Johannes (Jan-Willem) Alffenaar is Professor of Clinical Pharmacy at the Sydney School of Pharmacy, Faculty of Medicine and Health, The University of Sydney, Australia, and Chair of Clinical Pharmacy at Westmead Hospital. He is a Clinical Pharmacologist with expertise in therapeutic drug monitoring (TDM), clinical pharmacokinetics, pharmacotherapy, and personalised dosing in routine clinical care. He has served as Past President of the International Association of Therapeutic Drug Monitoring and Clinical Toxicology (IATDMCT). He is the Theme Lead for “Antimicrobial Resistance and Novel Therapies” at the University of Sydney Infectious Diseases Institute (Sydney ID) and is a member of the Antimicrobial Stewardship Committee, Drug Committee, Chair of the Scientific Advisory Committee, and member of the Human Research Ethics Committee at Westmead Hospital, and he also serves as a member of the WHO Technical Advisory Group on TB drug dosing. His research focuses on improving treatment outcomes through pharmacokinetic-guided dosing, therapeutic drug monitoring, antimicrobial stewardship, and innovative approaches to optimise drug exposure in patients using novel sampling techniques.