Vijay Bhoj

Therapeutic Induction of Regulatory, Cytotoxic CD8+ T Cells in Multiple Sclerosis

In the setting of autoimmunity, one of the goals of successful therapeutic immune modulation is the induction of peripheral tolerance, a large part of which is mediated by regulatory/suppressor T cells. In this report, we demonstrate a novel immunomodulatory mechanism by an FDA-approved, exogenous peptide-based therapy that incites an HLA class I-restricted, cytotoxic suppressor CD8+ T cell response. We have shown previously that treatment of multiple sclerosis (MS) with glatiramer acetate (GA; Copaxone) induces differential up-regulation of GA-reactive CD8+ T cell responses. We now show that these GA-induced CD8+ T cells are regulatory/suppressor in nature. Untreated patients show overall deficit in CD8+ T cell-mediated suppression, compared with healthy subjects. GA therapy significantly enhances this suppressive ability, which is mediated by cell contact-dependent mechanisms. CD8+ T cells from GA-treated patients and healthy subjects, but not those from untreated patients with MS, exhibit potent, HLA class I-restricted, GA-specific cytotoxicity. We further show that these GA-induced cytotoxic CD8+ T cells can directly kill CD4+ T cells in a GA-specific manner. Killing is enhanced by preactivation of target CD4+ T cells and may depend on presentation of GA through HLA-E. Thus, we demonstrate that GA therapy induces a suppressor/cytotoxic CD8+ T cell response, which is capable of modulating in vivo immune responses during ongoing therapy. These studies not only explain several prior observations relating to the mechanism of this drug but also provide important insights into the natural immune interplay underlying this human immune-mediated disease.

Chimeric Antigen Receptor T Cells in Refractory B-Cell Lymphomas

Background Patients with diffuse large B‐cell lymphoma or follicular lymphoma that is refractory to or that relapses after immunochemotherapy and transplantation have a poor prognosis. High response rates have been reported with the use of T cells modified by chimeric antigen receptor (CAR) that target CD19 in B‐cell cancers, although data regarding B‐cell lymphomas are limited. Methods We used autologous T cells that express a CD19‐directed CAR (CTL019) to treat patients with diffuse large B‐cell lymphoma or follicular lymphoma that had relapsed or was refractory to previous treatments. Patients were monitored for response to treatment, toxic effects, the expansion and persistence of CTL019 cells in vivo, and immune recovery. Results A total of 28 adult patients with lymphoma received CTL019 cells, and 18 of 28 had a response (64%; 95% confidence interval [CI], 44 to 81). Complete remission occurred in 6 of 14 patients with diffuse large B‐cell lymphoma (43%; 95% CI, 18 to 71) and 10 of 14 patients with follicular lymphoma (71%; 95% CI, 42 to 92). CTL019 cells proliferated in vivo and were detectable in the blood and bone marrow of patients who had a response and patients who did not have a response. Sustained remissions were achieved, and at a median follow‐up of 28.6 months, 86% of patients with diffuse large B‐cell lymphoma who had a response (95% CI, 33 to 98) and 89% of patients with follicular lymphoma who had a response (95% CI, 43 to 98) had maintained the response. Severe cytokine‐release syndrome occurred in 5 patients (18%). Serious encephalopathy occurred in 3 patients (11%); 2 cases were self‐limiting and 1 case was fatal. All patients in complete remission by 6 months remained in remission at 7.7 to 37.9 months (median, 29.3 months) after induction, with a sustained reappearance of B cells in 8 of 16 patients and with improvement in levels of IgG in 4 of 10 patients and of IgM in 6 of 10 patients at 6 months or later and in levels of IgA in 3 of 10 patients at 18 months or later. Conclusions CTL019 cells can be effective in the treatment of relapsed or refractory diffuse large B‐cell lymphoma and follicular lymphoma. High rates of durable remission were observed, with recovery of B cells and immunoglobulins in some patients. Transient encephalopathy developed in approximately one in three patients and severe cytokine‐release syndrome developed in one in five patients. (Funded by Novartis and others; ClinicalTrials.gov number, NCT02030834.)

