Inducible Apoptosis as a Safety Switch for Adoptive Cell Therapy

Center for Cell and Gene Therapy, Baylor College of Medicine, Texas Children's Hospital, Houston, TX 77030, USA.
New England Journal of Medicine (Impact Factor: 55.87). 11/2011; 365(18):1673-83. DOI: 10.1056/NEJMoa1106152
Source: PubMed


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.
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.
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.
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.).

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Available from: April G Durett
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    • "The lack of further aGVHD in these studies might suggest either (i) complete elimination of allo-reactive cells, or (ii) development of peripheral tolerance. Additionally, the incidence of cGvHD was low in the HSV-TK T cell studies, and absent in the iCasp9 trial (Di Stasi et al., 2011; Zhou et al., 2014), and lymphocytes recovering from infused HSCs did not cause GVHD likely because of thymic education (Vago et al., 2012). "
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    ABSTRACT: Adoptive T-cell therapy can involve donor lymphocyte infusion (DLI) after allogeneic hematopoietic stem cell transplantation, the administration of tumor infiltrating lymphocyte (TILs) expanded ex-vivo, or more recently the use of T cell receptor (TCR) or chimeric antigen receptor (CAR) redirected T cells. However cellular therapies can pose significant risks, including graft-versus-host-disease and other on and off-target effects, and therefore strategies need to be implemented to permanently reverse any sign of toxicity. A suicide gene is a genetically encoded molecule that allows selective destruction of adoptively transferred cells. Suicide gene addition to cellular therapeutic products can lead to selective ablation of gene-modified cells, preventing collateral damage to contiguous cells and/or tissues. The ‘ideal’ suicide gene would ensure the safety of gene modified cellular applications by granting irreversible elimination of ‘all’ and ‘only’ the cells responsible for the unwanted toxicity. This review presents the suicide gene safety systems reported to date, with a focus on the state-of-the-art and potential applications regarding two of the most extensively validated suicide genes, including the clinical setting: herpes-simplex-thymidine-kinase (HSV-TK) and inducible-caspase-9 (iCasp9).
    Full-text · Article · Oct 2014 · Frontiers in Pharmacology
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    • "In this regard, PSMA is physiologically expressed in kidney, nervous system glia, and small intestine [18], and the risk to damage these organs and structures cannot be excluded simply based on the fine target specificity demonstrated in an experimental setting by the novel mAb we used to design our CAR [19]. However, in a clinical scenario, this vector containing a bidirectional promoter could be exploited to address this safety issue, namely by driving the simultaneous expression of a CAR molecule and a “safety switch” suicide gene, such as an inducible caspase or the herpes simplex virus thymidine kinase (HSV-TK) [35], [42]; or alternatively a chimeric costimulatory receptor (CCR) for combinatorial antigen recognition [43]. "
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    ABSTRACT: Immunology-based interventions have been proposed as a promising curative chance to effectively attack postoperative minimal residual disease and distant metastatic localizations of prostate tumors. We developed a chimeric antigen receptor (CAR) construct targeting the human prostate-specific membrane antigen (hPSMA), based on a novel and high affinity specific mAb. As a transfer method, we employed last-generation lentiviral vectors (LV) carrying a synthetic bidirectional promoter capable of robust and coordinated expression of the CAR molecule, and a bioluminescent reporter gene to allow the tracking of transgenic T cells after in vivo adoptive transfer. Overall, we demonstrated that CAR-expressing LV efficiently transduced short-term activated PBMC, which in turn were readily stimulated to produce cytokines and to exert a relevant cytotoxic activity by engagement with PSMA+ prostate tumor cells. Upon in vivo transfer in tumor-bearing mice, CAR-transduced T cells were capable to completely eradicate a disseminated neoplasia in the majority of treated animals, thus supporting the translation of such approach in the clinical setting.
    Full-text · Article · Oct 2014 · PLoS ONE
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    • "In the future, we will compare the antitumor activity of adoptive HER2 CAR T-cell therapy with passive immunotherapy with trastuzumab. Importantly, incorporating a suicide gene, such as the inducible caspase 9 suicide gene system, within engineered CAR T cells would provide a safety control for clinical application [39]. Moreover, injections of transient CAR-expressing T cells electroporated with mRNAs appear to be safe, and the toxicity would be expected to abate rapidly [40]. "
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    ABSTRACT: Introduction The human epidermal growth factor receptor 2 (HER2) represents one of the most studied tumor-associated antigens (TAAs) for cancer immunotherapy. The monoclonal antibody (mAb) trastuzumab has improved the outcomes of patients with HER2+ breast cancer. However, a large number of HER2+ tumors are not responsive to, or become resistant to, trastuzumab-based therapy, and thus more effective therapies targeting HER2 are needed. Methods HER2-specific T cells were generated by the transfer of genes that encode chimeric antigen receptor (CAR). Using a multistep overlap extension PCR method, we constructed a novel, humanized HER2 CAR-containing, chA21 single-chain variable fragment (scFv) region of antigen-specific mAb and T-cell intracellular signaling chains made up of CD28 and CD3ζ. An interferon γ and interleukin 2 enzyme-linked immunosorbent assay and a chromium-51 release assay were used to evaluate the antitumor immune response of CAR T cells in coculture with tumor cells. Furthermore, SKBR3 tumor–bearing nonobese diabetic/severe combined immunodeficiency (NOD/SCID) mice were treated with HER2 CAR T cells to evaluate antitumor activity. Human CD3+ T cell accumulation in tumor xenograft was detected by immunohistochemistry. Results chA21-28z CAR was successfully constructed, and both CD4+ and CD8+ T cells were transduced. The expanded HER2 CAR T cells expressed a central memory phenotype and specifically reacted against HER2+ tumor cell lines. Furthermore, the SKBR3 tumor xenograft model revealed that HER2 CAR T cells significantly inhibited tumor growth in vivo. Immunohistochemical analysis showed robust accumulation of human CD3+ T cells in regressing SKBR3 lesions. Conclusions The results of this study show that novel chA21 scFv-based, HER2-specific CAR T cells not only recognized and killed HER2+ breast and ovarian cancer cells ex vivo but also induced regression of experimental breast cancer in vivo. Our data support further exploration of the HER2 CAR T-cell therapy for HER2-expressing cancers.
    Full-text · Article · Jun 2014 · Breast cancer research: BCR
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