Imagine a surgical patient on a blood-thinning drug who
starts bleeding more than expected, and an antidote that works immediately—because
the blood thinner and antidote were designed to work together. Researchers at Duke University
Medical Center
have engineered a way to do this for an entire, versatile class of drugs called
aptamers and published their findings in Nature Medicine.
"With any anticoagulant, you are trying to reduce your
chances of having clotting because it can lead to a heart attack or stroke
during treatment," said Bruce Sullenger, Ph.D., senior author and Vice
Chair for Research and Joseph W. and Dorothy W. Beard Professor of Surgery. Yet
bleeding is a common side effect during and after treatments that require
anticoagulation therapy such as surgery or angioplasty.
These new antidotes may give doctors a way to quickly and
precisely put the brakes on an anticoagulant if bleeding becomes a problem or
neutralize other adverse events or toxicities.
Duke researchers have just completed a series of successful
clinical trials in patients taking a blood-thinner aptamer and an antidote engineered
to reverse the effects of the aptamer.
"We have shown that this type of antidote can reverse
the action of any of the aptamer drugs, and there are many aptamers in
development," Sullenger said. Their approach amounts to a universal
antidote to the entire aptamer family. "We predict that this advance will
significantly expand the number of diseases that can be more safely treated
using antidote-controllable therapeutic agents," he said.
The new approach, called RNA-based aptamer technology,
"provides the opportunity to make safer drugs," said Sullenger, who
also directs the Duke Translational Research Institute. "And now that we
can engineer a universal antidote for aptamers, we can in principle for the
first time afford to provide additional control over drugs for patients and
their physicians."
Aptamers are oligonucelotides, short stretches of nucleic
acid that bind to a specific target molecule. If a patient takes an aptamer
drug, the drug is the only free oligonucleotide in the body.
The researchers studied eight aptamer drugs and showed that
the antidotes they introduced could reverse the activity of any of the drugs,
regardless of the sequence, shape or target of the drug.
One advantage of aptamer drugs, as opposed to antibody-based
drugs, is that nucleic acids aren't typically recognized by the human immune
system as foreign agents. Aptamers do not generally trigger an immune response,
Sullenger said.
"This technology could be applied to any
oligonucleotide-based therapeutic that is free in a patient's
circulation," said lead author Sabah Oney, Ph.D., formerly with the
Sullenger laboratory and now a senior scientist at b3bio, a biotechnology
company Sullenger helped co-found in the Research Triangle Park.
"With the ever-increasing number of such drugs in
clinical trials, we believe that this discovery can have very broad
applications and improve the safety profile of these therapeutics," Oney
said. "This could be rapidly translated into the clinic, and lead to a
whole new class of safer therapeutic agents."
To date, one aptamer has been approved by the U.S. Food and
Drug Administration, a drug for macular degeneration, a cause of blindness.
Several others are being tested and developed for use in cardiovascular,
hematology and cancer patients.
"This research potentially represents the next frontier
of controlled therapeutics using nucleic acids as highly selective
antithrombotics and neutralizing polymers," said Richard C. Becker, M.D.,
Professor of Medicine in the Duke Divisions of Cardiology and Hematology and a
scientist in the Duke Clinical Research Institute (DCRI) who has worked on
clinical trials with the aptamer antidotes. "The translational platform
for antithrombotic therapy pioneered by the Sullenger laboratory in
collaboration with the DCRI underscores the unlimited potential of clinicians
and scientists collaborating with purpose and commitment to advance patient
care."
"Future optimization should further improve the potency
of sequestering the aptamers from circulation, which will then spur the
development of many new aptamer drugs," said Kam Leong, a James B. Duke
professor of biomedical engineering and co-author of the study.
Other authors on the paper include Ruby T. S. Lam of the
Duke Department of Biomedical Engineering, Kristin M. Bompiani and Charlene M.
Blake of the Duke University Program in Genetics and Genomics and the Duke
Department of Surgery, George Quick of the Duke Translational Research
Institute, Jeremy Heidel and Joanna Yi-Ching Liu of Calando Pharmaceuticals,
and Brendan C. Mack and Mark E. Davis of the Department of Chemical Engineering
at the California Institute of Technology.
This work was supported by a grant from the National
Institutes of Health, a predoctoral fellowship from the American Heart Association,
and a grant from the National Cancer Institute.
Duke University Medical
Center
