Biosimilar epoetins: an analysis based on recently implemented European medicines evaluation agency guidelines on comparability of biopharmaceutical proteins.

Patents of innovator biopharmaceutical products, such as epoetin, are expiring, and biosimilar versions of these products may soon enter European and American markets. Copies of these products, termed biosimilars or follow-on biologics, are not truly equivalent and cannot gain market approval through the procedure typically applied to generic drugs. We evaluated literature reports of both analytic and clinical studies conducted with biosimilar epoetin products currently marketed outside the United States and Europe in light of recently implemented European Medicines Evaluation Agency guidelines. The analytic studies reported that products differed widely in composition, did not always meet self-declared specifications, and exhibited batch-to-batch variation. Although several clinical studies demonstrated correction of anemia with biosimilar epoetins by using an open-label or placebo-controlled study design, only 4 of 22 studies were competitor controlled. Most of the studies were small (median 41 patients, range 18-1079 patients) and of short duration (median 12 wks, range 6 wks-1 yr). Clinical experience with epoetin shows that the dosage required to achieve similar hemoglobin levels varies among patients, making it impossible to demonstrate bioequivalence without a comparator. The analytic reports did not demonstrate comparability of biosimilar epoetin products with innovator epoetin alfa, and the clinical studies were not rigorous enough to show equivalent safety and efficacy of a biopharmaceutical product. The variation between products illustrates the challenge in replicating and consistently producing biopharmaceutical proteins. Immunogenic reactions with epoetin indicate that large, long-term studies are needed to adequately monitor safety.