A publication at Science Daily recently announced that findings from Children’s Hospital of Philadelphia suggested that cysteamine bitartrate, already used for nephropathic cystinosis (a rare kidney disease), might potentially benefit patients with certain mitochondrial disorders.
“Virtual repurposing” is an increasingly popular way of bringing a drug to market quick and cheap. Rather than spend the millions of dollars and years of clinical research that are synonymous with new drug formulation, some drug companies are researching how many different conditions could be treated with a single, already extant drug.
Say it once to get it out of your head.
Yes, mitochondria are, famously, the powerhouse of the cell. They are responsible for producing the energy humans need to run their bodies, which they do through a complex series of chemical reactions called the respiratory chain.
Partially because mitochondrion have their own DNA that’s different from the stuff found in your cell nuclei (comprised of only 37 genes versus the some 24,000 genes in your nucleic DNA), there are hundreds upon hundreds of gene mutations associated with mitochondrial disease. Because there are so many genes that could potentially be linked, symptoms of mitochondrial disorders are often highly complex and varied.
Much of the damage in mitochondrial diseases comes from oxidative stress. This is a state in which certain oxidized molecules disrupt the energy-producing chain underway inside the mitochondria. Researchers hypothesized that certain antioxidants might offer some defense against oxidative stress, and therefore might minimize certain aspects of mitochondrial disease.
Repurposing a Kidney Drug for Mitochondria
The research team at Children’s Hospital of Philadelphia, led by Marni J. Falk, MD, started with that insight and researched a number of antioxidant compounds. One compound, N-acetylcysteine (NAC), showed promising results in animal tests.
Cysteamine bitartrate, an antioxidant compound approved for the treatment of kidney disease, was thought to act on pathways similar to NAC – so it was the next to be examined. Though the drug did not improve the glutathione (another antioxidant) levels in their subjects, it did seem to produce beneficial health effects from different mechanisms than were expected.
The drug improved the resiliency of human fibroblast cells taken from mitochondrial disease patients. The cells demonstrated improved hardiness when subjected to “chemical stressors.”
Falk noted that “cysteamine bitartrate might have the potential to improve overall health and stress resiliency in human patients,” though she called for caution and further research. Cysteamine bitartrate is toxic to a wide swath of human and animal cells in improper doses. Even small adjustments to dosage can create a toxic environment.
Ultimately she believes that improving our understanding of individual patients’ responses to oxidative stress will help improve the prognosis of patients with mitochondrial disease. Falk also cautioned against those who might be tempted to self-treat their illness with antioxidants, since safe and effective uses and dosages have yet to be determined.
The research is promising, of course. Drug repositioning is a comparatively cheap way of exploring available options for conditions that may currently have no approved treatment. As Dr. Falk and Children’s Hospital of Philadelphia have found, however, it still has its own associated difficulties.
What do you think about drug repositioning? Can you think of any examples where a treatment for one condition might also work for the treatment of another? Share your thoughts with Patient Worthy!