Dive Brief:

  • New results from two studies of CRISPR Therapeutics and Vertex Pharmaceuticals' gene editing therapy give further evidence treatment can dramatically benefit, and potentially functionally cure, people with the inherited blood diseases sickle cell and beta thalassemia.
  • Twenty-two participants in the companies' trials have now received the CRISPR-based therapy and been followed for at least three months. All 22 responded to treatment, free of the blood transfusions and pain crises that respectively characterize patients' experience with beta thalassemia and sickle cell.
  • The results, presented as part of the European Hematology Association's annual meeting, build on data CRISPR and Vertex presented last December from 10 patients. The companies have now treated a total of 40 patients with their treatment, dubbed CTX001, not all of whom have been followed for long enough to measure responses.

Dive Insight:

CRISPR and Vertex's update at EHA is the fourth time the companies have presented results from their sickle cell and beta thalassemia studies. With each cut of clinical trial data, their claim that treatment with CTX001 could dramatically alter the course of both diseases has looked stronger.

Fifteen patients with beta thalassemia, which leads to anemia and other major health problems, were included in the latest results. So far, CRISPR and Vertex have collected between four and 26 months' worth of follow-up data on those patients. None of them have needed the blood transfusions they regularly required before treatment, and testing from 10 showed durable effects of gene editing in the bone marrow.

The data from the seven patients with sickle cell disease included in Friday's data were similarly positive. Since being treated with CTX001, all seven haven't experienced the painful and dangerous vaso-occlusive crises common to people with sickle cell. The seven participants have so far been followed for between five and 22 months. Editing data from four of those patients also revealed a long-lasting effect.

CRISPR and Vertex are the furthest along in testing a CRISPR-based treatment in humans. Their therapy uses CRISPR gene editing to modify stem cells extracted from each patient they treat. The cells are engineered to produce a form of the oxygen-carrying protein hemoglobin that's present at birth but disappears with age.

Reinfusing these cells back into the body, where they take root in the bone marrow, is viewed as a potential way to cure both sickle cell and beta thalassemia, which are both caused by mutations in the genes that code for hemoglobin.

Several other companies are taking a similar approach with their gene editing tools.

Before receiving Vertex and CRISPR's treatment, patients are treated with a chemotherapy-based "preconditioning" regimen that's designed to clear out space in their bone marrows for the new, edited cells. One patient, who has not yet been followed for more than three months and therefore wasn't one of the 22 for which responses were counted, experienced a cerebral hemorrhage that researchers attributed to the chemo regimen. The bleeding has since resolved, Vertex and CRISPR said.

Preconditioning has emerged as one of the key safety risks in gene editing and in the related field of gene therapy. A number of biotechs are working to develop safe preconditioning regimens in response.

Other than the one patient who experienced a cerebral hemorrhage, there were no new significant safety events reported between last December and Friday's results.

CRISPR and Vertex plan to enroll as many as 45 patients in each of the sickle cell and beta thalassemia studies. The pace of dosing, which was disrupted somewhat by the coronavirus pandemic, appears to have picked up and the companies expect to complete study enrollment by the end of the year.

If results remain positive, a submission for approval could come by mid-2023, Geoffrey Porges, an analyst at SVB Leerink, estimated in a note to investors.

For Vertex, success with CTX001 is much needed. The company, which has had great success developing and marketing four drugs for cystic fibrosis, is searching for its next calling card. On Thursday, the biotech announced it would stop work on a closely followed drug for an inherited lung and liver disease that had been seen as one of its top research prospects.

In April, Vertex spent $900 million to amend its partnership with CRISPR and increase the stake it holds in any future profits from CTX001.

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