Last week, in a global milestone for medicine, U.K. regulators approved the first-ever CRISPR gene-editing drug. The treatment, from Vertex and CRISPR Therapeutics, will be licensed under the brand name Casgevy in the U.K. for patients with sickle cell disease (SCD) and beta thalassemia. The regulatory green light abroad isn’t surprising given the therapy’s established record of clinical trial success in treating these painful, and sometimes fatal, inherited blood disorders. But it marks a historic turning point for CRISPR and the genetic medicines of the future that are expected to reach the U.S. by year’s end.
Casgevy is the branded name for Vertex and CRISPR Therapeutics’ “exa-cel.” It uses a form of CRISPR gene editing that modifies extracted stem cells and reengineers them to boost the production of functional hemoglobin—a protein in red blood cells that’s critical to functions like getting oxygen to the tissue that makes up our muscles. Patients with SCD and beta thalassemia have a genetic kink that hinders hemoglobin in the bone marrow, with all kinds of painful health consequences, including liver and heart problems, anemia, and the need for regular blood transfusions and medication.
Through CRISRP gene editing, Casgevy, or exa-cel, provides a fix at the DNA level by editing the offending genes in a lab and then reinfusing the hemoglobin-producing cells into patients. The clinical evidence shows its benefits might last a lifetime, as the U.K.’s Medicines and Healthcare products Regulatory Agency (MHRA) noted in a statement announcing the approval on Thursday.
In the U.S., the Food and Drug Administration was already expected to approve the CRISPR drug by the end of the year to treat sickle cell disease, and by spring 2024 to treat beta thalassemia, barring any unforeseen consequences. The MHRA’s clearance might speed up that process—and fuel questions and concerns about the role of gene editing in medicine as groundbreaking science hits the market.
The MHRA cited clinical evidence to date for its approval decision. These studies involved a small number of patients, as trials for rare disorders often do, but the results were compelling in both SCD (97% of patients “free of severe pain crises” a year after treatment) and transfusion-dependent beta thalassemia (93% not requiring a blood transfusion a year after treatment, and a 70% reduction in need for blood transfusions in the remaining patients) with few safety concerns or side effects.
As impressive as that is, it’s still just 12 months of follow-up after treatment—and the U.K. regulators noted the need for continued surveillance as the therapy might impact thousands of patients (15,000 people have SCD in the U.K. alone).
That number grows to an estimated 100,000 sickle cell patients in the U.S., according to the Centers for Disease Control and Prevention. And in a broader sense, Casgevy’s breakthrough underscores gene editing and CRISPR’s role in modern medicine, including for the treatment of more far-reaching diseases like cancer, HIV- and HPV-related conditions, and beyond.
There were at least 71 separate clinical trials using just one form of CRISPR gene-editing technology publicly registered at the end of 2022. New forms of the technology—ones being tested for more precise DNA tweaking—seem destined to add dozens more efforts to biotech pipelines. Just last week, Boston-based Verve Therapeutics announced that its experimental VERVE-101 showed promise in shutting down a gene called PCSK9 linked to “bad” LDL-cholesterol production in the liver, with potential implications for treating maladies like cholesterol-related heart disease.
Efforts like Verve’s might flame out. Even if it proves safe and effective in larger trials, it might take years for such a treatment to get to market and impact real patients. But just a decade ago the same could have been said about Casgevy.
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