Q&A Part 4: Ensuring Lot-to-Lot Consistency

We have strict procedures in place that ensure a high degree of lot-to-lot constancy for antibodies. We maintain a large supply of unprocessed antiserum that allows for simple remanufacture and consistent performance across lots. However, if the supply becomes depleted and new antisera is manufactured, a bridging study is conducted to compare the performance of an antibody during the screening and final release validation against a gold-standard antibody. The gold-standard antibody was validated in one or more immunoassays at primary release and consists of retains from the original or previous lots. This ensures consistent performance is obtained by the researcher.

BD conducts rigorous QC testing of each antibody lot tested side-by-side with a previously produced lot as reference.

• By developing a high-quality clone, producing the antibody in a stable expression system (e.g. cultures using either hybridoma or recombinant cells), controlling production well, and carefully QC testing each lot, we can guarantee reproducible performance against endogenous targets.
• We have stringent quality systems that monitor each production lot and strive for continuous improvement over our already high standards.
• Each production lot is QC tested by a variety of biochemical assays, and in the most relevant functional assay for that antibody’s molecular target.

Each of our antibody products is managed by a team of scientists who are responsible for manufacturing and validating every new lot of antibody before it is released for sale. The process begins by a side-by side performance validation for each new lot against the previous lots for all approved applications. The new lot must perform the same or better than the previous lots before it is approved for release. We also validate each product lot on a regular basis to ensure product quality does not change over time. All of our monoclonal antibodies are manufactured under ISO-9001 guidelines, ensuring consistency and quality.

In addition, CST focuses on making our monoclonal antibodies using recombinant engineering technology, which offers benefits including lot-to-lot consistency, ease of characterization, and decreased production time. Currently, over 95% of our monoclonal antibodies are recombinant, and we’ve expanded this production method to select products made of an optimized mix of multiple recombinant monoclonal clones. Our MultiMabs™ offer all the benefits of a polyclonal without batch-to-batch variation.

Regardless of the production method, all of our antibodies go through a thorough lot-to-lot validation process to ensure that all of our products meet our quality control standards.

• For more consistent manufacturing processes, we consequently make use of recombinant antibody technology instead of hybridoma technology. This is the basis for lot-to-lot consistency.
• Recombinant expression, i.e. the expression of defined sequences in genetically modified organisms, not only enables better reproducibility, but also allows the targeted improvement of the antibody with regard to its application, for example the elimination of Fc receptor binding by mutations.
• Also important for high reproducibility are consistent and robust conjugation processes. With our conjugation and purification procedures we make sure that the final product contains neither free fluorochromes, nor unconjugated antibodies or activation reagents, all of which could compromise antibody sensitivity in the final product.
• Release testing for every batch includes an evaluation of purity, F/P ratio, sensitivity, specificity, and lot-to-lot consistency. For example, new lots of our flow cytometry antibodies are always tested against previous lots in a flow cytometry assay. If new batches do not meet defined criteria for mean fluorescence intensity (MFI), stain index (SI), target cell frequency, or other factors, such as background signal and staining pattern, in a given application, they are not released for sale.

We follow consistent protocols and keep retention lots for comparison. Our monoclonal antibody performance is highly consistent from lot to lot. However, with polyclonal antibodies some degree of variability is expected with different bleed times, but we ensure that they meet our specifications of selectivity, specificity, and sensitivity.