Rapid methodology for basal system selection of therapeutic proteins during the early stage biopharmaceutical development

  • Nam Ah Kim
  • Bora Heo
  • Seong Hoon JeongEmail author
Original Article



This study aimed to introduce a quick method for developing formulations during the early stages of biopharmaceutical drug development, starting from the isoelectric point (pI).


Human insulin and etanercept, an Fc fusion protein, were used as model proteins to observe the effects of pH, buffer, and buffer concentration on their physicochemical properties. For biophysical analysis, dynamic light scattering (DLS), micro differential scanning calorimetry (μDSC), and circular dichroism (CD) were utilized to measure zeta average size with zeta potential, transition melting temperature, and secondary structure, respectively. Furthermore, an accelerated storage test was performed at 4 °C, 25 °C, and 40 °C using size exclusion chromatography (SEC) to evaluate storage stability.


Zeta potential measurements showed that the practical pI of human insulin in solution was 5.8 to 6.0, and the pI of etanercept was 5.0 to 5.1. Acetate and phosphate were selected as buffering agents, and the pH range was pH 3.4 to 7.4 with different buffer concentrations, 10 mM and 50 mM. Protein stability was increased when the pH was away from the pI with a relatively high absolute zeta potential, resulting in increased conformational stability and storage stability. Response surface methodology (RSM) was also used to identify a suitable pH and buffer.


The determined pH and buffer were able to suppress protein aggregation and to sustain the monomer fraction, thereby increasing protein stability. Therefore, the approach in selecting basal system could be very useful during the early stage biopharmaceutical development.


Protein stability Isoelectric point Basal buffer system Response surface methodology 



This work was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF-2018R1D1A1B07045154) and by the Technology Innovation Program (20000265, Stabilization platform of high concentration and stable liquid injection based on physical properties of biomaterials) funded by the Ministry of Trade, Industry & Energy (MOTIE, Korea).

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

Statement of Human and Animal Rights

This article does not contain any studies with human and animal subjects performed by any of the authors.


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Copyright information

© The Korean Society of Pharmaceutical Sciences and Technology 2019

Authors and Affiliations

  1. 1.Department of Pharmaceutical Sciences, School of PharmacyUniversity of Colorado-DenverAuroraUSA
  2. 2.College of PharmacyDongguk University-SeoulGoyangRepublic of Korea

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