Immune Effector Cell Therapies Research Articles

Expanding the Role of CAR-T Cell Therapy to Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a chronic inflammatory autoimmune disorder resulting from autoantibodies produced by B-cell derived plasma cells. Clinical presentation ranges from mild skin rash to multiorgan failure. Regardless of the clinical presentation or severity of the disease, patients with SLE often require life-long treatment. Current treatment recommendations for SLE include hydroxychloroquine, glucocorticoids, immunomodulatory agents, cyclophosphamide, and biologic agents. Despite availability of these agents, the condition of some patients with SLE progressively worsens. With limited treatment options, new and novel therapeutic approaches are needed. Given the active role of B cells in the pathophysiology of SLE, they present an attractive target for therapies evolving in the oncology field. Amongst these, immune effector cell therapies, including chimeric antigen receptor (CAR)-T cell therapy, have proven beneficial in targeting B cells. The eradication of B cells, along with the potential for T cell persistence, has resulted in prolonged remission or stable disease. This review provides an overview of the pathophysiology of SLE; current treatment options, including monoclonal antibodies targeting cluster of differentiation-20 (CD20), CD22, and B cell-activating factor (BAFF); and explores why and how immune effector cell therapies may prove a promising therapeutic option for this patient population, particularly for individuals with refractory disease. Clinical implications from currently approved U.S. Food and Drug Administration (FDA) agents for haematologic malignancies are discussed and provide insight into considerations for applying this therapy to the patient population with SLE in the context of clinical trials.

Chimeric Antigen Receptor Therapy: How Are We Driving in Solid Tumors?

Immune effector cell (IEC) therapy is emerging as a promising approach in the field of cancer immunotherapy. Clinical IEC trials, predominantly using chimeric antigen receptor (CAR) T cells, have shown excellent responses in CD19+ B cell malignancies and multiple myeloma. In solid tumors, preclinical data are encouraging, but clinical data are in their infancy, and there are challenges in using CAR T therapy in this setting, including (1) on-target off-tumor toxicity, (2) optimal target identification, (3) effective trafficking into bulky tumor tissue, and (4) resistance to tumor immune evasion mechanisms. Novel techniques and modifications are being explored in both the preclinical and clinical settings, aiming to improve treatment efficacy and address the aforementioned obstacles to successful CAR T therapy in solid tumors. Here we review these challenges in a clinically oriented approach and summarize published clinical trials using CAR T therapy in a variety of solid tumors.

Indications for Hematopoietic Cell Transplantation and Immune Effector Cell Therapy: Guidelines from the American Society for Transplantation and Cellular Therapy.

The American Society for Transplantation and Cellular Therapy (ASTCT) published its first white paper on indications for autologous and allogeneic hematopoietic cell transplantation (HCT) in 2015. It was identified at the time that periodic updates of indications would be required to stay abreast with state of the art and emerging indications and therapy. In recent years the field has not only seen an improvement in transplantation technology, thus widening the therapeutic scope of HCT, but additionally a whole new treatment strategy using modified immune effector cells, including chimeric antigen receptor T cells and engineered T-cell receptors, has emerged. The guidelines review committee of the ASTCT deemed it optimal to update the ASTCT recommendations for indications for HCT to include new data and to incorporate indications for immune effector cell therapy (IECT) where appropriate. The guidelines committee established a multiple stakeholder task force consisting of transplant experts, payer representatives, and a patient advocate to provide guidance on indications for HCT and IECT. This article presents the updated recommendations from the ASTCT on indications for HCT and IECT. Indications for HCT/IECT were categorized as (1) Standard of care, where indication is well defined and supported by evidence; (2) Standard of care, clinical evidence available, where large clinical trials and observational studies are not available but have been shown to be effective therapy; (3) Standard of care, rare indication, for rare diseases where demonstrated effectiveness exists but large clinical trials and observational studies are not feasible; (4) Developmental, for diseases where preclinical and/or early-phase clinical studies show HCT/IECT to be a promising treatment option; and (5) Not generally recommended, where available evidence does not support the routine use of HCT/IECT. The ASTCT will continue to periodically review these guidelines and update them as new evidence becomes available.

