Tethered IL-15 augments antitumor activity and promotes a stem-cell memory subset in tumor-specific T cells

Abstract

Adoptive immunotherapy retargeting T cells to CD19 via a chimeric antigen receptor (CAR) is an investigational treatment capable of inducing complete tumor regression of B-cell malignancies when there is sustained survival of infused cells. T-memory stem cells (TSCM) retain superior potential for long-lived persistence, but challenges exist in manufacturing this T-cell subset because they are rare among circulating lymphocytes. We report a clinically relevant approach to generating CAR+T cells with preserved TSCMpotential using theSleeping Beautyplatform. Because IL-15 is fundamental to T-cell memory, we incorporated its costimulatory properties by coexpressing CAR with a membrane-bound chimeric IL-15 (mbIL15). The mbIL15-CAR T cells signaled through signal transducer and activator of transcription 5 to yield improved T-cell persistence independent of CAR signaling, without apparent autonomous growth or transformation, and achieved potent rejection of CD19+leukemia. Long-lived T cells were CD45ROnegCCR7+CD95+, phenotypically most similar to TSCM, and possessed a memory-like transcriptional profile. Overall, these results demonstrate that CAR+T cells can develop long-term persistence with a memory stem-cell phenotype sustained by signaling through mbIL15. This observation warrants evaluation in clinical trials.

Gene Therapy with the Sleeping Beauty Transposon System

“…The SB system can also be adapted to express more than one transposon. In a technology dubbed 'double transposition', three DNA plasmids (two transposons and one transposase) have been electrotransferred into T cells to co-express CAR and mbIL15 [114]. The signaling through the second-generation CAR and the common g-chain cytokine receptor results in a T cell that combines 'signal 1 and 2' with 'signal 3' [114].…”

“…In a technology dubbed 'double transposition', three DNA plasmids (two transposons and one transposase) have been electrotransferred into T cells to co-express CAR and mbIL15 [114]. The signaling through the second-generation CAR and the common g-chain cytokine receptor results in a T cell that combines 'signal 1 and 2' with 'signal 3' [114]. This results in fully competent activation and the preservation of the key stem cell memory T cell (T SCM ) subpopulation that is correlated with antitumor effects [115].…”

“…In situations where target cells are scarce and/or culturing and expansion of the transfected cells is impossible or cannot be solved without compromising cell identity and grafting potential, cytotoxicity of the transfection procedures is a serious issue that may undermine clinical applications. However, recent experimental data indicate that, by using transposon cassettes vectorized as MCs and by providing the transposase in the form of mRNA, cellular toxicity can be reduced [63] or overcome with in vivo selective proliferation based on cytokine signaling [114], thereby positioning clinical applications with SB well within reach, at least in the area of T cell engineering.…”

Debate: Transplant is Still Necessary in the Era of Targeted Cellular Therapy for ALL

“…The signaling through the second-generation CAR and the common g-chain cytokine receptor results in a T cell that combines "signal 1 and 2" with "signal 3", resulting in fully-competent activation, preservation of key stem-cell memory T-cell (T SCM ) sub-populations, and superior persistence and killing of CD19 + tumor in mice compared with current CAR + T cells. 28,29 The long-lived T cells were CD45RO neg CCR7 + CD95 + , phenotypically most similar to T SCM , and furthermore possessed a memory-like transcriptional profile. The PD-1/PD-L1 axis may impact CAR T cells similarly to nontransferred T cells.…”

CD19-targeted immunotherapies for treatment of patients with non-Hodgkin B-cell lymphomas

“…Preclinical trials in MCL have also shown improved CAR-T responses and reduced CRS when combined with ibrutinib (Bruton's tyrosine kinase inhibitor) and in CLL when ibrutinib is given prior to CAR-T cell infusion [73,74]. Other preclinical trials have developed CAR-T cells that co-express cytokines (IL-12, IL-15, IL-18 or interferon 1β) when the cells engage with a target cancer cell, to possibly enhance the CD19-directed anti-tumor effect [75][76][77][78][79]. However, a clinical trial of IL-12 coexpressing CAR-T cells in melanoma patients was recently discontinued due to severe IL-12 toxicity [80].…”