Going from the laboratory to an approved therapy in 11 years is no mean feat. That is the story of the world’s first approved CRISPR–Cas9 therapy, greenlit by the US Food and Drug Administration in December 2023. Casgevy (exagamglogene autotemcel), from Vertex and CRISPR Therapeutics, aims to cure sickle-cell disease in a ‘one and done’ treatment. Sickle-cell disease causes debilitating pain and organ damage that can lead to life-threatening disabilities and early death. In a clinical trial, 29 of 31 patients treated with Casgevy were free of severe pain for at least a year after receiving the therapy, which highlights the curative potential of CRISPR–Cas9. “It was an incredible, watershed moment for the field of gene editing,” says biochemist Jennifer Doudna, of the Innovative Genomics Institute at the University of California, Berkeley. “It's a huge step forward in our ongoing quest to treat and potentially cure genetic diseases.”