Patient Discharge Process Following Immune Effector Cell Therapy

Topic Significance & Study Purpose/Background/Rationale A Comprehensive Cancer Center (CCC) providing cellular immunotherapy treatments developed a standardized discharge process to ensure optimal continuity of care following immune effector cell (IEC) therapy. As utilization of IEC therapies increases, it is imperative to have an outlined comprehensive discharge plan to promote continuity of care, treatment-specific follow up, and ensure both patient and referring provider feel confident to assume follow-up care. Nurses are pivotal to this process development and implementation. Methods, Intervention, & Analysis Our center established a standardized discharge process which includes a summary conference where the attending physician and nurse coordinator outline the patient's treatment course, response to therapy and future treatment recommendations. Following the conference, the patient is seen in clinic as a final clinic visit to ensure patient understanding of discharge instructions. To ensure continuity, the nurse coordinator is present at all patient appointments. Education at these appointments include symptom management after discharge, medications, vaccination recommendations, and management of potential long-term side effects. A discharge packet with hardcopies of medical records and contact information is given to the patient and the referring provider. A phone call between the CCC attending provider and referring provider also occurs. Findings & Interpretation The comprehensive discharge process provides receiving providers with clinical and logistical information to support a successful transition plan for patients, and ensure the patients’ comprehensive understanding of their discharge summary and follow up plan. The development of an IEC Long Term Follow Up program is underway to ensure comprehensive follow up care for patients and to serve as a resource for referring providers following discharge. Discussion & Implications Nurses are on the forefront of caring for these novel IEC patients and play an integral role in the comprehensive, multidisciplinary discharge and follow up process. This includes reinforcing education regarding IEC therapy to patients and home facilities as well as providing clinical and logistical considerations essential for a successful transition home for patients.

Connecting on a Cellular Level

Topic Significance & Study Purpose/Background/Rationale • With the increase in Immune Effector Cell (IEC) technology in both research and clinical settings, clinicians are challenged with the task of treating acute known adverse events, including cytokine release syndrome (CRS) and IEC-associated neurotoxicity syndrome (ICANS), along with the determining and managing long-term complications of IEC therapies, many of which are unknown. Methods, Intervention, & Analysis • Initiate a standardized protocol for early intervention of treatment for CRS and ICANS with recommendations by the ASTCT (American Society of Transplant and Cellular Therapy). • Create an institutional framework for an IEC therapy long-term follow up clinic for. • Collect data on long-term adverse events post-IEC therapy and subsequently develop a standardized approach to appropriately diagnose and treat this patient population. Findings & Interpretation • The logistics of treating a patient with IEC therapy through clinical trials has helped standardize the process with commercial therapies. • Through IEC clinical research, acute care of adverse events has informed clinical care with commercial products and these lessons will inform long-term follow up care of this patient population. • The need for a dedicated long-term IEC follow up clinic, with specialized clinicians, has been identified to appropriately follow and treat side effects as needed. • The ever-increasing amount of data on patients that have received IEC therapies will continue to shape how these patients are followed in the future. • Focus on the long-term needs of IEC therapy patients will include: immunizations, hypogammaglobulinemia, HIV/other viral reactivation, increased infections, etc. Discussion & Implications • The vision of creating a long-term follow up clinic with dedicated clinicians to help create a standardized approach to surveillance of IEC patients post-therapy is undergoing feasibility assessment. • The integrated approach to implementing clinical trials processes within the commercial IEC environment has helped shape the way we treat and follow up with this patient population. With the lack of long-term data on late breaking side effects that may arise, these IEC patients should be followed by a specialized team/clinic to increase positive patient outcomes.

Building and Sailing the Ship Simultaneously: A Programmatic Ecosystem for Cellular Based Therapies

