Expanding the range of applications of ITC in the Pharmaceutical Industry with AFFINImeter: A practical Case.

Eva Muñoz Case of use, Isothermal Titration Calorimetry

Many Drug–receptor interactions are characterized by complex binding modes that are far away from the behavior of a standard 1:1 model. This is the case of Heparin (Hp), one of the most commonly prescribed anticoagulant drugs, which exerts its effect through its interaction with the serine protease Antithrombin (AT-III). Hp is a linear heterogeneous polysaccharide containing a specific pentasaccharide sequence that binds AT-III with high nanomolar affinity (responsible for the anticoagulant activity); but AT-III also binds other Hp sequences with lower affinity. Determining the content of AT-III binding pentasacchride in Low Molecular Weight (LMW) Heparins is a requirement for Pharmaceutical companies that manufacture this type of anticoagulants; due to the intrinsic heterogeneity of Hp, obtaining this information it is not straightforward (1).

We have developed a new protocol based on ITC and AFFINImeter to determine the content of AT-III binding pentasaccharide in Heparins, which is summarized in the following scheme:

New method based on AFFINImeter to determine the content of AT-III binding pentasacchride in LMW Hp: 1) use of a tailored binding model that describes the competitive binding between the pentasaccharide (A) and other low affinity sequences (B) with AT-III (M); 2) global fitting of several isotherms registered under different Hp and or AT-III concentrations where the parameters rA and rB (that account for the fraction of A and B in the Hp sample) are fitting parameters and common among the different isotherms.
New method based on AFFINImeter to determine the content of AT-III binding pentasacchride in LMW Hp: 1) use of a tailored binding model that describes the competitive binding between the pentasaccharide (A) and other low affinity sequences (B) with AT-III (M); 2) global fitting of several isotherms registered under different Hp and or AT-III concentrations where the parameters rA and rB (that account for the fraction of A and B in the Hp sample) are fitting parameters and common among the different isotherms.

 

This method illustrates the great potential of the model builder and global fitting AFFINImeter tools to develop protocols of practical utility in the Pharmaceutical industry (2). We have successfully validated the protocol in the analysis of unfractionated Hp and a series LMW Hp in collaboration with the Pharmaceutical company Laboratorios Rovi (http://www.rovi.es/).

References

  1. Nandurkar H., Chong B, Salem H, Gallus A, Ferro V, McKinnon R. Low-molecular-weight heparin biosimilars: potential implications for clinical practice. Internal Medicine Journal, 2012, 44(5), pp 497–500.

  2. For a detailed description of the protocol contact us at support@affinimeter.com

Eva Muñoz

Dr Muñoz has worked as a researcher for over 15 years in different international centers in Spain, Germany and the USA, focusing on the characterization of complex biomolecular interactions by different experimental techniques such as NMR, FT-IR, fluorescence and Surface Plasmon Resonance (SPR). She has a high publication record in this area as well as two patents on biotechnological developments. Eva is working with us in the validation and design of AFFINImeter as well as in the implementation of functionalities for the analysis of SPR measurements.