Molecule

Description

Cancer

Description

Clinofibrate inhibits hydroxymethylglutaryl coenzyme A reductase (HMGCR) with IC50 of 0.47 mM.

Targets

IC₅₀

In Vitro

Clinofibrate is an antihyperlipidemic agent with IC50 with 40 μM on the activities of human liver 3α-hydroxysteroid dehydrogenases. Clinofibrate stimulates the activity of AKR 1C4 by 2.0-fold. The concentration of Clinofibrate at which maximum stimulation is achieved is 50 μM. ^[1]

In Vivo

Clinofibrate significantly decreases the high plasma cholesterol level of atherosclerotic rats, which was 823 +/- 256 (mean +/- SD) mg/dl, or about ten times that of control rats (85 +/- 11 mg/dl). On treatment with Clinofibrate, the cholesterol level is reduced mostly in the very low density lipoprotein (VLDL) fraction (d less than 1.006). Heparin-releasable lipoprotein lipase activity in epididymal adipose tissue, lipoprotein lipase activity in post heparin plasma, and VLDL-triolein hydrolizing activity in adipose tissue stromal vessels are higher in Clinofibrate-treated rats than in atherosclerotic rats. Of the enzymes in the arterial wall concerned with cholesterol ester metabolism, acid cholesterol esterase activity is decreased in atherosclerotic rats, and Clinofibrate treatment increased this activity. The ratio of acyl-CoA cholesterol acyltransferase activity (ACAT) to neutral cholesterol esterase activity is higher in atherosclerotic rats than in control rats and is lower in Clinofibrate-treated rats than in atherosclerotic rats. ^[2]

Clinical Trials

Features

Dehydrogenase Activity Assay

Dehydrogenase activities of human liver and recombinant 3αHSDs are assayed spectrophotometrically or fluorometrically by recording the production of NADPH. The standard assay for the activity is performed in 2.0 mL of 0.1 M potassium phosphate, pH 7.4, containing 0.25 mM NADP ⁺, 2 mM S-indan-1-ol and enzyme. The activities of the K270M and R276M mutant enzymes are determined with 0.5 mM and 5 mM NADP⁺, respectively, in the above reaction mixture because of their high Km values for the coenzyme. One unit of the enzyme activity is defined as the amount catalyzing the formation of 1 μmol NADPH/min at 25 °C. The stoichiometry of the production of NADPH and oxidized product (1- indanone) is examined by measuring the amount of 1-indanone in the reaction mixture by high-performance liquid chromatography. The reaction iss started in the absence or presence of 50 μM fenofibric acid as the activator by the addition of the enzyme (50 μg), incubated for 5 minutes with monitoring the production of NADPH at 340 nm and then terminated by the addition 4 mL of ice-cold methanol containing benzaldehyde as the internal standard. After centrifugation at 10,000 × g for 10 minutes, 50 μL of the supernatant are subjected to reversed-phase high-performance liquid chromatography using a Nova- Pack C18 column (3.9 × 15 mm,) with a 4 to 40% (v/v) linear gradient of methanol/25 mM potassium phosphate buffer, pH 5.6, at a flow rate of 0.8 mL/min and at 25 °C. S-Indan-1-ol and 1-indanone are detected at 270 and 250 nm, respectively, and the respective retention times are 22.2 and 23.9 min. The concentrations of the substrate and product are determined by their peak area. The drugs and their derivatives with free carboxyl group are dissolved in 0.1 M NaOH, and then neutralized with 0.1 M HCl. Probucol, fenofibrate and clofibrate are dissolved in methanol, and added to the reaction mixture to give a final methanol concentration of 2.5%. The drugs and their derivatives are added to the reaction mixture just before the reaction is started by the addition of the enzyme. The pH dependency of the enzyme activity is determined with 0.1 M potassium phosphate buffers (pH 6.5–10.0) which are prepared by mixing solutions of H₃PO₄ and K₃PO₄. In a separate experiment to test the reversibility of the activation, the activating drugs-(50 or 200 μM) enzyme mixture is diluted 10-fold with 10 mM potassium phosphate buffer, pH 7.4, or dialyzed against the buffer containing 20% glycerol at 4 °C and then the activity of the preparation is assayed. Lineweaver-Burk analyses are performed in the presence of five different substrate concentrations with saturating NADP⁺ concentration of 0.25 mM, and then kinetic data is analyzed. The kinetic studies in the presence of inhibitors are carried out in a similar manner, and the inhibition constant (K_i) is determined. Initial velocity analyses for determination of the dissociation constant (K_A), α and β values for the activating drug are carried out in the presence of its six different concentrations ranging from 0.2 × K_A to 5 or 15 K_A values. The kinetic values are calculated from secondary replots of 1/Δ slope or 1/Δintercept versus 1/[drug]. The Δslope values and Δintercept values are obtained from individual Lineweaver-Burk plots. The values of the enzyme activity and kinetic constants are expressed as means 6 S.E. of at least three determinations.

Animal Models

Seven-week-old Sprague-Dawley rats (SLC), six-week-old ICR-SLC mice and a one-year-old beagle dog

Formulation

Doses

30 mg/kg

Administration

Administered orally or intravenously