Topic Significance & Study Purpose/Background/Rationale Immune effector cell (IEC) therapy is a rapidly changing scientific frontier. IEC therapies represent a significant novel opportunity to reduce morbidity and mortality of cancer. The complexity of developing these first-in-human therapies requires multidisciplinary engagement and infrastructure development beyond the scope of traditional modalities. In a large academic center, a need was identified to move these novel therapies from the bench to the bedside through a nurse led administration. Methods, Intervention, & Analysis Nursing led multi-disciplinary programmatic ecosystems supporting early phase clinical research, is essential for advancement of science and patient safety. The multidisciplinary ecosystem for IECs was designed to include 4 structured forums: Cell Therapy Forum, Clinical Trial Advisory Committee, Clinical Research Operations Meeting, and the Clinical Program Meeting. 1) The Cell Therapy Forum promotes early scientific development by engaging cross-divisional collaborations between faculty investigators to develop IEC therapies. 2) Prioritization of new IEC trials is accomplished in The Clinical Trial Advisory Committee; proposed trials are reviewed for scientific merit, and operational feasibility, with representation from investigators and administrative leaders. 3) Monitoring of the system wide IEC portfolio for compliance and safety issues is overseen by The Clinical Research Operations Meeting, with research, clinical, manufacturing, and administrative staff. 4) The Clinical Program Meeting is the platform for education and collaboration on policies and decision making for program development. Each of the 4 forums have a distinct and valuable role in influencing the scope, vision and mission of the IEC clinical research program. Findings & Interpretation Nursing leadership plays a pivotal role in the organization of an IEC program. The process to build an ecosystem that supports IEC novel agent inquiry from bench to bedside, and ultimately to formal dissemination of findings is a new frontier for oncology nurses. Discussion & Implications Nursing led collaboration enables initiation and scientific advancement of complex novel IEC therapies to facilitate evidence-based practice, engagement and dissemination of findings that effectively improves cancer outcomes.

Immune Effector Cell Associated Neurotoxicity (ICANS) Among Pediatric and AYA Patients: MD Anderson Cancer Center Experience

Introduction Immune effector cell associated neurotoxicity (ICANS) and cytokine release syndrome (CRS) are unique potentially life-threatening complications associated with immune effector cell (IEC) therapies. ICANS presents with varying symptoms ranging from confusion to seizure and cerebral edema. There is no consensus on the precise pathophysiology related to ICANS. The incidence of this toxicity may vary based on the specific product, underlying diagnosis and host factors. Here, we characterize ICANS in pediatric and adult young adolescent (AYA) patients receiving IEC therapy at our institution. Methods We reviewed clinical characteristics, neurological severity and outcomes in pediatric and AYA patients who received IEC standard of care products from 2018-2019 at MDACC. Severity was retrospectively assessed based on ASTCT Consensus Criteria. Results Nine patients, median age 15.5 (range: 3-25) years received standard of care, chimeric antigen receptor (CART) IEC therapy. The primary diagnoses were pre-B cell acute lymphoblastic leukemia (ALL) (n=8) and primary mediastinal large B-cell lymphoma (n=1). Of these patients, 4 (44%) developed ICANS within a median of 8 (range: 3-27) days of CAR T cell infusion. ICANS was associated with CRS in all affected patients, occurring within a median of 6 (range: 2-7) days after CRS. Median CRS and ICANS severity grade was 2 (range 1-4) in all 9 patients. Symptoms included altered mental status (AMS) (5), seizure (1), aphasia (2), impaired ability to write a standard sentence (4). Neuroimaging did not correlate to ICANS symptoms or severity. EEG was obtained in 3 affected patients but only correlated to background slowing in one with aphasia. Lumbar puncture was performed in 2 patients with ICANS and was remarkable for lymphocytosis. All patients had received prophylactic anti-epileptic medication. All patients received tocilizumab for concomitant CRS and 3 received steroids. Conclusion Almost half of pediatric patients receiving standard of care CART products may experience ICANS within one week CAR T cell infusion that is associated with CRS. Pleocytosis in the CSF may be due to CAR-T trafficking into the CSF and prospective studies may clarify its significance. Impaired ability to write a standard sentence and the Cornell Assessment of Pediatric Delirium (CAPD) may be early indicators of ICANS in pediatric/AYA patients.