Reengineering chimeric antigen receptor T cells for targeted therapy of autoimmune disease

Engineering T cells to treat autoimmunity Autoimmune diseases such as lupus and rheumatoid arthritis lack therapies that specifically target only the disease-causing cells. Inspired by the clinical success of using chimeric antigen receptor T cells to treat certain types of cancers, Ellebrecht et al. asked whether a similar approach might also work against antibody-driven autoimmune diseases. They engineered T cells to express chimeric receptors consisting of the disease-causing autoantigen desmoglein 3 fused to signaling domains that activate T cells. When given to diseased mice, the engineered T cells targeted and killed B cells that express antibodies targeting desmoglein 3, hinting that such a strategy may be an effective way to treat antibody-driven autoimmune diseases. Science, this issue p. 179 A proof-of-principle study indicates that engineered T cells may be an effective, targeted therapy for autoimmunity. Ideally, therapy for autoimmune diseases should eliminate pathogenic autoimmune cells while sparing protective immunity, but feasible strategies for such an approach have been elusive. Here, we show that in the antibody-mediated autoimmune disease pemphigus vulgaris (PV), autoantigen-based chimeric immunoreceptors can direct T cells to kill autoreactive B lymphocytes through the specificity of the B cell receptor (BCR). We engineered human T cells to express a chimeric autoantibody receptor (CAAR), consisting of the PV autoantigen, desmoglein (Dsg) 3, fused to CD137-CD3ζ signaling domains. Dsg3 CAAR-T cells exhibit specific cytotoxicity against cells expressing anti-Dsg3 BCRs in vitro and expand, persist, and specifically eliminate Dsg3-specific B cells in vivo. CAAR-T cells may provide an effective and universal strategy for specific targeting of autoreactive B cells in antibody-mediated autoimmune disease.

Persistence of long-lived plasma cells and humoral immunity in individuals responding to CD19-directed CAR T-cell therapy.

The mechanisms underlying the maintenance of long-lasting humoral immunity are not well understood. Studies in mice indicate that plasma cells (PCs) can survive up to a lifetime, even in the absence of regeneration by B cells, implying the presence of long-lived PCs as a mechanism for long-lasting immunity. Evidence from humans treated with anti-CD20, which depletes circulating B cells, also suggests B-cell-independent long-term survival of some PCs. On the other hand, antibody responses may be sustained solely by short-lived PCs with repopulation from clonally related memory B cells. To explore PC longevity and humoral immunity in humans, we investigated the fate of PCs and their antibodies in adult and pediatric patients who received chimeric antigen receptor-based adoptive T-cell immunotherapy targeting CD19 to treat B-cell lineage malignancies (CTL019). Treatment with CTL019 is frequently associated with B-cell aplasia that can persist for years. Serum antibody titers to vaccine-related antigens were measured, and quantitative assessment of B cells and PCs in blood and bone marrow was performed at various time points before and after CTL019 therapy. While total serum immunoglobulin concentrations decline following CTL019-induced B-cell aplasia, several vaccine/pathogen-specific serum immunoglobulin G and A (IgG and IgA) titers remain relatively stable for at least 6 and 12 months posttreatment, respectively. Analysis of bone marrow biopsies after CTL019 revealed 8 patients with persistence of antibody-secreting PCs at least 25 months post-CTL019 infusion despite absence of CD19(+)CD20(+) B cells. These results provide strong evidence for the existence of memory B-cell-independent, long-lived PCs in humans that contribute to long-lasting humoral immunity.

