Long-term follow-up for the development of subsequent malignancies in patients treated with genetically modified IECs

Current landscape of vector safety and genotoxicity after hematopoietic stem or immune cell gene therapy

Malignant transformation of gene modified haematopoietic stem cells caused anxiety following adverse events in early clinical trials using gamma-retroviral vectors (γRV) to correct haematopoietic stem cells (HSC) in monogenic immune disorders. Adoption of HIV-derived lentiviral vectors (LV) with SIN (self-inactivating) configurations greatly reduced risks and subsequently hundreds of patients have been dosed with HSC gene therapy for blood, immune and metabolic conditions. Nevertheless, as experience builds, it's now well recognised that vector integration can drive clonal expansions and these may carry long term safety risks. Documented cases of haematological malignancy after SIN-LV gene therapy have recently emerged, in particular where heterologous retroviral promoters were employed and there are concerns around certain insulator elements and other possible contributors to clonal expansions. Similarly, tens of thousands of subjects have now received engineered T cell products, and longstanding dogma that mature T cells cannot be transformed is being questioned, with reports of a small number of malignant transformation events and wider concerns around secondary malignancies in some groups of patients. We summarize current clinical information and revisit genotoxicity risks following ex-vivo gene modification of HSC and T cells.

Cardiovascular Complications of Immune Effector Cell Therapies in Pediatric Hematological and Solid Tumors

BACKGROUND

Immune effector cell (IEC) therapies, including chimeric antigen receptor (CAR)-modified T-cell therapy, have shown efficacy in pediatric B-cell acute lymphoblastic leukemia (B-ALL) and are being investigated for other malignancies. A common toxicity associated with IEC therapy is cytokine release syndrome (CRS), which can lead to cardiovascular decompensation due to systemic inflammation. Data are limited regarding cardiovascular adverse effects in children. This study aims to describe the cardiovascular adverse effect profile of IEC therapies in pediatric patients with hematologic and solid tumor malignancies.

METHODS

We retrospectively reviewed patients who received IECs directed towards various targets in patients with hematologic, solid, and brain tumor malignancies from January 2014 to June 2023 at Texas Children's Hospital. The primary end point was hypotension requiring vasoactive support and/or heart failure within 30 days of infusion.

RESULTS

A total of 203 patients met inclusion criteria. Pretreatment echocardiogram was available for 142 (70%) pediatric patients, of whom 140 (96%) had normal baseline systolic function. Hypotension requiring vasoactive support occurred in 26 (13%) patients. Hematologic malignancy indications (p = 0.002), total body irradiation (TBI) (p = 0.002), and allogenic hematopoietic stem cell transplants (HCT) (p = 0.035) were associated with increased risk of hypotension requiring vasoactive support. Follow-up echocardiograms were available for 14 patients who met the primary end point, and all showed return to baseline within 6 months.

CONCLUSIONS

Significant hemodynamic compromise occurred in a minority of patients treated with IEC therapies. All experiencing cardiac dysfunction had recovery of function, and there was no cardiovascular-related mortality.

Long-term outcomes of GD2-directed CAR-T cell therapy in patients with neuroblastoma

In a phase 1 clinical trial open to accrual from 2004 to 2009, we treated children with neuroblastoma with Epstein-Barr virus (EBV)-specific T lymphocytes and CD3-activated T cells-each expressing chimeric antigen receptors (CARs) targeting GD2 but without an embedded co-stimulatory sequence (first-generation CARs). These CARs incorporated barcoded sequences to track each infused population. We previously reported outcomes up to 5 years and now report long-term outcomes up to 18 years. Of 11 patients with active disease at infusion, three achieved a complete response that was sustained in two patients, one for 8 years until lost to follow-up and one for more than 18 years. Of eight patients with no evidence of disease at the time of CAR-T administration, five are disease free at their last follow-up between 10 years and 15 years after infusion. Intermittent low levels of transgene were detected during the follow-up period with significantly greater persistence in those who were long-term survivors. Despite using first-generation vectors that are no longer employed because of the lack of co-stimulatory domains, patients with relapsed/refractory neuroblastoma achieved long-term disease control after receiving GD2 CAR-T cell therapy, including one patient now in remission of relapsed disease for more than 18 years.ClinicalTrials.gov identifier: NCT00085930 .