Measuring the Effectiveness of CAR T-CELL Therapy Nursing Education

Topic Significance & Study Purpose/Background/Rationale Chimeric antigen receptor (CAR) T-Cell therapy standardized professional education is critical to help oncology team members understand the science behind this cellular immunotherapy and best practices for managing side effects. A multidisciplinary approach to education optimizes the focus of patient and caregiver centered care designed to meet not only the physical but emotional and educational needs. Interprofessional education (IPE) is thought to best prepare nurses and other health professionals for successful collaborative practice. Methods, Intervention, & Analysis Two short, highly interactive IPE 30-minute elearning modules were developed to serve as foundational CAR T-Cell therapy education for the five Sarah Cannon Blood Cancer Network Cellular Therapy Programs. The CAR T-Cell Therapy: A New Frontier module provides an overview of CAR T-Cell therapy, while the CAR T-Cell Therapy Toxicities module focuses on assessment and management of key side effects. Short term outcomes measurements assess current practice and intent to change practice immediately upon completion of the module. Findings & Interpretation The majority of participants included inpatient staff nurses, between the ages of 25-34 years of age with a bachelor's degree, and less than 3 years of oncology experience. Participants indicated an increase in confidence of understanding immune effector cell therapy and the process/timeline after completion of the Frontier module (N = 408) with 39% and 42% improvement respectively. After completion of the toxicity module (N = 195), there was significant intent to improve toxicity management (31% - 66%), patient education (33% - 64%), and psychosocial support (33-68%). Discussion & Implications Analysis at 3 months after the initial launch of these online modules demonstrates an improvement in self-reported knowledge. Evaluation is ongoing as more professionals complete the modules with over 1000 participant responses to be presented with the 2019 year-end data. Other outcomes measurements are being explored to measure the impact of this education. Overall, these modules are providing key information that nurses and other oncology team members need to care for patients receiving CAR T-Cell Therapy. These 2 modules are the first of a larger blood cancer oncology nursing curriculum aimed at standardizing education across a large network to improve outcomes for staff and patients.

Critical Care Management of Toxicities Associated With Targeted Agents and Immunotherapies for Cancer.

To describe the most common serious adverse effects and organ toxicities associated with emerging therapies for cancer that may necessitate admission to the ICU. PubMed and Medline search of relevant articles in English on the management of adverse effects of immunotherapy for cancer. Targeted therapies including tyrosine kinase inhibitors, monoclonal antibodies, checkpoint inhibitors, and immune effector cell therapy have improved the outcome and quality of life of patients with cancer. However, severe and life-threatening side effects can occur. These toxicities include infusion or hypersensitivity reactions, cytokine release syndrome, pulmonary, cardiac, renal, hepatic, and neurologic toxicities, hemophagocytic lymphohistiocytosis, opportunistic infections, and endocrinopathies. Cytokine release syndrome is the most common serious toxicity after administration of monoclonal antibodies and immune effector cell therapies. Most of the adverse events from immunotherapy results from an exaggerated T-cell response directed against normal tissue, resulting in the generation of high levels of proinflammatory cytokines. Toxicities from targeted therapies are usually secondary to "on target toxicities." Management is largely supportive and may include discontinuation of the specific agent, corticosteroids, and other immune suppressing agents for severe (grade 3 or 4) immune-related adverse events like neurotoxicity and pneumonitis. The complexity of toxicities associated with modern targeted and immunotherapeutic agents for cancer require a multidisciplinary approach among ICU staff, oncologists, and organ specialists and adoption of standardized treatment protocols to ensure the best possible patient outcomes.

A Study of Itacitinib for the Prevention of Cytokine Release Syndrome Induced by Immune Effector Cell Therapy

A Study of Itacitinib for the Prevention of Cytokine Release Syndrome Induced by Immune Effector Cell Therapy

