New Orders to an Old Soldier: Optimizing NK Cells for Adoptive Immunotherapy in Hematology.

NK (Natural Killer) cell-mediated adoptive immunotherapy has gained attention in hematology due to the progressing knowledge of NK cell receptor structure, biology and function. Today, challenges related to NK cell expansion and persistence in vivo as well as low cytotoxicity have been mostly overcome by pioneering trials that focused on harnessing NK cell functions. Recent technological advancements in gene delivery, gene editing and chimeric antigen receptors (CARs) have made it possible to generate genetically modified NK cells that enhance the anti-tumor efficacy and represent suitable "off-the-shelf" products with fewer side effects. In this review, we highlight recent advances in NK cell biology along with current approaches for potentiating NK cell proliferation and activity, redirecting NK cells using CARs and optimizing the procedure to manufacture clinical-grade NK and CAR NK cells for adoptive immunotherapy.

Engineered off-the-shelf therapeutic T cells resist host immune rejection.

Engineered T cells are effective therapies against a range of malignancies, but current approaches rely on autologous T cells, which are difficult and expensive to manufacture. Efforts to develop potent allogeneic T cells that are not rejected by the recipient's immune system require abrogating both T- and natural killer (NK)-cell responses, which eliminate foreign cells through various mechanisms. In the present study, we engineered a receptor that mediates deletion of activated host T and NK cells, preventing rejection of allogeneic T cells. Our alloimmune defense receptor (ADR) selectively recognizes 4-1BB, a cell surface receptor temporarily upregulated by activated lymphocytes. ADR-expressing T cells resist cellular rejection by targeting alloreactive lymphocytes in vitro and in vivo, while sparing resting lymphocytes. Cells co-expressing chimeric antigen receptors and ADRs persisted in mice and produced sustained tumor eradication in two mouse models of allogeneic T-cell therapy of hematopoietic and solid cancers. This approach enables generation of rejection-resistant, 'off-the-shelf', allogeneic T-cell products to produce long-term therapeutic benefit in immunocompetent recipients.

Modulating TNFα activity allows transgenic IL15-Expressing CLL-1 CAR T cells to safely eliminate acute myeloid leukemia.

BACKGROUND: C-type lectin-like molecule 1 (CLL-1) is highly expressed in acute myeloid leukemia (AML) but is absent in primitive hematopoietic progenitors, making it an attractive target for a chimeric antigen receptor (CAR) T-cell therapy. Here, we optimized our CLL-1 CAR for anti-leukemic activity in mouse xenograft models of aggressive AML. METHODS: First, we optimized the CLL-1 CAR using different spacer, transmembrane and costimulatory sequences. We used a second retroviral vector to coexpress transgenic IL15. We measured the effects of each construct on T cell phenotype and sequential (recursive) co culture assays with tumor cell targets to determine the durability of the anti tumor activity by flow cytometry. We administered CAR T cells to mice engrafted with patient derived xenografts (PDX) and AML cell line and determined anti tumor activity by bioluminescence imaging and weekly bleeding, measured serum cytokines by multiplex analysis. After euthanasia, we examined formalin-fixed/paraffin embedded sections. Unpaired two-tailed Student's t-tests were used and values of p<0.05 were considered significant. Survival was calculated using Mantel-Cox log-rank test. RESULTS: In vitro, CLL-1 CAR T cells with interleukin-15 (IL15) were less terminally differentiated (p<0.0001) and had superior expansion compared with CD28z-CD8 CAR T cells without IL15 (p<0.001). In both AML PDX and AML cell line animal models, CLL-1 CAR T coexpressing transgenic IL15 initially expanded better than CD28z-CD8 CAR T without IL15 (p<0.0001), but produced severe acute toxicity associated with high level production of human tumor necrosis factor α (TNFα), IL15 and IL2. Histopathology showed marked inflammatory changes with tissue damage in lung and liver. This acute toxicity could be managed by two strategies, individually or in combination. The excessive TNF alpha secretion could be blocked with anti-TNF alpha antibody, while excessive T cell expansion could be arrested by activation of an inducible caspase nine safety switch by administration of dimerizing drug. Both strategies successfully prolonged tumor-free survival. CONCLUSION: Combinatorial treatment with a TNFα blocking antibody and subsequent activation of the caspase-9 control switch increased the expansion, survival and antileukemic potency of CLL-1 CAR T-cells expressing transgenic IL15 while avoiding the toxicities associated with excessive cytokine production and long-term accumulation of activated T-cells.

Thyroid dysfunctions in adult patients after allogeneic hematopoietic stem cell transplantation.

