Phase 1 study of CAR-37 T cells in patients with relapsed or refractory CD37+ lymphoid malignancies.

We report on the first-in-human clinical trial using chimeric antigen receptor (CAR) T-cells targeting CD37, an antigen highly expressed in B- and T-cell malignancies (clinicaltrials.gov NCT04136275). Five patients with relapsed or refractory CD37+ lymphoid malignancies were enrolled and infused with autologous CAR-37 T-cells. CAR-37 T-cells expanded in the peripheral blood of all patients and, at peak, comprised >94% of the total lymphocytes in 4/5 patients. Tumor responses were observed in 4/5 patients, with 3 complete responses, 1 mixed response, and 1 patient whose disease progressed rapidly and with relative loss of CD37 expression. Three patients experienced prolonged and severe pancytopenia, and in two of these patients, efforts to ablate CAR-37 T-cells (which were engineered to co-express truncated EGFR) with cetuximab, were unsuccessful. Hematopoiesis was restored in these two patients following allogeneic hematopoietic stem cell transplantation. No other severe, non-hematopoietic toxicities occurred. We investigated the mechanisms of profound pancytopenia and did not observe activation of CAR-37 T-cells in response to hematopoietic stem cells in vitro or hematotoxicity in humanized models. Patients with pancytopenia had sustained high levels of IL-18, with low levels of IL-18 binding protein in their peripheral blood. IL-18 levels were significantly higher in CAR-37-treated patients relative to both cytopenic and non-cytopenic cohorts of CAR-19-treated cohorts of patients. In conclusion, CAR-37 T-cells exhibited anti-tumor activity, with significant CAR expansion and cytokine production. CAR-37 T-cells may be an effective therapy in hematologic malignancies as a bridge to hematopoietic stem cell transplant.

Lymphocyte adhesion to CCR5 ligands is reduced by anti-CCR5 gene delivery.

Immune-mediated damage to the central nervous system (CNS) is an important contributor to many CNS diseases, including epilepsy. Chemokines play a role in leukocyte recruitment to, and migration across, the blood-brain barrier (BBB) during many such processes. We previously investigated the role of the chemokine receptor CCR5 in a rat model of epilepsy based on intraperitoneal kainic acid (KA) administration. Before KA injection, rats were given intramarrow inoculations of SV(RNAiR5-RevM10.AU1), which carries an interfering RNA (RNAi) that targets CCR5. Decreased CCR5 expression in blood cells after vector administration reduced expression of CCR5 ligands MIP-1α and RANTES in the microvasculature, and strongly protected from BBB leakage, CNS loss and inflammation and facilitated CNS repair. We show here that rSV40-mediated downregulation of CCR5 in lymphocytes decreased cellular adhesion to surfaces carrying CCR5 ligands. These data suggest that reducing CCR5 in peripheral blood mononuclear cells (PBMCs) might alter their adhesion to the microvasculature and their participation in inflammatory processes.

Efficient CNS gene delivery by intravenous injection.

We administered recombinant SV40-derived viral vectors (rSV40s) intravenously to mice with or without prior intraperitoneal injection of mannitol to deliver transgenes to the central nervous system (CNS). We detected transgene-expressing cells (mainly neurons) most prominently in the cortex and spinal cord; prior intraperitoneal mannitol injection increased CNS gene delivery tenfold. Intravenous injection of rSV40s, particularly with mannitol pretreatment, resulted in extensive expression of multiple transgenes throughout the CNS.

Successful eradication of established peritoneal ovarian tumors in SCID-Beige mice following adoptive transfer of T cells genetically targeted to the MUC16 antigen.

PURPOSE: Most patients diagnosed with ovarian cancer will ultimately die from their disease. For this reason, novel approaches to the treatment of this malignancy are needed. Adoptive transfer of a patient's own T cells, genetically modified ex vivo through the introduction of a gene encoding a chimeric antigen receptor (CAR) targeted to a tumor-associated antigen, is a novel approach to the treatment of ovarian cancer. EXPERIMENTAL DESIGN: We have generated several CARs targeted to the retained extracellular domain of MUC16, termed MUC-CD, an antigen expressed on most ovarian carcinomas. We investigate the in vitro biology of human T cells retrovirally transduced to express these CARs by coculture assays on artificial antigen-presenting cells as well as by cytotoxicity and cytokine release assays using the human MUC-CD(+) ovarian tumor cell lines and primary patient tumor cells. Further, we assess the in vivo antitumor efficacy of MUC-CD-targeted T cells in SCID-Beige mice bearing peritoneal human MUC-CD(+) tumor cell lines. RESULTS: CAR-modified, MUC-CD-targeted T cells exhibited efficient MUC-CD-specific cytolytic activity against both human ovarian cell and primary ovarian carcinoma cells in vitro. Furthermore, expanded MUC-CD-targeted T cells infused through either i.p. injection or i.v. infusion into SCID-Beige mice bearing orthotopic human MUC-CD(+) ovarian carcinoma tumors either delayed progression or fully eradicated disease. CONCLUSION: These promising preclinical studies justify further investigation of MUC-CD-targeted T cells as a potential therapeutic approach for patients with high-risk MUC16(+) ovarian carcinomas.

Adoptive T cell immunotherapy strategies for the treatment of patients with ovarian cancer.

Ovarian cancer is the leading cause of cancer death among gynecological malignances. Despite the initial successful multimodality therapy with cytoreductive surgery and subsequent combination chemotherapy, most patients with advanced disease will ultimately relapse and become incurable. For this reason novel therapeutic approaches for the treatment of this malignancy are urgently needed. Adoptive transfer of genetically modified autologous tumor-reactive T cells is a promising novel antitumor therapy for many cancers. T cells may be genetically modified ex vivo to express chimeric antigen receptors (CARs), which are artificial T cell receptors targeted to specific tumor antigens. The resulting T cells are thus programmed to recognize tumor cells. Ovarian carcinomas in particular appear to be suited to this therapeutic approach based on the fact that these tumors are relatively immunogenic, inducing an endogenous T cell response. Furthermore, the degree to which this endogenous T cell mediated immune response is evident correlates to long-term patient prognosis following surgery and chemotherapy. To this end, adoptive T cell immunotherapy strategies for the treatment of ovarian carcinomas appear to be particularly promising and are currently being investigated at several centers in both pre-clinical and clinical settings.

Delivering genes to the organ-localized immune system: long-term results of direct intramarrow transduction.

We studied the distribution of transgene-expressing cells after direct gene transfer into the bone marrow (BM). Rats received direct injection into the femoral BM of SV(Nef-FLAG), a Tag-deleted recombinant SV40 carrying a marker gene (FLAG epitope). Controls received an unrelated rSV40 or saline. Blood cells (5%) and femoral marrow cells (25%) expressed FLAG throughout. FLAG expression was assessed in different organs at 1, 4 and 16 months. FLAG+ macrophages were seen throughout the body, and were prominent in the spleen. FLAG+ cells were common in pulmonary alveoli. The former included alveolar macrophages and type II pneumocytes. These cells were not detected at 1 month, occasional at 4 months and common at 16 months after intramarrow injection. Rare liver cells were positive for both FLAG and ferritin, indicating that some hepatocytes also expressed this BM-delivered transgene. Control animals were negative. Thus: (a) fixed tissue phagocytes may be accessible to gene delivery by intramarrow transduction of their progenitors; (b) transduced BM-resident cells or their derivatives may migrate to other organs (lungs) and may differentiate into epithelial cells; and (c) intramarrow injection of rSV40s does not detectably transduce parenchymal cells of other organs.