Scientists from the University of North Carolina School of Medicine led a team of researchers to demonstrate a potentially strong new method for treating cystic fibrosis (CF) and a variety of other illnesses. It entails the use of tiny nucleic acid molecules known as oligonucleotides, which can repair some of the gene abnormalities that cause CF but are not addressed by current modulator treatments. The researchers utilized a novel delivery technique that bypasses typical barriers to oligonucleotide distribution into lung cells.
Researchers Reveal New Ways To Treat Cystic Fibrosis
The researchers proved the surprising efficacy of their method in cells taken from a CF patient and in mice, as reported in the journal Nucleic Acids Research.
They were able to restore the activity of the protein that does not work normally in CF using the oligonucleotide delivery platform, and they saw a prolonged effect with just one modest dose, so they are excited about the potential of this strategy, said study senior author Silvia Kreda, Ph.D., an associate professor in the UNC Department of Medicine and the UNC Department of Biochemistry & Biophysics.
Rudolph Juliano, Ph.D., Boshamer Distinguished Professor Emeritus in the UNC Department of Pharmacology, and co-founder and Chief Scientific Officer of the biotech company Initos Pharmaceuticals, led the research team.
CF attacks around 30,000 persons in the United States. It is a hereditary illness caused by gene abnormalities that result in the functional lack of an essential protein called CFTR. In the absence of CFTR, the mucus covering the lungs and upper airways dehydrates and becomes particularly vulnerable to bacterial infections, which occur often and cause progressive lung damage.
CFTR modulator medicines, which effectively restore partial CFTR function in many patients, are now available as treatments for the disease. However, CFTR modulators cannot treat around 10% of CF patients, typically because the underlying gene abnormality is a splicing problem.
Splicing is the process by which genes are replicated – or transcribed – into temporary strands of RNA. The RNA strand is then cut up and reassembled by a complex of enzymes and other molecules, usually after removing undesirable portions. Splicing happens for the majority of human genes, and cells may reassemble the RNA segments in various ways to produce multiple copies of a protein from a single gene. However, splicing errors can cause a variety of illnesses, including CF when the CFTR gene transcript is mis-spliced.
In theory, appropriately designed oligonucleotides can repair some types of splicing errors. In recent years, the FDA has authorized two “splice switching oligonucleotide” treatments for hereditary muscle disorders.
In practice, however, certain organs have found it exceedingly difficult to deliver oligonucleotides into cells and to the sites within cells where they can repair RNA splicing abnormalities.
According to Kreda, getting large quantities of oligonucleotides into the lungs to target pulmonary illnesses has been extremely difficult.
When therapeutic oligonucleotides are injected into the blood, they must pass through a series of biological processes intended to protect the body against viruses and other undesirable molecules. Even when oligonucleotides enter cells, the majority of them are caught within vesicles known as endosomes and are either recycled outside the cell or destroyed by enzymes before they can accomplish their function.
The Kreda, Juliano, and colleagues method solve these challenges by including two new characteristics into splice switching oligonucleotides: To begin, the oligonucleotides are linked to small, protein-like molecules known as peptides, which are meant to aid in their distribution and entry into cells. Second, Juliano and Initos devised a different therapy using tiny compounds called OECs, which allow therapeutic oligonucleotides to escape confinement within endosomes.
This combination strategy was proven in cultured airway cells from a human CF patient with a common splicing-defect mutation.
The outcomes were much better with OECs than without them, and they improved with OEC dosage.
There is no animal model for splicing-defect CF, but the researchers successfully tested their general method in a mouse model of a splicing defect affecting a reporter gene using a different oligonucleotide. The researchers discovered that the repair of the splicing error in the mouse lungs persisted at least three weeks following a single therapy, implying that patients receiving such treatments may only require occasional dosing.
The researchers intend to do more preclinical investigations on their prospective CF therapy to prepare for clinical trials.