Long-term safety of lentiviral or gammaretroviral gene-modified T cell therapies

Long-term risks of gene therapy are not fully understood. In this study, we evaluated safety outcomes in 783 patients over more than 2,200 total patient-years of observation from 38 T cell therapy trials. The trials employed integrating gammaretroviral or lentiviral vectors to deliver engineered receptors to target HIV-1 infection or cancer. Eighteen patients (2.3%) developed secondary malignancies after treatment, with a median onset of 1.94 years (range: 51 d to 14 years). Where possible, incident tumor samples were analyzed for vector copy number, revealing no evidence of high-level marking or other indications of insertional mutagenesis. One T cell lymphoma was detected, but malignant T cells were not marked by vector integration. Analysis of vector integration sites in 176 patients revealed no pathological insertions linked to secondary malignancies, although, in some cases, integration in or near specific genes, including tumor suppressor genes, was associated with modest clonal expansion and sustained T cell persistence. These findings highlight the safety of engineered T cell therapies.

Clinical development of allogeneic chimeric antigen receptor αβ-T cells

Ready-made banks of allogeneic chimeric antigen receptor (CAR) T cells, produced to be available at the time of need, offer the prospect of accessible and cost-effective cellular therapies. Various strategies have been developed to overcome allogeneic barriers, drawing on cell engineering platforms including RNA interference, protein-based restriction, and genome editing, including RNA-guided CRISPR-Cas and base editing tools. Alloreactivity and the risk of graft-versus-host disease from non-matched donor cells have been mitigated by disruption of αβ-T cell receptor expression on the surface of T cells and stringent removal of any residual αβ-T cell populations. In addition, host-mediated rejection has been tackled through a combination of augmented lymphodepletion and cell engineering strategies that have allowed infused cells to evade immune recognition or conferred resistance to lymphodepleting agents to promote persistence and expansion of effector populations. Early-phase studies using off-the-shelf universal donor CAR T cells have been undertaken mainly in the context of blood malignancies, where emerging data of clinical responses have supported wider adoption and further applications. These developments offer the prospect of alternatives to current autologous approaches through the emerging application of genome engineering solutions to improve safety, persistence, and function of universal donor products.

An adjusted droplet digital PCR assay for quantification of vector copy number in CAR-T cell and TCR-T cell products

Background

Genetically engineered T-cell therapy holds immense promise in cancer immunotherapy. These T-cell products are typically engineered by vectors that permanently integrate into the T-cell genome, thus raising concerns about potential risks of insertional mutagenesis. Therefore, it becomes imperative to assess the integrated vector copy number (VCN) as a critical safety parameter for gene-engineered cell products.

Materials and methods

In this study, we developed a robust assay for assessing the VCN of chimeric antigen receptor-T cell and T-cell receptor T-cell products, based on the droplet digital polymerase chain reaction (ddPCR) method. To provide accurate representation of the VCN in gene-engineered cells, we implemented a calculation that factors in the putative transduction efficiency based on Poisson distribution statistics. The adjusted VCN value (VCNadj) was also compared with VCN value from sorted transgene-positive cell populations, to validate its accuracy.

Results

This assay consistently and accurately determines the average VCN for cell products. By comparing the VCN in sorted transgene-positive cell populations, we validated the refinement calculation provides a closer approximation to the actual VCN within transduced cells, offering a more realistic representation of the VCN for engineered cell products.

Conclusion

In summary, we present a reliable and robust ddPCR-based assay for quantification of VCN in gene-engineered cell products.

Chimeric Antigen Receptor-T Cells in the Modern Era of Chronic Lymphocytic Leukemia Treatment

Pathway inhibitors targeting Bruton tyrosine kinase (BTK) and B-cell lymphoma-2 (BCL-2) have dramatically changed the treatment landscape for both treatment-naïve and relapsed/refractory chronic lymphocytic leukemia (CLL). However, with increased utilization, a growing number of patients will experience progressive disease on both agents. This subgroup of "double refractory" patients has limited treatment options and poor prognosis. Chimeric antigen receptor (CAR)-T cells have transformed the treatment of relapsed/refractory B-cell malignancies. Although the earliest success of CAR-T cell therapy was in CLL, the clinical application of this modality has lagged until the recent approval of the first CAR-T cell product for CLL. In this review, we describe the current treatment options for upfront and subsequent therapies and the unmet need for novel agents highlighted by the burgeoning role and challenges of CAR-T cell therapy.

