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Chinese Base Editing Therapy Achieves First Clinical Cure of Beta Thalassaemia

Rare Disease

• Shanghai-based CorrectSequence Therapeutics has successfully treated a transfusion-dependent beta thalassaemia patient using their novel base editing therapy CS-101, marking a world first for this technology.

• The adolescent patient, who previously required blood transfusions every two weeks, has maintained normal hemoglobin levels above 130 g/L for over two months without transfusions or adverse effects.

• The transformer Base Editing (tBE) technology offers more efficient hematopoietic reconstruction with fewer safety risks compared to other CRISPR-based gene-editing therapies for blood disorders.

In a groundbreaking development for genetic medicine, Shanghai-based CorrectSequence Therapeutics and collaborators from Guangxi Medical University have announced the successful clinical cure of an adolescent patient with transfusion-dependent beta thalassaemia using innovative base-editing technology.
"To the best of our knowledge, this is the world's first report of a successful clinical cure of haemoglobinopathy with base-editing technology," CorrectSequence stated in their news release.
The patient, who previously required blood transfusions every two weeks to manage their condition, has maintained hemoglobin levels at or above 130 g/L for more than two months since receiving the one-time treatment in October 2023. According to the company, the patient "has resumed normal life" following the therapy, with no reported adverse effects related to the treatment.

The Breakthrough Technology

The treatment, designated CS-101, employs transformer Base Editing (tBE) technology, which offers significant advantages over existing gene-editing approaches. According to CorrectSequence, their method provides more efficient hematopoietic reconstruction and shorter timeframes for achieving transfusion independence compared to other CRISPR-based beta thalassaemia gene-editing therapies.
Importantly, the design minimizes safety risks commonly associated with gene editing, such as large DNA fragment deletions or off-target mutations. Androulla Eleftheriou, executive director of the Thalassaemia International Federation (TIF), noted that the design of CorrectSequence's editor "greatly enhances the safety of the approach compared to other advanced therapy applications."

Understanding Beta Thalassaemia

Beta thalassaemia is an inherited recessive blood disorder that results in a person's blood cells lacking sufficient hemoglobin, the blood protein responsible for carrying oxygen throughout the body. Patients with severe forms of the condition require regular blood transfusions to survive, significantly impacting their quality of life and placing them at risk for complications from chronic transfusion therapy.
The condition affects millions worldwide, with particularly high prevalence in Mediterranean, Middle Eastern, African, and Southeast Asian populations. Current standard treatments focus on managing symptoms rather than addressing the underlying genetic cause.

Expanding Treatment Horizons

Building on this success, CorrectSequence Therapeutics has already initiated an investigational study using CS-101 to treat sickle cell disease (SCD) patients, another severe hemoglobinopathy with limited treatment options.
The Thalassaemia International Federation has welcomed these advancements while maintaining a measured perspective. "While we remain optimistic about recent breakthroughs, we also remain mindful of these treatments still being in their infancy and not yet available to the majority," the organization stated.

Implications for Gene Therapy

This achievement represents a significant milestone in the field of genetic medicine, particularly for base editing, which is considered a more precise form of gene editing compared to traditional CRISPR-Cas9 approaches. Base editing allows for the direct conversion of one DNA base to another without cutting the DNA double helix, potentially reducing unintended effects.
While long-term data on CS-101 is still pending, the initial results suggest promising potential for patients with beta thalassaemia and possibly other genetic blood disorders. The ability to provide a one-time curative treatment could transform the standard of care for conditions that currently require lifelong management.

Access and Availability Challenges

Despite the excitement surrounding this breakthrough, significant challenges remain regarding the accessibility of such advanced therapies. TIF emphasized that while promoting innovative curative approaches, they continue advocating for basic care provision to improve patients' survival, wellbeing, quality of life, and social integration.
In collaboration with the World Health Organization, governments, and communities of patients and healthcare professionals, TIF actively works to protect patients' basic human rights and enhance access to innovative treatments that can transform lives.
As research continues and more data becomes available, this Chinese innovation could potentially reshape the treatment landscape for hemoglobinopathies worldwide, offering hope to millions affected by these genetic conditions.
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