Strengths, weaknesses and future challenges of biosimilars' development. An opinion on how to improve the knowledge and use of biosimilars in clinical practice.

Biosimilars started receiving the marketing authorization by European Medicine Agency since 2006. The development of biosimilars follows a well-defined step-wise approach, the so-called comparability exercise, which aims to compare non-clinical (mainly quality features and biological activity) and clinical (efficacy and safety profiles) features of new biosimilars with their respective reference products. Despite the undeniable advantages of such procedure, some concerns (such as the absence of switching studies or the evaluation of efficacy and safety in all therapeutic indications) still exist about its. In particular, the European regulatory framework on biosimilars approval does not include the conduction of switching studies demonstrating the interchangeability to be carried out before marketing authorization. This is one of the main aspects that negatively affects healthcare professionals' clinical decisions on switch. In order to achieve a better knowledge on safety and efficacy of biosimilar drugs, real world data should be collected and post-marketing efficacy and safety clinical studies (including those evaluating specific endpoints, therapeutic regimens and patients population), should be planned. also the conduction of well-designed switching studies is highly advisable, especially in the case of biosimilar drugs used in oncology settings. Lastly, considering the critical role of antidrug antibodies on efficacy/safety profile of biologic drugs, studies based on therapeutic drug monitoring would be useful in order to achieve treatment optimization. Implementing the above strategies could be helpful to fill the gap in knowledge observed in the present European biosimilar regulatory framework.