T-cell malignancies following CAR T-Cell therapy: insights from the FDA Adverse Event Reporting System (FAERS)

BACKGROUND

Concern about post-CAR T-cell lymphomas has recently emerged. Analysis of pharmacovigilance data contributes to continuous safety monitoring, especially for newly authorized medicines, like CAR-T therapies.

RESEARCH DESIGN AND METHODS

Individual case safety reports (ICSRs) reporting at least one CAR T-cell therapy as a suspect drug were extracted from the Food and Drug Administration Adverse Event Reporting System database up to 6 February 2024. Descriptive and disproportionality analysis were performed.

RESULTS

Seventeen ICSRs reported T-cell malignancies associated with CAR T-cell therapy. Gender distribution was similar between females and males, and adult patients accounted for 41.2% of ICSRs. All cases were serious, with 41.2% resulting in death. The most reported Preferred Terms (PTs) for T-cell malignancies was 'T-cell lymphoma' (70.6%). Over 70% of ICSRs reported at least one other adverse event, predominantly gastrointestinal disorders (14.3%). Axicabtagene ciloleucel and tisagenlecleucel were associated with a statistically higher reporting frequency of T-cell lymphoma compared to all other drugs (p-value <0.001, for both). Statistically higher reporting frequencies of 'Haematological malignant tumors' and 'Malignant lymphomas' SMQs emerged when tisagenlecleucel was compared with axicabtagene ciloleucel (p-value <0.001, for both).

CONCLUSIONS

Axicabtagene ciloleucel and tisagenlecleucel may be associated with a higher reporting frequency of T-cell lymphoma than other drugs.

T-cell lymphomas in recipients of CAR-T cells: assessing risks and causalities

ABSTRACT

The US Food and Drug Administration announcement in November 2023 regarding reports of the occurrence of secondary T-cell lymphomas in patients receiving chimeric antigen receptor T cells (CAR-Ts) for B-cell malignancies resulted in widespread concern among patients, clinicians, and scientists. Little information relevant to assessing causality, most importantly whether CAR retroviral or lentiviral vector genomic insertions contribute to oncogenesis, was initially available. However, since that time, several publications have provided clinical and molecular details on 3 cases showing clonal CAR vector insertions in tumor cells but without firm evidence these insertions played any role in oncogenic transformation. In addition, several other cases have been reported without vector detected in tumor cells. In addition, epidemiologic analyses as well as institutional long-term CAR-T recipient cohort studies provide important additional information suggesting the risk of T-cell lymphomas after CAR-T therapies is extremely low. This review will provide a summary of information available to date, as well as review relevant prior research suggesting a low susceptibility of mature T cells to insertional oncogenesis and documenting the almost complete lack of T-cell transformation after natural HIV infection. Alternative factors that may predispose patients treated with CAR-Ts to secondary hematologic malignancies, including immune dysfunction and clonal hematopoiesis, are discussed, and likely play a greater role than insertional mutagenesis in secondary malignancies after CAR therapies.

Second Primary Malignancies after CAR T-Cell Therapy: A Systematic Review and Meta-analysis of 5,517 Lymphoma and Myeloma Patients

PURPOSE

Chimeric antigen receptor (CAR) T-cell therapy is a potent immunotherapy for hematologic malignancies, but patients can develop long-term adverse events, including second primary malignancies (SPM) that impact morbidity and mortality. To delineate the frequency and subtypes of SPMs following CAR-T in lymphoma and myeloma, we performed a systematic review and meta-analysis.

EXPERIMENTAL DESIGN

A literature search was conducted in the MEDLINE, Embase, and Cochrane CENTRAL databases. Following the extraction of SPM cases and assignment of malignant origin, we analyzed SPM point estimates using random effects models.

