[Scientific rationale for the replacement of an in vivo bioassay for protein drugs with a physico-chemical assay].

Recent progress in both protein drug production technologies including biotechnology and protein characterization methodologies has enabled us to mass-produce and extensively characterize highly purified protein drugs. The quality control of these protein drugs, being based on such a background, should be carried out using various modern protein analytical methodologies. One of the points to be considered regarding control strategies for these protein drugs should be the development and standardization of more specific, precise, simple and economical assay methodology. The replacement of existing in vivo bioassays with certain in vitro assays, including physico-chemical assays, is one possible directions along this line. This paper describes strategies for the replacement of an in vivo bioassay for protein drugs with a physico-chemical assay. Such approaches have been applied for recombinant human growth hormone and recombinant human insulin, the potencies of which have been estimated by in vivo bioassay. Scientific rationale for such approaches are also discussed.