Purification Methods Introduction

The choice of a purification method is based on a number of different factors: the antibody, the feedstock, scale, economics, timing, and desired purity. As mentioned above, this article will concentrate on the most demanding type of antibody purification, that of multigram lots of monoclonal antibodies produced under GMP and for use in par-enteral formulations.

The purification process can be divided into four parts. Figure 1 presents a flow chart of these steps, along with the most common techniques used for each step. The purpose of the first part, sample preparation, is to ensure the readiness of the sample for the first purification step. Sample preparation is sometimes not necessary, depending on the nature of the crude feedstock and on the choice of the first purification step.

Precipitation SEC

Ultrafiltration Clarification

Affinity

Immunoaffinity Ion exchange IMAC HIC

Hydroxyapatite SEC

Initial capture techniques and specific impurity removal

Figure 1. A general flow path for antibody purification, showing (on left) techniques typically used at each step.

Sample preparation is followed by the first purification step, often known as initial product capture. Most typically, the methodology for this step is chosen to give a high purification factor. Indeed, for antibody products with less stringent purification requirements (e.g., for in vitro use), this may be the only purification step required, if properly chosen.

The third part of the procedure is any additional purification step(s) necessary to reach the purity goal. These steps are sometimes referred to as polishing steps.

The final part of the procedure is to put the product into its final formulation, that is, the desired final concentration and physical state. This may sometimes be accomplished by the final purification step itself, eliminating the need for separate additional steps.

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