Generation of Potent T-cell Immunotherapy for Cancer Using DAP12-Based, Multichain, Chimeric Immunoreceptors

Wang and colleagues describe a new multichain, chimeric antigen receptor (CAR) that uses portions of KIR2DS2 to engage DAP12, mimicking natural NK- and T-cell signaling. This new CAR triggers potent T-cell antitumor responses in vivo due to improved retention of CAR surface expression and effector function. Chimeric antigen receptors (CAR) bearing an antigen-binding domain linked in cis to the cytoplasmic domains of CD3ζ and costimulatory receptors have provided a potent method for engineering T-cell cytotoxicity toward B-cell leukemia and lymphoma. However, resistance to immunotherapy due to loss of T-cell effector function remains a significant barrier, especially in solid malignancies. We describe an alternative chimeric immunoreceptor design in which we have fused a single-chain variable fragment for antigen recognition to the transmembrane and cytoplasmic domains of KIR2DS2, a stimulatory killer immunoglobulin-like receptor (KIR). We show that this simple, KIR-based CAR (KIR-CAR) triggers robust antigen-specific proliferation and effector function in vitro when introduced into human T cells with DAP12, an immunotyrosine-based activation motifs-containing adaptor. T cells modified to express a KIR-CAR and DAP12 exhibit superior antitumor activity compared with standard first- and second-generation CD3ζ-based CARs in a xenograft model of mesothelioma highly resistant to immunotherapy. The enhanced antitumor activity is associated with improved retention of chimeric immunoreceptor expression and improved effector function of isolated tumor-infiltrating lymphocytes. These results support the exploration of KIR-CARs for adoptive T-cell immunotherapy, particularly in immunotherapy-resistant solid tumors. Cancer Immunol Res; 3(7); 815–26. ©2015 AACR.

Induction of resistance to chimeric antigen receptor T cell therapy by transduction of a single leukemic B cell.

We report a patient relapsing 9 months after CD19-targeted CAR T cell (CTL019) infusion with CD19– leukemia that aberrantly expressed the anti-CD19 CAR. The CAR gene was unintentionally introduced into a single leukemic B cell during T cell manufacturing, and its product bound in cis to the CD19 epitope on the surface of leukemic cells, masking it from recognition by and conferring resistance to CTL019.A CAR gene unintentionally introduced in a contaminating leukemia cell during the manufacturing of CAR T cells caused a patient to relapse after therapy.

The thrombotic microangiopathy Registry of North America: A United States multi-institutional TMA network.

The thrombotic microangiopathy (TMA) Registry Network of North America (TRNA) is a collaborative network organized for the purpose of developing a multi‐institutional registry and network to conduct clinical studies in a rare patient population. The TRNA was founded in 2013 by four academic medical centers (Columbia University Medical Center, Duke University Medical Center, University of Alabama at Birmingham, and University of Pennsylvania) to develop a national and demographically diverse dataset of patients with TMA. A clinical database was developed by network members using REDCap (Research Electronic Data Capture), a web‐based database developed for clinical research. To facilitate rapid Institutional Review Board (IRB) approval at multiple sites, the TRNA utilized IRBshare, a streamlined IRB process to allow patient recruitment and enrollment into the TMA registry. This article reviews the process used to establish the TRNA network and discusses the significance of the first multi‐institutional clinical apheresis network developed in the United States. J. Clin. Apheresis 31:448–453, 2016.

The Pharmacology of T Cell Therapies

Adoptive cellular therapy using T cells with tumor specificity derived from either natural T cell receptors (TCRs) or an artificial chimeric antigen receptor (CAR) has reached late phase clinical testing, with two CAR T cell therapies achieving regulatory approval within the United States in 2017. The effective use of these therapies depends upon an understanding of their pharmacology, which is quite divergent from traditional small molecule or biologic drugs. We review the different types of T cell therapy under clinical development, the factors affecting cellular kinetics following infusion, and the relationship between these cellular kinetics and anti-cancer activity. We also discuss the toxicity associated with T cell therapies, with an emphasis on cytokine release syndrome and neurotoxicity, and the gaps in knowledge regarding these frequent and unique adverse effects.

