Pragmatic rules for comparability of biological medicinal products.

Comparability is a key concept in the evaluation of both manufacturing changes and biosimilars. It constitutes a pragmatic and flexible approach which recognises that biologicals are inherently variable and that minor variations in quality attributes are often clinically irrelevant. In this discussion paper, we argue that comparability exercises rely on a number of pragmatic criteria. These criteria have been remarkably robust for 20 years of comparability exercises; however, the increased scrutiny of biosimilar applications provides an impetus for both codification and improvement of criteria for establishing comparability. Such a more rigorous, methodologically sound, approach towards comparability seems both feasible and beneficial.