Implementing Immune Effector Cell Education for Nursing Staff

Topic Significance & Study Purpose/Background/Rationale Immune effector cell therapy (IECT) has recently emerged as a revolutionary treatment approach for several hematologic malignancies but is associated with unique administration and management considerations. With the growing number of IECT products commercially available and in clinical trials, there is an educational need for staff caring for patients receiving these therapies. Oncology nurses play a crucial role in IECT toxicity assessment/management and patient education, and thus require immunotherapy-specific training. In order to meet this need in a National Cancer Institute-Designated Comprehensive Cancer Center, a nursing specific IECT class was designed to train nurses and meet regulatory requirements. Methods, Intervention, & Analysis Class materials were created using resources from the National Cancer Institute, Society for Immunotherapy of Cancer, the Food and Drug Administration, Foundation for the Accreditation of Cellular Therapy, and package inserts. Topics reviewed included scientific underpinnings of immunology and IECT, cellular therapy products, toxicity assessment and management for cytokine release syndrome and neurotoxicity, administration considerations, regulatory standards, and future directions. Nurses also completed mandatory Risk Evaluation Mitigation Strategy programs for commercially available IECTs. Hematology/HCT nurse educators and a clinical nurse specialist delivered the content over two hours. Teaching methods included lecture, printed material, video, and case studies. Nurses who administer IECT or provide patient care post-therapy were required to attend the training. Upon completion of a class evaluation, attendees received continuing education credits. Findings & Interpretation Thirty sessions were offered over a three month period. Over 100 inpatient, outpatient, and triage nurses attended the training. Class evaluations revealed the content and materials met the participants' educational needs. Many nurses stated the class increased their knowledge of IECT treatment principles and nursing specific considerations, and commonly cited toxicity management strategies as the topic most useful to their practice. Discussion & Implications Due to the rapid changing landscape of cancer care, education must focus on the current and future state of immuno-oncology. Because IECT differs significantly from traditional cancer treatments, even experienced oncology nurses will require education and training specific to these new therapies. Understanding principles of immunotherapies and side effect profiles is fundamental to establishing a solid knowledge base for oncology nurses in this new age of cancer treatment.

Development of Chimeric Antigen Receptor (CAR) T Processes

Topic Significance & Study Purpose/Background/Rationale Chimeric antigen receptor therapy (CAR-T) is an autologous genetically engineered cell that can lead to dramatic responses in patients with refractory or relapsed leukemia and lymphoma. As a result, two new commercial products, Yescarta and Kymriah, were approved by the Food and Drug Administration (FDA) in October 2017 and May 2018, respectively. CAR-T cell therapy is also associated with a high risk of toxicities prompting many institutions to provide care to these patients on the blood and marrow transplant (BMT) unit. Incorporating this new therapy into existing BMT units presents both challenges and opportunities. The impact has created a dynamic process of change. The purpose of this abstract to describe our experience in developing the infrastructure for the safe administration of CAR-T therapies into an established BMT program. Carefully developing a comprehensive and dynamic approach to CAR-T cell therapies will serve as a foundation for other immune effector cell therapies that will arise in the future. Methods, Intervention, & Analysis To develop the infrastructure, consideration must be given to workflow, policy development, staff and patient education and developing quality metrics to monitor and improve patient care. We developed nursing policies and standards of care. Standards of care specify required assessments and interventions. A key component of the education included standardizing the grading of toxicities so that communication between team members is consistent. All members of the multidisciplinary team needed to complete Risk Evaluation and Mitigation System (REMS) education. New templates for the documentation were developed. We developed metrics for the quality management plan that included expected outcomes. Thresholds for metrics were developed to ensure that if standards are not met there is a plan to investigate. Collaboration with specialists, such as neurology and emergency room staff to inform our management of toxicities. Findings & Interpretation Incorporating a high-risk treatment on an established BMT unit, a thoughtful and comprehensive review of current practices must be performed to develop the infrastructure to ensure the safe and effective administration of the new therapy. Discussion & Implications To optimize the success of CAR -T therapy outcomes, collaboration, education and a comprehensive review of the programs infrastructure must be evaluated and revised.

Development of Electronic Medical Record Solutions for Immune Effector Cell Therapies: Single Institution Implementation in an Academic Medical Center

