The peer-reviewed journal Cell Stem Cell published a study online on September 7 from CorrectSequence Therapeutics (Correctseq), a private, clinical-stage Chinese biotech, describing base-editing gene therapies CS-101 and CS-206 in nine patients with sickle cell disease (SCD) or transfusion-dependent beta-thalassemia (TDT) across several countries. The paper, co-authored with multiple Chinese academic and hospital institutions, extends the company’s earlier published results in five Chinese TDT patients to four new patients from Nigeria, Laos, Malaysia, and Pakistan, with genetically diverse forms of the same underlying diseases. Correctseq is privately held and does not trade under a stock ticker.

How the Therapy Works

SCD and TDT are both among the most common single-gene disorders worldwide, with SCD affecting more than 300,000 and TDT more than 40,000 newborns globally each year, according to figures Correctseq cites, and the specific genetic mutations causing each disease vary significantly by population and ethnic background. Both diseases stem from mutations affecting the beta-globin gene, and CS-101 and CS-206 work by editing a different part of the genome, the promoter region controlling two fetal hemoglobin genes (HBG1 and HBG2), to reactivate a form of hemoglobin the body normally stops producing after infancy. Producing more of this fetal hemoglobin can compensate for the defective adult hemoglobin that causes both diseases. The editing tool itself, called transformer base editor (tBE), makes a single-letter change to the DNA rather than cutting both strands the way CRISPR-Cas9 and other nuclease-based editors do; Correctseq says this avoids some safety risks associated with double-strand breaks, including larger unintended deletions, and that a built-in “lock-and-key” design keeps the editor inactive except at its intended target.

What the Patient Data Showed

The most detailed result is from a 21-year-old woman from Nigeria with SCD, who had experienced more than four vaso-occlusive crises (VOCs), the severe pain episodes characteristic of the disease, in the year before treatment. After receiving CS-206, her total hemoglobin rose from 7.7 to 12.9 g/dL by three months, her fetal hemoglobin rose from 3.5% to 62.2%, and her sickle hemoglobin fell from 76.1% to 31.6%. She had no VOCs over 15.5 months of follow-up. The three TDT patients, ages 3 to 29, reached a mean hemoglobin level of 11.6 g/dL and all achieved sustained transfusion independence at a median follow-up of 17.5 months. No off-target genetic edits or product-related adverse events were reported, though this is a very small, single-arm study without a control group, and the true rate of rare side effects cannot be established from nine total patients across both papers.

A Cross-Trial Comparison, Not a Head-to-Head Study

Correctseq also presents a cross-trial comparison, saying tBE-treated patients engrafted faster (a median of 13 days to recover neutrophils) than patients in separate sickle cell trials using Cas9 or Cas12a nuclease-based editors (27 and 23 days respectively), and reached higher sustained fetal hemoglobin levels. Because this compares results across different trials, sponsors, and patient populations rather than a head-to-head study, it should be read as suggestive rather than definitive evidence that tBE outperforms its nuclease-based rivals.

The Competition Is Already on the Market

Those nuclease-based rivals are not experimental long shots; two gene therapies for SCD and TDT are already FDA-approved and commercially available: Casgevy (exagamglogene autotemcel), developed by Vertex Pharmaceuticals (Nasdaq: VRTX) and CRISPR Therapeutics (Nasdaq: CRSP), and Lyfgenia (lovotibeglogene autotemcel), developed by bluebird bio (Nasdaq: BLUE), both approved in December 2023. Correctseq’s therapies would need to complete additional trials and regulatory review before reaching that same commercial stage, and the company says CS-101 has completed Phase 1 and is now in pivotal trials, without giving a specific expected approval date.

A Claim Worth Treating With Caution

One claim in the release is worth treating with particular caution: Correctseq describes CS-101 as the world’s first ongoing base-editing therapy candidate to enter clinical development, dosing its first patient in October 2023. That timeline appears to conflict with the broader base-editing field’s own history: Verve Therapeutics dosed the first human ever treated with a base editor in July 2022, and Beam Therapeutics’ base-editing sickle cell program, BEAM-101, also began dosing patients before October 2023. Correctseq may intend a narrower claim, such as being first for a specific disease category, but the release does not specify that qualification, so the broader claim as stated should not be taken at face value.

What’s Next

Correctseq describes itself as founded around the work of Chen Jia, director of the Gene Editing Center at ShanghaiTech University, who is quoted saying the team is also exploring RNA editing, prime editing, and mitochondrial DNA editing for other disease areas. Correctseq says CS-101 and CS-206 have now treated more than 30 patients total across China, Africa, and South and Southeast Asia, all achieving transfusion independence or freedom from VOCs, and that the company is expanding its base-editing platform into metabolic and cardiovascular diseases, including familial chylomicronemia syndrome and homozygous familial hypercholesterolemia, though those programs remain in earlier, non-clinical stages. This article covers a peer-reviewed clinical publication and is not medical or investment advice.

Sources

CorrectSequence Therapeutics: Cell Stem Cell: tBE-mediated Base Editing Therapy Achieves Durable Clinical Remission in Sickle Cell Disease and β-Thalassemia Across Different Genetic Backgrounds, PRNewswire, September 7, 2026.

BioSpace: Beam Enrolls Trial’s First Patient in “Step Forward” for Base Editing, cited for background on the base-editing field’s clinical timeline, including Verve Therapeutics’ 2022 first-in-human base editor dose.

Editorial Disclosure

This article is based on a press release issued by CorrectSequence Therapeutics on September 7, 2026, distributed via PRNewswire, describing a study published in Cell Stem Cell, with background on the base-editing field’s clinical history drawn from independent trade press cited above. CorrectSequence Therapeutics is a privately held company and does not trade under a stock ticker; Vertex Pharmaceuticals, CRISPR Therapeutics, and bluebird bio, named for competitive context, trade on the Nasdaq under the tickers VRTX, CRSP, and BLUE respectively. BioTech Stocks Daily was not compensated for this coverage. The company’s claim that CS-101 was the world’s first base-editing therapy to enter clinical development appears to conflict with other companies’ publicly reported timelines and should not be taken at face value. This article is for informational and educational purposes only and is not medical advice. Consult a qualified healthcare professional for medical guidance. See our full DISCLAIMER.