Application Note. Separation of three monoclonal antibody variants using MCSGP. Summary

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1 Application Note Separation of three monoclonal antibody variants using MCSGP Category Matrix Method Keywords Analytes ID Continuous chromatography, Biochromatography; FPLC Protein A-purified monoclonal antibody from cell culture MCSGP Monoclonal antibody, MCSGP, FPLC, continuous chromatography, biological activity, mab purification, lysine variant, mab isoform Monoclonal antibody variants VBS0037N Summary This application note describes the separation of three mab variants on a preparative weak cation-exchange resin using the Multi-Column Countercurrent Solvent Gradient Purification (MCSGP) process. The KNAUER Contichrom system that is offered in a cooperation of KNAUER and Chromacon is the only system in the market that can be used in MCSGP mode for difficult bio-separations. MCSGP is a countercurrent chromatographic process developed that is particularly suited for applications in the field of bioseparations 1. Like batch chromatography, MCSGP is suitable for three-fraction chromatographic separations and able to perform solvent gradients but it is superior in terms of solvent consumption, yield, purity and productivity due to the countercurrent movement of the liquid and the solid phase. In the example shown in this application note, MCSGP clearly outperformed the batch reference process, reaching yield and purity values of the target variant of 93%, respectively 1.

2 Introduction The increasing production volumes of biomolecules, especially therapeutic proteins, and a rising cost pressure from the market, has engendered a strong interest in the chromatographic purification step in the downstream processing of biomolecules 3. Traditionally, recombinant protein drugs are produced by fermentation which leads to the generation of a large number of impurities such as host cell proteins (HCP) and DNA 1. As a consequence, the fulfillment of the strict purity requirements by downstream purification of the desired components is the major cost factor in production with 50-80% of the total manufacturing costs 2. Chromatography steps are often irreplaceable and also a major cost driver in downstream processing 3. At the present, chromatography processes are mainly operated in batch mode 1. This application note describes the use of countercurrent chromatography (MCSGP) for the separation of three mab variants that differ only in the number of their C-terminal lysine groups. The separation is very challenging, since only minor differences in the amino acid sequence exist and the adsorptive properties of the mab variants are very similar. Since mab variants can have significantly different activities ( 10x difference in activity is possible!) 4, the separation of more active variants can help in the life cycle management of drugs and the production of more efficient drugs. Furthermore the isolation of mab variants is required for characterization purposes during drug development. The separation of mab variants cannot be achieved by Protein A based affinity chromatography since Protein A specifically targets the Fc region that is common to all mab variants of interest 1. Suitable affinity materials are not commercially available as protein A materials would not specifically bind to one of the antibody variants 1. Contichrom with MCSGP is the only technology that can separate mab charge variants in preparative amounts up to process scale with cation exchange chromatography at a high yield. This application note shows the separation of three mab variants containing none, one and two lysine groups at the C-terminal using the MCSGP process 1. Fig. 1 Analytical chromatogram of the three mab variants Analytical chromatogram of the three mab variants. The separation challenge is to separate mab variant with 1 terminal lysine group (F 1 ) from mab variants with 0 and 2 terminal lysine groups (F 0 and F 2 ). VBS0037N Page 2 of 6

3 Experimental sample preparation The feed solution consisted of protein A-purified antibody solution containing three mab variants and was obtained from Novartis (Basel, Switzerland) 5. The solution was diluted with buffer A to a total concentration of c Feed = 0.11 g/l mab and adjusted to ph 6.3. KNAUER recommends filtering the sample through a 0.45 µm syringe filter prior to injection. Purification method for transfer to MCSGP Before starting the MCSGP process, a reference batch chromatography was performed using a weak cation exchange column. Column Fractogel EMD COO (S) 30 µm, 100x 4.6 mm (Merck) Buffer A phosphate buffer (ph 6.3) Buffer B Gradient Flow rate Injection volume Column temperature System pressure Detection Run time phosphate buffer (ph 6.3), 0.25 M NaCl Time [min] % A % B ml/min 2 ml ambient below 8 bar UV at 220 nm and 280 nm 150 min Fig. 2 Batch chromatogram of the purification method Black line: Linear salt gradient, dashed line: summed concentration curve; markers: experimental data from offline analysis of fractions; solid lines: simulation; blue squares: mab variant F 0 ; red triangles: mab variant F 1 ; green circles: mab variant F 2 VBS0037N Page 3 of 6