Introduction/Objectives Immune effector cell (IEC) therapy is a novel treatment modality which can result in significant toxicities including cytokine release syndrome (CRS) and neurotoxicity. Consistent and thorough clinical monitoring is paramount to patient outcomes. Our goal was to create solutions in our electronic medical record (EMR), Epic®, to support our treating team in monitoring and providing treatment of these complex patients as well to aid in quality data monitoring that is essential for regulatory requirements. Methods Monitoring solutions created include a CARTOX10 nursing flowsheet (Figure 1), rounding synopsis (Figure 2), a CRS/neurotoxicity grading assessment tool (Figure 3), and two best practice advisories (BPA) (Figure 4). Results/Conclusion The CARTOX10 nursing flowsheet auto-calculates the patient's CARTOX10 score after the assessment is completed by the nurse [1]. The rounding synopsis is a data collection tool used by the treatment team to complete a review of toxicities and minimizes the amount of time it takes to navigate patients' charts. The grading assessment tool optimizes and standardizes provider documentation. It features drop-down menus for grading of CRS and neurotoxicity. Documentation with this tool includes discrete data elements that are easy to use and standardized focusing on the organs affected by CRS. The tool can efficiently be carried into the providers' daily progress note and tracks the patient's daily trends. Additionally, this documentation tool is helpful for data reporting purposes and quality monitoring. Our best practice advisories are used to notify providers to avoid corticosteroids outside the context of neurotoxicity or treatment resistant CRS as this has been proven to impact the effectiveness of IEC therapy.1 In the event that the patient presents acutely to the emergency department during the initial 4-week monitoring period, our second BPA notifies the emergency room staff to notify the treating team and to avoid the administration of corticosteroids. Lastly, our electronic orders include both admission and toxicity order sets. The admission order set features all supportive care and communication orders for staff to monitor patients. The toxicity order set mirrors our treatment algorithm and contains drop-down menus for each grade of toxicity with corresponding monitoring parameters.Utilization of these tools in our EMR has greatly streamlined our documentation, increased our treatment teams' ability to efficiently make critical treatment decisions in a timely manner as well as meet all data reporting regulatory requirements.

American Society for Blood and Marrow Transplantation Pharmacy Special Interest Group Survey on Chimeric Antigen Receptor T Cell Therapy Administrative, Logistic, and Toxicity Management Practices in the United States

Administration of immune effector cell (IEC) therapy is a complex endeavor requiring extensive coordination and communication of various healthcare and administrative teams. Chimeric antigen receptor (CAR) T cells are the most established IEC therapy available. As of July 2018 two commercial gene therapy products, tisagenlecleucel and axicabtagene ciloleucel, have been approved by the US Food and Drug Administration. To gain insight into the infrastructure and practices across the country, the American Society for Blood and Marrow Transplantation Pharmacy Special Interest Group conducted an electronic survey on the current administrative, logistic, and toxicity management practices of CAR T cell therapy across the United States. This survey consists of 52 responses from institutions of varying sizes, most of which (∼80%) had previous investigational experience with CAR T cell therapy. Absorbing the energy of this exciting new treatment has challenged hematopoietic cell transplant programs across the country to strengthen department infrastructure, develop new committees and policies, and implement significant education to ensure safe administration. With the variety of experience with CAR T cell therapy, we hope this survey can contribute to the existing published literature and provide support and consensus to established and developing IEC programs and practice guidelines.

Synergistic Effects of Cabozantinib and EGFR-Specific CAR-NK-92 Cells in Renal Cell Carcinoma.

The chimeric antigen receptor-modified immune effector cell (CAR-T and CAR-NK) therapies are newly developed adoptive treatments of cancers. However, their therapeutic efficacy against solid tumors is limited. Combining CAR-T or CAR-NK cells with chemotherapeutic drugs to treat solid tumor may be a promising strategy. We developed an epidermal growth factor- (EGFR-) specific third-generation CAR. NK-92 cells were modified with the CAR by lentivirus infection. The specific killing ability of the CAR-modified NK-92 cells (CAR-NK-92) against renal cell carcinoma (RCC) cell lines was confirmed in vitro. The synergistic effects of cabozantinib and EGFR-specific CAR-NK-92 cells were investigated in vitro and in vivo. Our results showed that the CAR-NK-92 cells lyse RCC cells in an EGFR-specific manner. Treatment with cabozantinib could increase EGFR and decrease PD-L1 membrane surface expression in RCC cells and enhance the killing ability of CAR-NK-92 cells against the RCC cells in vitro. Furthermore, the CAR-NK-92 cells show synergistic therapeutic efficacy with cabozantinib against human RCC xenograft models. Our results provided the basis for combination with chemotherapy as a novel strategy for enhancing the therapeutic efficacy of CAR-modified immune effector cells for solid tumors.

