Genome editing’s third act

The first gene editors designed to fix genetic lesions in mutation-agnostic ways are poised to enter the clinic. Tessera Therapeutics and Alltrna, two Flagship Pioneering-funded companies, are gearing up to test novel genetic medicines in humans. Tessera received regulatory clearance in both the United States and Australia to begin clinical trials with its gene writer therapy, on the heels of announcing a $150 million partnership with Regeneron. Meanwhile, Alltrna will be filing an Investigational New Drug application in the United States in 2026 for its engineered transfer RNA (tRNA) that corrects shared premature stop codons and thereby corrects protein production, regardless of the protein that is affected.

These programs signal a welcome shift away from individualized N-of-1 therapies for rare diseases. The recent case of Baby KJ, whose specific mutation in a urea cycle gene was corrected in just six months after diagnosis, was truly remarkable. But, as extraordinary and life changing as these individualized therapies are, they offer little comfort for families with children who have inherited rare disorders, as few centers are equipped to produce such costly...