RESULTS

We identified 326 SPMs across 5,517 patients from 18 clinical trials and 7 real-world studies. With a median follow-up of 21.7 months, the overall SPM point estimate was 6.0% (95% confidence interval, 4.8%-7.4%). SPM estimates were associated with treatment setting (clinical trials > real-world studies), duration of follow-up, and number of prior treatment lines, which were each confirmed as independent study-level risk factors of SPM in a meta-regression model. A subgroup meta-analysis of the four trials that randomized CAR-T versus standard-of-care revealed a similar risk of SPM with either treatment strategy (P = 0.92). In a distribution analysis of SPM subtypes, hematologic malignancies were the most common entity (37%), followed by solid tumors (27%) and non-melanoma skin cancers (16%). T-cell malignancies represented a small minority of events (1.5%). We noted disease- and product-specific variations in SPM distribution.

CONCLUSIONS

These data raise awareness of SPM as a clinically relevant long-term adverse event in patients receiving CAR T-cell therapy. However, our findings do not indicate that SPM frequency is higher with CAR-T versus previous standard-of-care strategies.

Subsequent Malignancies After CD19-Targeted Chimeric Antigen Receptor T Cells in Patients With Lymphoma

Chimeric antigen receptor (CAR) T cells are an established treatment for B cell non-Hodgkin lymphomas (B-NHL). With the remarkable success in improving survival, understanding the late effects of CAR T cell therapy is becoming more relevant. The aim of this study is to determine the incidence of subsequent malignancies in adult patients with B-NHL. We retrospectively studied 355 patients from 2 different medical centers treated with four different CAR T cell products from 2016 to 2022. The overall cumulative incidence for subsequent malignancies at 36 months was 14% (95% CI: 9.2%, 19%). Subsequent malignancies were grouped into 3 primary categories: solid tumor, hematologic malignancy, and dermatologic malignancy with cumulative incidences at 36 months of 6.1% (95% CI: 3.1%-10%), 4.5% (95% CI: 2.1%-8.1%) and 4.2% (95% CI: 2.1%-7.5%) respectively. Notably, no cases of T cell malignancies were observed. In univariable analysis, increasing age was associated with higher risk for subsequent malignancy. While the overall benefits of CAR T products continue to outweigh their potential risks, more studies and longer follow ups are needed to further demonstrate the risks, patterns, and molecular pathways that lead to the development of subsequent malignancies.

The Current Landscape of Secondary Malignancies after CAR T-Cell Therapies: How Could Malignancies Be Prevented?

Chimeric antigen receptor (CAR) T-cell therapies have revolutionised the field of haematological malignancies by achieving impressive remission rates in patients with highly refractory haematological malignancies, improving overall survival. To date, six commercial anti-CD19 and anti-BCMA CAR T-cell products have been approved by the Food and Drug Administration (FDA) for the treatment of relapsed/refractory B-cell haematological malignancies and multiple myeloma. The indications for CAR T-cell therapies are gradually expanding, with these therapies being investigated in a variety of diseases, including non-malignant ones. Despite the great success, there are several challenges surrounding CAR T-cell therapies, such as non-durable responses and high-grade toxicities. In addition, a new safety concern was added by the FDA on 28 November 2023 following reports of T-cell malignancies in patients previously treated with either anti-CD19 or anti-BCMA autologous CAR T-cell therapies both in clinical trials and in the real-world setting. Since then, several reports have been published presenting the incidence and analysing the risks of other secondary malignancies after CAR T-cell therapies. In this opinion article, the current landscape of secondary malignancies after CAR T-cell therapies is presented, along with a proposed strategy for future research aiming at potentially diminishing or abrogating the risk of developing secondary malignancies after CAR T-cell therapies.

The underlying mechanism of chimeric antigen receptor (CAR)-T cell therapy triggering secondary T-cell cancers: Mystery of the Sphinx?

The U.S. Food and Drug Administration (FDA) has reported cases of T-cell malignancies, including CAR-positive lymphomas, in patients receiving B cell maturation antigen (BCMA)- or CD19-targeted autologous CAR-T cell immunotherapy. These reports were derived from clinical trials and/or post-marketing adverse event data. This finding has attracted widespread attention. Therefore, it is essential to explore the potential mechanisms by which chimeric antigen receptor (CAR)-T cell therapy triggers secondary T-cell cancers to further guarantee the safety of CAR-T cell therapy.

Risk of Second Tumors and T-Cell Lymphoma after CAR T-Cell Therapy

BACKGROUND

The risk of second tumors after chimeric antigen receptor (CAR) T-cell therapy, especially the risk of T-cell neoplasms related to viral vector integration, is an emerging concern.

