Protein Purification Using Hydroxyapatite for LMW and Basic Variant Separation
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Solution Overview
Problem
Existing purification methods for monoclonal antibodies and fusion proteins are inadequate in effectively removing low molecular weight aggregates (LMWs) and basic variants, leading to potential safety issues and manufacturing inefficiencies, and existing chromatography techniques can induce aggregate formation or result in significant dilution, leakage of ligands, and incomplete separation due to isoelectric point similarities.
Innovation Solution
A scalable purification process using ceramic hydroxyapatite chromatography (CHT) with phosphate elution gradients to separate LMWs and basic variants, combined with anion exchange chromatography to reduce high molecular weight impurities and acidic variants, achieving high purity levels of antibodies or fusion proteins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If ion exchange chromatography is used to separate antibodies based on charge, then charge variants can be separated, but aggregates may form due to increased protein concentration or buffer changes
Solution Approach 1:
The patent divides the purification process into multiple distinct chromatography steps (hydroxyapatite chromatography for size separation, ion exchange chromatography for charge separation, and affinity chromatography for specific binding). Each step targets specific impurities separately, preventing the formation of aggregates that would occur if all separations were attempted simultaneously at high concentration.
Solution Approach 2:
The patent employs different buffer conditions and pH levels for each chromatography step. The hydroxyapatite step uses buffered saline, the ion exchange step uses buffered saline with specific pH control, and the affinity step uses buffered saline. These parameter changes allow each step to function optimally without inducing aggregate formation.
2Manufacturing precision
If size exclusion chromatography is used to separate molecular weight variants, then LMWs and HMWs can be separated, but significant dilution of the product occurs
Solution Approach 1:
The patent segments the separation process across multiple columns with different mechanisms. The hydroxyapatite column handles size-based separation, while the ion exchange and affinity columns handle charge-based and specific binding-based separation respectively. This segmentation allows efficient separation without requiring the high concentrations needed for single-step size exclusion.
Solution Approach 2:
The patent uses buffered saline as an intermediary medium that maintains appropriate ionic strength and pH between chromatography steps. This intermediary buffer system allows the protein to be transferred between columns without sudden concentration changes or dilution, while still enabling effective separation at each stage.
3Manufacturing precision
If affinity chromatography is used to purify antibodies through specific binding, then high purity can be achieved, but ligand leakage from columns occurs
Solution Approach 1:
The patent places the affinity chromatography step at the end of the purification sequence, after hydroxyapatite and ion exchange columns. By this stage, the protein has already been pre-purified and concentrated through the previous steps, so the affinity column operates at lower concentrations, minimizing ligand leakage while still achieving high final purity.
Solution Approach 2:
The patent performs preliminary purification through hydroxyapatite and ion exchange chromatography before the affinity step. This preliminary action removes the bulk of impurities and concentrates the protein, ensuring that when the affinity column is used, the ligand loading is optimized and leakage is minimized while maintaining high purity.
4Manufacturing precision
If multiple chromatography steps are combined to achieve high purity, then impurities can be effectively removed, but process complexity increases
Solution Approach 1:
The patent segments the purification process into three distinct functional steps: hydroxyapatite chromatography for size-based separation, ion exchange chromatography for charge-based separation, and affinity chromatography for specific binding. Each step has a clear purpose and uses different mechanisms, allowing systematic removal of different impurity types while maintaining manageable process complexity.
Solution Approach 2:
The patent uses buffered saline as a universal buffer system across all three chromatography steps. This universal buffer maintains consistent ionic strength and pH conditions throughout the process, simplifying the overall system design and reducing the need for multiple specialized buffers or complex conditioning procedures.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The process achieves purity levels of 90% or higher for monomeric proteins, significantly reducing LMWs to below 0.4% and basic variants to below 15%, while maintaining efficiency and avoiding the drawbacks of other chromatography methods.
Implementation Method 1
Hydroxyapatite chromatography is shown to be a method for chromatographically purifying monoclonal antibodies (Mab). Ceramic hydroxyapatite (CHT) chromatography is reported for the separation of HMW by using sodium chloride or calcium chloride.
Implementation Method 2
In the present invention, we successfully attempted to separate low molecular weight aggregates (LMWs) and Basic Variants (BVs) from an antibody preparation using ceramic hydroxyapatite chromatography with phosphate elution gradient
Implementation Method 3
the present invention uses anion exchange which significantly reduce high molecular weight impurity and acidic variants
Data Source
AI summary
The invention provides a process of purification of antibody or fusion protein from protein mixture comprising product and process related impurities. The process provides the use of hydroxyapatite chromatography for the separation of low molecular weight impurities and basic variants. In addition, invention further provides a scalable purification process to remove product and process related impurities.