The Chinese biotech CorrectSequence Therapeutics, also known as Correctseq, reports good results from a Phase I study of its technology involving editing a person’s hematopoietic stem cells to treat beta thalassemia.
The trial, published in Nature, included five patients with transfusion dependent beta thalassemia who were able to stop red blood cell transfusions, the standard treatment for the condition, after receiving the base-edited treatment CS-101. The participants continued to have good levels of hemoglobin with no serious side effects during follow-up.
Beta thalassemia is a rare inherited condition affecting around one in 100,000 people in the U.S. Mutations in the beta‑globin gene HBB reduce or stop production of the beta chains of hemoglobin, leading to chronic anemia that varies in its severity.
There are already several therapies on the market for beta thalassemia. The most common treatment is still regular blood transfusions to treat the anemia, but recently the genetic therapies Zynteglo, a lentiviral gene therapy developed by Bluebird Bio, and Casgevy, a CRISPR edited therapy developed by Vertex Pharmaceuticals and CRISPR Therapeutics were approved by the FDA.
Casgevy works by boosting fetal hemoglobin levels to treat the anemia seen in thalassemia patients. It uses CRISPR–Cas9 to cut both strands of DNA at the BCL11A enhancer site, which relies on error‑prone repair and can theoretically generate insertions, deletions, and larger rearrangements.
Correctseq is also aiming to raise fetal hemoglobin levels with CS-101, targeting the same site, but is only changing individual bases without making a full cut, which should reduce risks linked to double‑strand breaks, such as large deletions or chromosomal translocations.
In this study, CS-101 was given to five patients with beta thalassemia, previously treated with blood transfusions. The process involves extracting their stem cells, reactivating fetal hemoglobin production using base editing, giving the patients chemotherapy to clear existing stem cells and make way for the newly edited population, and finally injecting the patients with the edited stem cells.
All five patients were able to stop red blood cell transfusions and had maintained good levels of hemoglobin at three months. These levels stayed at a similar level through a median follow up period of 23 months. No deaths or reported cancers due to the chemotherapy treatment were observed and the safety profile so far is acceptable.
Although these results are promising, this trial is just a small initial study and further work is needed to confirm safety and efficacy of CS-101.“The planned Phase II/III trial will be crucial for evaluating a larger and more genetically diverse patient population across multiple centers,” write the authors.
“Extended follow-up will be required to enable comprehensive analyses of chimerism and clonality, which will facilitate more definitive assessment of long-term safety, engraftment dynamics and clinical benefit.”
One Correctseq’s main competitors is U.S.-based Beam Therapeutics, which is developing a similar base edited treatment. Beam is behind Correctseq in developing its edited therapy for beta thalassemia, but ahead with its therapy for sickle cell disease, something Correctseq are also targeting using a similar pathway.
The Chinese biotech industry is currently on an upward trajectory. Correctseq is one of many Chinese biotech companies currently working to produce competitors for gene therapies like Casgevy and Zynteglo at a more affordable price than those seen in the U.S.
The post Base Editing Shows Early Promise for Treating Beta Thalassemia appeared first on Inside Precision Medicine.