Unlocking the potential of anti-CD33 therapy in adult and childhood acute myeloid leukemia

A dual-targeting approach with anti-IL10R CAR-T cells engineered to release anti-CD33 bispecific antibody in enhancing killing effect on acute myeloid leukemia cells

BACKGROUND

Immunotherapies, including chimeric antigen receptor (CAR) T cells and bispecific antibodies (BsAbs), encounter several challenges in the management of acute myeloid leukemia (AML), including limited persistence of these treatments, antigen loss and resistance of leukemia stem cells (LSCs) to therapy.

METHODS

Here, we proposed a novel dual-targeting approach utilizing engineered anti-IL10R CAR-T cells to secrete bispecific antibodies targeting CD33. This innovative strategy, rooted in our previous research which established a connection between IL-10 and the stemness of AML cells, designed to improve targeting efficiency and eradicate both LSCs and AML blasts.

RESULTS

We first demonstrated the superior efficacy of this synergistic approach in eliminating AML cell lines and primary cells expressing different levels of the target antigens, even in cases of low CD33 or IL10R expression. Furthermore, the IL10R CAR-T cells that secret anti-CD33 bsAbs (CAR.BsAb-T), exhibited an enhanced activation and induction of cytotoxicity not only in IL10R CAR-T cells but also in bystander T cells, thereby more effectively targeting CD33-positive tumor cells. Our in vivo experiments provided additional evidence that CAR.BsAb-T cells could efficiently redirect T cells, reduce tumor burden, and demonstrate no significant toxicity. Additionally, delivering bsAbs locally to the tumor sites through this strategy helps mitigate the pharmacokinetic challenges typically associated with the rapid clearance of prototypical bsAbs.

CONCLUSIONS

Overall, the engineering of a single-vector targeting IL10R CAR, which subsequently secretes CD33-targeted bsAb, addresses the issue of immune escape due to the heterogeneous expression of IL10R and CD33, and represents a promising progress in AML therapy aimed at improving treatment outcomes.

HuM195 and its single-chain variable fragment increase Aβ phagocytosis in microglia via elimination of CD33 inhibitory signaling

CD33 is a transmembrane receptor expressed on cells of myeloid lineage and regulates innate immunity. CD33 is a risk factor for Alzheimer's disease (AD) and targeting CD33 has been a promising strategy drug development. However, the mechanism of CD33's action is poorly understood. Here we investigate the mechanism of anti-CD33 antibody HuM195 (Lintuzumab) and its single-chain variable fragment (scFv) and examine their therapeutic potential. Treatment with HuM195 full-length antibody or its scFv increased phagocytosis of β-amyloid 42 (Aβ42) in human microglia and monocytes. This activation of phagocytosis was driven by internalization and degradation of CD33, thereby downregulating its inhibitory signal. HumM195 transiently induced CD33 phosphorylation and its signaling via receptor dimerization. However, this signaling decayed with degradation of CD33. scFv binding to CD33 leads to a degradation of CD33 without detection of the CD33 dimerization and signaling. Moreover, we found that treatments with either HuM195 or scFv promotes the secretion of IL33, a cytokine implicated in microglia reprogramming. Importantly, recombinant IL33 potentiates the uptake of Aβ42 in monocytes. Collectively, our findings provide unanticipated mechanistic insight into the role of CD33 signaling in both monocytes and microglia and define a molecular basis for the development of CD33-based therapy of AD.

Pediatric acute myeloid leukemia: Insight into genetic landscape and novel targeted approaches

Acute myeloid leukemia (AML) is a very heterogeneous hematological malignancy that accounts for approximately 20% of all pediatric leukemia cases. The outcome of pediatric AML has improved over the last decades, with overall survival rates reaching up to 70%. Still, AML is among the leading types of pediatric cancers by its high mortality rate. Modulation of standard therapy, like chemotherapy intensification, hematopoietic stem cell transplantation and optimized supportive care, could only get this far, but for the significant improvement of the outcome in pediatric AML, development of novel targeted therapy approaches is necessary. In recent years the advances in genomic techniques have greatly expanded our knowledge of the AML biology, revealing molecular landscape and complexity of the disease, which in turn have led to the identification of novel therapeutic targets. This review provides a brief overview of the genetic landscape of pediatric AML, and how it's used for precise molecular characterization and risk stratification of the patients, and also for the development of effective targeted therapy. Furthermore, this review presents recent advances in molecular targeted therapy and immunotherapy with an emphasis on the therapeutic approaches with significant clinical benefits for pediatric AML.

