The pharmaceutical industry has recently introduced a number of biotherapeutics with alternative types of scaffolds and mechanisms of action. Concepts that were proposed several years or, in some cases, decades ago are starting to become a reality, with a number of new and exciting compounds achieving regulatory approval status. As the field evolves, appropriate bioanalytical applications must be developed and adapted. Highly sensitive, accurate and specific bioanalytical methods are now required to measure drug concentration and immunogenicity responses, and bioanalytical protocols must undergo formal validation prior to being applied in support of regulated nonclinical or clinical studies. The six chapters of this book introduce important and exciting challenges for the bioanalysis of peptides, oligonucleotides, antibody–drug conjugates and antibody-based compounds.