Crystal L. Mackall

Tumor Regression in Patients With Metastatic Synovial Cell Sarcoma and Melanoma Using Genetically Engineered Lymphocytes Reactive With NY-ESO-1

PURPOSE Adoptive immunotherapy using tumor-infiltrating lymphocytes represents an effective cancer treatment for patients with metastatic melanoma. The NY-ESO-1 cancer/testis antigen, which is expressed in 80% of patients with synovial cell sarcoma and approximately 25% of patients with melanoma and common epithelial tumors, represents an attractive target for immune-based therapies. The current trial was carried out to evaluate the ability of adoptively transferred autologous T cells transduced with a T-cell receptor (TCR) directed against NY-ESO-1 to mediate tumor regression in patients with metastatic melanoma and synovial cell sarcoma. PATIENTS AND METHODS A clinical trial was performed in patients with metastatic melanoma or metastatic synovial cell sarcoma refractory to all standard treatments. Patients with NY-ESO-1-positive tumors were treated with autologous TCR-transduced T cells plus 720,000 iU/kg of interleukin-2 to tolerance after preparative chemotherapy. Objective clinical responses were evaluated using Response Evaluation Criteria in Solid Tumors (RECIST). RESULTS Objective clinical responses were observed in four of six patients with synovial cell sarcoma and five of 11 patients with melanoma bearing tumors expressing NY-ESO-1. Two of 11 patients with melanoma demonstrated complete regressions that persisted after 1 year. A partial response lasting 18 months was observed in one patient with synovial cell sarcoma. CONCLUSION These observations indicate that TCR-based gene therapies directed against NY-ESO-1 represent a new and effective therapeutic approach for patients with melanoma and synovial cell sarcoma. To our knowledge, this represents the first demonstration of the successful treatment of a nonmelanoma tumor using TCR-transduced T cells.

T cells expressing CD19 chimeric antigen receptors for acute lymphoblastic leukaemia in children and young adults: a phase 1 dose-escalation trial.

BACKGROUND Chimeric antigen receptor (CAR) modified T cells targeting CD19 have shown activity in case series of patients with acute and chronic lymphocytic leukaemia and B-cell lymphomas, but feasibility, toxicity, and response rates of consecutively enrolled patients treated with a consistent regimen and assessed on an intention-to-treat basis have not been reported. We aimed to define feasibility, toxicity, maximum tolerated dose, response rate, and biological correlates of response in children and young adults with refractory B-cell malignancies treated with CD19-CAR T cells. METHODS This phase 1, dose-escalation trial consecutively enrolled children and young adults (aged 1-30 years) with relapsed or refractory acute lymphoblastic leukaemia or non-Hodgkin lymphoma. Autologous T cells were engineered via an 11-day manufacturing process to express a CD19-CAR incorporating an anti-CD19 single-chain variable fragment plus TCR zeta and CD28 signalling domains. All patients received fludarabine and cyclophosphamide before a single infusion of CD19-CAR T cells. Using a standard 3 + 3 design to establish the maximum tolerated dose, patients received either 1 × 10(6) CAR-transduced T cells per kg (dose 1), 3 × 10(6) CAR-transduced T cells per kg (dose 2), or the entire CAR T-cell product if sufficient numbers of cells to meet the assigned dose were not generated. After the dose-escalation phase, an expansion cohort was treated at the maximum tolerated dose. The trial is registered with ClinicalTrials.gov, number NCT01593696. FINDINGS Between July 2, 2012, and June 20, 2014, 21 patients (including eight who had previously undergone allogeneic haematopoietic stem-cell transplantation) were enrolled and infused with CD19-CAR T cells. 19 received the prescribed dose of CD19-CAR T cells, whereas the assigned dose concentration could not be generated for two patients (90% feasible). All patients enrolled were assessed for response. The maximum tolerated dose was defined as 1 × 10(6) CD19-CAR T cells per kg. All toxicities were fully reversible, with the most severe being grade 4 cytokine release syndrome that occurred in three (14%) of 21 patients (95% CI 3·0-36·3). The most common non-haematological grade 3 adverse events were fever (nine [43%] of 21 patients), hypokalaemia (nine [43%] of 21 patients), fever and neutropenia (eight [38%] of 21 patients), and cytokine release syndrome (three [14%) of 21 patients). INTERPRETATION CD19-CAR T cell therapy is feasible, safe, and mediates potent anti-leukaemic activity in children and young adults with chemotherapy-resistant B-precursor acute lymphoblastic leukaemia. All toxicities were reversible and prolonged B-cell aplasia did not occur. FUNDING National Institutes of Health Intramural funds and St Baldricks Foundation.