The Research Advances of Aptamers in Hematologic Malignancies

Currently, research for hematological malignancies is very intensive, with many breakthroughs. Among them, aptamer-based targeted therapies could be counted. Aptamer is a targeting tool with many unique advantages (easy synthesis, low toxicity, easy modification, low immunogenicity, nano size, long stability, etc.), therefore many experts screened corresponding aptamers in various hematological malignancies for diagnosis and treatment. In this review, we try to summarize and provide the recent progress of aptamer research in the diagnosis and treatment of hematologic malignancies. Until now, 29 aptamer studies were reported in hematologic malignancies, of which 12 aptamers were tested in vivo and the remaining 17 aptamers were only tested in vitro. In this case, 11 aptamers were combined with chemotherapeutic drugs for the treatment of hematologic malignancies, 4 aptamers were used in combination with nanomaterials for the diagnosis and treatment of hematologic malignancies, and some studies used aptamers for the targeted transportation of siRNA and miRNA for targeted therapeutic effects. Their research provides multiple approaches to achieve more targeted goals. These findings show promising and encouraging future for both hematological malignancies basic and clinical trials research.

CD33-directed immunotherapy with third-generation chimeric antigen receptor T cells and gemtuzumab ozogamicin in intact and CD33-edited acute myeloid leukemia and hematopoietic stem and progenitor cells

Immunotherapies, such as chimeric antigen receptor (CAR) modified T cells and antibody-drug conjugates (ADCs), have revolutionized the treatment of cancer, especially of lymphoid malignancies. The application of targeted immunotherapy to patients with acute myeloid leukemia (AML) has been limited in particular by the lack of a tumor-specific target antigen. Gemtuzumab ozogamicin (GO), an ADC targeting CD33, is the only approved immunotherapeutic agent in AML. In our study, we introduce a CD33-directed third-generation CAR T-cell product (3G.CAR33-T) for the treatment of patients with AML. 3G.CAR33-T cells could be expanded up to the end-of-culture, that is, 17 days after transduction, and displayed significant cytokine secretion and robust cytotoxic activity when incubated with CD33-positive cells including cell lines, drug-resistant cells, primary blasts as well as normal hematopoietic stem and progenitor cells (HSPCs). When compared to second-generation CAR33-T cells, 3G.CAR33-T cells exhibited higher viability, increased proliferation and stronger cytotoxicity. Also, GO exerted strong antileukemia activity against CD33-positive AML cells. Upon genomic deletion of CD33 in HSPCs, 3G.CAR33-T cells and GO preferentially killed wildtype leukemia cells, while sparing CD33-deficient HSPCs. Our data provide evidence for the applicability of CD33-targeted immunotherapies in AML and its potential implementation in CD33 genome-edited stem cell transplantation approaches.

Insights into the molecular profiles of adult and paediatric acute myeloid leukaemia

Acute myeloid leukaemia (AML) is a clinically and molecularly heterogeneous disease characterised by uncontrolled proliferation, block in differentiation and acquired self-renewal of hematopoietic stem and myeloid progenitor cells. This results in the clonal expansion of myeloid blasts within the bone marrow and peripheral blood. The incidence of AML increases with age, and in childhood, AML accounts for 20% of all leukaemias. Whilst there are many clinical and biological similarities between paediatric and adult AML with continuum across the age range, many characteristics of AML are associated with age of disease onset. These include chromosomal aberrations, gene mutations and differentiation lineage. Following chemotherapy, AML cells that survive and result in disease relapse exist in an altered chemoresistant state. Molecular profiling currently represents a powerful avenue of experimentation to study AML cells from adults and children pre- and postchemotherapy as a means of identifying prognostic biomarkers and targetable molecular vulnerabilities that may be age-specific. This review highlights recent advances in our knowledge of the molecular profiles with a focus on transcriptomes and metabolomes, leukaemia stem cells and chemoresistant cells in adult and paediatric AML and focus on areas that hold promise for future therapies.

