Intention-to-treat outcomes utilising a stringent event definition in children and young people treated with tisagenlecleucel for r/r ALL through a national access scheme.

CAR T-cell therapy has transformed relapsed/refractory (r/r) B-cell precursor acute lymphoblastic leukaemia (B-ALL) management and outcomes, but following CAR T infusion, interventions are often needed. In a UK multicentre study, we retrospectively evaluated tisagenlecleucel outcomes in all eligible patients, analysing overall survival (OS) and event-free survival (EFS) with standard and stringent definitions, the latter including measurable residual disease (MRD) emergence and further anti-leukaemic therapy. Both intention-to-treat and infused cohorts were considered. We collected data on feasibility of delivery, manufacture, toxicity, cause of therapy failure and followed patients until death from any cause. Of 142 eligible patients, 125 received tisagenlecleucel, 115/125 (92%) achieved complete remission (CR/CRi). Severe cytokine release syndrome and neurotoxicity occurred in 16/123 (13%) and 10/123 (8.1%), procedural mortality was 3/126 (2.4%). The 2-year intent to treat OS and EFS were 65.2% (95%CI 57.2-74.2%) and 46.5% (95%CI 37.6-57.6%), 2-year intent to treat stringent EFS was 35.6% (95%CI 28.1-44.9%). Median OS was not reached. Sixty-two responding patients experienced CAR T failure by the stringent event definition. Post failure, 1-year OS and standard EFS were 61.2% (95%CI 49.3-75.8) and 55.3% (95%CI 43.6-70.2). Investigation of CAR T-cell therapy for B-ALL delivered on a country-wide basis, including following patients beyond therapy failure, provides clinicians with robust outcome measures. Previously, outcomes post CAR T-cell therapy failure were under-reported. Our data show that patients can be successfully salvaged in this context with good short-term survival.

Clinical application of tumour-in-normal contamination assessment from whole genome sequencing.

The unexpected contamination of normal samples with tumour cells reduces variant detection sensitivity, compromising downstream analyses in canonical tumour-normal analyses. Leveraging whole-genome sequencing data available at Genomics England, we develop a tool for normal sample contamination assessment, which we validate in silico and against minimal residual disease testing. From a systematic review of [Formula: see text] patients with haematological malignancies and sarcomas, we find contamination across a range of cancer clinical indications and DNA sources, with highest prevalence in saliva samples from acute myeloid leukaemia patients, and sorted CD3+ T-cells from myeloproliferative neoplasms. Further exploration reveals 108 hotspot mutations in genes associated with haematological cancers at risk of being subtracted by standard variant calling pipelines. Our work highlights the importance of contamination assessment for accurate somatic variants detection in research and clinical settings, especially with large-scale sequencing projects being utilised to deliver accurate data from which to make clinical decisions for patient care.

Noncoding mutations drive persistence of a founder preleukemic clone which initiates late relapse in T-ALL.

ABSTRACT: T-ALL relapse usually occurs early but can occur much later, which has been suggested to represent a de novo leukemia. However, we conclusively demonstrate late relapse can evolve from a pre-leukemic subclone harbouring a non-coding mutation that evades initial chemotherapy.

CD19/CD22 targeting with cotransduced CAR T cells to prevent antigen-negative relapse after CAR T-cell therapy for B-cell ALL.

ABSTRACT: CD19-negative relapse is a leading cause of treatment failure after chimeric antigen receptor (CAR) T-cell therapy for acute lymphoblastic leukemia. We investigated a CAR T-cell product targeting CD19 and CD22 generated by lentiviral cotransduction with vectors encoding our previously described fast-off rate CD19 CAR (AUTO1) combined with a novel CD22 CAR capable of effective signaling at low antigen density. Twelve patients with advanced B-cell acute lymphoblastic leukemia were treated (CARPALL [Immunotherapy with CD19/22 CAR Redirected T Cells for High Risk/Relapsed Paediatric CD19+ and/or CD22+ Acute Lymphoblastic Leukaemia] study, NCT02443831), a third of whom had failed prior licensed CAR therapy. Toxicity was similar to that of AUTO1 alone, with no cases of severe cytokine release syndrome. Of 12 patients, 10 (83%) achieved a measurable residual disease (MRD)-negative complete remission at 2 months after infusion. Of 10 responding patients, 5 had emergence of MRD (n = 2) or relapse (n = 3) with CD19- and CD22-expressing disease associated with loss of CAR T-cell persistence. With a median follow-up of 8.7 months, there were no cases of relapse due to antigen-negative escape. Overall survival was 75% (95% confidence interval [CI], 41%-91%) at 6 and 12 months. The 6- and 12-month event-free survival rates were 75% (95% CI, 41%-91%) and 60% (95% CI, 23%-84%), respectively. These data suggest dual targeting with cotransduction may prevent antigen-negative relapse after CAR T-cell therapy.

