host cell protein assay

One of the objectives in designing a downstream process for biopharmaceutical products is to remove any possible contaminating proteins, including host cell proteins (HCPs). HCPs can still be present at significant concentrations following several purification steps and can even be co-purified and concentrated with the drug substance itself. Multiple purification steps may be needed to remove HCPs, however, each purification step also has the potential for additional loss of product. Therefore, during the development of a downstream process, suitable assays must be available to determine both the concentration of the product and the amount of HCP present.
The type of assay required to determine HCP concentration is dependent upon the phase of product development. In the early process development phase as well as in early clinical phases, generic assays are normally acceptable. Charles River offers generic host cell protein assays for E. coli and CHO-derived products. These assays have been developed and validated on a generic sample matrix. They may be useful in the early stages of process development for a general investigation into HCP burden. Additionally, kits on any kind of cell systems may be used and adapted for a client matrix as well.
However, once the biopharmaceutical is used in clinical phase III studies, a validated, product-specific HCP assay is normally required. We have developed many specific assays on different cell matrices to quantify HCP using either ILA or ELISA. Assay development starts with testing for a suitable, specific antigen which has been produced by our client. This antigen will be used to immunize the animals from which the antisera will be obtained. After purification and qualification of the antibodies, a specific detection system is developed and optimized for the specific matrix. According to regulatory authorities, the assay should be validated prior to use in the quality control of a biopharmaceutical. The development and validation of a client-specific HCP assay normally requires between six and twelve months. Therefore, development of the assay should begin as soon as the downstream process development has been finalized.