Companies and academic groups have begun to use the genome editor CRISPR to try to correct various diseases, but none has so far published, or even announced, evidence that patients have been helped—until this week. In an update for investors today, CRISPR Therapeutics of Zug, Switzerland, reported that one patient with sickle cell anemia and another with beta thalassemia appear to have benefited from the same CRISPR-based intervention for up to 9 months, STAT reports. (The company gave STAT an early look at the data but did not allow outside commenters to see the results.) Before the treatment, both patients required multiple infusions each year of red blood cells. CRISPR Therapeutics, collaborating with Vertex Pharmaceuticals, removed blood stem cells from their bodies and modified them with CRISPR to knock out a gene that shuts down production of fetal hemoglobin. When the edited cells were put back in each patient’s body through a stem cell transplant—which required a toxic chemotherapy to kill their own stem cells—both people produced high levels of fetal hemoglobin and no longer needed transfusions. “These early findings are a triumph for patients, CRISPR, and genetics,” Bruce Conklin, a clinician who focuses on stem cell treatments of cardiovascular disease at the University of California, San Francisco, told Science after reviewing the limited data the companies provided in the call and a press release. “They chose patients with severe versions of the disease and the results are truly remarkable.” Other companies are working on competing gene therapy and gene-editing technologies for the same disorders.