Susceptibility of pediatric acute lymphoblastic leukemia to STAT3 inhibition depends on p53 induction.

Advances in the clinical management of pediatric B-cell acute lymphoblastic leukemia (B-ALL) have dramatically improved outcomes for this disease. However, relapsed and high-risk disease still contribute to significant numbers of treatment failures. Development of new, broad range therapies is urgently needed for these cases. We previously reported the susceptibility of ETV6-RUNX1+ pediatric B-ALL to inhibition of signal transducer and activator of transcription 3 (STAT3) activity. In the present study, we demonstrate that pharmacological or genetic inhibition of STAT3 results in p53 induction and that CRISPR-mediated TP53 knockout substantially reverses susceptibility to STAT3 inhibition. Furthermore, we demonstrate that sensitivity to STAT3 inhibition in patient-derived xenograft (PDX) B-ALL samples is not restricted to any particular disease subtype, but rather depends on TP53 status, the only resistant samples being TP53 mutant. Induction of p53 following STAT3 inhibition is not directly dependent on MDM2 but correlates with degradation of MDM4. As such, STAT3 inhibition exhibits synergistic in vitro and in vivo anti-leukemia activity when combined with MDM2 inhibition. Taken together with the relatively low frequency of TP53 mutations in this disease, these data support the future development of combined STAT3/ MDM2 inhibition in the therapy of refractory and relapsed pediatric B-ALL.

Myeloproliferative Neoplasm Driven by ETV6-ABL1 in an Adolescent with Recent History of Burkitt Leukemia.

ETV6-ABL1 gene fusion is a rare genetic rearrangement in a variety of malignancies, including myeloproliferative neoplasms (MPN), acute lymphoblastic leukemia (ALL), and acute myeloid leukemia (AML). Here, we report the case of a 16-year-old male diagnosed with a MPN, 7 months post-completion of treatment for Burkitt leukaemia. RNA sequencing analysis confirmed the presence of an ETV6-ABL1 fusion transcript, with an intact, in-frame ABL tyrosine-kinase domain. Of note, secondary ETV6-ABL1-rearranged neoplastic diseases have not been reported to date. The patient was started on a tyrosine kinase inhibitor (TKI; imatinib) and, subsequently, underwent a 10/10 matched unrelated haematopoietic stem cell transplant. He is disease-free five years post-transplant. Definitive evidence of the prognostic influence of the ETV6-ABL1 fusion in haematological neoplasms is lacking; however, overall data suggest that it is a poor prognostic factor, particularly in patients with ALL and AML. The presence of this ETV6-ABL1 fusion should be more routinely investigated, especially in patients with a CML-like picture. More routine use of whole-genome and RNA sequencing analyses in clinical diagnostic care, in conjunction with conventional cytogenetics, will facilitate these investigations.

Clonal origin of KMT2A wild-type lineage-switch leukemia following CAR-T cell and blinatumomab therapy.

Children with acute lymphoblastic leukemia (ALL) undergoing anti-CD19 therapy occasionally develop acute myeloid leukemia (AML). The clonal origin of such lineage-switch leukemias1-4 remains unresolved. Here, we reconstructed the phylogeny of multiple leukemias in a girl who, following multiply relapsed ALL, received anti-CD19 cellular and antibody treatment and subsequently developed AML. Whole genome sequencing unambiguously revealed the AML derived from the initial ALL, with distinct driver mutations that were detectable before emergence. Extensive prior diversification and subsequent clonal selection underpins this fatal lineage switch. Genomic monitoring of primary leukemias and recurrences may predict therapy resistance, especially regarding anti-CD19 treatment.

