Tuesday, April 30, 2013
Where Are All the New Anti-Craving Drugs?
The dilemma of dwindling drug development.
Drugs for the treatment of addiction are now a fact of life. For alcoholism alone, the medications legally available by prescription include disulfiram (Antabuse), naltrexone (Revia and Vivitrol)—and acamprosate (Campral), the most recent FDA-approved entry. A fourth entry, topiramate (Topamax), is currently only approved by the Food and Drug Administration (FDA) for other uses. But none of these are miracle medications, and more to the point, no bright new stars have come through the FDA pipeline for a long time.
New approvals for drugs in this category, like psychiatric drugs in general, have lately been confined to repurposed, “me-too” medications—which, insurance companies complain, are far too expensive. As health insurance giant Cigna explains on its website: “If anticraving medications are not covered by your insurance plan, keep in mind that the price of anticraving medications is usually small compared to the cost of alcohol and/or other drugs.” Perhaps so, but evidently not small enough for the expense to be routinely covered by the prescription portion of insurance policies.
Federal health officials have the same complaints. In a 2004 report entitled “Innovation or Stagnation: Challenge and Opportunity on the Critical Path to New Medical Products,” the U.S. Food and Drug Administration called for increased public-private collaboration and a “critical development path that leads from scientific discovery to the patient.”
As detailed by Professor Mary Jeanne Kreek, a senior attending physician at the Laboratory of the Biology of Addictive Diseases at Rockefeller University and one of the primary developers of methadone therapy:
Toxicity, destruction of previously formed synapses, formation of new synapses, enhancement or reduction of cognition and the development of specific memories of the drug of abuse, which are coupled with the conditioned cues for enhancing relapse to drug use, all have a role in addiction. And each of these provides numerous potential targets for pharmacotherapies for the future.
In other words, when an addiction has been active for a sustained period, the first-line treatment of the future is likely to come in the form of a pill. New addiction treatments will come—and in many cases already do come—in the form of drugs to treat drug addiction. Every day, addicts are quitting drugs and alcohol by availing themselves of pharmaceutical treatments that did not exist twenty years ago.
But things have changed. “This scientific stall may have seemed to come out of the blue,” writes Dr. Steven E. Hyman, Professor of Stem Cell and Regenerative Biology at Harvard University, in the Dana Foundation publication, Cerebrum. Hyman sketches a dismal picture:
The molecular and cellular underpinnings of psychiatric disorders remain unknown; there is broad disillusionment with the animal models used for decades to predict therapeutic efficacy; psychiatric diagnoses seem arbitrary and lack objective tests; and there are no validated biomarkers with which to judge the success of clinical trials. As a result, pharmaceutical companies do not see a feasible path to the discovery and development of novel and effective treatments…. progress for the many patients who respond only partially or not at all to current treatments requires the discovery of medications that act differently in the brain than the limited drugs that we now possess…. and regulatory agencies have given up their willingness to accept even more expensive new drugs.
Genes aren’t simple, and the kinds of studies that would lead to new anti-craving drugs are not cheap. Moreover, the medications themselves do not represent cures. Even if drugs that block dopamine receptors treat psychotic symptoms, Hyman writes, “it does not follow that the fundamental problem is excess dopamine any more than pain relief in response to morphine suggests that the original problem is a deficiency of endogenous opiates.”
What can change this picture for the better? “One exciting recent development is the emerging recognition that genes involved in schizophrenia, bipolar disorder, and autism do not represent a random sample of the genome,” Hyman writes. “Rather, the genes are beginning to coalesce into identifiable biochemical pathways and components of familiar neural structures…. Many researchers hope that such efforts will help attract the pharmaceutical industry back to psychiatry by demonstrating new paths to treatment development. The emerging genetic results may be the best clues we have ever had to the etiology of psychiatric disorders.”
Detractors worry, naturally enough, about the shrinking pie of funds available for this sort of endeavor. According to Steven Paul, president of Lilly Research Laboratories, “I am worried that obtaining the kind of molecular probes required for even in vivo testing may prove to be too time-consuming and expensive, and may divert precious NIH funds away from basic or clinical biomedical research.”
But Hyman remains optimistic, “based partly on the extraordinary vitality of neuroscience and perhaps, even more important, on the emergence of remarkable new tools and technologies to identify the genetic risk factors for psychiatric disorders, to investigate the circuitry of the human brain, and to replace current animal models that have failed to predict efficacious new drugs that act by novel mechanisms in the brain.”
Photo Credit: http://www.insidecounsel.com/