Like the gift that keeps on giving, great research just keeps emerging from SITC 2019. Sunday, Nov. 10, 2019, was all about Innovations in Cellular Therapies.
When (CAR) T Cells Get Exhausted…
While receiving CAR-T cell therapy is a life saver for some patients with blood cancers, there is a downside: T cells entering solid tumors can stop working due to a phenomenon called T cell exhaustion. Scientists are working on counteracting or reversing this phenomenon, and some of this outstanding work was presented in the session entitled “Innovations in Cellular Therapy for Therapeutically Targeting Advanced Malignancies” at SITC.
Dr. Crystal Mackall, MD from Stanford University, described how her team engineered exhaustion resistant CAR-T cells to act as efficient CAR-T cells in solid tumors. CAR-T cells targeting the disialoganglioside GD2 have potent antitumor activity but lose efficiency over time due to early exhaustion induced by Tonic signaling. In exhausted T cells, AP-1/bZIP/IRF transcription factors were overexpressed, implying that an imbalance of AP-1 family member expression renders dysfunction in the activation of c-Fos/c-Jun heterodimers. In this study, c-Jun overexpression induced transcriptional reprogramming, enhanced proliferative capacity of T cells expressing CD19 CAR receptors and decreased exhaustion. For instance, c-Jun overexpression in GD2-HA.28.z-CAR-T cells enhanced antitumor activity against GD2+ leukemia. Because regulation of CAR cell surface expression levels controls CAR activity, transient inhibition of CAR signaling prevented exhaustion in tonically signaling CAR-T cells and could also reverse exhaustion.
Metabolism drives T cell differentiation. Another way to counteract exhaustion explores the use of metabolism-targeting drugs to alter the differentiation of tumor-specific T cells into potent effector T cells and long-living memory cells, thus preventing the accumulation of exhausted T cells.
Dr. Imene Hamaidi, PhD from Moffit Cancer Center talked about how “Sirt2 inhibition enhances anti-tumor immunity by promoting T cell metabolism”. Sirt2 is an NAD+ dependent histone deacetylase that is induced under caloric restriction. Upregulation of Sirt2 expression in human TILs compared to peripheral blood mononuclear cells (PBMCs) from patients enrolled in a phase I clinical trial of nivolumab as well as TILs in advanced NSCLC correlated with a poor clinical response to immunotherapy. In Sirt2-/- T cells, glycolytic enzyme activities were increased, and hyper-reactivity to tumor was dependent on glycolysis. In a preclinical model, Sirt2 deficiency delayed tumor progression and enhanced the efficiency of PD-1 blockade. Next, the effect of Sirt2 inhibition with AGK2 was examined in human TILs. Sirt2 inhibition augmented the metabolic fitness (glycolytic rate) and enhanced effector functions such as IFN-γ production in NSCLC TILs. Overall, Sirt2 is a metabolic immune checkpoint and its abrogation enhances the metabolic and functional fitness of tumor reactive T cells to augment cancer immunotherapy.
…You Move On to CAR-NK Cells
CAR-T cell therapy has its limitations: for example, patients who lack sufficient T cells for CAR-T cell generation cannot afford to wait the time it takes to generate more T cells. To provide a viable alternative for this situation, Dr. Katy Rezvani from the University of Texas MD Anderson Cancer Center has turned to natural killer (NK) cells to expand the use of CAR-directed therapy in patients with B cell malignancies, as NK cells can overcome these limitations.
In her presentation at SITC, Dr. Rezvani described a first human trial of NK cell therapy. There are multiple advantages to using NK cells over T cells for CAR-directed therapy. For instance, CAR-NK cells are allogeneic with low or no graft versus host disease (GVHD) risk, and their activity can be induced by the NK receptor plus a CAR for a synergistic effect. CAR-NK cells persisted and controlled Raji tumor in the NSG (NOD scid gamma) mouse model. Currently, a first-in-human clinical trial to test the safety and efficacy of CAR19/IL-15/Cas9 transduced cord blood NK cells is ongoing. In this study, CAR-NK cells trafficked to disease sites in patients with relapsed/refractory B lymphoid malignancies, and 8 of 11 patients achieved clinical response. No cytokine release syndrome (CRS) or neurotoxicity has been observed to date. CAR-NK cells were detectable up to 12 months post infusion.
NK cells have the potential to be an allogeneic therapy, as they do not require strict HLA matching or carry the risk of graft-versus-host disease. CAR-NK cells do not present the same safety concerns as CAR-T cells, such as the CRS observed in many CAR-T clinical trials. In addition to reducing safety concerns, using off-the-shelf NK cells as a standard cancer therapy has the potential to dramatically cut costs associated with autologous CAR-T cells.
Jeffrey S. Miller, MD from the University of Minnesota started his presentation “Off the Shelf” by describing how allogeneic NK cell adaptive transfer has been used on hundreds of patients in the last two decades. Cytomegalovirus (CMV) induced adaptive NK cells, a NKG2C+/CD57+ NK subset from CMV+ individuals, have shown increased efficiency for cancer cell therapy. A first-generation adaptive NK cell product from CMV+ donors, FATE-NK100, demonstrated cell expansion in the presence of IL-14 plus GSK3βi, and induced potent cytotoxic activity to solid tumor targets. In an ovarian cancer study (the Apollo trial), some patients partially responded to FATE-NK100 with 47% reduction in tumor size. For individual-patient cell therapies; however, there are limitations for blood-derived NK cell products. To address this limitation, Dr. Miller’s group designed off-the-shelf NK cells derived from renewable, engineered pluripotent cell lines. Dr. Miller explained the manufacturing process of iNK cells derived from induced pluripotent stem cells (iPSC) and functional tests to characterize iNK cells. iNK cytotoxic function was superior to expanded adult peripheral blood- or umbilical cord blood-derived NK cells. Moreover, iNK cells promoted T cell recruitment, synergized with T cells & PD-1 blockade in a solid tumor spheroid model and in vivo. The first clinical trials of iPSC-derived NK cell therapy are ongoing.
NanoString® Technologies is at the Forefront in Supporting the Fifth Pillar of Cancer Therapy
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FOR RESEARCH USE ONLY. NOT FOR USE IN DIAGNOSTIC PROCEDURES.