Pharmaceutical Chemistry Department

Empirical Phase Diagram (EPD) Approach

An Empirical Phase Diagram (EPD) is a visual representation of the stability of a macromolecule. Constructed with vast amounts of data obtained from different instruments (UV, CD, fluorescence, DLS, DSC, FTIR), this unique approach has proven to be powerful and efficient in providing comprehensive stability profiles that facilitate formulation development and optimization (Figure 1). Edited

Figure 1. Empirical Phase Diagrams: General Approach for Visualizing Large Amounts of Biophysical Data









The EPD approach has been applied to various biopharmaceuticals, from simple peptides and nucleic acids to complex systems such as attenuated live viruses and bacteria (Figure 2, References). Two non-color based versions of EPDs are currently being developed based on Chernoff faces and radar diagrams.  In these approaches, facial dimensions and distorted polygons are used to represent data.

Incorporation of protein dynamic measurements into an EPD provides greater insight into protein biophysical stability than can be obtained using static spectroscopic methods (Figure 3). With the ability to construct both static and dynamic EPDs, the MVSC provides comprehensive preformulation studies on biopharmaceuticals in a timely manner.

Selected Instruments

  • Olis Protein Machine
  • Applied Photophysics Chirascan Plus
  • Jasco J-810 circular dichroism spectropolarimeter
  • Jasco J-815 circular dichroism spectropolarimeter
  • Brucker Tensor 27 FTIR spectrometer
  • Agilent HP 8453 UV-Vis spectrophotometer
  • PTI T-format fluorometer
  • PTI L-format fluorometer
  • Wyatt Dynapro DLS
  • HR-US 102 ultrasonic spectrometer
  • Microcal VP-DSC with pressure perturbation capability
  • Fluorescence Innovations MATRIX-UV lifetime spectrometers
  • Red-edge excitation fluorescence measurements using Olis Protein Machine or PTI fluorometers

For further information about the individual techniques, see the descriptions at Secondary Structure and Tertiary Structure

Figure 2. Examples of Static Empirical Phase Diagrams



Figure 3. Static (A) and Dynamic (B) Empirical Phase Diagrams of IgG


Selected Publications: Review Articles

Joshi, SB., Bhambhani, A., Zeng, Y. and Middaugh, C. R. (2010) An Empirical Phase Diagram/High Throughput Screening Approach to the Characterization and Formulation of Biopharmaceuticals in “Formulation and Process Development Strategies for Manufacturing Biopharmaceuticals”, Jameel, F and Hershenson, S (editors), Wiley & Sons publication, p173-204.

Maddux, N.R., Joshi, S.B., Volkin, D.B., Ralston, J.R. and Middaugh, C.R. (2011) Multidimensional Methods for the Formulation of Biopharmaceuticals and Vaccines. J. Pharm. Sci. in press. PMID 21647886: