Potentially a big step toward ability to hit it right with the first prescription and avoid the often lengthy Rx trial & error process
Loyola University Medical Center researchers believe they’ve identified the first reliable method for predicting whether a specific antidepressant will help a depressed patient. (Antidepressant prescription tends to be a trial and error process, since different people are helped by different drugs, and nobody really knows why.)
The researchers found that blood tests for a protein called vascular endothelial growth factor (VEGF) largely separated out those depressed patients likely to respond well to the SSRI drug escitalopram (brand name Lexapro®) and who would not. Of 35 patients with major depression who were treated with escitalopram:
• More than 85% of those with higher than normal blood levels of VEGF experienced partial or complete relief from depression after taking escitalopram.
• By comparison, fewer than 10% of those who had low levels of VEGF responded to the drug.
Since currently 60% of depression patients will not respond well to the first drug prescribed and it can take a month to achieve a drug response, such strategies promise a considerable improvment in time to benefit.
SSRIs - selective serotonin reuptake inhibitors - are a class of drugs that support an increase of serotonin levels in the brain. Other common SSRIs are Prozac®, Paxil® and Zoloft®. VEGF is a signal protein that cells produce to encourage vessel growth when they sense blood circulation/oxygen supply is inadequate.
"This would be the first time we would have a predictor for how well a patient would respond to an antidepressant," says Loyola neuroscientist Angelos Halaris, MD, PhD, who presented the study at the 2011 Society of Biological Psychiatry and Illinois Brain, Behavior & Immunity annual meetings. "It would greatly benefit our patients if we could predict ahead of time whether a given medication would be effective for a certain patient."
How Might VEGF Support SSRI Effectiveness?
Scientists aren't certain why SSRIs work in some patients but not in others. One possible mechanism is that SSRIs help restore a chemical balance in the brain.
Some scientists recently have proposed a second possible mechanism, called neurogenesis – that SSRIs help to regenerate brain cells in specific parts of the brain that have atrophied in depressed patients. The Loyola study supports the neurogenesis theory.
It appears that escitalopram, the SSRI used in the Loyola study, jump-starts brain cells that have become inactive. This regeneration is fueled by VEGF's ability to stimulate vessel growth and other activities that keep brain cells healthy and active.
It appears that in patients with higher levels of VEGF, there was more regeneration, helping to reduce depression. Conversely, in patients with lower VEGF levels, there was less regeneration of brain cells and less relief from depression.
If the finding is confirmed by further studies, it could lead to a blood test that would help physicians tailor treatment. If, for example, a patient had low levels of VEGF, the physician might skip SSRIs and try alternative classes of antidepressants, such as bupropion, or alternative therapies, such as psychotherapy or Transcranial Magnetic Stimulation (TMG).
Though the VEGF test is currently ‘expensive’ - nearly $300 at one leading lab – Dr. Halaris suggests the cost likely would come down significantly if it were to become widely used. (And patient benefit in time to therapeutic relief would presumably be a major consideration.)
Source: Based on Loyola University Medical Center news release, Dec 15, 2010