This study describes the development of an immunosensory label-free quantification methodology based on surface plasmon resonance (SPR) and its applicability in measuring/evaluating therapeutic drug monitoring (TDM) of anti-TNF-α monoclonal antibody (adalimumab) in rheumatoid arthritis (RA) patients. The experimental parameters evaluated in this study were immobilising ligands by pre-concentration assays, sensor surface regeneration, ascertaining the method’s sensitivity and correlating the results from quantifying plasma samples by ELISA immunoassay. The results showed that TNF-α quantification values (in RU) were significantly different when comparing patients (~50–250 RU) to controls (~10–20 RU). Likewise, there was 0.97 correlation for patients and 0.91 for healthy volunteers using SPR and ELISA comparison methodologies. SPR immunosensory detection provided a precise, sensitive strategy, along with real-time determination, for quantifying adalimumab, having great potential for clinical routine regarding TDM.

Developing new biologics has led to regulations and norms aimed at guaranteeing their safety, quality and effectiveness, in terms of marketing, prescription, use, interchangeability and switching. Biologics are of great importance in treating patients suffering from rheumatic, autoimmune, inflammatory and neoplastic diseases. The expiry/lapse of reference biologics or originators’ patents has meant that developing biosimilars involves accompanying legal requirements for their approval in countries worldwide. This paper has thus approached the situation of biosimilar regulation worldwide, the pertinent technical concepts and regulatory differences in some countries of interest.