A domestically developed gene-editing therapy has successfully treated patients with beta-thalassemia, allowing them to live without the need for lifelong blood transfusions, according to a study recently published in the journal Nature.

All five patients in the trial received CS-101, a treatment developed by Chinese researchers, and achieved fast hematopoietic reconstruction. This process allows the body to restart its blood-making factory and produce healthy cells, leading to total transfusion independence.

Beta-thalassemia is a genetic blood disorder that impacts more than 40,000 newborns globally each year. It interferes with the body's ability to produce hemoglobin, the protein in red blood cells that carries oxygen.

Until this innovation, many patients required regular blood transfusions for survival. Experts say the study represents a milestone as the first base-editing clinical trial published in Nature. The "transformer base editor" used in this study is a highly precise form of gene editing tool that acts like a "pencil and eraser" to fix specific genetic letters without inducing DNA double-strand breaks.

Peer reviews of the research noted that the CS-101 injection sets a "new high-watermark" for ex vivo edited hematopoietic stem cell therapy for beta-thalassemia. In these treatments, a patient's stem cells are collected, edited in a cGMP-compliant — or Current Good Manufacturing Practices — facility, and then injected back into the body. This approach was developed through a collaboration between Shanghai-based CorrectSequence Therapeutics, the First Affiliated Hospital of Guangxi Medical University, ShanghaiT-ech University, Fudan University, as well as the Shanghai Clinical Research and Trial Center.

Chen Jia, co-founder of CorrectSequence Therapeutics and the director of Gene Editing Center at ShanghaiTech University's School of Life Science and Technology, explained that the team used "transformer base editor" technology.

Unlike older gene-editing methods that create DNA double-strand breaks — essentially cutting the DNA like scissors — this new method avoids those breaks.

This precision reduces the risk of large genomic deletions, where chunks of genetic information are lost, and chromosomal rearrangements, which occur when DNA pieces reattach in the wrong places. It also prevents off-target mutations, or unintended changes to parts of the genome that were not meant to be edited.

The first participant in the trial received the treatment in October 2023 and has remained transfusion-free for more than 28 months. To date, CS-101 has been used to treat nearly 20 patients suffering from beta-thalassemia and sickle cell anemia. The company reports a 100 percent success rate so far, with all patients achieving sustained high levels of hemoglobin.

CorrectSequence Therapeutics is currently moving forward with the commercialization process to bring the drug to the global market. Mou Xiaodun, CEO of CorrectSequence Therapeutics, noted that, besides patients from China, four patients from Laos, Malaysia, Pakistan and Nigeria proactively applied to join the clinical trials. The research team expressed hope that the medicine will be able to offer help to all families worldwide affected by beta-hemoglobinopathies, a group of disorders that impair red blood cells.

zhouwenting@chinadaily.com.cn