While the effects of process equipment-related leachables (PERLs) from single-use equipment are well-known, their interactions with cells have only just been measured.

“In the case of molecular biologics, the major concern is the potential impact on product quality and process performance, (such as) cell productivity,” Maximilian Bossong, scientist, raw materials for cell culture media, Sartorius Stedim Biotech, tells GEN. “In the case of cell- or tissue-based therapeutics, the downstream process is less extensive and patient safety assessments to PERLs should be performed. This requires considering both the liquid phase and the therapeutic cells.”

Writing in a recent paper, Bossong and colleagues from the Institute of Pharmaceutical and Biomedical Sciences at Johannes Gutenberg University (JGU), Mainz, Germany, and Sartorius outlined a quantitative adsorption study of ten well-known leachable compounds, in aqueous suspensions of Chinese hamster ovary (CHO) and T cells.

Interactions vary by cell and substance

In these studies, 67% of the bis(2,4-di-tert-butylphenyl)phosphate (bDtBPP) was recovered from CHO cell suspension samples (versus the average of more than 90% of most compounds), and 80% was recovered from T cells. Bossong and colleagues found that hydrophobic leachables had the most interaction with CHO and T cells, with recovery rates approximately 10% lower than for other compounds. The most hydrophilic compounds—benzyl alcohol and acetophenone—and ionizable compounds—specifically, fenozan—either did not show or only minimally showed association effects with the CHO and T cells.

Interaction levels vary based upon a variety of conditions, including the leachable compound, cell type, and process conditions. Therefore, risk assessments and process validations procedures should consider these interactions between process cells and PERLs.

For molecular biologics, the use of high-density cell cultivations and continuous manufacturing using perfusion bioreactors tends to reduce the effects of interactions between leachables and cells. “For therapeutic cells, PERL exposure estimations should include patient exposure with the therapeutic cell,” Bossong says.

“As measurements of leachables that are associated to cells are very challenging, taking advantage of model-based approaches will allow scientists to predict expected exposures,” he continues. “Attention also should be paid to the effects of cell culture media, as some have been shown to reduce the level of dissolved leachables in cell suspensions.”

Bossong and colleagues are continuing to advance this research by investigating the effect of leachables on physiological cell parameters, he says, applying their expertise in toxicology and morphological profiling. Bossong anticipates publication of additional study results in the near future.

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