Many years ago, drug development in psychiatry turned to control of specific symptoms across disorders rather than within disorders, but regulatory agencies are still not yet on board, according to an expert psychopharmacologist outlining the ongoing evolution at the virtual Psychopharmacology Update presented by Current Psychiatry and the American Academy of Clinical Psychiatrists, sponsored by Medscape Live.
If this reorientation is going to lead to the broad indications the newer drugs likely deserve, which is control of specific types of symptoms regardless of the diagnosis, “we have to move the [Food and Drug Administration] along,” said Stephen M. Stahl, MD, PhD, chairman of the Neuroscience Institute and an adjunct professor of psychiatry at the University of California, San Diego.
On the side of drug development and clinical practice, the reorientation has already taken place. Dr. Stahl described numerous brain circuits known to produce symptoms when function is altered that are now treatment targets. This includes the ventral medial prefrontal cortex where deficient information processing leads to depression and the orbital frontal cortex where altered function leads to impulsivity.
“It is not like each part of the brain does a little bit of everything. Rather, each part of the brain has an assignment and duty and function,” Dr. Stahl explained. By addressing the disturbed signaling in brain circuits that lead to depression, impulsivity, agitation, or other symptoms, there is an opportunity for control, regardless of the psychiatric diagnosis with which the symptom is associated.
For example, Dr. Stahl predicted that pimavanserin, a highly selective 5-HT2A inverse agonist that is already approved for psychosis in Parkinson’s disease, is now likely to be approved for psychosis associated with other conditions on the basis of recent positive clinical studies in these other disorders.
Brexpiprazole, a serotonin-dopamine activity modulator already known to be useful for control of the agitation characteristic of schizophrenia, is now showing the same type of activity against agitation when it is associated with Alzheimer’s disease. Again, Dr. Stahl thinks this drug is on course for an indication across diseases once studies are conducted in each disease individually.
Another drug being evaluated for agitation, the N-methyl-D-aspartate receptor antagonist dextromethorphan bupropion, is also being tested for treatment of symptoms across multiple disorders, he reported.
However, the FDA has so far taken the position that each drug must be tested separately for a given symptom in each disorder for which it is being considered despite the underlying premise that it is the symptom, not the disease, that is important.
Unlike physiological diseases where symptoms, like a fever or abdominal cramps, are the product of a disease, psychiatric symptoms are the disease and a fundamental target – regardless of the DSM-based diagnosis.
To some degree, the symptoms of psychiatric disorders have always been the focus of treatment, but a pivot toward developing therapies that will control a symptom regardless of the underlying diagnosis is an important conceptual change. It is being made possible by advances in the detail with which the neuropathology of these symptoms is understood .
“By my count, 79 symptoms are described in DSM-5, but they are spread across hundreds of syndromes because they are grouped together in different ways,” Dr. Stahl observed.
He noted that clinicians make a diagnosis on the basis symptom groupings, but their interventions are selected to address the manifestations of the disease, not the disease itself.
“If you are a real psychopharmacologist treating real patients, you are treating the specific symptoms of the specific patient,” according to Dr. Stahl.
So far, the FDA has not made this leap, insisting on trials in these categorical disorders rather than permitting trial designs that allow benefit to be demonstrated against a symptom regardless of the syndrome with which it is associated.
Of egregious examples, Dr. Stahl recounted a recent trial of a 5-HT2 antagonist that looked so promising against psychosis in Alzheimer’s disease that the trialists enrolled patients with psychosis regardless of type of dementia, such as vascular dementia and Lewy body disease. The efficacy was impressive.
“It worked so well that they stopped the trial, but the FDA declined to approve it,” Dr. Stahl recounted. Despite clear evidence of benefit, the regulators insisted that the investigators needed to show a significant benefit in each condition individually.
While the trial investigators acknowledged that there was not enough power in the trial to show a statistically significant benefit in each category, they argued that the overall benefit and the consistent response across categories required them to stop the trial for ethical reasons.
“That’s your problem, the FDA said to the investigators,” according to Dr. Stahl.
The failure of the FDA to recognize the efficacy of psychopharmacologic therapies across symptoms regardless of the associated disease is a failure to stay current with an important evolution in medicine, Dr. Stahl indicated.
“What we have come to understand is the neurobiology of any given symptom is likely to be the same across disorders,” he said.