Background A biosimilar is a copy version of an approved original biological medicine whose data protection has expired. Aim To provide an overview of the development of biosimilars worldwide. Methods Literature review of manufacturing processes of biosimilars, differences and similarities between biosimilars and the reference product, approval pathways for biosimilars, challenges in clinical trial study design and available data from clinical trials. Results Biosimilars have the same amino acid sequence and highly similar glycosylation patterns that overlap with the originator product. Both efficacy and toxicity are difficult to predict due to subtle molecular changes that might have profound effects on clinical efficacy, safety and immunogenicity. Their main advantage is related to cost savings. Direct evidence of safety and benefit from clinical trials, post-marketing pharmacoviligance and unequivocal identification of the product as a biosimilar are requirements before approval. Non-inferiority or equivalence trials are required by regulatory agencies. Over the past years, several biosimilars have been approved such as erythropoietin or growth factors. Recently, two monoclonal antibodies, Remsima and Inflectra, have been shown to be equivalent to infliximab (INX) in safety and efficacy in rheumatologic conditions. Interchangeability, automatic substitution and switching are key issues when treating patients with biosimilars in clinical practice. Conclusions Biosimilars represent a new generation of drugs in liver and gastrointestinal diseases. On June 27, 2013, Hospira's Inflectra (INX) was the first biosimilar monoclonal antibody to receive positive opinion from European Medicines Agency's Committee for Medicinal Products for Human Use for rheumatoid arthritis, inflammatory bowel disease and plaque psoriasis.