Overview

Peptides, peptidomimetics and oligonucleic acid compounds have been notoriously difficult to test for their ability to bind plasma proteins. Conventional methods such as equilibrium dialysis and analytical ultracentrifugation mostly generate false results for members of these compound classes.

3B Pharmaceuticals is offering the novel EScalate® equilibrium-shift assay, which was developed in collaboration with the German ADMET expert Sovicell. EScalate® represents the first assay technology by which the plasma protein binding capacity of mid-sized organic molecules can be reliably determined. The assay’s key differentiators are:


  1. Excellent data accuracy even for very strong serum binders
  2. Ability to cope with non-specific interactions of the test compounds (“stickiness”)
  3. Rapid equilibration enabling the analysis of less stable  compounds
  4. Compound-specific adaptation of sample preparation and analytical method
  5. Highly selective MS detection excluding distortion caused by metabolites
  6. Rigorous data quality control

3B Pharmaceuticals has thoroughly validated the EScalate® assay’s accuracy with a set of well-studied reference drugs. Application notes and a fact sheet can be requested here.

Scientific Questions To Be Answered
The EScalate® assay can be employed to answer the following experimental questions:


  • What is the free fraction (fu) of my experimental compound in plasma?
  • How does the fu of my compound compare to that of a specific reference compound?
  • Is the free fraction in plasma consistent across a set of relevant experimental models (mouse, rat, human, cynomolgus, mini-pig, etc.) ?
  • What is the free fraction of my compound when tested with pure HSA (human serum albumin) or AGP (alpha 1 acid glycoprotein) instead of plasma?
  • Which chemical derivative of my compound leads to the desired level of plasma protein binding and is this finding consistent across all investigated species?
The EScalate® assay. Innovative in-vitro ADME.Plasma Protein Binding