METHODS

We reviewed our clinical experience with adoptive cellular CAR T-cell therapy at our institution since 2016 and ascertained the occurrence of second tumors. In one case of secondary T-cell lymphoma, a broad array of molecular, genetic, and cellular techniques were used to interrogate the tumor, the CAR T cells, and the normal hematopoietic cells in the patient.

RESULTS

A total of 724 patients who had received T-cell therapies at our center were included in the study. A lethal T-cell lymphoma was identified in a patient who had received axicabtagene ciloleucel therapy for diffuse large B-cell lymphoma, and both lymphomas were deeply profiled. Each lymphoma had molecularly distinct immunophenotypes and genomic profiles, but both were positive for Epstein-Barr virus and were associated with DNMT3A and TET2 mutant clonal hematopoiesis. No evidence of oncogenic retroviral integration was found with the use of multiple techniques.

CONCLUSIONS

Our results highlight the rarity of second tumors and provide a framework for defining clonal relationships and viral vector monitoring. (Funded by the National Cancer Institute and others.).

T-Cell Malignant Neoplasms After Chimeric Antigen Receptor T-Cell Therapy

This cohort study assesses the increase in second primary malignant neoplasms and T-cell malignant neoplasm cases associated with chimeric antigen receptor–T cells.

Eighteen-year survival after GD2-directed Chimeric Antigen Receptor-Modified Immune Effector Cell Treatment for Neuroblastoma

We report long-term outcomes up to 18 years of a clinical trial treating children with neuroblastoma with EBV-specific T lymphocytes and CD3-activated T cells - each expressing a first-generation chimeric antigen receptor targeting GD2 with barcoded transgenes to allow tracking of each population. Of 11 patients with active disease at infusion, three patients achieved a complete response that was sustained in 2, one for 8 years until lost to follow up and one for 18+ years. Of eight patients with a history of relapse or at high risk of recurrence, five are disease-free at their last follow-up between 10-14 years post-infusion. Intermittent low levels of transgene were detected during the follow up period with significantly greater persistence in those who were long-term survivors. In conclusion, patients with relapsed/refractory neuroblastoma achieved long-term disease control after receiving GD2 CAR-T cell therapy including one patient now in remission of relapsed disease for >18 years.

T cell lymphoma and secondary primary malignancy risk after commercial CAR T cell therapy

We report a T cell lymphoma (TCL) occurring 3 months after anti-CD19 chimeric antigen receptor (CAR) T cell immunotherapy for non-Hodgkin B cell lymphoma. The TCL was diagnosed from a thoracic lymph node upon surgery for lung cancer. The TCL exhibited CD8+ cytotoxic phenotype and a JAK3 variant, while the CAR transgene was very low. The T cell clone was identified at low levels in the blood before CAR T infusion and in lung cancer. To assess the overall risk of secondary primary malignancy after commercial CAR T (CD19, BCMA), we analyzed 449 patients treated at the University of Pennsylvania. At a median follow-up of 10.3 months, 16 patients (3.6%) had a secondary primary malignancy. The median onset time was 26.4 and 9.7 months for solid and hematological malignancies, respectively. The projected 5-year cumulative incidence is 15.2% for solid and 2.3% for hematological malignancies. Overall, one case of TCL was observed, suggesting a low risk of TCL after CAR T.

BCMA-directed therapy, new treatments in the myeloma toolbox, and how to use them

To address the dearth of therapeutic options available for relapsed-refractory multiple myeloma (RRMM), attention has shifted to immunotherapeutic strategies, with most products in development targeting the B-cell maturation antigen (BCMA). BCMA is a transmembrane receptor of the tumor necrosis factor receptor superfamily, essential for plasma cell survival and minimally expressed on non-hematopoietic tissues; it represents an ideal therapeutic target. Three categories of BCMA-directed therapies exist, with distinct strengths and weaknesses. Antibody-drug conjugates (ADCs) are immediately available with modest single-agent efficacy in RRMM, but deliverability is hampered by corneal toxicity. CAR T-cells are the most effective class but face significant logistical and financial barriers. Bispecific antibodies offer superior efficacy and tolerability compared to ADCs, but prolonged exposure causes significant cumulative infectious risk. In this review, we will examine the role of BCMA in MM biology, the approved and emerging therapies targeting this antigen, and how these agents can be optimally sequenced.

