Inducible apoptosis as a safety switch for adoptive cell therapy

N Engl J Med. 2011 Nov 3;365(18):1673-83. doi: 10.1056/NEJMoa1106152.


Background: Cellular therapies could play a role in cancer treatment and regenerative medicine if it were possible to quickly eliminate the infused cells in case of adverse events. We devised an inducible T-cell safety switch that is based on the fusion of human caspase 9 to a modified human FK-binding protein, allowing conditional dimerization. When exposed to a synthetic dimerizing drug, the inducible caspase 9 (iCasp9) becomes activated and leads to the rapid death of cells expressing this construct.

Methods: We tested the activity of our safety switch by introducing the gene into donor T cells given to enhance immune reconstitution in recipients of haploidentical stem-cell transplants. Patients received AP1903, an otherwise bioinert small-molecule dimerizing drug, if graft-versus-host disease (GVHD) developed. We measured the effects of AP1903 on GVHD and on the function and persistence of the cells containing the iCasp9 safety switch.

Results: Five patients between the ages of 3 and 17 years who had undergone stem-cell transplantation for relapsed acute leukemia were treated with the genetically modified T cells. The cells were detected in peripheral blood from all five patients and increased in number over time, despite their constitutive transgene expression. A single dose of dimerizing drug, given to four patients in whom GVHD developed, eliminated more than 90% of the modified T cells within 30 minutes after administration and ended the GVHD without recurrence.

Conclusions: The iCasp9 cell-suicide system may increase the safety of cellular therapies and expand their clinical applications. (Funded by the National Heart, Lung, and Blood Institute and the National Cancer Institute; number, NCT00710892.).

Publication types

  • Clinical Trial
  • Research Support, N.I.H., Extramural

MeSH terms

  • Adolescent
  • Apoptosis
  • Caspase 9 / genetics*
  • Caspase 9 / metabolism
  • Child
  • Child, Preschool
  • Female
  • Gene Transfer Techniques
  • Genes, Transgenic, Suicide*
  • Graft vs Host Disease / therapy*
  • Humans
  • Immunotherapy, Adoptive*
  • Leukemia / therapy
  • Male
  • Organic Chemicals / therapeutic use
  • Recurrence
  • Stem Cell Transplantation
  • T-Lymphocytes / immunology
  • T-Lymphocytes / transplantation*
  • Tacrolimus Binding Proteins / genetics*


  • Organic Chemicals
  • Caspase 9
  • Tacrolimus Binding Proteins
  • AP 1903 reagent

Associated data