Hydrophobic Interaction Chromatography Screens for Downstream Process Development I Scanlon, B Galarza, L Pepperell, G Clifton, Astrea Bioseparations Ltd, Horizon Park, Barton Road, Comberton, Cambridge, CB23 7AJ, UK
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Abstract
Hydrophobic Interaction Chromatography (HIC) is a versatile purification technique used across many targets in the biopharma industry, from the polishing of monoclonal antibodies (mAb) and plasmid DNA (pDNA), to primary capture of more complex targets. One of the key advantages of HIC is that the complex interactions between the hydrophobic regions on the target or the impurity can be exploited to achieve selectivity with both the ligand used on the adsorber and the strength and characteristics of the lyotropic salts used to “salt out” the target molecules. A typical strategy in process development would be to screen ligands and conditions for a HIC purification step. Astrea Bioseparations has launched a HIC screening selection kit containing four different ligands to enable end users to screen their process. All four HIC resins can be produced at scale for full cGMP manufacturing implementation. This poster outlines a screening process for Butyl, Hexyl, Octyl and Phenyl ligands for several targets: • mAb polishing step post-Protein A • AAV 2 and AAV 9 capture from lysate • pDNA polishing step post-AEX
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Using Pre-Packed HIC Columns to Screen AAV Binding from Lysate
In addition to loose resin, HIC ligands are available in 1mL pre-packed column kits. PEG-precipitated lysates of AAV 9 and AAV 2, purchased from a commercial supplier, were conditioned to 1.5M K2HPO4 and 1% glucose, pH 7.0. The sample was loaded onto the 1mL prepacked column at 1mL/min, and the column was washed with 1.5M K2HPO4 1% glucose. For elution, the flow rate was set to 1 mL/min, and a gradient was run over 20 column volumes (CV) from 0% to 100% 50mM K2HPO4 and 1% glucose, pH 7.0. Recovery of AAV was measured using serotypespecific capsid ELISA of the non-bound, post-load wash and elution.
Study 1: Removal of Aggregate from mAb feed.
The four Astrea Bioseparations HIC ligands were packed into individual 0.5mm x 200mm columns to give a column volume of 3.9mL. Each column was equilibrated with 100mM sodium phosphate, 900mM ammonium sulphate pH 7.0. A load solution of a monoclonal antibody, containing dimer as 4.8% of the mAb total by SEC-HPLC, was prepared from a post-Protein A elution pool and made up to 100mM sodium phosphate, 900mM ammonium sulphate pH 7.0. Each column was loaded to 8mg/mL mAb, and eluted with a linear gradient to 100mM sodium phosphate pH 7.0 over 18CV, followed by a CIP with 0.5M NaOH for 5CV.
Chromatogram overlay comparing HIC performance Hexyl Phenyl
AAV 9/ 2 Recovery from lysate Recovery was calculated using a serotype-specific capsid ELISA.
70 AAV2 60
AAV9
50 40
From the conditions screened, the AAV 9 phenyl process gave the highest recovery.
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HCP clearance and hcDNA clearance were measured.
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A subsequent polishing step with the Astrea Bioseparations IEX resin Q PuraBead® HF is to be optimised to deliver purified AAV vector suitable for transfection.
10 0
Phenyl
Octyl
Hexyl
Butyl
Butyl Octyl
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pDNA Polishing with Butyl & Phenyl HIC Resins
Plasmid DNA (pDNA, 5Kb), purchased from a commercial supplier, was diluted into 3M ammonium sulphate in 50mM Tris 5mM EDTA and loaded onto the 1mL Butyl and Phenyl pre-packed columns. A gradient elution to 50mM Tris 5mM EDTA was used.
Butyl
SDS-PAGE analysis of fractions from the mAb HIC screen Butyl M L
1
2
3
4 5 6
7 8
Hexyl 9 10 11 12 13
M
L
1
2
3
4
Phenyl
Octyl 5
6
7
8
M L
9 10
11 12 13 14 15 16
M L
14 15 16 17 18 19 20 21 22 23 24
kDa
kDa
kDa
kDa
191
191
191
191
Dimer Monomer
97
97
97
97
64
64
64
64
51
51
51
51
39
39
39
39
28
28
28
28
19 14
19 14
19 14
19 14
Of the four screened ligands under the conditions above, only the Phenyl gave an elution pool with no monomer. This was used for further optimisation with a step gradient. The Phenyl ligand was able to reduce the amount of dimer in the mAb pool to below 1%.
Reference Phenyl gradient elution
Phenyl step elution
Sample
Dimer %
Load
4.80
Non-bound
Phenyl
N/A
Elution
N/A
Load
8.25
Non-bound
N/A
Elution
0.65
Step gradient to remove dimer from mAb elution pool
The pDNA bound to the Butyl resin but not the Phenyl resin. Optimisation of either a bind/elute or a flow through purification is possible.
Summary
The HIC resins included in the screening kit provide a toolbox for screening a range of proteins, nucleic acids, and vector targets for polishing of primary capture applications. Pre-packed 1mL and 5mL columns provide a quick and easy option for the R&D lab. For later stage process development or characterisation, loose resin is available.
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