• Erica B Esrick, Leslie E Lehmann, Alessandra Biffi, Maureen Achebe, Christian Brendel, Marioara F Ciuculescu, Heather Daley, Brenda MacKinnon, Emily Morris, Amy Federico, Daniela Abriss, Kari Boardman, Radia Khelladi, Kit Shaw, Helene Negre, Olivier Negre, Sarah Nikiforow, Jerome Ritz, Sung-Yun Pai, Wendy B London, Colleen Dansereau, Matthew M Heeney, Myriam Armant, John P Manis, and David A Williams.
• From the Dana-Farber/Boston Children's Cancer and Blood Disorders Center, Harvard Medical School (E.B.E., L.E.L., A.B., C.B., M.F.C., B.M., K.B., S.-Y.P., W.B.L., C.D., M.M.H., D.A.W.), the Harvard Stem Cell Institute, Harvard Medical School (A.B., C.B.), the Gene Therapy Program, Dana-Farber/Boston Children's Cancer and Blood Disorders Center (A.B., M.F.C., B.M., E.M., A.F., S.-Y.P., C.D., D.A.W.), the Division of Hematology, Brigham and Women's Hospital, Harvard Medical School (M. Achebe), the Connell and O'Reilly Families Cell Manipulation Core Facility, Dana-Farber Cancer Institute (H.D., R.K., K.S., H.N., S.N., J.R.), the TransLab, Boston Children's Hospital (D.A., M. Armant), and the Department of Laboratory Medicine, Boston Children's Hospital, Harvard Medical School (J.P.M.) - all in Boston; and Bluebird Bio, Cambridge, MA (O.N.).
• N. Engl. J. Med. 2021 Jan 21; 384 (3): 205-215.

BackgroundSickle cell disease is characterized by hemolytic anemia, pain, and progressive organ damage. A high level of erythrocyte fetal hemoglobin (HbF) comprising α- and γ-globins may ameliorate these manifestations by mitigating sickle hemoglobin polymerization and erythrocyte sickling. BCL11A is a repressor of γ-globin expression and HbF production in adult erythrocytes. Its down-regulation is a promising therapeutic strategy for induction of HbF.MethodsWe enrolled patients with sickle cell disease in a single-center, open-label pilot study. The investigational therapy involved infusion of autologous CD34+ cells transduced with the BCH-BB694 lentiviral vector, which encodes a short hairpin RNA (shRNA) targeting BCL11A mRNA embedded in a microRNA (shmiR), allowing erythroid lineage-specific knockdown. Patients were assessed for primary end points of engraftment and safety and for hematologic and clinical responses to treatment.ResultsAs of October 2020, six patients had been followed for at least 6 months after receiving BCH-BB694 gene therapy; median follow-up was 18 months (range, 7 to 29). All patients had engraftment, and adverse events were consistent with effects of the preparative chemotherapy. All the patients who could be fully evaluated achieved robust and stable HbF induction (percentage HbF/(F+S) at most recent follow-up, 20.4 to 41.3%), with HbF broadly distributed in red cells (F-cells 58.9 to 93.6% of untransfused red cells) and HbF per F-cell of 9.0 to 18.6 pg per cell. Clinical manifestations of sickle cell disease were reduced or absent during the follow-up period.ConclusionsThis study validates BCL11A inhibition as an effective target for HbF induction and provides preliminary evidence that shmiR-based gene knockdown offers a favorable risk-benefit profile in sickle cell disease. (Funded by the National Institutes of Health; ClinicalTrials.gov number, NCT03282656).Copyright © 2020 Massachusetts Medical Society.

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