America’s first CRISPR trial is still nearly 100% effective 3 years on

Incredible new data presented recently at the European Hematology Association Congress has revealed an experimental CRISPR gene editing therapy is both safe and effective up to three years after treatment. The follow-up results come from one of the longest-running human trials using CRISPR technology to treat a pair of rare genetic blood diseases.

The first human trial in the United States to test CRISPR gene editing technology started back in 2019. The trial focused on two rare blood diseases: beta-thalassemia and sickle cell disease.

The treatment involves first gathering stem cells from a patient’s blood. Using CRISPR technology a single genetic change is made, designed to raise levels of fetal hemoglobin in red blood cells. The stem cells are then re-administered into the patients.

Initial results were extraordinarily promising. The first two patients treated were essentially cured within months, but questions over long-term efficacy remained.

A follow-up announcement last year continued the impressive results with 22 patients treated and all demonstrating 100 percent success. Importantly, seven of those patients were 12 months past the initial treatment with no waning of efficacy.

Now, a new data release is offering results from 75 patients treated with the groundbreaking CRISPR therapy, now dubbed exa-cel (exagamglogene autotemcel). Of those 75 patients treated, 44 were suffering transfusion-dependent beta thalassemia (TDT) and 31 had severe sickle cell disease (SCD).

All but two of the 44 patients with TDT were essentially cured of their disease, needing no more blood transfusions. The two TDT patients still requiring blood transfusions had 75 percent and 89 percent reductions in transfusion volumes respectively. All 31 SCD patients were also free of disease symptoms at long-term follow-up.

The data, yet to be published in a peer-reviewed journal, also reports no waning of treatment efficacy with the longest follow-up period stretching to 37 months beyond the initial therapy.

“These robust data from 75 patients, of which 33 have one year or more of follow-up after exa-cel infusion, further demonstrate the potential of this investigational therapy as a one-time functional cure for patients with transfusion-dependent beta thalassemia or severe sickle cell disease,” said Chief Medical Officer Carmen Bozic, from Vertex, the biotech company developing the treatment.

These Phase 3 trials are fully enrolled, and are the most advanced CRISPR trials in the United States. The researchers are looking to evaluate each patient with a follow-up period of 24 months.

The U.S. Food and Drug Administration (FDA) has given exa-cel a Fast Track designation. Vertex is hoping to submit exa-cel to the FDA for market approval by the end of the year. If it is authorized in early 2023, it will be the first CRISPR-based gene editing treatment to be approved for public use in the United States.

Source: CRISPR Therapeutics, Children’s Hospital of Philadelphia