Advances in biological sciences have led to innovations in therapeutic development to assist human health. Biologics, or biological drugs, are a complex mixture of several thousand macromolecular species. They are manufactured using living systems including microorganisms, and plant and animal cells. Host cell proteins (HCPs) are by-products of these cellular factories and are among the major class of impurities in biologics. HCPs are released by dying or damaged cells in harvested cell cultures and can severely influence the final drug product’s quality, efficacy, and toxicity, as well as enhance or induce immunogenicity. As such, HCP detection and removal is a crucial aspect of drug manufacturing and development. HCP levels, post purification of a biologic product, must be monitored and controlled to provide for general safety, shelf-life stability, and reduce the possibilities of adverse reactions.
Various host cell lines can be utilized to work as factories to produce biologics alongside their molecular by-products. Each cell line is characterized by its unique population of proteins. These proteins themselves are influenced differently by external conditions such as temperature, nutrient supply, and acidity, to name a few. Thus, assays used to detect the product’s HCPs must offer high sensitivity and selectivity to identify complex mixtures of HCP populations. Following detection, appropriate purification processes to reduce HCP content must be regulated to ensure the final product’s safety and efficacy.
The gold standard for HCP detection
The most common method used to detect and monitor HCP levels in biologics is the enzyme-linked immunosorbent assay (ELISA). Considered the gold standard for HCP quantitation, ELISA is highly sensitive, selective, and can be automated for high-throughput workflows. This makes ELISA kits an integral part of HCP analysis for detection, quantitation, and identification. ELISA is composed of multiple reagents, some of which can be identified as critical reagents, with specific activity and specificity for biomolecular interactions. These reagents, including the capture and detection antibodies, and the specific HCP protein reference standard make up the ELISA kit. This reference standard can be used to create the standard curve to appropriately quantify and extrapolate HCP values from the assay.
Reagents, specifically the proteins standards and antibodies, are critical to the supply chain as they are biologic in nature and reproducibility is a challenge. For ELISA to be used as an effective analytical tool in a laboratory’s workflow, reagents and assays must be well-validated and kept under control. From a manufacturing viewpoint, strategies must be in place from the manufacturer and the end-user to control the consistency of reagents and ensure a good supply chain providing access to essential reagents, like protein standards and antibodies. This is especially significant as the detection and quantification of HCPs are critical to biopharmaceutical development and production workflows. For example, in the case when one’s HCP ELISA kit runs out, it is essential to distinguish between two major scenarios: (i) the kit runs out but can be replaced with a kit of the same batches of the critical reagents, and (ii) the kit runs out but there is no more of that batch of the critical reagents available. The former provides for a straightforward solution if the batches have been placed on reserve, but for the latter, a new batch will have to be qualified, and for a whole new batch, revalidation and a side-by-side bridging study of the reagents will be necessary. This is a time-consuming process that can be avoided with better stock and supply management of critical reagents.
Explore your supply options
In mitigating the risks associated with said scenarios where delays, loss of supply, and supply chain issues are imminent, it is necessary to plan and store critical reagents for the long haul. For the former, planning for several years on relevant HCP analysis needs and securing a good supply chain ensures that HCP reagents behave consistently and reduce the necessity for requalification and revalidation. Therefore, it is advisable to secure an antisera pool of the antibody for periods of five to 10 years or longer. In reserving enough stocks of critical reagents, the client is also assured that the supplier will not use critical reagents for the kits to different customers. As antisera can be stored frozen for over 10 years, if not longer, with little to no reduction in activity for antibody reactivity, securing a long-term supply of critical reagents is a viable approach. With proper purification processes, antibodies derived from the antisera pool, even despite long-term storage, remain consistent in specificity and sensitivity. These steps help in streamlining the HCP analysis workflow and further strengthen its resilience during potential supply disruptions.
Ensuring that a secure supply of critical reagents is available for HCP analysis is important. In approaching an HCP ELISA kit strategy, it is imperative to explore all available options on the market while taking the necessary steps to stock long-term supplies of reagents. The testing of different ELISA kits is most beneficial during early process development. This allows researchers to confirm the best suitable kit for their specific drug development and manufacturing needs as only one kit from a given manufacturer can be used when applying for regulatory approval. This circumvents scenarios requiring the switching of ELISA kits during the drug lifecycle stages. Testing a diverse range of ELISA kits ensures there is a solution for every situation and safeguards the supply chain between the manufacturer and the end-user while reducing workflow delays that can be detrimental to laboratories. Take the time to test different ELISA kits before making a final decision.
To learn more, visit: cytiva.com/HCPQuantCho