The Many Faces of IL-7: From Lymphopoiesis to Peripheral T Cell Maintenance

IL-7 is well known as a lymphopoietic cytokine, but recent studies have also identified a critical role for IL-7 in peripheral T cell homeostasis. IL-7 is well poised to serve as a homeostatic cytokine because it is produced by resting stromal cells, the IL-7R is present on most T cells, and IL-7 down-regulates its own receptor. These features allow IL-7 to signal large numbers of resting T cells and to be efficiently used when supplies are limiting. Consistent with this, in normal hosts, IL-7 is required for survival of naive T cell populations, and IL-7 contributes to homeostatic cycling of naive and memory cells. In addition, lymphopenic hosts accumulate increased levels of IL-7, and the supranormal levels are largely responsible for inducing homeostatic peripheral expansion in response to lymphopenia. Thus, IL-7 plays critical and nonredundant roles in both T cell lymphopoiesis and in maintaining and restoring peripheral T cell homeostasis.

Current concepts in the diagnosis and management of cytokine release syndrome

As immune-based therapies for cancer become potent, more effective, and more widely available, optimal management of their unique toxicities becomes increasingly important. Cytokine release syndrome (CRS) is a potentially life-threatening toxicity that has been observed following administration of natural and bispecific antibodies and, more recently, following adoptive T-cell therapies for cancer. CRS is associated with elevated circulating levels of several cytokines including interleukin (IL)-6 and interferon γ, and uncontrolled studies demonstrate that immunosuppression using tocilizumab, an anti-IL-6 receptor antibody, with or without corticosteroids, can reverse the syndrome. However, because early and aggressive immunosuppression could limit the efficacy of the immunotherapy, current approaches seek to limit administration of immunosuppressive therapy to patients at risk for life-threatening consequences of the syndrome. This report presents a novel system to grade the severity of CRS in individual patients and a treatment algorithm for management of CRS based on severity. The goal of our approach is to maximize the chance for therapeutic benefit from the immunotherapy while minimizing the risk for life threatening complications of CRS.

Lymphopenia and interleukin-2 therapy alter homeostasis of CD4+CD25+ regulatory T cells

CD4+CD25+ regulatory T (Treg) cells have a crucial role in maintaining immune tolerance. Mice and humans born lacking Treg cells develop severe autoimmune disease, and depletion of Treg cells in lymphopenic mice induces autoimmunity. Interleukin (IL)-2 signaling is required for thymic development, peripheral expansion and suppressive activity of Treg cells. Animals lacking IL-2 die of autoimmunity, which is prevented by administration of IL-2–responsive Treg cells. In light of the emerging evidence that one of the primary physiologic roles of IL-2 is to generate and maintain Treg cells, the question arises as to the effects of IL-2 therapy on them. We monitored Treg cells during immune reconstitution in individuals with cancer who did or did not receive IL-2 therapy. CD4+CD25hi cells underwent homeostatic peripheral expansion during immune reconstitution, and in lymphopenic individuals receiving IL-2, the Treg cell compartment was markedly increased. Mouse studies showed that IL-2 therapy induced expansion of existent Treg cells in normal hosts, and IL-2–induced Treg cell expansion was further augmented by lymphopenia. On a per-cell basis, Treg cells generated by IL-2 therapy expressed similar levels of FOXP3 and had similar potency for suppression compared to Treg cells present in normal hosts. These studies suggest that IL-2 and lymphopenia are primary modulators of CD4+CD25+ Treg cell homeostasis.

IL-7 administration to humans leads to expansion of CD8+ and CD4+ cells but a relative decrease of CD4+ T-regulatory cells

Lymphopenia is a serious consequence of HIV infection and the administration of cancer chemotherapeutic agents. Although growth factors can be administered to patients to increase circulating neutrophils, there is no effective method to stimulate CD8+ lymphocyte production in humans, in vivo. This report is the first to describe the administration of recombinant interleukin-7 to humans and demonstrates the ability of this cytokine to mediate selective increases in CD4+ and CD8+ lymphocytes along with a decrease in the percentage of CD4+ T-regulatory cells. These studies suggest an important role for interleukin-7 in the treatment of patients with lymphopenia.