Abstract 2295: GDNF family receptor alpha 4 (GFRa4)-targeted adoptive T-cell immunotherapy for medullary thyroid carcinoma

Metastatic medullary thyroid cancer (MTC) is a rare, but often aggressive, thyroid malignancy with a 5-year survival rate of 28% and few effective therapeutic options. Adoptive T-cell immunotherapy using chimeric antigen receptor (CAR)-modified T cells (CARTs) is showing encouraging results in the treatment of cancer, but development is challenged by the availability of suitable target antigens. We identified glial-derived neurotrophic factor (GDNF) family receptor alpha 4 (GFRα4), which associates with the RET receptor tyrosine kinase, as a putative antigenic target for CAR-based therapy of MTC. Using RNA in situ hybridization (RNAscope) and quantitative RT-PCR, we show that GFRα4 is highly expressed in MTC. Normal tissue expression of GFRα4 mRNA is restricted to parafollicular cells (C-cells) within the thyroid, the normal cell type from which MTC originates, and normal thymus.Based upon the highly restricted expression, we generated two high affinity single chain variable fragments (scFvs) targeting GFRα4 isoforms a and b by selecting a naive rabbit antibody library by phage display. Second generation CARs bearing the CD137 costimulatory domain were constructed using these GFRα4-specific scFvs. GFRα4-specific CARTs trigger antigen-dependent cytotoxicity and cytokine production in vitro, and they are able to control pre-established TT cell tumors in an immunodeficient mouse xenograft model of MTC. These data demonstrate the feasibility of targeting GFRα4 by CARTs, and support this molecule as a promising target for adoptive T cell immunotherapy and other antibody-based therapy of MTC. Citation Format: Vijay G. Bhoj, Selene Nunez-Cruz, Kenneth Zhou, Dimitrios Arhontoulis, Michael Feldman, Keith Mansfield, Haiyong Peng, Christoph Rader, Don L. Siegel, Michael C. Milone. GDNF family receptor alpha 4 (GFRa4)-targeted adoptive T-cell immunotherapy for medullary thyroid carcinoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2295.

399. Evaluation of CD123 Targeting CART Cells in Non-Human Primates

The CAR-T platform has provided an exceptionally potent means to treat cancers that have proven resistant to standard treatments. This potency, however, can work against normal tissue as well. Some clinical trials have identified adverse consequences as a result of CAR-T cell targeting of critical normal tissue. To enable as many targets as possible using the CAR-T cell approach, it is important to understand the potential liabilities of those targets in normal tissues prior to initiating clinical trials. CD123, the IL-3 receptor alpha subunit, is a viable target for treatment of acute myeloid leukemia, as it is expressed highly on primary AML blasts. We have previously shown that, in mice transplanted with human hematopoietic stem cells, CD123 targeting CAR T-cells eradicated these precursors and, in turn, normal hematopoiesis (Gill et al 2014xPreclinical targeting of human acute myeloid leukemia and myeloablation using chimeric antigen receptor-modified T cells. Gill, Saar, Tasian, Sarah K., Ruella, Marco, Shestova, Olga, Li, Yong, Porter, David L., Carroll, Martin, Danet-Desnoyers, Gwenn, Scholler, John, Grupp, Stephan A., June, Carl H., and Kalos, Michael. Blood. 2014; 123: 2343–2354Crossref | PubMed | Scopus (120)See all ReferencesGill et al 2014). Here, we describe an animal model developed to address the potential effects of targeting CD123 on non-hematopoietic tissue, namely endothelial cells that are found to express significant levels of CD123. An scFv that bound cynomolgus monkey CD123 was identified and a chimeric lentivirus that efficiently transduced monkey PBMCs was developed. Cells were demonstrated to be active in vitro and dosed into monkeys, after which cellular expansion was observed. In vivo safety assessments and histopathology results will be discussed.