INTRODUCTION: Thyroid dysfunction (TD) is one of the major endocrinopathies shown after allogeneic hematopoietic stem cell transplantation over the long term. The incidence and the risk factors for TD have varied widely. PATIENTS AND METHODS: Two hundred and fifty-nine patients with pre-transplant normal thyroid function tests who survived at least 1 year after allo-HSCT between 2006-2016 were included in the study. RESULTS: Sixty-four patients (25%) developed TD at median of 34 months (range, 1-112 months). Hypothyroidism was detected in 32 patients (12%): 5 patients had primary hypothyroidism, and subclinical hypothyroidism occurred in 27 patients. 18 patients (7%) were diagnosed with hyperthyroidism: 2 patients (0.07%) were treated for primary hyperthyroidism, and 16 patients (6%) were followed for subclinical hyperthyroidism. Euthyroid sick syndrome occurred in 14 cases. None of the patients with thyroid dysfunction developed secondary thyroid malignancy. Receiving high-dose TBI (P = .001) was found to be significant risk for hypothyroidism; older age than median (P = .01) and pre-transplant active disease (P < .0001) were related to hyperthyroidism. CONCLUSIONS: Thyroid dysfunction, mostly hypothyroidism, is a long-term complication after allo-HSCT in 25% of patients. Older age, pre-transplant active disease, and receiving TBI are among the risk factors. Sustained long-term monitoring of thyroid function test should be considered post allo-HSCT.

Prospective Analysis of Hemorrhagic Cystitis and BK Viremia in Allogeneic Hematopoietic Stem Cell Transplantation

Objective: BK virus (BKV) infection has been shown to be related to hemorrhagic cystitis (HC) in allogeneic hematopoietic stem cell transplantation (allo-HSCT). There are conflicting data regarding the association between BKV titers in plasma and clinical disease as well as the risk factors for BKV-related HC. Our aim is to study the risk factors and relationship with plasma BK viral load for development of HC in a prospective analysis. Materials and Methods: We prospectively evaluated 59 patients who received allo-HSCT between 2014 and 2016 by quantitative BK virus polymerase chain reaction (PCR) (Altona Diagnostics, Germany) from blood samples at days 0, 30, 60, and 90 after allo-HSCT. The patients were monitored for signs and symptoms of HC. Results: HC was diagnosed in 22 patients (37%) at a mean of 100 days (range: 0-367 days). In multivariate analysis, the usage of cyclophosphamide (sub-distribution hazard ratio [sdHR]: 7.82, confidence interval [CI]: 1.375-39.645, p=0.02), reactivated CMV (sdHR: 6.105, CI: 1.614-23.094, p=0.008), and positive BKV viremia (sdHR: 2.15, CI: 1.456-22.065, p=0.01) significantly increased the risk of developing HC. Patients with higher viral loads at day 30 and day 60 were diagnosed with more severe HC (p<0.001). Median BK viral loads of >101.5 copies/mL at day 0 (sensitivity 0.727, specificity 0.875), >98.5 copies/mL at day 30 (sensitivity 0.909, specificity 0.875), and >90.0 copies/mL at day 60 (sensitivity 0.909, specificity 0.875) were indicative of HC. Conclusion: Our study showed that administration of cyclophosphamide, CMV reactivation, and BK virus positivity were associated with HC. Plasma BK virus PCR titers at days 0, 30, and 60 after transplant were sensitive tools for predicting clinically proven HC.

Hepatitis B Reactivation Rate and Fate Among Multiple Myeloma Patients Receiving Regimens Containing Lenalidomide and/or Bortezomib

Objective: Reactivation of the hepatitis B virus (HBV) refers to an increase in HBV replication in a patient with inactive or resolved HBV. In this retrospective study, our aim is to present and compare HBV reactivation in multiple myeloma (MM) patients who received lenalidomide and/or bortezomib at any time during treatment, evaluate the factors associated with reactivation, and demonstrate the outcome of patients. Materials and Methods: We evaluated 178 MM patients who received lenalidomide (n=102) and/or bortezomib (n=174) during their treatment schedules. The HBsAg, anti-HBc, anti-HBs, HBeAg, and anti-HBe were detected by chemiluminescence by ARCHITECT lab analyzers using commercially available kits (Abbott, USA). HBV-DNA titers were determined by quantitative PCR. The results were evaluated by IBM SPSS Statistics for Windows, Version 20.0 (IBM Corp., Armonk, NY, USA). Results: HBV reactivation was diagnosed in 6 patients (3%) after bortezomib and in 8 patients (8%) after bortezomib and lenalidomide. Three of the patients in each group had HBsAg+, HBeAg+, AntiHBeAg-, AntiHBc-, and AntiHBS+ status, whereas 5 patients in the bortezomib- and lenalidomide-treated group and 3 patients in the bortezomib-treated group had HBsAg-, HBeAg-, AntiHBeAg-, AntiHBc-, and AntiHBS+ status prior to treatment. There were no statistical differences observed between HBV reactivation in the bortezomib-treated or bortezomib- and lenalidomide-treated groups in terms of age at diagnosis, sex, International Staging System subtype, frequency of extramedullary disease, dialysis requirement, or receiving of autologous stem cell transplantation. In patients who received antiviral prophylaxis, a higher incidence of HBV reactivation was detected in HBsAg-positive patients compared to HBsAg-negative patients (4/4, 100% vs. 2/7, 29%; p=0.045). The 3-year and 5-year overall survival rates were similar in patients with or without HBV reactivation (83% vs. 84%, 73% vs. 74%, p=0.84). Conclusion: Close follow-up is recommended for not only HBsAg-positive but also HBsAg-negative patients.

