The FDA's assessment of follow-on protein products: a historical perspective.

The scientific and regulatory issues that are associated with the possible introduction of 'follow-on' versions of protein drug products are the topic of considerable debate at present. Because of the differences between protein drug products and small-molecule drugs, the development of follow-on versions of protein products presents more complex scientific challenges than those presented by the development of generic versions of small-molecule drugs. Here, with a view to illustrating the Food and Drug Administration's (FDA's) scientific reasoning and experience in this area, we discuss past examples of the FDA's actions involving the evaluation of various types of follow-on and second-generation protein products and within-product manufacturing changes. The FDA believes its evaluation of the safety and effectiveness of follow-on protein products will evolve as scientific and technological advances in product characterization and manufacturing continue to reduce some of the complexity and uncertainty that are inherent in the manufacturing of protein products.

The effect of contaminant proteases in testicular hyaluronidase preparations on the immunological properties of bovine nasal cartilage proteoglycan.

Commercial testicular hyaluronidase preparations are contaminated by a small amount of protease activity which is partially inhibited by serine-protease inhibitors or pepstatin. These protease inhibitors can be shown by Sepharose gel column chromatography to abolish or reduce hyaluronidase-induced degradation of bovine nasal cartilage proteoglycan subunit without affecting the ability of the enzyme to degrade chondroitin sulfate. In addition, immunodiffusion studies indicate that pretreatment of hyaluronidase with these protease inhibitors reduces or abolishes the ability of the enzyme to produce a second "link-related" immunoprecipitin line upon digestion of link protein-containing proteoglycan fractions. Thus, the enhancement of immune reactivity and the unmasking of an additional antigen noted after digestion of cartilage proteoglycan with testicular hyaluronidase are most likely due to the exposure of additional antigenic sites or the the release of more highly immunoreactive fragments by the contaminant proteases rather than to the action of hyaluronidase itself.