Bioassays

A bioassay or biological assay is a testing procedure for estimating the concentration of an active pharmaceutical ingredient that can be samples taken from in-process, the bulk drug substance or from a formulated product.  Compared to physical or chemical methods, a bioassay results in data on the biological activity of a substance.   Bioassays often involve cells or animals and as a consequence can be extremely challenging to perform as well as slow, often taking anywhere between 3  days for a cell based assay to over a month for animal based assays.  Given the variance typically seen with bioassays, biostatistical analysis is critical if the assays are to be effectively used to control the quality of biopharmaceutical product in development or being manufactured.  Often the bioassay is the KEY potency assay for a biopharmaceutical and undergoes heavy scrutiny by the regulatory agencies given the importance of the data for safety and efficacy of the product.

Generally, when performing bioassays, it is very common to perform a dilution assay measuring the biological responses across a number of doses.  The reference preparations (standards and controls) used are important for the assay so that standard units can be provided for the readout.  However for novel products under development, accepted reference preparations don’t exist.  Therefore the data generated may simply be on a relative scale.

Various line fits can be used when fitting data, whether it’s a parallel-line assay, logit or some other fit.  The model used must be determined to be appropriate for the assay.