Commercial enzyme-linked immunosorbent assay (ELISA) kits are great at removing residual host cell proteins (HCPs) during a therapeutic’s early development stages, but aren’t designed for proprietary cell lines and, at commercial scale, lack lot-to-lot consistency.

To address those challenges, researchers at the healthcare business sector of Merck in Italy are beginning to develop a proprietary Chinese hamster ovary (CHO)-based HCP platform for ELISAs that can be used throughout all stages of development rather than a commercial assay. A recent paper compared it favorably to a commercial kit, concluding that this in-house platform quantifies CHO HCPs accurately and precisely “during the early-phase product and process development.”

“A platform assay is certainly more representative of what we have in our processes,” Elisa Giordano, PhD, corresponding author, and a Merck analytical scientist, tells GEN. “The results are more reliable, accurate, and—most importantly—the assay will likely guarantee a superior coverage with respect to the commercial one. This will help scientists to have a better knowledge of their process to avoid future surprises or unnecessary rework.” If no significant changes are introduced for large-scale production, a bridging study may not be required.

Performance comparison

After selecting a robust antigen-antibody couple for use as a capture antibody and a labeled detector, the scientists compared its performance to that of a commercial ELISA kit. Results showed the in-house assay captured more HCPs than the commercial kit, and that they were distributed over a wider range of molecular weights and isoelectric points.

Specifically, with acrylamide gel at 4–20%, the in-house assay captured 905 HCP-related spots, versus 633 for the commercial assay. A similar spread remained at the acrylamide gel percentages of 8–16% and 18%. The commercial assay generally revealed more exclusive silver-stained spots for the lower two gel percentages, while the in-house assay revealed more exclusive chemiluminescent spots for the lower two gel percentages.

When comparing the assays in terms of common spots, the results were similarly significant. Overall, the in-house method was more specific and sensitive than the commercial assay, and comparable in terms of linearity range, accuracy, and precision.

“We encourage biopharmaceutical manufacturers to develop their own platform in-house assay that will represent their processes, using what Merck researchers have done as an example,” Giordano says. “In fact, the future in-house CHO HCPs platform will be used internally without being commercialized.

“We are advancing several tests to perform the large-scale study by selecting Merck materials from CHO cell lines to develop this in-house CHO HCPs platform. We will use it for CHO HCPs quantification during the early-phase product and process development.”

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