Safety and Efficacy of CTX001 in Patients with Transfusion-Dependent β-Thalassemia and Sickle Cell Disease: Early Results from the Climb THAL-111 and Climb SCD-121 Studies of Autologous CRISPR-CAS9-Modified CD34+ Hematopoietic Stem and Progenitor Cells

• Published in: Blood 2020-11, Vol.136 (Supplement 1), p.3-4
• Main Authors: Frangoul, Haydar, Bobruff, Yael, Cappellini, Maria Domenica, Corbacioglu, Selim, Fernandez, Christine Marie, de la Fuente, Josu, Grupp, Stephan A, Handgretinger, Rupert, Ho, Tony W., Imren, Suzan, Kattamis, Antonis, Lekstrom-Himes, Julie, Locatelli, Franco, Lu, Yimeng, Mapara, Markus Y, de Montalembert, Mariane, Mulcahey, Sarah D., Rondelli, Damiano, Shanbhag, Niraj, Sheth, Sujit, Soni, Sandeep, Steinberg, Martin H., Weinstein, Michael J., Wu, John K., Wall, Donna
• Format: Article
• Language: English
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood-2020-139575

Background: BCL11A is a key transcription factor that suppresses the production of fetal hemoglobin (HbF) in red blood cells (RBCs), leading to the production of adult Hb (HbA). In diseases with hemoglobin production defects such as b-thalassemia, or in sickle cell disease (SCD), HbF upregulation could ameliorate anemia and reduce transfusion requirements, such as in β-thalassemia, or reduce clinical complications, including vaso-occlusive crises (VOCs), in SCD. To induce potentially curative levels of HbF in erythrocytes, we used the ex vivo CRISPR-Cas9-based gene-editing platform to edit the erythroid enhancer region of BCL11A in hematopoietic stem and progenitor cells (HSPCs), producing CTX001. Aims: CLIMB THAL-111 (NCT03655678) and CLIMB SCD-121 (NCT03745287) are multi-center, first-in-human studies of CTX001 for transfusion-dependent b-thalassemia (TDT) and SCD, respectively. Here, we present available safety and efficacy results from all patients with at least 3 months of follow-up from both studies as of July 2020. Methods: Patients (aged 18 to 35 years) with TDT receiving packed red blood cell (pRBC) transfusions of ≥100 mL/kg/year or ≥10 units/year in the previous 2 years, and those with severe SCD, defined as ≥2 VOCs/year requiring medical care in the previous 2 years, were eligible. Peripheral CD34+ HSPCs were collected by apheresis after mobilization with G-CSF (filgrastim) and plerixafor (for TDT) or plerixafor alone (SCD). The erythroid enhancer region of BCL11A was edited in CD34+ cells using a specific CRISPR guide RNA and Cas9 nuclease. Prior to CTX001 infusion on Day +1, patients received myeloablation with 4 days of busulfan. Patients were monitored for stem cell engraftment and hematopoietic recovery, adverse events, total Hb and HbF production, hemolysis, F-cells, pRBC transfusion requirements (TDT), and VOCs (SCD) during follow-up. Results: Data are presented for patients with TDT (N=5; RBC transfusion history range: 23.5 to 61 units/year; CTX001 post-infusion follow-up through Months 15, 6, 4, 4, and 3, respectively) and with SCD (N=2; 7 VOCs/year and 7.5 VOCs/year, respectively, annualized over 2 years prior to consent; CTX001 post-infusion follow-up through Months 12 and 3, respectively). In the patients with TDT, median neutrophil engraftment occurred on Day +32 (range: +27 to +36); median platelet engraftment occurred on Day +37 (range: +34 to +52). In the patients with SCD, neutrophil engraftment occurred on Day +30 and Day +22