Clinical Trial

Disease: Transfusion-Dependent Beta-Thalassemia, TDT, (NCT05444894)

Disease info:

Beta thalassemia is a group of blood disorders characterised by a reduction in the production of haemoglobin. Haemoglobin is the iron-containing protein in red blood cells that carries oxygen to cells throughout the body.

Haemoglobin is encoded by genes that encode the building blocks of the haemoglobin protein. Mutations in these genes can produce abnormal haemoglobins leading to a family of conditions termed "haemoglobinopathies". Abnormal haemoglobin appears in one of three basic circumstances:

  1. Structural defects in the haemoglobin molecule. Alterations in the gene for one of the two haemoglobin subunit chains, alpha (a) or beta (b), are called mutations. Often, mutations change a single amino acid building block in the subunit. Most commonly the change is innocuous, perturbing neither the structure nor function of the haemoglobin molecule. Occasionally, alteration of a single amino acid dramatically disturbs the behaviour of the haemoglobin molecule and produces a disease state. Sickle haemoglobin exemplifies this phenomenon.
  2. Diminished production of one of the two subunits of the haemoglobin molecule. Mutations that produce this condition are termed "thalassemias." Equal numbers of haemoglobin alpha and beta chains are necessary for normal function. Haemoglobin chain imbalance damages and destroys red cells thereby producing anaemia. Although there is a dearth of the affected haemoglobin subunit, with most thalassemias the few subunits synthesised are structurally normal.
  3. Abnormal associations of otherwise normal subunits. A single subunit of the alpha chain (from the a-globin locus) and a single subunit from the b-globin locus combine to produce a normal haemoglobin dimer. With severe a-thalassemia, the b-globin subunits begin to associate into groups of four (tetramers) due to the paucity of potential a-chain partners. These tetramers of b-globin subunits are functionally inactive and do not transport oxygen. No comparable tetramers of alpha globin subunits form with severe beta-thalassemia. Alpha subunits are rapidly degraded in the absence of a partner from the beta-globin gene cluster (gamma, delta, beta globin subunits).

In individuals suffering from beta-thalassemia, low levels of haemoglobin lead to a lack of oxygen in many parts of the body. People with beta-thalassemia are at an increased risk of developing abnormal blood clots.

Beta-thalassemia is classified into two types depending on symptom severity. Transfusion-dependent thalassemia, also known as thalassemia major, is the more severe, while thalassemia intermedia is less severe-

Annually, approximately 1 in 100,000 cases are diagnosed worldwide. Beta-thalassaemia occurs most frequently in people from Mediterranean countries, North Africa, the Middle East, India, China and South East Asia.
Official title:
A Multicenter Study to Evaluate the Safety, Tolerability, and Efficacy of a Single Dose of Autologous Clustered Regularly Interspaced Short Palindromic Repeats Gene-edited Cluster of Differentiation 34 (CD34+) Human Hematopoietic Stem and Progenitor Cells (HSPC) (EDIT-301) in Transfusion-Dependent Beta Thalassemia (TDT)


Editas Medicine Clinical Trial Team

Phone: 617-401-9007 



United States, California

University of California San Francisco, Oakland, California, United States, 94609


United States, Minnesota

University of Minnesota, Minneapolis, Minnesota, United States, 55410


United States, New York

Columbia University Medical Center - Department of Pediatrics, New York, New York, United States, 10032

Columbia University Medical Center, New York, New York, United States, 10032


United States, Pennsylvania

Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, United States, 19104


United States, Tennessee

Tristar Medical Group Children's Specialists/Sarah Cannon Center for Blood Cancers, Nashville, Tennessee, United States, 37203

Study start:
Apr. 29, 2022
6 participants
Gene editing method:
Type of edit:
Gene enhancement
Hemoglobin Subunit Gamma 1/2 - HBG1/2 promoter
Delivery method:
Electroporation - Ex-vivo
EDIT-301 is currently being investigated in clinical studies in patients with severe sickle cell disease (RUBY trial, NCT04853576) and transfusion-dependent beta thalassemia (EDITHAL trial, NCT05444894).
IND Enabling Pre-clinical
Phase I Safety
Phase II Safety and Dosing
Phase III Safety and Efficacy

Status: Active recruiting


This is a Phase 1/2 single-arm, open-label, multicenter study evaluating the safety, tolerability, and efficacy of a single unit dose of EDIT-301 for autologous haematopoietic stem cell transplant in adult participants with TDT, age 18 to 35 years, inclusive.

Last updated: Apr. 20, 2024
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