Unanswered questions following reports of secondary malignancies after CAR-T cell therapy

Reports of T cell malignancies after CAR-T cell therapy should be investigated, but existing data from follow-up studies suggest a low risk compared with other cancer treatments.

Long-term survivorship care after CAR-T cell therapy

While cytokine release syndrome and immune effector cell-associated neurotoxicity syndrome are well-recognized acute toxicities of chimeric antigen receptor (CAR) T cell therapy, these complications have become increasingly manageable by protocolized treatment algorithms incorporating the early administration of tocilizumab and corticosteroids. As CAR-T cell therapy expands to new disease indications and the number of long-term survivors steadily increases, there is growing recognition of the need to appropriately evaluate and manage the late effects of CAR-T cell therapy, including late-onset or persistent neurotoxicity, prolonged cytopenias, delayed immune reconstitution and infections, subsequent malignancies, organ dysfunction, psychological distress, and fertility implications. In this review, we provide a practical approach to the long-term survivorship care of the CAR-T cell recipient, with a focus on the optimal strategies to address the common and challenging late complications affecting this unique population.

Long-term follow-up of CD19-CAR T-cell therapy in children and young adults with B-ALL

The tremendous successes of CD19-directed CAR T cells in children and young adults with B-cell acute lymphoblastic leukemia (B-ALL) has led to the more widespread use of this important treatment modality. With an ability to induce remission and potentially lead to long-term survival in patients with multiply relapsed/chemotherapy refractory disease, more children are now receiving this therapy with the hope of inducing a long-term durable remission (with or without consolidative hematopoietic cell transplantation). While overcoming the acute toxicities was critical to its broad implementation, the emerging utilization requires close evaluation of subacute and delayed toxicities alongside a consideration of late effects and issues related to survivorship following CAR T cells. In this underexplored area of toxicity monitoring, this article reviews the current state of the art in relationship to delayed toxicities while highlighting areas of future research in the study of late effects in children and young adults receiving CAR T cells.

Chimeric Antigen Receptor T Cells as Salvage Therapy for Post-Chimeric Antigen Receptor T Cell Failure

Outcomes for post-chimeric antigen receptor (CAR) T cell therapy (CART) relapse are poor. The utilization of a unique CAR T cell construct for post-CART failure is increasing, but this approach is not well described. In this study, with CART-A the first unique CAR T cell construct received and CART-B the second, the primary objective was to characterize outcomes following CART-B. Secondary objectives included evaluating safety and toxicity with sequential CART infusions; investigating the impact of potential factors, such as antigen modulation and interval therapy, on CART-B response; and characterizing long-term outcomes in patients receiving multiple CARTs. This was a retrospective review (NCT03827343) of children and young adults with B cell acute lymphoblastic leukemia (B-ALL) undergoing CART therapy who received at least 2 unique CART constructs, excluding interim CART reinfusions of the same product. Of 135 patients, 61 (45.1%) received 2 unique CART constructs, including 13 who received >2 CARTs over time. Patients included in this analysis received 14 distinct CARTs targeting CD19 and/or CD22. The median age at CART-A was 12.6 years (range, 3.3 to 30.4 years). The median time from CART-A to CART-B was 302 days (range, 53 to 1183 days). CART-B targeted a different antigen than CART-A in 48 patients (78.7%), owing primarily to loss of CART-A antigen target. The rate of complete remission (CR) was lower with CART-B (65.5%; 40 of 61) than with CART-A (88.5%; 54 of 61; P = .0043); 35 of 40 (87.5%) CART-B responders had CART-B targeting a different antigen than CART-A. Among the 21 patients with a partial response or nonresponse to CART-B, 8 (38.1%) received CART-B with the same antigen target as CART-A. Of 40 patients with CART-B complete response (CR), 29 (72.5%) relapsed. For the 21 patients with evaluable data, the relapse immunophenotype was antigennegative in 3 (14.3%), antigendim in 7 (33.3%), antigenpositive in 10 (47.6%), and lineage switch in 1 (4.8%). The median relapse-free survival following CART-B CR was 9.4 months (95% confidence interval [CI], 6.1 to 13.2 months), and overall survival was 15.0 months (95% CI, 13.0 to 22.7 months). Given the limited salvage options for post-CART relapse, identifying optimizing strategies for CART-B is critical. We raise awareness about the emerging use of CART for post-CART failure and highlight clinical implications accompanying this paradigm shift.

