Effect of minimal lymphodepletion prior to ACT with TBI-1301, NY-ESO-1 specific gene-engineered TCR-T cells, on clinical responses and CRS.

2537 Background: Adoptive transfer of T cell receptor (TCR) gene-engineered T cells can induce durable anti-cancer responses. Post-infusion cytokine release syndrome (CRS) has been associated with clinical utility. Pre-infusion lymphodepletion (LD) may influence CRS, graft persistence, and clinical responses. While the optimal LD regimen is not yet defined, most include both cyclophosphamide (CY) and fludarabine (FLU). TBI-1301 is a novel gene therapy produced by engineering autologous lymphocytes to express an NY-ESO-1-specific TCR using a retrovirus vector that encodes siRNA to silence endogenous TCR. Since less intensive LD may be sufficient with the use of this novel vector, we are conducting a study where patients are treated with TBI-1301 following LD with CY alone. Methods: Eligibility includes informed consent, HLA-A*02:01 or A*02:06 haplotype, and NY-ESO-1 expression by immunohistochemistry. Eligible patients undergo harvest of PBMC which are then processed locally to generate engineered TBI-1301 cells. The study design is to infuse 5x109 cells (day 0) to patients following LD with CY (750 mg/m2 on day -3 and -2). Endpoints include safety, efficacy, and biological correlates for persistence of NY-ESO-1-specific T cells post infusion. Results: Thus far, 9 patients have been treated, and 8 have received the target dose. To date, 8 patients are evaluable for response and toxicity, and no DLTs have been observed. Despite LD with CY alone, all 4 patients with synovial sarcoma and 1 with melanoma experienced clinical and laboratory evidence of grade 1-2 CRS with increased CRP, ferritin, and IL-6 levels. CRS resolved spontaneously in all but one patient who required tocilizumab due to grade 2 nausea/vomiting. Two subjects experienced grade 3 tumor-associated pain. Other treatment-associated grade 3 or 4 toxicities included neutropenia and hypophosphatemia. Best overall response by RECIST is as follows: 2 partial responses, 5 stable disease, and 1 progressive disease. Biomarker analysis demonstrates persistence of transferred TBI-1301 cells, > 100 days in some patients. Conclusions: TBI-1301 appears to be safe and to possess anti-tumor activity. Despite LD with CY alone, grade 1-2 CRS is induced. Additional cohorts to this study will examine the role of repeat infusions to enhance anti-tumor activity. Clinical trial information: NCT02869217.

Oligodendrocytes in the mouse optic nerve originate in the preoptic area

The present study aims to examine the origin of oligodendrocyte progenitor cells (OPCs) in the mouse optic nerve (ON) by labeling OPCs in the fetal forebrain. The labeling of OPCs in the ON was performed by injection of a retrovirus vector carrying the lacZ gene into the lateral ventricle, or by inducible Cre/loxP of Olig2-positive cells. The retrovirus labeling revealed that ventricular zone-derived cells of the fetal forebrain relocated to the ON and differentiated into oligodendrocytes. In addition, lineage tracing of Olig2-positive cells and whole mount staining of PDGFRα-positive cells demonstrated that OPCs appeared by E12.5 in the preoptic area, and spread caudally to enter the ON. Our results also suggest that OPCs generated during the early stage are depleted from the ON after maturation.

Tumor-Specific TCR-Engineered Donor Lymphocyte Infusion Therapy with Reduced GvHD Induction Utilizing Novel Retrovirus Vector Silencing Endogenous TCR Expression

Background The patients with relapsed hematological malignancy after allogeneic hematopoetic stem cell transplantation (HSCT) can be treated by donor lymphocyte infusion (DLI). However, the efficacy is often limited in association with the development of Graft-versus-Host Disease (GVHD) as a serious adverse event. By the use of the novel retrovirus vector that specifically silences endogenous T cell receptor (TCR) in gene-engineered T cells, here we demonstrate the development of DLI with lymphocytes engineered to express tumor-specific TCR that exhibit increased tumor-specificity in combination with decreased GVHD-inducing potential (Summarized in the figure). Methods Human PBMC were transduced with a high affinity TCR specific to a cancer/testis antigen, NY-ESO-1, by the retrovirus vector with siRNA specific to the endogenous TCR (siTCR vector). Resulting TCR gene-transduced T cells were examined for the expression of their endogenous TCR by flow cytometry and for their reactivity to allogeneic LCL by 3H uptake proliferation assay. Immunodeficient NOG mice were innoculated with a NY-ESO-1 expressing human tumor cell line NW-MEL-38, received TCR gene-transduced T cells, and monitored for the tumor growth and the development of GVHD. Results Human lymphocytes that were genetically engineered to express a high affinity NY-ESO-1-specific TCR with siTCR vector showed significantly reduced expression of endogenous TCR associated with dramatically diminished reactivity to allogeneic LCL. When adoptively transferred into NOG mice, control non-engineered T cells failed to control the growth of human tumor cells despite the fact that the lymphocytes were allogeneic to the tumor cells and developed lethal GVHD including severe bone-marrow destruction. The development of GVHD was dependent on both the CD4+ and CD8+ T cells suggesting that the simple purification of CD8+ T cells was not a sufficient enough strategy to prevent GVHD. In contrast, adoptive transfer of NY-ESO-1-specific TCR gene-transduced T cells induced complete tumor regression without the development of GVHD. Conclusions The results here suggest that the allogeneic T cells transduced with a tumor-specific TCR by siTCR vector showed increased tumor-reactivity with diminished GVHD potential. These T cells will be applicable to the donor lymphocytes infusion therapy after allogeneic stem cell transplantation for the treatment of hematological malignacy. Currently we plan a clinical trial of DLI with siTCR technology for the patients with relapsed NY-ESO-1 positive adult T cell leukemia/lymphoma after HSCT. Figure 1 Figure 1. Disclosures Ikeda: Takara Bio Inc.: Research Funding. Kawamura:Takara Bio Inc.: Employment. Imai:Takara Bio Inc.: Research Funding. Okamoto:CDM Center, Takara Bio Inc.: Employment. Mineno:Takara Bio Inc.: Membership on an entity's Board of Directors or advisory committees. Takesako:Takara Bio Inc.: Membership on an entity's Board of Directors or advisory committees. Shiku:Takara Bio Inc.: Research Funding.