Optimizing DMPK Properties: Experiences from a Big Pharma DMPK Department.

BACKGROUND: The disposition of a drug is dependent on interactions between the body and the drug, its molecular properties and the physical and biological barriers presented in the body. In order for a drug to have a desired pharmacological effect it has to have the right properties to be able to reach the target site in sufficient concentration. This review details how drug metabolism and pharmacokinetics (DMPK) and physicochemical deliveries played an important role in data interpretation and compound optimization at AstraZeneca R&D in Södertälje, Sweden. METHODS: A selection of assays central in the evaluation of the DMPK properties of new chemical entities is presented, with guidance and consideration on assay outcome interpretation. Early in projects, solubility, LogD, permeability and metabolic stability were measured to support effective optimization of DMPK properties. Changes made to facilitate high throughput, efficient bioanalysis and the handling of large amounts of samples are described. Already early in drug discovery, we used an integrated approach for the prediction of the fate of drugs in human (early dose to man) based on data obtained from in vitro experiments. The early dose to man was refined with project progression, which triggered more intricate assays and experiments. At later stages, preclinical in vivo pharmacokinetic (PK) data was integrated with pharmacodynamics (PD) to allow predictions of required dose, dose intervals and exposure profile to achieve the desired effect in man. RESULTS AND CONCLUSIONS: A well-defined work flow of DMPK activities from early lead identification up to the selection of a candidate drug was developed. This resulted in a cost effective and efficient optimization of chemical series, and facilitated informed decision making throughout project progress.

Discovery and characterization of AZD9272 and AZD6538-Two novel mGluR5 negative allosteric modulators selected for clinical development.

AZD9272 and AZD6538 are two novel mGluR5 negative allosteric modulators selected for further clinical development. An initial high-throughput screening revealed leads with promising profiles, which were further optimized by minor, yet indispensable, structural modifications to bring forth these drug candidates. Advantageously, both compounds may be synthesized in as little as one step. Both are highly potent and selective for the human as well as the rat mGluR5 where they interact at the same binding site than MPEP. They are orally available, allow for long interval administration due to a high metabolic stability and long half-lives in rats and permeate the blood brain barrier to a high extent. AZD9272 has progressed into phase I clinical studies.

MEPS as a rapid sample preparation method to handle unstable compounds in a complex matrix: determination of AZD3409 in plasma samples utilizing MEPS-LC-MS-MS.

The aim of the present investigation is to develop a simple, fast, and sensitive method for the determination of a new candidate drug, AZD3409, in rat, dog, and human plasma samples. AZD3409 is stable in aqueous solutions at low pH (< 4) but not in whole blood or in plasma. In rat plasma at 25 degrees C, more than 90% of the compound is degraded within 40 min. When 20 mg of NaF and 50 microL of protease inhibitor cocktail are added to 1.0 mL of rat blood, AZD3409 is stable for up to about 90 min. Due to the instability of AZD3409, microextraction in packed syringe (MEPS) is used as an online and fast sample-preparation method, followed by liquid chromatography-tandem mass spectrometry (LC-MS-MS) for the quantitation of this compound in plasma samples. In MEPS, the sampling sorbent is 1 mg of polystyrene polymer packed in a 250-microL syringe. When the plasma sample (50-250 microL) is withdrawn through the syringe by an autosampler, the analyte is adsorbed to the solid phase. The analyte is then eluted with an organic solvent such as methanol or the LC mobile phase (20-50 microL) directly into the instrument's injector. MEPS is rapid and easy to use. The lower limit of quantitation for AZD3409 is established to be 0.024 microM. The accuracy of the quality-control samples ranged from 89% to 102%, and the precision (C.V.%) had a value of 11-16% for the plasma samples. The calibration curve in plasma is obtained in the concentration range 0.022-9.0 microM. The coefficients of determination (R2) for plasma samples were > or = 0.998 for all runs. The present method is used for the analysis of rat and dog plasma samples.

Pharmacokinetics of NXY-059, a nitrone-based free radical trapping agent, in healthy young and elderly subjects.

The tolerability, safety, and pharmacokinetics of NXY-059, a nitrone-based free radical trapping agent under development for the treatment of acute ischemic stroke, were investigated in 2 double-blind, placebo-controlled dose-escalation studies in healthy subjects. In the first study in 6 panels of young male subjects (n = 48, 22-45 years), constant rate infusions lasted 8 hours and ranged from 0.16 to 5.25 micromol/kg/h (0.06 to 2.0 mg/kg/h). In the second study, elderly male and female subjects (n = 24, 57-72 years) were infused over 24 hours or 72 hours to reach target plasma levels of 30 micromol/L or 60 micromol/L, respectively, using doses in the range 1.4-4.0 micromol/kg/h. With a 1-hour loading infusion set at 3 times the maintenance infusion rate, the target plasma level was reached in 1 hour. Adverse events were mild or moderate, and no clinically relevant changes in vital signs, ECG recordings, or laboratory values were noted. Steady-state levels in both studies increased proportionally to the infusion rate, indicating linear kinetics. Renal elimination was predominant, the recovery of unchanged drug in urine being 80% to 90% irrespective of age. The average plasma clearance in young and elderly subjects was 7.0 L/h and 4.1 L/h, respectively. It was estimated that glomerular filtration and active tubular secretion of NXY-059 accounted for approximately two-thirds and one-third of its renal clearance, respectively. In the elderly, clearance of NXY-059 was significantly correlated to creatinine clearance. The renal clearance was insensitive to variations in urine pH and urine flow rate. It appears that NXY-059 is well tolerated and has a highly predictable pharmacokinetic profile.