Cytogenetics of Pediatric Acute Myeloid Leukemia: A Review of the Current Knowledge

Pediatric acute myeloid leukemia is a rare and heterogeneous disease in relation to morphology, immunophenotyping, germline and somatic cytogenetic and genetic abnormalities. Over recent decades, outcomes have greatly improved, although survival rates remain around 70% and the relapse rate is high, at around 30%. Cytogenetics is an important factor for diagnosis and indication of prognosis. The main cytogenetic abnormalities are referenced in the current WHO classification of acute myeloid leukemia, where there is an indication for risk-adapted therapy. The aim of this article is to provide an updated review of cytogenetics in pediatric AML, describing well-known WHO entities, as well as new subgroups and germline mutations with therapeutic implications. We describe the main chromosomal abnormalities, their frequency according to age and AML subtypes, and their prognostic relevance within current therapeutic protocols. We focus on de novo AML and on cytogenetic diagnosis, including the practical difficulties encountered, based on the most recent hematological and cytogenetic recommendations.

Treatment outcomes of pediatric acute myeloid leukemia: a retrospective analysis from 1996 to 2019 in Taiwan

Improvement in outcomes of children with acute myeloid leukemia (AML) is attributed to several refinements in clinical management. We evaluated treatment outcomes of Taiwanese pediatric AML patients in the past 20 years. Overall, 860 de novo AML patients aged 0-18 years and registered in the Childhood Cancer Foundation of R.O.C during January 1996-December 2019 were included. Survival analysis was performed to identify factors that improved treatment outcomes. Regardless of treatment modalities used, patients during 2008-2019 had better 5-year event-free survival (EFS) and overall survival (OS) rates than patients during 1996-2007. For patients received the TPOG-AML-97A treatment, only 5-year OS rates were significantly different between patients diagnosed before and after 2008. Patients with RUNX1-RUNX1T1 had similar relapse-free survival rates, but 5-year OS rates were better during 2008-2019. However, the survival of patients who received hematopoietic stem-cell transplantations (HSCT) did not differ significantly before and after 2008. For patients without relapse, the 5-year OS improved during 2008-2019. Non-relapse mortality decreased annually, and cumulative relapse rates were similar. In conclusion, 5-year EFS and OS rates improved during 2008-2019, though intensities of chemotherapy treatments were similar before and after 2008. Non-relapse mortality decreased gradually. Further treatment strategies including more intensive chemotherapy, novel agents' use, identification of high-risk patients using genotyping and minimal residual disease, early intervention of HSCT, and antibiotic prophylaxis can be considered for future clinical protocol designs in Taiwan.

Siglec-15 as an Emerging Target for Next-generation Cancer Immunotherapy

Immunomodulatory agents blocking the PD-1/PD-L1 pathway have shown a new way to treat cancer. The explanation underlying the success of these agents may be the selective expression of PD-L1 with dominant immune-suppressive activities in the tumor microenvironment (TME), supporting a more favorable tumor response-to-toxicity ratio. However, despite the big success of these drugs, most patients with cancer show primary or acquired resistance, calling for the identification of new immune modulators in the TME. Using a genome-scale T-cell activity array in combination with bioinformatic analysis of human cancer databases, we identified Siglec-15 as a critical immune suppressor with broad upregulation on various cancer types and a potential target for cancer immunotherapy. Siglec-15 has unique molecular features compared with many other known checkpoint inhibitory ligands. It shows prominent expression on macrophages and cancer cells and a mutually exclusive expression with PD-L1, suggesting that it may be a critical immune evasion mechanism in PD-L1-negative patients. Interestingly, Siglec-15 has also been identified as a key regulator for osteoclast differentiation and may have potential implications in bone disorders not limited to osteoporosis. Here, we provide an overview of Siglec-15 biology, its role in cancer immune regulation, the preliminary and encouraging clinical data related to the first-in-class Siglec-15 targeting mAb, as well as many unsolved questions in this pathway. As a new player in the cancer immunotherapeutic arena, Siglec-15 may represent a novel class of immune inhibitors with tumor-associated expression and divergent mechanisms of action to PD-L1, with potential implications in anti-PD-1/PD-L1-resistant patients.

Regulation of N6-Methyladenosine in the Differentiation of Cancer Stem Cells and Their Fate

N6-methyladenosine (m6A) is one of the most common internal RNA modifications in eukaryotes. It is a dynamic and reversible process that requires an orchestrated participation of methyltransferase, demethylase, and methylated binding protein. m6A modification can affect RNA degradation, translation, and microRNA processing. m6A plays an important role in the regulation of various processes in living organisms. In addition to being involved in normal physiological processes such as sperm development, immunity, fat differentiation, cell development, and differentiation, it is also involved in tumor progression and stem cell differentiation. Curiously enough, cancer stem cells, a rare group of cells present in malignant tumors, retain the characteristics of stem cells and play an important role in the survival, proliferation, metastasis, and recurrence of cancers. Recently, studies demonstrated that m6A participates in the self-renewal and pluripotent regulation of these stem cells. However, considering that multiple targets of m6A are involved in different physiological processes, the exact role of m6A in cancer progression remains controversial. This article focuses on the mechanism of m6A and its effects on the differentiation of cancer stem cells, to provide a basis for elucidating the tumorigenesis mechanisms and exploring new potential therapeutic approaches.

