CorrectSequence Therapeutics, a Shanghai-based biotech company incubated at ShanghaiTech University that has pioneered transformer base editing technology for severe diseases, said on Tuesday it has successfully treated the first sickle cell disease patient using its high-precision base-editing therapy CS-101.

The breakthrough came in an investigator-initiated trial with the First Affiliated Hospital of Guangxi Medical University. The patient, a 21-year-old woman from Nigeria, saw her disease-related indicators return to normal and remain stable over a six-month follow-up period, the company said.

Her fetal hemoglobin levels rose significantly and were sustained, while sickle hemoglobin dropped. She experienced no vaso-occlusive crises — when sickled red blood cells block blood flow to the point that tissues become deprived of oxygen — and has been in good health.

"The patient has successfully resumed normal daily activities — marking the first reported clinical cure of sickle cell disease in China using base editing technology," said Mou Xiaodun, CEO of CorrectSequence Therapeutics.

Hemoglobinopathies, including sickle cell disease and beta-thalassemia, are the world's most common group of monogenic diseases, with about 7 percent of the global population carrying a pathogenic variant. Sickle cell disease, caused by mutations in the beta-globin gene, leads to abnormal, sickle-shaped red blood cells that cause chronic anemia, recurrent pain, increased infection risk and progressive organ damage. Globally, about 3.5 percent of the population carries the sickle mutation, with roughly 300,000 affected infants born each year, especially in Africa, the Mediterranean, the Middle East and South Asia.

Existing treatments, including symptom-managing drugs and blood transfusions, can ease complications but do not provide a cure.

Chen Jia, co-founder of Correct-Sequence Therapeutics and a professor at the School of Life Science and Technology at ShanghaiTech University, said gene-editing approaches — particularly base editing — can activate fetal hemoglobin in a patient's own blood cells. This eliminates the need to wait for a matched donor to provide hematopoietic stem cell transplantation and offers a shorter, potentially safer treatment path.

The CS-101 treatment involves collecting a patient's hematopoietic stem cells and using transformer base editing to precisely edit specific regions within them. This mimics beneficial natural base mutations in healthy individuals, reactivating the expression of certain proteins. The edited stem cells are then reinfused into the patient, leading to a rapid increase in fetal hemoglobin concentration, which inhibits red blood cell sickling and reduces vaso-occlusive crises and hemolysis, Chen said.

So far, CS-101 has been used in nearly 20 patients with beta-thalassemia or sickle cell disease in clinical trials. The first beta-thalassemia patient treated has remained transfusion-free for more than 22 months, according to the company.

"The Phase I trial of CS-101 for beta-thalassemia has been completed, with all patients achieving transfusion independence. Phase II and III trials are set to begin soon, and global recruitment for both sickle cell disease and beta-thalassemia trials is underway," Mou said.

"CorrectSequence is committed to advancing CS-101 — a first-in-class, China-originated base-editing therapy — to deliver safe, effective and accessible treatments for patients worldwide living with severe hemoglobin disorders," she said.