Pharmacogenetics: Where Is It Headed?

In today’s clinical setting, it is “well accepted” to test for genetic mutation or downstream protein expression prior to the use of certain therapies.¹ The author attributes this to strong data pointing to poor efficacy, or absence of data pointing to good efficacy, in individuals lacking the genetic mutation, as well as endorsement by the CPIC. However, the author notes, “use of pharmacogenetics data in clinical practice is still far from the norm.”

Barriers and Challenges to Clinical Implementation

The author lists barriers to the clinical implementation of pharmacogenetics, including:

• Test-related concerns, as tests must be performed in a regulated clinical laboratory, often with rapid turnaround time, at high cost, and with potential lack of reimbursement.
• Knowledge barriers, which necessitate increased genetics education among medical, pharmacy, and other health professionals. The author notes that these educational efforts may be insufficient and advises the use of clinical decision support tools, which offer clear guidance on therapeutic options, based on genotype.
• Evidence barriers—ie, controversies over the level of evidence required for clinical implementation of pharmacogenetics. For example, recent consensus guidelines for warfarin and clopidogrel recommend against routine pharmacogenetics testing, based on lack of evidence of benefit.^9,10,11 However, the author anticipates “increasing clarity regarding the evidentiary standards for clinical implementation of pharmacogenetics” in the coming years.
• Ethical, legal, and social implications of testing (eg, concerns about inclusion of genetic information in the medical record, with potential for genetic discrimination, or questions about sharing pharmacogenetics findings with family members) remain significant barriers.

Conclusion

Since 2001, there have been “substantial advances in pharmacogenetics,” including drugs developed under a genetically targeted approach (mostly for cancer), and advances in understanding the genetic determinants of drug response, which may lead to more frequent use of pharmacogenetics data to inform drug therapy decisions. 

The author concludes that “it is anticipated that the next five to 10 years will define the importance of pharmacogenetics in the clinical setting” and that “all signs point to continued advances, such that the projection of clinical use of pharmacogenetics data in 2020 will occur.”

References

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8. Crews KR, Gaedigk A, Dunnenberger HM, et al. Clinical Pharmacogenetics Implementation Consortium (CPIC) guidelines for codeine therapy in the context of cytochrome P450 2D6 (CYP2D6) genotype. Clin Pharmacol Ther. 2012;91(2):321-326.

9. Holbrook A, Schulman S, Witt DM, et al. Evidence-based management of anticoagulant therapy: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines. Chest. 2012;141(2 Suppl):e152S-84S.

10. Levine GN, Bates ER, Blankenship JC, et al. 2011 ACCF/AHA/SCAI Guideline for   Percutaneous Coronary Intervention: executive summary: a report of the American  College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines and the Society for Cardiovascular Angiography and  Interventions.  Circulation. 2011;124(23):2574-2609.

11. Wright RS, Anderson JL, Adams CD, et al. 2011 ACCF/AHA focused update incorporated into the ACC/AHA 2007 Guidelines for the Management of Patients with Unstable Angina/Non-ST-Elevation Myocardial Infarction: a report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines developed in collaboration with the American Academy of Family Physicians, Society for Cardiovascular Angiography and Interventions, and the Society of Thoracic Surgeons. J Am Coll Cardiol. 2011;57(19):e215-367.