Structural Basis of the Drug-Binding Specificity of Human Serum Albumin.

Background and Objective: Dabigatran etexilate is an oral direct thrombin inhibitor in clinical development for the prevention and treatment of thromboembolic disorders. Following oral administration, dabigatran etexilate is rapidly absorbed and converted into its active form, dabigatran. The aim of this study was to investigate the effect of renal impairment on the pharmacokinetics and pharmacodynamics of dabigatran following administration of a single oral dose of dabigatran etexilate in subjects with renal impairment (150 mg) or end-stage renal disease (ESRD) on maintenance haemodialysis (50 mg). Methods: This open-label, parallel-group, single-centre study enrolled 23 subjects with mild, moderate or severe renal impairment (creatinine clearance >50 to ≤80, >30 to ≤50 and ≤30 mL/min, respectively), 6 patients with ESRD and 6 healthy subjects. Blood and urine samples were collected up to 96 hours after dosing for determination of dabigatran pharmacokinetic and pharmacodynamic parameters. Results: Compared with the values in healthy subjects, the area under the plasma concentration-time curve from time zero to infinity (AUC∞) values were 1.5-, 3.2- and 6.3-fold higher in subjects with mild, moderate and severe renal impairment. Changes in the maximum plasma concentration (Cmax) were modest, and the time to reach the Cmax was unchanged. In subjects with severe renal impairment, the mean terminal elimination half-life was doubled (28 hours vs 14 hours for control). The AUC for prolongation of pharmacodynamic parameters (the activated partial thromboplastin time and ecarin clotting time) increased in line with the pharmacokinetic changes. In patients with ESRD, the dose-normalized AUC∞ was approximately twice the value in the control group. Haemodialysis removed 62–68% of the dose. Dabigatran etexilate was well tolerated in all groups. Conclusions: Exposure to dabigatran is increased by renal impairment and correlates with the severity of renal dysfunction. A decrease in the dose and/or an increase in the administration interval in these patients may be appropriate. In patients with ESRD, dabigatran can be partly removed from the plasma by haemodialysis.

Influence of renal impairment on the pharmacokinetics and pharmacodynamics of oral dabigatran etexilate: an open-label, parallel-group, single-centre study.

Importance of the field: The role of lipophilicity in determining the overall quality of candidate drug molecules is of paramount importance. Recent developments suggest that, as well as determinin...

Lipophilicity in drug discovery.

Taxanes are standard treatment for metastatic breast cancer; however, the solvents used as vehicles in these formulations cause severe toxicities The FDA recently approved a solvent-free formulati

http://www.protocol-online.org/forums/uploads/monthly_11_2009/msg-6644-1257363554.ipb

Albumin-bound paclitaxel: a next-generation taxane

For about half a century, the binding of drugs to plasma albumin, the “silent receptor,” has been recognized as one of the major determinants of drug action, distribution, and disposition. In the last decade, the binding of drugs, especially but not exclusively basic entities, to another plasma protein, alpha 1-acid glycoprotein (AAG), has increasingly become important in this regard. The present review points out that hundreds of drugs with diverse structures bind to this glycoprotein. Although plasma concentration of AAG is much lower than that of albumin, AAG can become the major drug binding macromolecule in plasma with significant clinical implications. Also, briefly reviewed are the physiological, pathological, and genetic factors that influence binding, the role of AAG in drug-drug interactions, especially the displacement of drugs and endogenous substances from AAG binding sites, and pharmacokinetic and clinical consequences of such interactions. It can be predicted that in the fulture, rapid auto...

Human alpha-1-glycoprotein and its interactions with drugs

The ligands are generally bound in plasma to a significant extent by several transport proteins (both high and low affinity), irrespective of their endogenous or exogenous origin. The protein binding of endogenous compounds (such as hormones) exhibits higher affinity and specificity than those of exogenous compounds (such as drugs). For plasma proteins that bind the same ligand(s), structural similarities or a common genetic origin may be found, although this is not a general rule. Alterations in ligand binding may be due to modifications of either the structure or the level of the binding protein. These modifications may result from genetic make up, physiology or pathology. In some situations, plasma binding may impair the distribution of drugs to tissues, with drug distribution then mainly restricted to the distribution compartment of the drug-binding protein. In other instances, the plasma drug-binding is permissive, and does not limit drug distribution to tissues. A given drug-transport protein system may have either a permissive or a restrictive effect on the drug distribution, depending on the tissue. The physiological significance of the high-affinity transport proteins is not completely understood. These proteins may increase the plasma concentration of poorly hydrosoluble ligands, ensure a more uniform tissue distribution and increase the life of the ligands. The life of the protein may also be increased by ligand binding. High-affinity transport proteins are also involved in some specific carrier mediated transfer mechanisms. It is possible to demonstrate structure-binding relationships or binding selectivity for the plasma transport proteins, but these are quite independent of relationships observed at the receptor level.

Jean-Claude Duché

Papers

Drug binding in plasma. A summary of recent trends in the study of drug and hormone binding.

Expression of the genetic variants of human alpha-1-acid glycoprotein in cancer.

Use of tumor markers for differential diagnosis of mesothelioma and secondary pleural malignancies