Abstract
The goal of the study was to evaluate the possibilities offered by a new generation of metal-free SEC column to perform direct SEC-MS of protein biopharmaceuticals using ammonium acetate as the main mobile phase additive. The prototype metal-free SEC column hardware used in this work was a polyether ether ketone (PEEK) infused stainless steel tube including PEEK frits. This PEEK-lined column provides a fully bioinert and metal-free fluidic path, while maintaining the stability of the metal hardware, and could be a good solution to limit possible undesired interactions between proteins and column wall/frits.This prototype metal-free SEC column was systematically compared with a conventional stainless-steel SEC column hardware packed with the same stationary phase material. Four different mAb products, namely trastuzumab, palivizumab, bevacizumab and NISTmAb, and one antibody drug conjugate (ADC), trastuzumab emtansine, were selected as test samples.It appears that peak symmetry, separation of low molecular weight species (LMWS), and the recovery of high molecular weight species (HMWS) were significantly improved for the different biopharmaceutical products on the metal-free SEC column. It has also been demonstrated that the largest differences between standard and metal-free SEC columns were observed for the most basic mAbs (high pI), which confirms that electrostatic interactions between the mAb and the metallic parts of the column (frits and inlet tube) could be responsible for the issues observed when performing SEC analysis with volatile mobile phase.Finally, it was feasible to perform SEC-MS analysis for a wide range of biopharmaceutical products using volatile mobile phase. Our results also highlight that an inappropriate column could bias the quantification of size variants when using MS-compatible mobile phases. Therefore, metal-free column, such as the PEEK-lined column, should be preferentially selected for SEC-MS analysis.
Highlights
Antibody-based drugs can undergo several enzymatic and chemical posttranslational modifications (PTMs) as well as degradations, resulting in variants that can be considered as critical quality attributes (CQAs) [1]
size exclusion chromatography (SEC), it is well known that particle size has an impact on chromatographic efficiency, while pore size may alter the selectivity between size variants
The reverse scenario was observed for low molecular weight species (LMWS), and the separation was much better on the column with smaller nominal pore size
Summary
Antibody-based drugs can undergo several enzymatic and chemical posttranslational modifications (PTMs) as well as degradations, resulting in variants that can be considered as critical quality attributes (CQAs) [1]. According to the ICH guidance Q8, CQAs are physical, chemical, biological or microbiological attributes that should be defined, measured, and continuously monitored to ensure the desired quality of a drug product [2]. Among these CQAs, high molecular weight species (HMWS) resulting from therapeutic protein aggregation are critical and require an accurate analytical characterization. These size variants can generate adverse immune reaction, alter the drug pharmacokinetics and reduce the potency of the desired biopharmaceutical product [3e5]. At least reduce the electrostatic interactions, the salt concentration and ionic strength of the mobile phase need to be sufficiently high (i.e., phosphate buffer in combination with sodium chloride or potassium chloride), making SEC inherently incompatible with mass spectrometry (MS) [12e14]
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