Immune Escape after Hematopoietic Stem Cell Transplantation (HSCT): From Mechanisms to Novel Therapies

Acute myeloid leukemia (AML) is the most common type of acute leukemia in adults. Recent advances in understanding its molecular basis have opened the way to new therapeutic strategies, including targeted therapies. However, despite an improvement in prognosis it has been documented in recent years (especially in younger patients) that allogenic hematopoietic stem cell transplantation (allo-HSCT) remains the only curative treatment in AML and the first therapeutic option for high-risk patients. After allo-HSCT, relapse is still a major complication, and is observed in about 50% of patients. Current evidence suggests that relapse is not due to clonal evolution, but instead to the ability of the AML cell population to escape immune control by a variety of mechanisms including the altered expression of HLA-molecules, production of anti-inflammatory cytokines, relevant metabolic changes and expression of immune checkpoint (ICP) inhibitors capable of “switching-off” the immune response against leukemic cells. Here, we review the main mechanisms of immune escape and identify potential strategies to overcome these mechanisms.

Reinforcing the primary immunotherapy modulators against acute leukemia; monoclonal antibodies in AML

Recent therapeutic advances in cancer treatment recruit immune system potentiation against malignant cells. Numerous ongoing clinical trials on immunotherapy methods, either monotherapy or combination therapy, are investigating the impeding factors on the way of acute myeloid leukemia (AML) treatment. Due to the genetic diversity in AML progenitors, combining various strategies is more likely to be useful for improving patient outcomes. This review describes the details of applying monoclonal antibodies against AML, focusing on CD33, CD123, FLT3, CD45 and CD66 targeting. Furthermore, it clarifies the importance of immunotoxins, bispecific antibodies, chimeric antigen receptor (CAR)-T cells and T cell receptor-modified cells as reinforcing agents for monoclonal antibodies.

Single-Chain Variable Fragment-Based Bispecific Antibodies: Hitting Two Targets with One Sophisticated Arrow

Despite the success of monoclonal antibodies (mAbs) to treat some disorders, the monospecific molecular entity of mAbs as well as the presence of multiple factors and pathways involved in the pathogenesis of disorders, such as various malignancies, infectious diseases, and autoimmune disorders, and resistance to therapy have restricted the therapeutic efficacy of mAbs in clinical use. Bispecific antibodies (bsAbs), by concurrently recognizing two targets, can partly circumvent these problems. Serial killing of tumor cells by bsAb-redirected T cells, simultaneous blocking of two antigens involved in the HIV-1 infection, and concurrent targeting of the activating and inhibitory receptors on B cells to modulate autoimmunity are part of the capabilities of bsAbs. After designing and developing a large number of bsAbs for years, catumaxomab, a full-length bsAb targeting EpCAM and CD3, was approved in 2009 to treat EpCAM-positive carcinomas besides blinatumomab, a bispecific T cell engager antibody targeting CD19 and CD3, which was approved in 2014 to treat relapsed or refractory acute lymphoblastic leukemia. Furthermore, approximately 60 bsAbs are under investigation in clinical trials. The current review aims at portraying different formats of the single-chain variable fragment (scFv)-based bsAbs and shedding light on the scFv-based bsAbs in preclinical development, different phases of clinical trials, and the market.

Rapid identification of specific DNA aptamers precisely targeting CD33 positive leukemia cells through a paired cell-based approach

Aptamers are short single-stranded DNA or RNA molecules, which have recently been developed for potential broad applications such as clinical therapeutics, diagnosis and tumor-targeted drug delivery. However, the selection of specific aptamers is often unsatisfactory using the classical protein or cell-based SELEX. Herein, we modified the paired cell line approach to identify aptamers targeting leukemia cells expressing the CD33 antigen. Our strategy artfully used the same cells for negative (HEK293T cells) and positive (CD33 transfected-HEK293T cells) aptamer selections, and the negative selections were performed adequately before the positive selection to remove unspecific sequences. The advantages of this strategy are that it is fast and accurate, where only a few rounds of selection together with PCR amplifications are sufficient to obtain high binding affinity antigen-targeted aptamers. By using our modified approach, we successfully obtained the CD33-targeting aptamer S30, which could highly recognize the C2 domain of the CD33 antigen in vitro and in vivo. Moreover, the optimized aptamer S30-T1 (i.e., core region of S30) was conjugated with doxorubicin (Dox) to synthesize S30-T1-Dox conjugates, which could specifically inhibit CD33 positive acute myeloid leukemia HL-60 cell proliferation by arresting the cell cycle at the G2 phase. Thus, our modified approach can rapidly screen reliable, stable and high binding affinity aptamers for precise cancer treatment.