4 The experimental points were obtained by the offline analysis of the fractions of the batch chromatogram. The simulation experiments were obtained from isotherm model calculations 1. In the batch run, first the variant containing no lysine groups (F 0 ) elutes, then the variant containing one lysine group (F 1 ) and finally the variant containing two lysine groups (F 2 ). Offline analysis showed that the maximum purity of the intermediately eluting mab variant F 1 at 5% yield is approximately only 80%. Although the separation conditions were not optimized, there is little room for improvement, since the gradient is already very shallow and long and the variants elute late with no baseline separation. The results show, that it is not possible to separate the three mab variants with high purity and sufficient yield on a preparative resin in a single batch column. Fig. 3 Principle of the MCSGP Process Simplified chromatogram of generic chromatographic purification problem (time axis from right to left); S: strong adsorbing, late eluting impurities; P: product; W: weak adsorbing, early eluting impurities. The generic problem in the chromatographic purification of biomolecules can be simplified to the chromatogram as shown in Figure 3. It can be cut into five fractions as indicated by the numbers on the time axis: 1 = Weak adsorbing impurities 2 = Product contaminated by weak adsorbing impurities 3 = Product 4 = Product contaminated with strong adsorbing impurities 5 = Strong adsorbing impurities. Automatic method transfer from batch to MCSGP The aim of an ideal purification process is to recover the product contained in fractions 2, 3 and 4 while removing the impurities present in fractions 1,2 (W) and 4,5 (S), respectively. These tasks can be transferred to a MCSGP process with 2 (identical) columns, where the columns are alternating switched in series and batch mode. The definition of the fractions 1-5 and therefore the operating parameters of the MCSGP process are based on the experimental data from offline analysis of the preparative batch chromatogram (Fig. 2). For the MCSGP process the same stationary phase as for the batch experiments is used. The transfer from the results obtained in a batch process to a MCSGP method can be automatically done using the software-wizard of the Contichrom system. In the MCSGP process the two columns are connected in series by valve-switching to recycle fractions 2 and 4 and they are switched to batch mode to elute the impurity fractions 1 and 5 and to collect the pure product fraction 3. VBS0037N Page 4 of 6

5 Figure 3 shows the analytical chromatogram of the feed mixture (blue) compared to the chromatogram of the target compound F 1 after the purification using MCSGP (pink). Offline analysis showed that the MCSGP process led to a purity of 93% with a yield of 93%. Fig. 4 Analytical chromatograms of mab variants. Blue: feed mixture; pink: mab variant F1 purified with MCSGP process A220 [mau] (norm.) g p feed crude Product purifiedf t [min] Conclusion The MCSGP process was successfully applied for the purification of the intermediately eluting monoclonal antibody variant from a mixture of three monoclonal antibody variants on a preparative cation exchange resin. Using batch linear gradient chromatography a purity of 80% with only 5% yield were obtained. Using the MCSGP process that exploits the advantage of solvent gradients and countercurrent movement of the stationary and mobile phase, it was possible to overcome the difficulty of the separation posed by the similar selectivites of the variants and to reach high purity and yield values of both 93%. For MCSGP design and operation, the twin-column KNAUER Contichrom system is recommended. References 1. Müller-Späth, T., Aumann, L., Melter, L., Ströhlein, G., Morbidelli, M.: Biotechnology and Bioengineering, Vol. 100, Number 6, (2008). 2. Roque, ACA., Lowe, CR., Taipa, MA.: Biotechnology Progress, Vol. 3, (2004). 3. Sröhlein, G., Aumann, L., Müller-Späth, T., Tarafder, A., Morbidelli, M. : BioPharm International (2007). 4. Harris RJ, Kabakoff B., Macchi FD, Shen FJ, Kwong M., Andya JD, Shire SJ, Bjork N., Totpal K, Chen AB: Journal Chromatogr B, 752(2): (2001). 5. Melter, L., PhD Thesis, Number 16971, ETH Zürich (2006). Authors Dr. Friederike Sander, Columns and Applications Department, KNAUER. Dr. Thomas Müller-Späth, ChromaCon AG. VBS0037N Page 5 of 6

6 Physical properties of recommended column Stationary phase Fractogel EMD COO 30 µm, 100 x 4.6 mm (Merck) Pore size 800 Å Particle size µm Matrix Crosslinked polymethacrylate Functional groups Carboxy ethyl group Pressure limit 8 bar Working range ph 2-12 Dimensions 100 x 4.6 mm Symbolic photo Recommended instrumentation KNAUER Contichrom system Description Order No. Contichrom Lab 10 System C Contichrom Prep 100 System C Contact information Wissenschaftliche Gerätebau Tel: Dr. Ing. Herbert Knauer GmbH Fax: Hegauer Weg 38 info@knauer.net Berlin, Germany Internet: ChromaCon AG Tel: Technoparkstraße 1 sales@chromacon.ch 8005 Zurich, Switzerland Internet: VBS0037N Page 6 of 6