Inducible Caspase 9 Suicide Gene to Improve the Safety of Allodepleted T Cells after Haploidentical Stem Cell Transplantation

Siok Keen Tey, Gianpietro Dotti, Cliona M. Rooney, Helen E. Heslop, Malcolm K. Brenner

Research output: Contribution to journalArticlepeer-review

154 Scopus citations


Addback of donor T cells following T cell-depleted stem cell transplantation (SCT) can accelerate immune reconstitution and be effective against relapsed malignancy. After haploidentical SCT, a high risk of graft-versus-host disease (GVHD) essentially precludes this option, unless the T cells are first depleted of alloreactive precursor cells. Even then, the risks of severe GVHD remain significant. To increase the safety of the approach and thereby permit administration of larger T cell doses, we used a suicide gene, inducible caspase 9 (iCasp9), to transduce allodepleted T cells, permitting their destruction should administration have adverse effects. We made a retroviral vector encoding iCasp9 and a selectable marker (truncated CD19). Even after allodepletion (using anti-CD25 immunotoxin), donor T cells could be efficiently transduced, expanded, and subsequently enriched by CD19 immunomagnetic selection to >90% purity. These engineered cells retained antiviral specificity and functionality, and contained a subset with regulatory phenotype and function. Activating iCasp9 with a small-molecule dimerizer rapidly produced >90% apoptosis. Although transgene expression was downregulated in quiescent T cells, iCasp9 remained an efficient suicide gene, as expression was rapidly upregulated in activated (alloreactive) T cells. We have demonstrated the clinical feasibility of this approach after haploidentical transplantation by scaling up production using clinical grade materials.

Original languageEnglish (US)
Pages (from-to)913-924
Number of pages12
JournalBiology of Blood and Marrow Transplantation
Issue number8
StatePublished - Aug 2007


  • Gene therapy
  • Graft-versus-host disease
  • Haploidentical
  • Hematopoietic stem cell transplantation
  • Immunotherapy
  • T lymphocyte

ASJC Scopus subject areas

  • Transplantation


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