Gene-edited stem cells enable CD33-directed immune therapy for myeloid malignancies

Acute myeloid leukemia is a disease that lacks effective therapies, especially in postremission patients. Immunotherapies directed against a lineage-specific antigen (LSA), such as CD33 has demonstrated on-target effects on AML cells but is limited by toxicities because normal myeloid cells and hematopoietic progenitors also express CD33. Here we show that genetically ablating CD33 in human stem/progenitor cells, using Cas9/guide RNA mediated strategies, enables immunotherapy against leukemias using anti-CD33 CAR-T or antibody therapy. We model a postremission human marrow with minimal residual leukemic disease in mice and show effective clearance of acute myeloid leukemia and the reconstitution of the CD33-deleted human graft, enabling future clinical studies. This study presents an approach to treat myeloid leukemias and could be extended to other cancers and other antigens.

Antigen-directed immunotherapies for acute myeloid leukemia (AML), such as chimeric antigen receptor T cells (CAR-Ts) or antibody-drug conjugates (ADCs), are associated with severe toxicities due to the lack of unique targetable antigens that can distinguish leukemic cells from normal myeloid cells or myeloid progenitors. Here, we present an approach to treat AML by targeting the lineage-specific myeloid antigen CD33. Our approach combines CD33-targeted CAR-T cells, or the ADC Gemtuzumab Ozogamicin with the transplantation of hematopoietic stem cells that have been engineered to ablate CD33 expression using genomic engineering methods. We show highly efficient genetic ablation of CD33 antigen using CRISPR/Cas9 technology in human stem/progenitor cells (HSPC) and provide evidence that the deletion of CD33 in HSPC doesn’t impair their ability to engraft and to repopulate a functional multilineage hematopoietic system in vivo. Whole-genome sequencing and RNA sequencing analysis revealed no detectable off-target mutagenesis and no loss of functional p53 pathways. Using a human AML cell line (HL-60), we modeled a postremission marrow with minimal residual disease and showed that the transplantation of CD33-ablated HSPCs with CD33-targeted immunotherapy leads to leukemia clearance, without myelosuppression, as demonstrated by the engraftment and recovery of multilineage descendants of CD33-ablated HSPCs. Our study thus contributes to the advancement of targeted immunotherapy and could be replicated in other malignancies.

Antigenic Targets for the Immunotherapy of Acute Myeloid Leukaemia

One of the most promising approaches to preventing relapse is the stimulation of the body’s own immune system to kill residual cancer cells after conventional therapy has destroyed the bulk of the tumour. In acute myeloid leukaemia (AML), the high frequency with which patients achieve first remission, and the diffuse nature of the disease throughout the periphery, makes immunotherapy particularly appealing following induction and consolidation therapy, using chemotherapy, and where possible stem cell transplantation. Immunotherapy could be used to remove residual disease, including leukaemic stem cells from the farthest recesses of the body, reducing, if not eliminating, the prospect of relapse. The identification of novel antigens that exist at disease presentation and can act as targets for immunotherapy have also proved useful in helping us to gain a better understand of the biology that belies AML. It appears that there is an additional function of leukaemia associated antigens as biomarkers of disease state and survival. Here, we discuss these findings.

An mTORC1/2 kinase inhibitor enhances the cytotoxicity of gemtuzumab ozogamicin by activation of lysosomal function