Harnessing the biology of IL-7 for therapeutic application.

Interleukin-7 (IL-7) is required for T cell development and for maintaining and restoring homeostasis of mature T cells. IL-7 is a limiting resource under normal conditions, but it accumulates during lymphopaenia, leading to increased T cell proliferation. The administration of recombinant human IL-7 to normal or lymphopenic mice, non-human primates and humans results in widespread T cell proliferation, increased T cell numbers, modulation of peripheral T cell subsets and increased T cell receptor repertoire diversity. These effects raise the prospect that IL-7 could mediate therapeutic benefits in several clinical settings. This Review summarizes the biology of IL-7 and the results of its clinical use that are available so far to provide a perspective on the opportunities for clinical application of this cytokine.

4-1BB Costimulation Ameliorates T Cell Exhaustion Induced by Tonic Signaling of Chimeric Antigen Receptors

Chimeric antigen receptors (CARs) targeting CD19 have mediated dramatic antitumor responses in hematologic malignancies, but tumor regression has rarely occurred using CARs targeting other antigens. It remains unknown whether the impressive effects of CD19 CARs relate to greater susceptibility of hematologic malignancies to CAR therapies, or superior functionality of the CD19 CAR itself. We show that tonic CAR CD3-ζ phosphorylation, triggered by antigen-independent clustering of CAR single-chain variable fragments, can induce early exhaustion of CAR T cells that limits antitumor efficacy. Such activation is present to varying degrees in all CARs studied, except the highly effective CD19 CAR. We further determine that CD28 costimulation augments, whereas 4-1BB costimulation reduces, exhaustion induced by persistent CAR signaling. Our results provide biological explanations for the antitumor effects of CD19 CARs and for the observations that CD19 CAR T cells incorporating the 4-1BB costimulatory domain are more persistent than those incorporating CD28 in clinical trials.

Interleukin-7: master regulator of peripheral T-cell homeostasis?

Recent evidence has implicated interleukin-7 (IL-7) as a master regulator of T-cell homeostasis, based upon its essential role in the homeostatic expansion of naive T-cell populations in response to low-affinity antigens (Ags) and its capacity to enhance dramatically the expansion of peripheral T-cell populations in response to high-affinity Ags. Furthermore, T-cell-depleted humans have a unique inverse relationship between the peripheral CD4(+) T-cell count and the level of circulating IL-7. Together, these data suggest that increased amounts of IL-7 become available following T-cell depletion, thus, enhancing the high- and low-affinity Ag-driven expansion of the population of residual, mature T cells and boosting thymic regenerative capacity, as a means to restore T-cell homeostasis.

Pathways of T-cell regeneration in mice and humans : implications for bone marrow transplantation and immmunotherapy

Summary: Much of our understanding of the immunobiology of bone marrow transplantation (BMT) has come from studies in young adult mice reconstituted with T‐cell‐depleted bone marrow after lethal irradiation. Recent evidence indicates, however, that the applicability of conclusions drawn from this model to human BMT may be limited. While mice retain essentially normal thymic function well past sexual maturity, humans show significant age‐related declines in thymic function age‐early in life. Therefore, thymic‐deficient mice may provide a more accurate model for study of the immunobiology of BMT T‐cell regeneration in thymic‐deficient mice occurs primarily via antigen‐driven expansion of mature peripheral T cells resulting m limited immune competence due to quantitative deficiencies in T‐cell number and severe restriction in the diversity of the regenerated T‐cell receptor (TCR) repertoire. Similarly, immune reconstitution in adult humans after BMT is marked by quantitative T‐cell deficiencies, especially in the CD4+ subset, and loss of TCR diversity. Taken together, prevailing evidence suggests that thymic function is suboptimal in most BMT recipients, and that thymic‐independent pathways of T‐cell regeneration are generally limited in their ability to restore host immune competence. New strategies to enhance thymic function in man after BMT would hold great therapeutic potential.