New data from the United States’ first CRISPR gene editing clinical trial indicates the treatment is safe and effective more than two years after initial dosing. Targeting a pair of rare genetic blood diseases, the experimental therapy has so far been 100 percent effective in all 22 patients treated.
Back in 2019 the first CRISPR human clinical trials kicked off in the United States. The trials were aimed at beta-thalassemia and sickle cell disease, two rare blood diseases. The treatment involves harvesting stem cells from a patient’s blood and using CRISPR technology to make a single genetic change designed to raise levels of fetal hemoglobin in red blood cells.
Early data from the first few patients treated offered promising indications of the therapy’s safety and efficacy. Now researchers are revealing continuing positive data nearly three years into this ongoing Phase1/2 clinical trial.
So far, data from 22 patients has been announced, and the results are about as good as one could hope. All 15 beta-thalassemia patients displayed clinically meaningful improvements to fetal hemoglobin levels. Before the CRISPR therapy each of the patients required ongoing blood transfusions, sometimes monthly, but since the infusion every one of them has been transfusion-free.
All seven sickle cell patients also showed significant improvement, free of any vaso-occlusive crises, the primary clinical indication of disease.
"What we're seeing in these early days is how transformational this is for the sickle cell patients we've seen," says Stephen Grupp, a researcher working on the trials. "We are hearing that it is life-changing."
Only one patient displayed serious adverse effects thought to be connected to the CRISPR therapy. However, that was effectively treated and did not lead to death. Otherwise, the safety profile is consistent with prior stem cell transplant treatments, with only temporary mild and moderate side effects.
Before the CRISPR therapy each of the patients required ongoing blood transfusions, sometimes monthly, but since the infusion every one of them has been transfusion-free.
Grupp indicates the long-term efficacy of the treatment is being closely investigated. Exactly how long this kind of treatment lasts is a big unanswered question. Follow-up data in seven patients show no waning of efficacy after more than 12 months.
"As we continue, the big question is whether it is lasting," notes Grupp. "The evidence so far indicates that it is durable in the time frame we've seen, and we just have to continue to follow the patients."
Over 40 patients have been administered the CRISPR treatment and the trial is still ongoing. Ultimately the researchers are looking to enroll 45 patients with beta-thalassemia and 45 with sickle cell disease, and follow each patient for two years after dosing.
Source: Children’s Hospital of Philadelphia, CRISPR Therapeutics