Gemtuzumab ozogamicin (GO), the first antibody-drug conjugate (ADC), has attracted the interest of hematologists because more than 90% of acute myeloid leukemia (AML) blasts express its target, CD33. Although GO and subsequently developed ADCs depend on lysosomes for activation, lysosome number and activity in tumor cells has not been well elucidated. In this study, we investigated whether an mTORC1/2 kinase inhibitor, PP242, which was reported to activate lysosomal function, potentiates the cytotoxicity of GO in AML cells. Eight AML cell lines (U937, THP-1, SKM-1, SKK-1, SKNO-1, HL-60, MARIMO and KO52) were treated with GO and PP242. The cytotoxic effect of GO was enhanced by concurrent treatment with a non-cytotoxic concentration (500 nM) of PP242 in most cell lines, except MARIMO and KO52 cells. We then used LysoTracker to label acidic lysosomes in U937, THP-1, SKM-1, MARIMO and KO52 cells. LysoTracker fluorescence was dramatically increased by treatment with PP242 in U937, THP-1 and SKM-1 cells, and the intensified fluorescence was retained with PP242 + GO. In contrast, PP242 did not induce a significant increase in fluorescence in MARIMO cells, consistent with the lack of combinatory cytotoxicity. LysoTracker fluorescence was also increased by PP242 in KO52 cells, which have been reported to strongly express multidrug resistance (MDR). Further, PP242 suppressed GO-induced Chk1 activation and G2/M cell cycle arrest, which in turn triggered cell cycle promotion and cell death. These results indicate that inhibition of mTORC1/2 kinase by PP242 enhanced the cytotoxicity of GO by increasing lysosomal compartments and promoting the cell cycle via suppression of GO-induced Chk1 activation. This combination may represent an attractive new therapeutic strategy for the treatment of leukemia.

An Anti-CLL-1 Antibody-Drug Conjugate for the Treatment of Acute Myeloid Leukemia

PURPOSE

The treatment of acute myeloid leukemia (AML) has not significantly changed in 40 years. Cytarabine- and anthracycline-based chemotherapy induction regimens (7 + 3) remain the standard of care, and most patients have poor long-term survival. The reapproval of Mylotarg, an anti-CD33-calicheamicin antibody-drug conjugate (ADC), has demonstrated ADCs as a clinically validated option to enhance the effectiveness of induction therapy. We are interested in developing a next-generation ADC for AML to improve upon the initial success of Mylotarg.

EXPERIMENTAL DESIGN

The expression pattern of CLL-1 and its hematopoietic potential were investigated. A novel anti-CLL-1-ADC, with a highly potent pyrrolobenzodiazepine (PBD) dimer conjugated through a self-immolative disulfide linker, was developed. The efficacy and safety profiles of this ADC were evaluated in mouse xenograft models and in cynomolgus monkeys.

RESULTS

We demonstrate that CLL-1 shares similar prevalence and trafficking properties that make CD33 an excellent ADC target for AML, but lacks expression on hematopoietic stem cells that hampers current CD33-targeted ADCs. Our anti-CLL-1-ADC is highly effective at depleting tumor cells in AML xenograft models and lacks target independent toxicities at doses that depleted target monocytes and neutrophils in cynomolgus monkeys.

CONCLUSIONS

Collectively, our data suggest that an anti-CLL-1-ADC has the potential to become an effective and safer treatment for AML in humans, by reducing and allowing for faster recovery from initial cytopenias than the current generation of ADCs for AML.

Harnessing the potential of epigenetic therapies for childhood acute myeloid leukemia

There is a desperate need for new and effective therapeutic approaches to acute myeloid leukemia (AML) in both children and adults. Epigenetic aberrations are common in adult AML, and many novel epigenetic compounds that may improve patient outcomes are in clinical development. Mutations in epigenetic regulators occur less frequently in AML in children than in adults. Investigating the potential benefits of epigenetic therapy in pediatric AML is an important issue and is discussed in this review.

Pediatric Cancer Immunotherapy: Opportunities and Challenges

Cancer immunotherapies, widely heralded as transformational for many adult cancer patients, are becoming viable options for selected subsets of pediatric cancer patients. Many therapies are currently being investigated, from immunomodulatory agents to adoptive cell therapy, bispecific T-cell engagers, oncolytic virotherapy, and checkpoint inhibition. One of the most exciting immunotherapies recently FDA approved is the use of CD19 chimeric antigen receptor T cells for pre-B-cell acute lymphoblastic leukemia. With this approval and others, immunotherapy for pediatric cancers is gaining traction. One of the caveats to many of these immunotherapies is the challenge of predictive biomarkers; determining which patients will respond to a given therapy is not yet possible. Much research is being focused on which biomarkers will be predictive and prognostic for these patients. Despite many benefits of immunotherapy, including less long-term side effects, some treatments are fraught with immediate side effects that range from mild to severe, although most are manageable. With few downsides and the potential for disease cures, immunotherapy in the pediatric population has the potential to move to the front-line of therapeutic options.