Pharmacokinetic (PK) pharmacodynamic (PD) modeling was applied to understand and quantitate the interplay between tesaglitazar (a peroxisome proliferator-activated receptor alpha/gamma agonist) exposure, fasting plasma glucose (FPG), hemoglobin (Hb), and glycosylated hemoglobin (HbA1c) in type 2 diabetic patients. Data originated from a 12-week dose-ranging study with tesaglitazar. The primary objective was to develop a mechanism-based PD model for the FPG-HbA1c relationship. The secondary objective was to investigate possible mechanisms for the tesaglitazar effect on Hb. Following initiation of tesaglitazar therapy, time to new FPG steady state was approximately 9 weeks, and tesaglitazar potency in females was twice that in males. The model included aging of red blood cells (RBCs) using a transit compartment approach. The RBC life span was estimated to 135 days. The transformation from RBC to HbA1c was modeled as an FPG-dependent process. The model indicated that the tesaglitazar effect on Hb was caused by hemodilution of RBCs.

Clevidipine is a high clearance drug, which is rapidly metabolized to the corresponding inactive acid. The tmax value of the primary metabolite, and a virtually identical value of the initial half-life and the half-life for elimination from the central compartment, indicate that the initial rapid decline of the post-infusion blood levels is mainly due to elimination rather than distribution. The duration of action of clevidipine is short.

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WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT • AZD7325 is an orally administered, potent, selective gamma-amino-butyric acid (GABAA) a2,3 receptor modulator intended for the treatment of anxiety. • The induction effects of AZD7325 on CYP1A2 and CYP3A4 have not been systematically studied. WHAT THIS STUDY ADDS • The in vitro studies showed that AZD7325 was a moderate CYP1A2 inducer and potent CYP3A4 inducer. • The follow-up clinical studies in healthy volunteers demonstrated that the expected efficacious daily dose of AZD7325 only weakly induced the pharmacokinetics of the CYP3A4 sensitive substrate, midazolam, and had no effect on the pharmacokinetics of the CYP1A2 substrate, caffeine. There was no apparent change in AZD7325 exposure following co-administration of midazolam or caffeine compared with AZD7325 alone. • The study demonstrated that clinical exposure of the inducer plays a critical role in the determination of cytochrome P450 induction risk of a drug candidate. AIM(S) To investigate the potential of AZD7325 to induce CYP1A2 and CYP3A4 enzyme activities. METHODS Induction of CYP1A2 and CYP3A4 by AZD7325 was first evaluated using cultured human hepatocytes. The effect of multiple doses of 10 mg AZD7325 on the pharmacokinetics of midazolam and caffeine was then examined in healthy subjects. RESULTS The highest CYP1A2 and CYP3A4 induction responses were observed in human hepatocytes treated with 1 or 10 mM of AZD7325, in the range of 17.9%-54.9% and 76.9%-85.7% of the positive control responses, respectively. The results triggered the further clinical evaluation of AZD7325 induction potential. AZD7325 reached a plasma Cmax of 0.2 mM after 10 mg daily dosing to steady-state. AZD7325 decreased midazolam geometric mean AUC by 19% (0.81-fold, 90% CI 0.77, 0.87), but had no effect on midazolam Cmax (90% CI 0.82, 0.97). The mean CL/F of midazolam increased from 62 l h-1 (midazolam alone) to 76 l h-1 when co-administered with AZD7325. The AUC and Cmax of caffeine were not changed after co-administration of AZD7325, with geometric mean ratios (90% CI) of 1.17 (1.12, 1.23) and 0.99 (0.95, 1.03), respectively. CONCLUSIONS While AZD7325 appeared to be a potent CYP3A4 inducer and a moderate CYP1A2 inducer from in vitro studies, the expected efficacious dose of AZD7325 had no effect on CYP1A2 activity and only a weak inducing effect on CYP3A4 activity. This comparison of in vitro and in vivo results demonstrates the critical role that clinical exposure plays in evaluating the CYP induction risk of a drug candidate.

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