Approval of biosimilars: a review of unsuccessful regulatory filings.

INTRODUCTION: Over the past three decades, biotherapeutics have transformed health care by offering effective treatments for complex diseases that were otherwise difficult to deal with via small molecule pharmaceuticals. Patents on several biotherapeutics have expired or are due to expire in recent times, and this has fueled the growth in biosimilars, products that are deemed to be similar to the already-approved innovator products in terms of safety and efficacy. Production of biosimilars is complicated by the fact that in biotech processes, the process is the product and there have been many instances where a small change in the manufacturing process results in significant undesirable clinical impact. This is why regulatory authorities around the world have formulated stringent guidelines for the approval of biosimilars. AREAS COVERED: This article aims to review unsuccessful regulatory filings for biosimilar approval. EXPERT OPINION: We have focused on regulatory submissions to EMA and FDA. Key shortcomings of the filings that failed to receive approval have been identified and discussed.