MYC Inhibition and TP53 Activation Synergistically Suppress Immune Checkpoint Ligand PD-L1 Expression in AML Cells

Expression of immune checkpoint ligands is a mechanism that many tumors use to escape attack by host immune cells. PD-L1, the ligand for checkpoint receptor PD-1 on T cells, is often expressed on tumor cells. Engagement of PD-1 on T cells by PD-L1 on tumor cells attenuates T-cell receptor signaling and suppresses anti-tumor response. PD-1 and PD-L1 blocking antibodies have been implemented clinically as treatment for many cancers, but the pattern of PD-L1 expression on AML is not well characterized. To answer this question, we studied how PD-L1 expression on AML is regulated under in vitro conditions that simulate the leukemia-host microenvironment.We examined surface expression of PD-L1 by flow cytometry on 4 AML lines, THP-1, KG1, KG1a, HL60, and a CML line, K562. Under basal conditions, these lines expressed no or low levels of PDL1. The AML cells were then subjected to conditions that mimic the leukemia-host microenvironment. AML cells were stained with the green fluorescent dye CFSE and co-cultured with Ficoll-separated PMNCs from healthy donors. After a day of co-culture, expression of PD-L1 was analyzed on AML cells and PD-1, CD25 and CD69 activation markers on PMNCs. Only a small increase of PD-L1, up to 2-4 fold, was seen on AML cells under this condition. To simulate the pro-inflammatory milieu in the tumor microenvironment, anti-CD3/CD28 microbeads were then added in culture to activate T cells. We observed a marked up-regulation of PD-L1 on AML cells, up to 5-60 fold, plus prominent expression of PD-1, CD25 and CD69 on T cells. These findings were confirmed by an alternative method of T cell activation in which AML cells were first coated with an anti-CD123 antibody, linked to anti-CD3/CD28 antibodies via a biotin-streptavidin bridge, and then cultured with PMNCs. To test whether pro-inflammatory cytokines were the sole inducers of PD-L1 expression, AML cells were treated with IFN-γ or TNF-α alone. IFN-γ treatment enhanced PD-L1 expression by 2-10 fold, while TNF-α showed a <2-fold increase. These results show that expression of PD-L1 on AML is dynamically regulated through interaction with activated T cells, by multiple mechanisms including cytokine production and cell-cell interaction.MYC has been shown to regulate PD-L1 expression on T-ALL and solid tumors (Science 2016; 352:227). We asked whether MYC inhibition would suppress PD-L1 on AML. AML and PMNCs were co-cultured in the presence of anti-CD3/CD28 beads, with JQ1, a BET bromodomain inhibitor that blocks MYC expression. JQ1 inhibited PD-L1 expression by >90%. Dose-effect titration showed sigmoidal curves with ED50 of 0.03 to 0.1 μM for the 5 AML lines. Treatment with another MYC inhibitor, CPI-203, yielded similar results. These observations indicate that MYC inhibition can suppress PD-L1 expression on AML induced by activated T cells. TP53 has been shown to regulate PD-L1 expression on non-small cell lung cancer (JNCI 2016; 108:djv303). We asked whether TP53 activation in AML would also affect PD-L1 expression. Since the AML lines we used did not express wild-type TP53, we overexpressed TP53 in these cells by transfecting with a TP53-GFP plasmid. Expression of TP53 in the cells decreased PD-L1 levels by >80%. Treatment of the cells with pifithrin, an inhibitor that blocks trans-activating function of TP53, did not rescue PD-L1 expression, suggesting that the effect of TP53 on PD-L1 expression is independent of its canonical trans-activating pathway. We asked if MYC and TP53 would synergistically affect PD-L1 expression on AML. We transfected AML cells with the TP53-GFP plasmid and co-cultured the cells with PMNCs and anti-CD3-/CD28 beads, in the presence or absence of JQ1. We found that JQ1 treatment of TP53-transfected cells further decreased PD-L1 expression by another 15%, indicating that MYC and TP53 independently and synergistically affect PD-L1 expression on AML.In summary, PD-L1 expression on AML cells is dynamically up-regulated upon interaction with activated T cells and suppressed by perturbation of the MYC and TP53 pathways. These findings have implications in the use of immune effector cell therapy against AML, since the activated effector cells could up-regulate PD-L1 expression on target cells and attenuate anti-leukemia effects. MYC inhibitors and TP53 activators could potentially be used in combination to suppress PD-L1 up-regulation and abrogate the ability of AML cells to escape host immune elimination. DisclosuresNo relevant conflicts of interest to declare.