ORLANDO — Vertex Pharmaceuticals’ genetic medicine Casgevy hit an early goal in two late-stage trials focused on children with uncommon blood disorders, helping them avoid damaging vessel blockages and the need for transfusions in a setting expected to be among the first to receive an extra-speedy review from the Food and Drug Administration.
The data, disclosed Saturday at the American Society of Hematology scientific meeting in Orlando, may help boost disappointing sales for Casgevy, the first therapeutic to use CRISPR gene-editing technology to modify human diseases. Casgevy is a cell therapy made from patients’ own tissues and engineered to embed in the bone marrow and stimulate a protein called fetal hemoglobin. In sickle cell disease, this protein prevents the characteristic bending that results in blockages, while, in another disorder called beta thalassemia, it can prevent anemia and the need for frequent transfusions.
Casgevy is in two separate trials of children age 5 to 11, with one directed at each disease.
In the sickle cell study, 11 children have been dosed with Casgevy and are being followed to see if they had “vaso-occlusive crises,” the trial’s primary endpoint. All four who have completed at least a year of follow-up so far have been free of those episodes for 12 consecutive months. One had gone nearly two years without a crisis, and no patient in the trial has had one so far, Vertex said.
The beta thalassemia experiment recruited children who depend on transfusions to maintain target hemoglobin levels. There, researchers have dosed 13 participants and are seeing if they can hit the trial’s main goal by going transfusion-free for at least 12 consecutive months. Of the six who’ve been followed long enough, all have succeeded on this measure. The longest an enrollee has been transfusion-free is nearly two years.
One patient in the beta thalassemia trial died of pneumonia following the “preconditioning” regimen that weakens the immune system to prevent it from attacking the engineered cells.
“I am excited to hopefully be able to offer this option to my younger patients soon, early in life, before some of the most devastating impacts of these diseases begin,” Haydar Frangoul, a trial investigator and medical director of pediatric hematology and oncology at Sarah Cannon Research Institute, said in a statement provided by Vertex.
In 5 to 11-year-olds, Casgevy is one of 15 drugs awarded a “national priority” review voucher under a program instituted by FDA Commissioner Martin Makary, which could shorten its review period to just one or two months. Vertex said it plans to ask for approval in that setting in the first half of 2026.
Hailed as a long-term, if not permanent, treatment for the disorders when it gained approval, Casgevy has so far been a far greater scientific achievement than it has a commercial product. Vertex recorded about $43 million of revenue from the therapy since its launch two years ago, although company executives believe it could make $100 million this year.
While the impact of the drug appears long-term, patients must be able to tolerate a long process that involves removal of their blood cells for remodeling, as well as that preconditioning regimen, which carries severe side effects.
