Leflunomide (HWA486) is an immunomodulatory agent used in the therapy of rheumatoid arthritis and psoriatic arthritis.

Leflunomide能够防止和逆转啮齿动物、狗、猴等体内同种异体移植物和异种移植物排斥.

Leflunomide是一种免疫调节药物,可通过抑制线粒体酶二氢乳清脱氢酶发挥作用。Leflunomide能够抑制抗CD3-和白细胞介素-2（IL-2）刺激的T细胞增殖。Leflunomide也抑制抗CD3单克隆抗体刺激的反应,即人T淋巴细胞中IL-2产生和IL-2受体的表达。Leflunomide也抑制CTLL-4细胞中IL-2刺激的酪氨酸磷酸化。Leflunomide通过干扰由于rUMP产生不足和利用涉及p53的机制而引起的细胞周期进展来阻止活化和自身免疫淋巴细胞的扩增。Leflunomide在体外酪氨酸激酶测定中,能够抑制p59fyn和p56lck活性。

DHODase activity is measured by the DCIP colorimetric assay. This is a coupled assay in which oxidation of DHO and subsequent reduction of ubiquinone are stoichiometrically equivalent to the reduction of DCIP. Reduction of DCIP is accompanied by a loss of absorbance at 610 nm (ε=21500 M/cm). The assay is performed in a 96-well microtiter plate at ambient temperature (ca. 25°C). Stock solutions of 10 mM leflunomide and A771726 are prepared in dimethyl sulfoxide (DMSO) and these are diluted with reaction buffer (100 mM Tris and 0.1 % Triton X-100, pH 8.0) to prepare working stocks of the inhibitors at varying concentrations. For each reaction, the well contained 10 nM DHODase, 68 μM DCIP, 0.16 mg/mL gelatin, the stated concentration of ubiquinone, 10 μL of an inhibitor working stock to give the stated final concentration, and reaction buffer. After a 5-min equilibration period, the reaction is initiated by addition of DHO to the stated final concentrations. The total volume of reaction mixture for each assay is 150 μL, and the final DMSO concentration is ≤ 0.01% (v/v). The reaction progress is followed by recording the loss of absorbance at 610 nm over a 10-min period (during which the velocity remained linear). Velocities are reported as the change in absorbance at 610 nm per minute, and each reported value is the average of three replicates. In experiments where the DHO or ubiquinone concentration is varied, the other substrate is held constant at 200 μM. To determine the inhibitor potency of leflunomide and A771726, the effects of varying concentrations of the two compounds on the initial velocity of the DHODase reaction is measured over a concentration range of 0.01?1.0 μM. In these experiments the DHO and ubiquinone concentrations are held constant at 200 and 100 μM, respectively.