New form of efficient gene editing for the treatment of AATD, liver and lung diseases

New research results show that a new form of gene editing is effective in correcting a mutation in patient cells with monogenic disease Antitrypsin deficiency Alpha-1 (AATD), a common inherited disease that affects the liver and the lungs. This new approach, called base editing, is different from other forms of editing, including CRISPR, because base editors do not induce a DNA break, which helps prevent double-strand breaks, possible edits outside of the target and unwanted mutations during cell repair. .

Directed by Andrew Wilson, MD and Rhiannon Werder, Ph.D. from the Center for Regenerative Medicine (CReM) at Boston Medical Center and Boston University, the researchers used patient derivatives liver cells called “iHeps,” which mimic the biology of liver hepatocytes, the body’s major producers of alpha-1 antitrypsin protein that also perform important metabolic, endocrine, and secretory functions. The base editing technology corrected the Z mutation responsible for AATD and reduced the effects of the disease in hepatocytes, demonstrating successful baseline editing in human cells. These results, published in Molecular therapy, can help pave the way for future human trials.

“This study shows the successful application of baseline editing technology to correct responsible mutation of AATD in liver cells derived from patients with this disease,” says Wilson, a pulmonologist at Boston Medical Center and associate professor. of Medicine at the Boston University School of Medicine, who was the corresponding author of the study. “I hope these results create a way to use this technology to help patients with AATD and other monogenic diseases.”

The base editors created by Beam Therapeutics were applied to inducers pluripotent stem cells (iPS cells) from patients with AATD and, again, in iPS cell-derived hepatocytes. This was done to study the correction of the “Z” mutation of the gene responsible for AATD a human cells.

The Z mutation in the SERPINA1 gene is responsible for causing chronic, progressive lung and liver disease in the AATD. In patients with AATD, mutant AAT proteins fold poorly and form protein aggregates that accumulate inside hepatocytes and cause damage.

For this study, researchers began with mutant iPSCs (ZZs) created from a patient with AATD. After completing the baseline editing process, DNA from the edited cells was sequenced to determine if the SERPINA1 gene had been corrected. Clonal populations of cells with one (MZ) or both (MM) copies of the corrected gene expanded and then differentiated over 25 days to generate hepatocytes. After sequencing the entire genome of the edited cells, there was no evidence of involuntary mutations in the genome of the baseline editors, and misfolding and associated protein accumulation was partially corrected in MZ cells. and completely in normal cells MM.

The process was repeated using hepatocytes derived from the mutant iPSCs. Two basic editors under different conditions were used to test the efficiency of this process. Under the best conditions, about 50% of the mutant genes were successfully edited. Cells were then analyzed to see if they still looked “hepatic” and if there were fewer signs of the disease in the edited cells, compared to mutant ZZ cells. The results showed that baseline editing did not alter the liver program and liver cells still expressed liver genes and proteins at normal levels. In addition, there was a lower accumulation of aggregated folded AAT “Z” protein, showing less evidence of disease. cells.

Although augmentation therapy has been shown to slow the progression of lung disease in patients with AATD, there are currently no treatments available for AATD-associated liver disease. Emerging treatment strategies have focused on correcting the Z mutation.

Base editing is being evaluated as a treatment modality for various monogenic diseases. Alpha-1 antitrypsin deficiency is a major target for baseline editing, which is likely to be one of the previous diseases in which baseline editors are tested in human studies. Additional targets of the disease include retinal diseases, hereditary tyrosinemia, sickle cell anemia, progeria, cystic fibrosis, and others.

The results of this study suggest that future research may explore the usefulness of baseline editors for editing other resting cell populations. In addition, it has recently been shown that basic editors it can edit RNA in addition to DNA in immortalized cell lines and justifies further research.