The attempt to personalize the diabetes treatment as much as possible is currently based on the growing knowledge of drug mechanism of action and genetic-driven pharmacokinetics differences: for example, glucagon-peptide-1 receptor agonists (GLP-1 RA) will not be successful in subjects with severe insulin deficiency and thiazolidinediones (TZD) work better in insulin-resistant obese patients than in normal-weight patients [181,182]. The gene discussed is INS; the disease is diabetes mellitus.