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Ready-to-use assay systems for DMPK and ADMET studies

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A fast high throughput assay for measuring the dissociation constant of drugs from α1-acid glycoprotein (AGP or AAG). The dissociation constant is used to model plasma binding under various physiological and disease states using our spreadsheet software or Simcyp™.

  • Ready-to-use 96-well microtiter plates carrying TRANSIL beads with AGP immobilized in random orientation to expose all binding sites, designed to conveniently measure AGP binding of drugs, which is essential for predicting plasma proteins binding of drugs under disease states.
  • In combination with TRANSILXL HSA Binding assay, accurately predicts plasma proteins' binding of drugs.
  • Includes spreadsheet, facilitating manipulation of statistical parameters and calculation of final results.
  • Designed for automated liquid handlers or manual pipetting.
  • TRANSIL beads are integrated into 96-well microtiter plates to enable easy handling.
  • One plate can be used for measuring AGP binding of up to 12 compounds.
  • Only 12 minutes assay incubation time.
  • Rapid compound quantification due to immobilized AGP (e.g. injection via RapidFire™).
  • Highly reproducible results and robust correlation with conventional dialysis technique.
Background and Technical Information

Human AGP (or AAG), also called orosomucoid, is a small acute-phase glycoprotein (about 40 kDa), synthesized mostly by hepatocytes and is present in the plasma of healthy subjects at concentrations that range from 0.36 and 1.46 g/L with a mean of 0.77 g/L, accounting for about 1% to 3% of total plasma protein. AGP exhibits a sequence homology of 75% with immunoglobulins and functions as a carrier protein for basic and neutral lipophilic endogenous compounds such as steroid hormones or xenobiotics. AGP levels can vary considerably in response to disease with values up to 2.8 g/L observed in patients with viral or bacterial infections or 10-fold differences (0.33 g/L) being found in cancer patients. Moreover, AGP is expressed at lower levels in the fetus (0.15 g/L) than the mother (0.5 g/L), resulting in a higher free fraction of drugs e.g propranolol and lidocaine in neonatal blood than in maternal blood. It has been shown that plasma levels of AGP inversely correlate with the fu of alprenolol, docetaxel, disopyramide, imipramine, and propranolol. Significant differences in the fu of disopyramide between population of Black, Chinese and White backgrounds suggest differences in AGP levels. In a recent clinical study, AGP could be identified as an independent predictor for a clinical endpoint, i.e. survival in patients with non-small cell lung cancer treated with docetaxel.

Conventional methods for plasma binding (e.g. dialysis, ultrafiltration) typically assess a drugs’ free fraction in an unknown plasma composition. Hence, it is impossible to infer how different physiological or disease states affect plasma binding as a result of a decreased or increased AGP level. Only the TRANSILXL AGP Binding kit allows the assessment of the drugs’ dissociation constant to AGP and thus the evaluation of the dynamic change in plasma binding as a result of different AGP levels in blood.

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