Emerging small molecular inhibitors as targeted therapies for high-risk acute myeloid leukemias

INTRODUCTION

Acute myeloid leukemia (AML) is an aggressive disease which has traditionally been treated with intensive chemotherapy. Survival in patients with high-risk cytogenetic and molecular subsets has been poor with this approach due to suboptimal responses seen with intensive chemotherapy and due to many patients with higher risk disease being older and unable to tolerate intensive therapies. In recent years, several targeted therapies have been under investigation for patients with high-risk AML subsets.

AREAS COVERED

This review covers four different subsets of high-risk AML including TP53-mutated, KMT2A-rearranged, FLT3-mutated, and secondary AML developing after prior hypomethylating agent exposure. The research discussed in this review focuses on small molecule inhibitors that have been studied in the treatment of these high-risk AML subsets.

EXPERT OPINION

There are several small molecule inhibitors that have demonstrated promise in these high-risk AML subsets. Longer follow-up and ongoing investigation are needed to continue to optimize therapy for patients with high-risk AML.

Long-term outcomes following CAR T cell therapy: what we know so far

Chimeric antigen receptors (CAR) are engineered fusion proteins designed to target T cells to antigens expressed on cancer cells. CAR T cells are now an established treatment for patients with relapsed and/or refractory B cell lymphomas, B cell acute lymphoblastic leukaemia and multiple myeloma. At the time of this writing, over a decade of follow-up data are available from the initial patients who received CD19-targeted CAR T cells for B cell malignancies. Data on the outcomes of patients who received B cell maturation antigen (BCMA)-targeted CAR T cells for multiple myeloma are more limited owing to the more recent development of these constructs. In this Review, we summarize long-term follow-up data on efficacy and toxicities from patients treated with CAR T cells targeting CD19 or BCMA. Overall, the data demonstrate that CD19-targeted CAR T cells can induce prolonged remissions in patients with B cell malignancies, often with minimal long-term toxicities, and are probably curative for a subset of patients. By contrast, remissions induced by BCMA-targeted CAR T cells are typically more short-lived but also generally have only limited long-term toxicities. We discuss factors associated with long-term remissions, including the depth of initial response, malignancy characteristics predictive of response, peak circulating CAR levels and the role of lymphodepleting chemotherapy. We also discuss ongoing investigational strategies designed to improve the length of remission following CAR T cell therapy.

Genome-edited allogeneic donor "universal" chimeric antigen receptor T cells

αβ T cell receptor (TCRαβ) T cells modified to express chimeric antigen receptors (CAR), are now available as authorized therapies for certain B-cell malignancies. However the process of autologous harvest and generation of patient-specific products is costly, with complex logistics and infrastructure requirements. Premanufactured banks of allogeneic donor-derived CAR T cells could help widen applicability if the challenges of HLA-mismatched T-cell therapy can be addressed. Genome editing is being applied to overcome allogeneic barriers, most notably, by disrupting TCRαβ to prevent graft-versus-host disease, and multiple competing editing technologies, including CRISPR/Cas9 and base editing, have reached clinical phase testing. Improvements in accuracy and efficiency have unlocked applications for a wider range of blood malignancies, with multiplexed editing incorporated to target HLA molecules, shared antigens and checkpoint pathways. Clinical trials will help establish safety profiles and determine the durability of responses as well as the role of consolidation with allogeneic transplantation.

Emerging Challenges to Cellular Therapy of Cancer

ABSTRACT

Cellular immunotherapy of cancer in the form of chimeric antigen receptor-modified T-cell therapy has become a standard treatment for lymphoid and more recently plasma cell malignancies. Although their successes in these cancers represent a breakthrough for adoptive cell therapy, there are several challenges to their continued growth in the field of cancer medicine. In this review, we discuss the progress made thus far toward achieving "off-the-shelf" accessibility of cell therapies that has the potential to greatly offset the costs associated with the current practice of making patient-specific products. We also review the innovations under investigation that attempt to make cellular therapy applicable to solid tumors as well.