Current approach to early gastrointestinal and liver complications of hematopoietic stem cell transplantation.

The gastrointestinal (GI) system is one of the most commonly affected sites during a hematopoietic stem cell transplantation (HSCT) due to toxicities of preparative regimens, the accompanying immunodeficiency, and organ damage caused by graft versus host disease. In this review, we focus on early GI and liver complications following autologous (auto-) and allogeneic (allo-) HSCT and clarify both the risk factors and therapeutic strategies. Early GI and liver complications associated with HSCT remain challenging issues. Despite the improvements in this field during the last decade, treatments for these complications still place a significant burden on both patients and the physicians treating these patients. GI and liver complications remain some of the causes of mortality associated with HSCT. For practicing hematologists, oncologists, and gastroenterologists in this field, the awareness and early diagnosis of the GI complications remain important factors to obtain optimal outcomes in this patient population.

A Review of Myeloablative vs Reduced Intensity/Non-Myeloablative Regimens in Allogeneic Hematopoietic Stem Cell Transplantations.

Allogeneic hematopoietic stem cell transplantation (Allo-HSCT) is a curative treatment option for both malignant and some benign hematological diseases. During the last decade, many of the newer high-dose regimens in different intensity have been developed specifically for patients with hematologic malignancies and solid tumors. Today there are three main approaches used prior to allogeneic transplantation: Myeloablative (MA), Reduced Intensity Conditioning (RIC) and Non-MA (NMA) regimens. MA regimens cause irreversible cytopenia and there is a requirement for stem cell support. Patients who receive NMA regimen have minimal cytopenia and this type of regimen can be given without stem cell support. RIC regimens do not fit the criteria of MA and NMA: the cytopenia is reversible and the stem cell support is necessary. NMA/RIC for Allo-HSCT has opened a new era for treating elderly patients and those with comorbidities. The RIC conditioning was used for 40% of all Allo-HSCT and this trend continue to increase. In this paper, we will review these regimens in the setting of especially allogeneic HSCT and our aim is to describe the history, features and impact of these conditioning regimens on specific diseases.

How to manage poor mobilizers for high dose chemotherapy and autologous stem cell transplantation?

Today, peripheral blood stem cells are the preferred source of stem cells over bone marrow. Therefore, mobilization plays a crutial role in successful autologous stem cell transplantation. Poor mobilization is generally defined as failure to achieve the target level of at least 2×106 CD34+ cells/kg body weight. There are several strategies to overcome poor mobilization: 1) Larger volume Leukapheresis (LVL) 2) Re-mobilization 3) Plerixafor 4) CM+Plerixafor (P)+G-CSF and 5) Bone Marrow Harvest. In this review, the definitions of successful and poor mobilization are discussed. Management strategies for poor mobilization are defined. The recent research on new agents are included.

An overview of hematopoietic stem cell transplantation related thrombotic complications.

Thrombotic episodes are far less common than bleeding complications after hematopoietic stem cell transplantation (HSCT). However, they lead to significant morbidity and mortality. These complications are classified into four groups, including venous thromboembolic events (VTE), catheter-induced thrombosis (CIT), transplant-associated thrombotic microangiopathy (TA-TMA) and sinusoidal obstruction syndrome (SOS) or veno-occlusive disease (VOD). The frequency of VTE is increased among patients undergoing HSCT due to some acquired conditions including underlying malignancy, infections, administration of myeloablative conditioning regimens and/or total body irradiation, prolonged hospitalizations leading to immobility and presence of central venous catheters. Central venous catheters provide a convenient long-term venous access during HSCT. But they may lead to VTE and related complications such as pulmonary embolism or post-thrombotic syndrome by inducing endothelial trauma and inflammation. TA-TMA is a heterogeneous, fatal disorder seen within 100days post-transplant and presents with thrombocytopenia, hemolysis, acute renal failure, mental status changes and involvement of other organs. SOS or VOD is another life threatening complication occuring within the first 35-40days following a myeloablative regimen and presents with painful hepatomegaly, weight gain and elevated serum bilirubin levels. In this review, we aimed to define the epidemiology, specific risk factors, prevention and management of each group of complications in view of the recent relevant literature.