title: Analysis of therapeutic growth hormone preparations: report of an interlaboratory collaborative study on growth hormone assay methodologies.
abstract: Recombinant DNA-derived human growth hormone (somatotropin) is widely used to treat growth hormone-deficient children. The potency of this product is determined by in-vivo bioassay in hypophysectomized rats, which is imprecise, costly and invasive, and there have been suggestions that it could safely be replaced with in-vitro or physico-chemical alternatives. In this report we present the results of a collaborative study designed to test this proposal. Somatotropin was modified by mild or severe proteolysis, mild or severe oxidation or treatment at high pH, and compared in a multi-centre collaborative study with unmodified somatotropin or with dimerized somatotropin. Participating laboratories included manufacturers and national control laboratories, and pharmacopoeial bioassays were compared with in-house in-vitro and physico-chemical bioassays. Although performing adequately with untreated somatotropin, for degraded samples the in-vivo bioassays were relatively unresponsive to changes in the growth hormone molecule. In contrast, the physico-chemical assays, in particular the reverse-phase HPLC, performed with a high degree of selectivity. We conclude that in the case of somatotropin, the in-vivo bioassay can be removed from the routine product specification with an acceptable degree of security. This however does not obviate the requirement rigorously to demonstrate biological activity in-vivo during product development, nor may the conclusions of this study be applied to other therapeutic recombinant proteins without similar collaborative investigations.
authors.affiliation: National Institute for Biological Standards and Control, Potters Bar, Herts, U.K.
authors.forename: A F
authors.initials: AF
authors.lastname: Bristow
authors.forename: S L
authors.initials: SL
authors.lastname: Jeffcoate
mesh_terms: D000818:Animals; D001681:Biological Assay / Q000379:methods*; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D005069:Evaluation Studies as Topic; D006128:Growth / Q000187:drug effects; D013006:Growth Hormone / Q000032:analysis* / Q000494:pharmacology / Q000592:standards; D006801:Humans; D007118:Immunoassay / Q000379:methods; D010084:Oxidation-Reduction; D051381:Rats; D011994:Recombinant Proteins / Q000032:analysis / Q000592:standards; D012015:Reference Standards
chemical_list: D011994:Recombinant Proteins; D013006:Growth Hormone