More early data revealed from landmark CRISPR gene editing human trial

Vertex and CRISPR Therapeutics have presented new data from one of the first trials testing gene-editing therapy in human subjects. Fifteen months on from the first patient treatment, the highly experimental therapy is showing remarkable efficacy treating two rare genetic blood diseases.

Early in 2019 the first CRISPR-based gene editing human trials began in the United States. At the time these patients were the first humans outside of China to be administered this highly experimental gene editing therapy.

The treatment is dubbed CTX001, and it was designed to treat two types of rare blood disease; beta-thalassemia and sickle cell disease. The treatment involves harvesting hematopoietic stem cells from a patient’s blood sample, using CRISPR to edit a single genetic change in those stem cells designed to raise levels of fetal hemoglobin in red blood cells, and then transplanting the stem cells back into the patient.

Late last year the first data from these preliminary trials was released revealing extraordinarily promising results. The first two patients treated with CTX001 were essentially cured of their genetic disease.

Now, a few months later, more clinical data has been presented at the European Hematology Association virtual congress. The data reveals seven patients have been treated with the CRISPR therapy so far, five for beta-thalassemia and two for sickle cell disease.

All seven subjects have shown what the researchers call successful engraftment, meaning the gene edited cells effectively produced mature red blood cells after transplantation into the patient. Consistent with the prior data announcement, a small number of serious adverse events were noted in some of the patients, but these are not thought to be related to the CTX001 therapy. Instead, those adverse effects are consistent with what has previously been seen in more general stem cell transplantation treatments.

“With these new data, we are beginning to see early evidence of the potential durability of benefit from treatment with CTX001, as well as consistency of the therapeutic effect across patients,” says Samarth Kulkarni, CEO of CRISPR Therapeutics. “These highly encouraging early data represent one more step toward delivering on the promise and potential of CRISPR/Cas9 therapies as a new class of potentially transformative medicines to treat serious diseases.”

The very first patient treated with CTX001 is now at a 15-month follow-up point, and the data suggests the therapy is still efficacious with no long-term complications detected. Nine months on from treatment the first sickle cell disease patient is also displaying promising results, free of any sickle cell-related adverse events.

“In my 25 years of caring for children and young adults facing both sickle cell disease and beta thalassemia, I have seen how these diseases can adversely affect patients’ lives in very significant ways,” says Haydar Frangoul, from the Sarah Cannon Research Institute. “I am encouraged by the preliminary results, which demonstrate, in essence, a functional cure for patients with beta thalassemia and sickle cell disease.”

It’s still early days for this research, and the overall goal for these trials will be to recruit 45 patients for each disease, with a two-year follow-up period. So there is still lots of work to be completed before we even see the final results of this Phase 1/2 trial. And even after that, considering how new and experimental CRISPR gene editing is in humans, there will surely be several years of large, long-term Phase 3 trialing before the therapy reaches the market. However, this new release of data is about as promising as early clinical data can be, so far suggesting CRISPR gene editing is safe and works as well as can be hoped.

Source: CRISPR Therapeutics

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