Pharmacogenetics (PGt) is the study of the influence of individual variations in deoxyribonucleic acid sequence on drug response. Drug response includes drug disposition (pharmacokinetics) and drug effect (pharmacodynamics). PGt is applicable to activities such as drug discovery, drug development and clinical practise. Currently, there are more than 200 drugs whose labelling includes pharmacogenetic information. ‘Test required’ examples: Cetuximab, Trastuzumab, Maraviroc, Abacavir, Dasatinib, Glivec, Tasigna, Gefitinib and Herceptin; ‘Test recommended’ examples: Carbamazepine, warfarin, azathioprine, etc. In the coming years, evaluation by regulatory authorities of new medicines may involve increasingly PGt components in pre- and post-approval development, and may therefore depend on reliable PGt information. PGt is a rapidly and continuously evolving field; therefore, PGt studies should reflect on the ‘principles’ or necessary qualities of developing well-controlled, rigorous and reproducible sample handling and testing procedures.

Key Concepts:

• Pharmacogenetics define populations that can have most benefit from a drug.
  
• Pharmacogenetics improve drug development.
  
• Pharmacogenetics predict disease course (to justify more intense or prolonged treatments) (diagnostics and prognostics).
  
• Pharmacogenetics can be used to monitor the effects of the therapy (pharmacodynamics).
  
• Genomic biomarkers predict clinical outcomes (surrogate endpoints).
  
• Pharmacogenetics can be useful to identify new biological pathways involved in drug metabolism and therefore new treatment opportunities.
  
• Pharmacogenetics is applicable to activities such as drug discovery, drug development and clinical practise.
  
• Pharmacogenetics is applicable also in drug disposition (PK) and drug effect (PD).
  
• Pharmacogenetics is necessary to define individual dose adaptation of chemotherapeutics and in general for personalised medicine.
  
• Pharmacogenetics is crucial in genomic biomarkers identification.