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Results summary of St. Jude clinical trial: 



A Pilot Feasibility Study of Gene Transfer for X-Linked Severe Combined Immunodeficiency in Newly Diagnosed Infants Using a Self-inactivating Lentiviral Vector to Transduce Autologous CD34+ Hematopoietic Cells (LVXSCID-ND)

Why was this study done?

X-linked severe combined immunodeficiency (X-SCID) is a disorder that is inherited (passed down through families). X-SCID is caused by a change (mutation) in a gene that is involved in the immune system. Children with X-SCID have problems fighting off infections.

Past treatments used bone marrow transplants from matched-sibling (brother or sister) donors. But 80% of patients do not have a perfect match. This study is designed to help infants with X-SCID who lack matched donors.

The study evaluates a treatment called lentiviral gene transfer. This involves taking bone marrow stem cells from the child and transferring a normal (corrected) copy of the gene into these cells in the lab. The child then receives a low dose of a chemotherapy (chemo) drug called busulfan, to make room in the bone marrow, before the stem cells with the corrected gene copy are given back.

The study’s main goals were to find out if:

  • lentiviral gene transfer is safe
  • it can be done using the methods St. Jude developed
  • it can provide a normal immune system for the patient
  • there are long-term effects of the treatment
  • it is safe and effective to use busulfan as part of the therapy

When was this study done?

The study opened in August 2016 and is scheduled to close in May 2022.

What did the study consist of?

  • Tests were done to find out if this study was a good option for the child.
  • Clinicians collected bone marrow cells from the child. These cells contained the mutated gene.
  • A corrected version of the gene was inserted into the collected cells.
  • The child received busulfan to make room for the new cells.
  • The cells with the inserted gene were given back into the child’s vein.
  • The medical team watched the child closely until the immune system recovered.
  • Ten-year follow-up began after the child left the hospital.

What did we learn from this study?

The first eight infants in this study are producing functional immune cells for the first time.

Early results show that low doses of busulfan increase engraftment of gene-corrected stem cells in the bone marrow without causing the side effects found with standard doses.

All eight patients who had infections before gene therapy have recovered. They are developing and growing normally. None has developed a life-threatening infection since receiving gene therapy. No patients have developed leukemia, a side effect of an earlier gene therapy study done elsewhere for X-SCID.

What are the next research steps as a result of this study?

This study will continue to enroll infants, so we can learn more about lentiviral gene therapy and low-dose busulfan use.

How does this study affect my child?

Every survivor of X-SCID gene therapy should receive long-term follow-up care. Your child will receive information and guidance for care. Please speak with your doctor about specific guidelines that apply to your child.

For more information

Please talk with your child’s doctor about questions or concerns you have as a result of this study.

Publications generated from this study:

Lentiviral Gene Therapy Combined with Low-Dose Busulfan in Infants with SCID-X1. E. Mamcarz, S. Zhou, T. Lockey, H. Abdelsamed, S.J. Cross, G. Kang, Z. Ma, J. Condori, J. Dowdy, B. Triplett, C. Li, G. Maron, J.C. Aldave Becerra, J.A. Church, E. Dokmeci, J.T. Love, A.C. da Matta Ain, H. van der Watt, X. Tang, W. Janssen, B.Y. Ryu, S.S. De Ravin, M.J. Weiss, B. Youngblood, J.R. Long‑Boyle, S. Gottschalk, M.M. Meagher, H.L. Malech, J.M. Puck, M.J. Cowan, B.P. Sorrentino. N Engl J Med. 2019 Apr 18; 380(16): 1525–1534.