Track: Manufacturing and Analytical Characterization - Biomolecular - Innovative/Novel Processing Technologies and Concepts - For Use in Drug Product Manufacture
Category: Late Breaking Poster Abstract
Exploring Enhanced Selectivity of an Innovative Ion Exchange Resin in ADC Polishing
Purpose: The purification process for antibody drug conjugate molecules is still a challenging task. The efficacy and efficiency of this pharmaceutical molecule depends on the DAR (drug antibody ratio). The DAR is a critical quality attribute, as a high DAR may affect the safety profile of the ADC, while a low DAR may decrease its efficacy. Current state of the art technologies are labor intensive and expensive, limiting the economically efficient ADC manufacturing. We developed a mixed mode ion exchange chromatography showing significant economic advantages. Case studies show separation of each individual DAR species without high levels of salt or use of organic solvents. A broad window of operation was defined after investigating the influence of a variety of different factors (pH, conductivity, additives, etc.) on DAR species selectivity. Successful case studies on the variety of ADCs show the potential to use this as a template approach for an economical manufacturing process step. Methods: Eshmuno® CMX is a mixed mode resin built on the proven Eshmuno® resin technology, that has unique properties in selectivity. Based on the weak cation exchange group with moderate hydrophobicity, this resin combines the best of two worlds: enhanced selectivity based on the pI and hydrophobicity of the target molecule. >90% recovery rates are obtained using this resin while high product binding capacity of >60 mg/ml. With a broad operational window, Eshmuno® CMX chromatography resin enables use of various pH and conductivity levels to obtain high product recovery. It is also the only mixed mode resin enabling elution of hydrophobic molecules. Results: Eshmuno® CMX chromatography resin can be used to remove undesired low DAR and high DAR species, enabling the best pharmacokinetics, efficacy, half-life and tolerability. The mixed mode cation exchange step follows the conjugation step to separate antibody drug conjugate species, and usually operates in a bind and elute mode at a pH between 4 to 5 and 150 to 250 mM NaCl. Under these conditions, most antibody drug conjugates will bind to the resin and separation of too low or too high DAR/antibody drug conjugate species can be achieved by selecting the optimal elution conditions. Elution conditions include a pH change and/or conductivity change, that increases the selectivity of the mixed mode cation exchange resin. This is achieved by operating a gradient mode or in a step elution mode, where buffers having different pH and/or conductivity are applied. Due to the hydrophobic character of the linker or drug molecule there may be a need to add organic solvent, like dimethylsulfoxide (DMSO) and dimethylacetamide (DMAc), to the conjugation mixture to ensure solubility. Addition of up to 20% organic solvent to the sample does not have an influence on the DAR separation on Eshmuno® CMX. Increasing amounts of organic solvents reduce binding of the least hydrophobic variant (DAR 2). Conclusion: For the economic evaluation a simulated process for the purification of a 500 liter bioreactor with a titer of 5 mg/mL was used. The 500 liters were purified in five batches on a 20 cm diameter column with 20 cm bed height. The new innovative process on Eshmuno® CMX was compared to a standard HIC process on Capto™ Butyl. For the binding on Capto™ Butyl a 0.6 M sodium sulfate buffer was used, due to strong binding of the ADC 20% organic solvent was added to the elution buffer to enable the elution. The target was eluted using a linear pH gradient. The calculated costs are based on lab scale purification of the two processes. The significant higher process costs of Capto™ Butyl are a result from higher buffer costs per liter buffer. By reducing the complexity of the buffer systems Eshmuno® CMX enables a purification process cost reduction by factor five without losing selectivity.