Discovery of Clinical Candidate 2-(4-(2-((1H-Benzo[d]imidazol-2-yl)thio)ethyl)piperazin-1-yl)-N-(6-methyl-2,4-bis(methylthio)pyridin-3-yl)acetamide Hydrochloride [K-604], an Aqueous-Soluble Acyl-CoA:Cholesterol O-Acyltransferase-1 Inhibitor

Abstract

[2][3][4]imidazol-2-yl)thio)ethyl)piperazin-1-yl)-N-(6-methyl-2,4-bis(methylthio)pyridin-3-yl)acetamide hydrochloride (K-604, 2) has been identified as an aqueous-soluble potent inhibitor of human acyl-coenzyme A:cholesterol O-acyltransferase (ACAT, also known as SOAT)-1 that exhibits 229-fold selectivity for human ACAT-1 over human ACAT-2. In our molecular design, the insertion of a piperazine unit in place of a 6methylene chain in the linker between the head (pyridylacetamide) and tail (benzimidazole) moieties led to a marked enhancement of the aqueous solubility (up to 19 mg/mL at pH 1.2) and a significant improvement of the oral absorption (the C max of 2 was 1100-fold higher than that of 1 in fasted dogs) compared with those of the previously selected compound, 1. After ensuring the pharmacological effects and safety, we designated 2 as a clinical candidate, named K-604. Considering the therapeutic results of ACAT inhibitors in past clinical trials, we believe that K-604 will be useful for the treatment of incurable diseases involving ACAT-1 overexpression.

Brain Targeting of Acyl-CoA:Cholesterol O-Acyltransferase-1 Inhibitor K-604 via the Intranasal Route Using a Hydroxycarboxylic Acid Solution

“…Although an extremely high aqueous solubility (19 mg/mL) of K-604 has been reported at pH 1.2, this solution formulation is very invasive to nasal epithelial tissues because of its corrosive acidity. When using a 0.01 N HCl solution, the acidity was somewhat weakened to 2.3, but the solubility decreased to 3.24 mg/mL.…”

“…K-604 was developed for the treatment of acute coronary syndrome in this Phase II study by Kowa Company Ltd. (Tokyo, Japan) according to a previously reported method. 17 For use as an internal standard for the low-level quantification of K-604 in plasma and brain tissues, a highly deuterium-labeled compound, 2-(4-(2-((1 H -benzo[ d ]imidazol-2-yl-4,5,6,7- d 4 )thio)ethyl)piperazin-1-yl)- N -(6-methyl-2,4-bis(methylthio)pyridin-3-yl)acetamide was also prepared by Kowa Company Ltd. Hyaluronic acid (HA), citric acid (CA), and d -gluconic acid (GA) were purchased from Tokyo Chemical Industry Co., Ltd. (Tokyo, Japan). Sodium 2-(6-oxido-3-oxo-3,10-dihydroanthracen-9-yl)benzoate (uranine) and 5 H -dibenzo[ b , f ]azepine-5-carboxamide (carbamazepine) were purchased from FUJIFILM Wako Pure Chemicals Corporation (Osaka, Japan).…”

“…Therefore, these fascinating trends prompted us to apply our developed ACAT-1 inhibitor to brain disease. 2-(4-(2-((1 H -Benzo­[ d ]­imidazol-2-yl)­thio)­ethyl)­piperazin-1-yl)- N -(6-methyl-2,4-bis­(methylthio)­pyridin-3-yl)­acetamide hydrochloride, (K-604), − shown in Figure , is the first potent and selective inhibitor of ACAT-1.…”

“…However, the solubility is only 0.05 mg/mL at pH 6.8. Therefore, K-604 requires an acidic pH, which allows for good oral absorption because of its high solubility in stomach fluid . It remains uncertain whether K-604 can transport across the BBB, which often obstructs the development of brain-targeted therapeutic agents that are orally administered.…”

Design, Synthesis and Anti-Tumor Activity of Novel Benzimidazole-Chalcone Hybrids as Non-Intercalative Topoisomerase II Catalytic Inhibitors

“…Benzimidazoles have various of biological activities, such as anti-bacterial, anti-inflammatory, anti-tumor, and so on [11][12][13][14][15]. Studies have shown that the benzimidazole scaffold rings play a critical role in the antitumor activity [16,17].…”