Researchers have developed a new method to precisely and rapidly correct genetic alterations in cultured patient cells.
The genetically corrected stem cells are produced from a 2–3 mm skin biopsy taken from patients with different genetic diseases. The corrected stem cells are essential in the research and for the development of new therapies for the diseases in question.
The scientists based the new method on previous groundbreaking research in the fields of stem cells and gene editing; the first technique is the invention of induced pluripotent stem cells, iPSCs from differentiated cells, which won the Nobel in 2012. The other technique is the CRISPR-Cas9 ‘gene scissors’, which got the prize in 2020. The new method combines these techniques to correct gene alterations that cause inherited diseases, creating fully functional new stem cells.
The researchers aim to eventually produce autologous cells with therapeutic properties. The use of the patient’s own corrected cells could help in avoiding the immunological challenges hampering the organ and tissue transplantation from a donor. The new method was developed by PhD student Sami Jalil and is published in Stem Cell Reports.
More than 6000 inherited diseases are known to exist, which are caused by various gene alterations. Currently, some are treated with a cell or organ transplant from a healthy donor, if available.
“Our new system is much faster and more precise than the older methods in correcting the DNA errors, and the speed makes it easier and diminishes also the risk of unwanted changes,” commented adjunct professor Kirmo Wartiovaara, who supervised the work.
“In perfect conditions, we have reached up to 100 percent efficacy, although one has to remember that the correction of cultured cells is still far away from proven therapeutic applications. But it is a very positive start” Prof Wartiovaara added.
An intravenous CRISPR gene editing infusion lowered levels of a disease-causing protein in vivo for the first time in humans, according to interim findings from a phase I trial.
Hereditary (ATTR) amyloidosis is a rare, rapidly progressive disease caused by a mutation in the serum transthyretin (TTR) gene that results in the buildup of misfolded transthyretin and leads to the formation of amyloid deposits in the heart, gastrointestinal tract, and peripheral nerves. Life expectancy is about 3 to 15 years after the onset of neuropathy. Researchers used the DNA-editing tool CRISPR-Cas9 to inactivate the TTR gene in liver cells to prevent misfolded TTR protein from being produced. The liver produces almost all circulating TTR.
The treatment reduced TTR by 87% in three people with hereditary transthyretin (ATTR) amyloidosis with polyneuropathy. The findings were published in the New England Journal of Medicine.
“This is the first successful demonstration of therapeutic gene editing within patients’ bodies, making it a watershed moment in modern medicine,” noted Kiran Musunuru, MD, PhD, MPH, director of the Genetic and Epigenetic Origins of Disease Program at the University of Pennsylvania in Philadelphia, who was not involved with the study.
“The investigators used lipid nanoparticle technology — the same technology used in COVID mRNA vaccines — to deliver CRISPR into the liver, with the goal of turning down a gene responsible for hereditary ATTR amyloidosis,” Dr Musunuru told MedPage Today.
“What was astonishing about this first-in-human study is not just that the treatment worked, but that it worked extremely well in patients, in one case turning off the disease gene close to 100%. It’s like launching a rocket ship in the hope of just getting into orbit, but making it all the way to the moon on the first try.”
Previously, other studies have removed blood stem cells from people with sickle cell anaemia and beta-thalassemia, editing them using CRISPR, and infusing them back into patients. In a trial of people with inherited blindness, a subretinal injection also has delivered CRISPR treatment. Towever, the findings of NTLA-2001 represent the “first-ever clinical data suggesting that we can precisely edit target cells within the body to treat genetic disease with a single intravenous infusion of CRISPR,” noted John Leonard, MD, president and CEO of Intellia Therapeutics, which co-sponsored the trial with Regeneron Pharmaceuticals.
“Solving the challenge of targeted delivery of CRISPR-Cas9 to the liver, as we have with NTLA-2001, also unlocks the door to treating a wide array of other genetic diseases with our modular platform, and we intend to move quickly to advance and expand our pipeline,” said Dr Leonard in a statement.
NTLA-2001 is based on the clustered regularly interspaced short palindromic repeats and associated Cas9 endonuclease (CRISPR-Cas9) system. It consists of a lipid nanoparticle encapsulating messenger RNA for Cas9 protein and a single guide RNA targeting TTR.
The ongoing phase I study looked at safety and pharmacodynamic effects of single doses of NTLA-2001 in six patients with hereditary ATTR amyloidosis with polyneuropathy. Half received 0.1 mg/kg, the other received 0.3 mg/kg. Three patients had a p.T80A mutation, two a p.S97Y mutation, and one a p.H110D mutation. Three patients received no prior therapy; three previously had received diflunisal.
Dose-dependent reductions in serum TTR were seen from treatment with NTLA-2001. At day 28, mean serum TTR levels declined by 52% in the 0.1 mg/kg group and by 87% in the 0.3 mg/kg group. No serious adverse events were recorded.
Two treatments for hereditary ATTR amyloidosis nerve pain won FDA approval in 2018: patisiran (Onpattro), an RNA interference drug, and inotersen (Tegsedi), an RNA-targeting drug that reduces the production of TTR protein.
The NTLA-2001 study could have profound clinical implications, noted Joel Buxbaum, MD, of Scripps Research Institute in La Jolla, California, who was not involved with the study. “If, as the authors surmise, the effect is permanent, and without off-target effects when studied in a much larger patient population, it would be a significant improvement [over] current therapies for this class of disorders, at least with respect to frequency of therapy,” he said.
“However, all that depends on the clinical effect of long-term suppression of hepatic TTR synthesis,” Buxbaum told MedPage Today. “In the published studies of the various currently available ATTR therapeutics, approximately one-third of subjects have little or no clinical response, regardless of the degree of suppression of circulating protein levels, suggesting that while diminishing the supply side for TTR aggregation is likely to be necessary for clinical responsiveness, it may not be sufficient for optimal or profound therapeutic efficacy.”
After phase I studies are complete, the company plans to move forward to pivotal studies for both polyneuropathy and cardiomyopathy manifestations of ATTR amyloidosis.
Journal information: Gillmore JD, et al “CRISPR-Cas9 in vivo gene editing for transthyretin amyloidosis” N Engl J Med 2021; DOI: 10.1056/NEJMoa2107454.
