Review ArticleMonoclonal Antibody Monitoring: Clinically Relevant Aspects, A Systematic Critical ReviewRegazzi, Mario PharmD*; Golay, Joseè PhD†,‡; Molinaro, Mariadelfina MScBiol§Author Information *S.I.F.E.B., Società Italiana di Farmacocinetica e Biofarmaceutica, Pavia; †Center of Cellular Therapy “G. Lanzani”, UOC Ematologia, Azienda Socio Sanitaria Territoriale Papa Giovanni XXIII, Bergamo; ‡Fondazione per la Ricerca Ospedale Maggiore (FROM), Bergamo; and §Department of Diagnostic Medicine; Clinical and Experimental Pharmacokinetics Unit, Fondazione IRCCS Policlinico San Matteo, Pavia, Italy. Correspondence: Mario Regazzi, PharmD, S.I.F.E.B., Società Italiana di Farmacocinetica e Biofarmaceutica, Via dei Liguri 38, 27100 Pavia, Italy (e-mail: [email protected]). The authors declare no conflict of interest. Therapeutic Drug Monitoring: February 2020 - Volume 42 - Issue 1 - p 45-56 doi: 10.1097/FTD.0000000000000681 Buy Metrics Abstract Monoclonal antibody (mAb) therapy does not usually lead to a clinical response in all patients and resistance may increase over time after repeated mAb administration. This lack or loss of response to the treatment may originate from different and little-known epigenetic, biomolecular, or pathophysiological mechanisms, although an inadequate serum concentration is perhaps the most likely cause, even if not widely recognized and investigated yet. Patient factors that influence the pharmacokinetics (PK) of a mAb should be taken into account. Multiple analyses of patient-derived PK data have identified various factors influencing the clearance of mAbs. These factors include the presence of antidrug antibodies, low serum albumin, high serum levels of C-reactive protein, high body weight, and gender differences among others. The same clearance processes involved in systemic clearance after intravenous administration are also involved in local first-pass catabolism after subcutaneous administration of mAbs. Therapeutic drug monitoring has been proposed as a way to understand and respond to the variability in clinical response and remission. For both classes of mAbs with anti-inflammatory and antitumor effects, dose-guided optimization based on the measurement of serum concentrations in individual patients could be the next step for a personalized and targeted mAb therapy. Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved.