were almost superimposable, except for the phenyl ring of 6, suggesting that filling in the pocket under Helix F by the displacement of a water molecule with the phenyl ring and replacing thiocarbonyl with the carbonyl group significantly contributed to enhanced potency (Figure 3b)

Summary

■ INTRODUCTION

Cholesterol homeostasis is independently regulated in the brain, while the liver plays a pivotal role in the peripheral tissues. 4-Phenylpyridine is expected to be a rigid and effective fragment that makes two important interactions one is the binding mode different from 1, displaying that its thiocarbonyl direct coordination to the heme iron by its pyridine nitrogen moiety recruited Arg[226] along with Phe[80] into the active site and the other is the hydrophobic interaction with the pocket of CH24H (Figure 1b) These amino acid residues fill the under Helix F by its phenyl ring. The reaction of commercially available 4-acetylpyridine with 1,3-dimethyl-2,3-dihydro-2oxopyrimidinium sulfate, which proceeded smoothly under mild conditions in the presence of triethylamine, followed by heating with ammonium acetate in acetic acid, completed the pyridine ring formation to form 33.20 Bromide was coupled with ethyl isonipecotate in the presence of DABCO to yield an ester 34, which was converted into the desired cyclopropylamides 7 and 15 via hydrolysis and condensation with cyclopropylamine and dimethylamine, respectively. Nucleophilic substitution of the fluoro group in with N,N-dimethylpiperidine-4-carboxamide under basic

23. RESULTS AND DISCUSSION

■ CONCLUSIONS

■ ACKNOWLEDGMENTS

■ REFERENCES