Feb 13, 2012
By: Dr. Evian Gordon
(Editor’s Note: this is Part 1 of the new 3-part series written by Dr. Evian Gordon drawing from his participation at the Personalized Medicine World Congress on January, 23, 2012 at Stanford University.)
On average, the medications prescribed for brain-related conditions benefit approximately 50% of patients. But which 50%?
Personalized Medicine seeks to move away from the current “1 size fits all, trial and error” approach that has been necessary because of a lack of evidence. Instead, it focuses on matching the biological characteristics of each person with the best medication and dose for them. Tests that measure these characteristics are called “biomarkers”.
The bottom line of Personalized Medicine is to improve outcomes that matter to both the doctor and the patient, and reduce the current costs. So far, the focus of Personalized Medicine has been in cancer and some chronic medical conditions. It is new to conditions of brain health and to psychiatry.
Personalized Medicine is being driven by the FDA (Federal Drug Administration in Washington) and is being adopted to different extents, by the stakeholder groups we will outline in the third and final part of this series.
With the completion of the Genome Project in 2003, expectations were high that genetic variants would help objectively determine diagnostic categories and predict individualized treatment response. But Genomics (“Pan-omics”) of the growing number of molecular measures (Genes [DNA], Gene Expression [RNA], Proteomics and Metabolomics) have to some extent “overpromised and under-delivered”. This is especially true in Psychiatry where the conditions we are tackling involve a complex combination of genetics and gene-experience interactions.
But, other medical conditions are also complex, and involve gene-experience interactions. According to the Personalized Medicine Coalition (PMC) in Washington, there were 13 examples of Personalized Medicine diagnostic Biomarkers and medications in 2006 and 72 in 2011.
Specific outcomes in Cancer are promising for the development of Personalized Medicine in Psychiatry. Some exemplar successes are outlined below.
Personalized Medicine Successes in Medicine
Selected Examples of Personalized Medicine Biomarkers in Cancer:
- Herceptin ® (trastuzumab) treatment – is identified by the HER-2/neu receptor – and is used in Breast cancer: about 30% of cancers have an over-expression of HER-2 protein, which respond to Herceptin.
- Gleevec ® (Imatinib mesylate) – is identified via BCR-ABL – and used to treat Chronic Myloid Leukemia: increases life expectancy from 5% — 95% at 5 years.
- Zelboraf ®(Vemurafenib) – is identified by BRAFV600E – and used to treat Melanoma, where the late stage prognosis is poor: 60% of patient have a defect in their DNA and the drug only benefits those with the V600E defect.
- Other successful Personalized Medicine examples of “Treatment – Biomarker” combinations are in Colon Cancer (Erbitux – EFGR), and Lung Cancer (Xalkori – ALK).
There are also examples of Biomarkers that are not specific to 1 drug, but affect the metabolism in the liver of many drugs, with effects on dosage. The best known example is the CYP 450 enzyme and its application to Coumadin Warfarin). PGx® Predicts the CYP2C9 enzyme, which in cardiovascular disease predicts the likelihood of adverse events with Warfarin therapy. The Amplichip® CYP2D6 is linked to approximately 25% of all Psychiatric drugs prescribed and can be used to avoid dose ‘toxicity’ and possible adverse events in individuals who are high metabolizers.
*Personalized Medicine Molecular Tests recommended by the FDA are listed on the FDA’s website Here.
The Personalized Medicine Coalition (website here) provides an exceptional ongoing summary of new Biomarkers in Personalized Medicine.
The extent of the benefits of real world examples of Personalized Medicine are growing. I list three examples below.
Dr Shankaran found that $604 mill could be saved per annum if Vectibix and Erbitux medication for metastatic Colorectal cancer was restricted to patients whose KRAS gene was not mutated, since only they would be the patients likely to benefit (more here).
Dr Barker (former Deputy Director of the National Cancer Institute) reported that cancer fatalities have declined by 22% in men and 14% in women over the past 40 years, thanks in part to Personalized Therapies such as Gleevac and Tarceva.
A real world example of CYP is the prediction that correct personalized dosing of Warfarin could prevent 17,000 strokes in the U.S. and avoid 43,000 emergency room visits. The Mayo Clinic and Medco tested this prediction in 3,600 patients and found hospitalizations for heart rate patents were reduced by 30% (Epstein RS et al. J American College Cardiology. 55:2804–12. 2010).
In contrast to these successes, most Personalized Medicine research in Psychiatry using molecular measures alone have failed to replicate. Whilst disappointing, this is not surprising, since 80% of human 25,000 genes have some effect on the brain.
To Be Continued…
New Series on Personalized Medicine and the Brain:
- Monday, February 13th: The State of Personalized Medicine (above)
- Monday, February 20th: Challenges and Opportunities of Personalized Medicine in Psychiatry
- Monday, February 27th: Working with Health Care Industry Stakeholders Towards Brain-based Personalized Medicine