Old drugs, new uses
By Mary Loftus
It’s a wonder new medications are ever developed at all. Taking a new drug from promising molecule to marketable drug can cost upwards of a billion dollars and take a decade or more. Oh, and the overall failure rate hovers near 95 percent.
Not surprisingly, the pharmaceutical industry has become interested in repurposing already approved drugs. These may be medications on the market for a different condition or those that didn’t pan out for their original use.
Repurposing an existing drug can save developers years of time, preliminary clinical trials, and almost 40 percent in costs. “The amount needed to bring these drugs to market is often less, which is why smaller companies are interested: some of the risk has been taken out of the equation,” says Cliff Michaels, senior licensing associate with Emory’s Office of Technology Transfer (OTT). Well-known repurposed drug success stories include the following:
Rogaine, the hair regrowth treatment was developed from the oral blood pressure medication minoxidil after researchers noticed that hair growth was a common side effect.
Thalidomide, first positioned as a cure for morning sickness in pregnant women and taken off the market in 1961 after being linked to severe birth defects, was approved by the FDA in 1998 for use in patients with leprosy and again in 2006 for those with multiple myeloma.
Viagra was developed to treat pulmonary arterial hypertension before gaining approval in 1998 to treat erectile dysfunction.
As the cost to develop drugs continues to go up, there is also an increased interest from the public and the federal government to make the most of drugs that have been approved. The NIH’s Chemical Genomics Center recently opened its Pharmaceutical Collection database for public screening of nearly 27,000 active pharmaceutical ingredients, including 2,750 approved small-molecule drugs and all compounds registered for human clinical trials.
NIH Director Francis Collins said the agency would be leading a “comprehensive effort to identify appropriate abandoned compounds, establish master agreements, match partners, make data resources available, and provide a central access point to relevant resources and expertise.”
Emory’s OTT already has several repurposed drug candidates in development to treat conditions from post-traumatic stress disorder (PTSD) to hypersomnia to stroke.
Flumazenil was developed for treating overdoses of benzodiazepine sedative hypnotics but was found by Emory School of Medicine sleep researchers David Rye and Andrew Jenkins to be useful for patients with hypersomnia, or excessive sleepiness—even those who hadn’t responded to traditional treatments like stimulants.
Rapamycin was originally developed as an antifungal agent but was discovered to have potent immunosuppressive and anti-inflammatory properties and has been used to prevent rejection of transplanted organs. School of Medicine Dean Christian Larsen, Emory Vaccine Center Director Rafi Ahmed, and colleagues at the Emory transplant and vaccine centers found that the drug could also boost T cell immunity from immunizations.
Metformin, used to treat type 2 diabetes, may be effective in treating nephrogenic diabetes insipidus as well, found researcher Jeff Sands. People with this rare condition (which is related to diabetes only in name) can’t regulate water in their body versus urine output. Sands, chair of nephrology, says these individuals may produce gallons of urine over 24 hours, which makes life difficult during the day but even harder at night. Children with this genetic condition can make up to a liter of urine per hour, and must also drink that much to rehydrate.
Nephrogenic diabetes insipidus can also be a side effect of chronic lithium use, so it is sometimes seen in adults being treated for bipolar disorder. The drug has proven effective in mice. Larry Greenbaum, of pediatric nephrology, is doing a pilot study to see if what has been observed in animals can be duplicated in humans.
Osanetant was first tested to treat schizophrenia but did not show a clear advantage over traditional treatments and was abandoned. Yerkes National Primate Research Center scientists Kerry Ressler, Raül Andero Galí, and Brian Dias discovered that osanetant made memories of frightening events less durable in mice by blocking the pathway involved in fear learning and the consolidation of fear memories. The drug may prove to be therapeutic for people with anxiety or fear disorders, such as PTSD.
A combination of rapamycin and the drug imatinib (Gleevec), used in the treatment of chronic myeloid leukemia, was found by researcher Jack Arbiser in dermatology to be highly effective in decreasing tumors in mouse models of tuberous sclerosis, a genetic disorder that causes non-malignant tumors to form in many different organs, primarily the brain, eyes, heart, kidney, skin, and lungs.
TAK-242 a Japanese drug that was originally developed to treat sepsis, went through safety trials but didn’t show efficacy. Researchers Fang Hua, Donald Stein, and Iqbal Sayeed, in emergency medicine, found that TAK-242 could be used as a non-surgical treatment for ischemic stroke by blocking inflammation and lessening brain injury.
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