Clinical trial design in biosimilar drug development.

In contrast to most drugs which are chemically synthesized and have a known structure, biological drugs are derived from living organisms or their products. Biologicals are structurally more complex and unique from chemically synthesized small drug molecules because of their larger size and intricate manufacturing process. Secondary to their protein structure, they are also more prone to acute and chronic immune responses. Biosimilars are intended to offer comparable safety and efficacy relative to reference brand biologicals, yet they are not generic alternatives to the original compounds and so are currently not considered interchangeable. Given their structural complexity, multifaceted manufacturing processes and risk for immunogenicity, biosimilars require class-specific regulatory approval pathways. Here we seek to provide a general overview of clinical trial design in the era of biosimilar drug development. This will include a review of the regulatory requirements for clinical trials in Europe and the United States, followed by a review of two biosimilars that have recently reported results of randomized trials against branded biologicals.