Transitioning from first- to second-generation biosimilars: An appraisal of regulatory and post-marketing challenges.

Second-generation biosimilars (i.e. monoclonal antibodies or proteins generated by fusion of antibody and receptor moieties) differ in several respects as compared to first-generation ones (e.g. epoetins, bone marrow stimulating factors, somatotropins). In this respect, as second-generation biosimilars are endowed with much greater structural and molecular complexity, which might translate into a number of pharmacological and therapeutic issues, they raise new challenges for manufacturers and regulatory authorities as well as new concerns for clinicians. Based on these arguments, the present article was intended to review information on the main differences between first- and second-generation biosimilars for treatment of immune-mediated inflammatory diseases, as well as their impact on immunogenicity, the design of clinical trials and the critical issue of extrapolation of therapeutic indications. The positions taken by relevant medical associations and the crucial role of pharmacovigilance are also reviewed. According to current knowledge, the initial post-marketing clinical experience with second-generation biosimilars is providing encouraging results, though their long-term safety and efficacy as well as the scientific basis underlying the extrapolation of therapeutic indications are still matter of discussion. There is some consensus that marketing applications should rely on studies supporting the clinical use of biosimilars in their different target diseases and patient populations. In parallel, clinical safety must be ensured by a strict control of the manufacturing processes and a solid pharmacovigilance program. It remains then a responsibility of the physician to drive a proper use of second-generation biosimilars into clinical practice, in accordance with guidelines issued by scientific societies.