Survival outcomes of children with relapsed or refractory myeloid leukemia associated with Down syndrome.

Children with Down syndrome (DS) are at a significantly higher risk of developing acute myeloid leukemia, also termed myeloid leukemia associated with DS (ML-DS). In contrast to the highly favorable prognosis of primary ML-DS, the limited data that are available for children who relapse or who have refractory ML-DS (r/r ML-DS) suggest a dismal prognosis. There are few clinical trials and no standardized treatment approach for this population. We conducted a retrospective analysis of international study groups and pediatric oncology centers and identified 62 patients who received treatment with curative intent for r/r ML-DS between year 2000 to 2021. Median time from diagnosis to relapse was 6.8 (range, 1.1-45.5) months. Three-year event-free survival (EFS) and overall survival (OS) were 20.9 ± 5.3% and 22.1 ± 5.4%, respectively. Survival was associated with receipt of hematopoietic stem cell transplantation (HSCT) (hazard ratio [HR], 0.28), duration of first complete remission (CR1) (HR, 0.31 for > 12 months) and attainment of remission after relapse (HR, 4.03). Patients who achieved complete remission (CR) before HSCT, had an improved OS and EFS of 56.0 ± 11.8% and 50.5 ± 11.9%, respectively compared to those who underwent HSCT without CR (3-year OS and EFS of 10.0 ± 9.5%). Treatment failure after HSCT was predominantly because of disease recurrence (52%) followed by treatment-related mortality (10%). The prognosis of r/r ML-DS remains dismal even in the current treatment period and serve as a reference point for current prognostication and future interventional studies. Clinical trials aimed at improving the survival of patients with r/r ML-DS are needed.

EBV-driven lymphoid neoplasms associated with pediatric ALL maintenance therapy.

The development of a second malignancy after the diagnosis of childhood acute lymphoblastic leukemia (ALL) is a rare event. Certain second malignancies have been linked with specific elements of leukemia therapy, yet the etiology of most second neoplasms remains obscure and their optimal management strategies are unclear. This is a first comprehensive report of non-Hodgkin lymphomas (NHLs) following pediatric ALL therapy, excluding stem-cell transplantation. We analyzed data of patients who developed NHL following ALL diagnosis and were enrolled in 12 collaborative pediatric ALL trials between 1980-2018. Eighty-five patients developed NHL, with mature B-cell lymphoproliferations as the dominant subtype (56 of 85 cases). Forty-six of these 56 cases (82%) occurred during or within 6 months of maintenance therapy. The majority exhibited histopathological characteristics associated with immunodeficiency (65%), predominantly evidence of Epstein-Barr virus-driven lymphoproliferation. We investigated 66 cases of post-ALL immunodeficiency-associated lymphoid neoplasms, 52 from our study and 14 additional cases from a literature search. With a median follow-up of 4.9 years, the 5-year overall survival for the 66 patients with immunodeficiency-associated lymphoid neoplasms was 67.4% (95% confidence interval [CI], 56-81). Five-year cumulative risks of lymphoid neoplasm- and leukemia-related mortality were 20% (95% CI, 10.2-30) and 12.4% (95% CI, 2.7-22), respectively. Concurrent hemophagocytic lymphohistiocytosis was associated with increased mortality (hazard ratio, 7.32; 95% CI, 1.62-32.98; P = .01). A large proportion of post-ALL lymphoid neoplasms are associated with an immunodeficient state, likely precipitated by ALL maintenance therapy. Awareness of this underrecognized entity and pertinent diagnostic tests are crucial for early diagnosis and optimal therapy.

Distorted TCR repertoires define multisystem inflammatory syndrome in children.

While the majority of children infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) display mild or no symptoms, rare individuals develop severe disease presenting with multisystem inflammatory syndrome (MIS-C). The reason for variable clinical manifestations is not understood. Here, we carried out TCR sequencing and conducted comparative analyses of TCR repertoires between children with MIS-C (n = 12) and mild (n = 8) COVID-19. We compared these repertoires with unexposed individuals (samples collected pre-COVID-19 pandemic: n = 8) and with the Adaptive Biotechnologies MIRA dataset, which includes over 135,000 high-confidence SARS-CoV-2-specific TCRs. We show that the repertoires of children with MIS-C are characterised by the expansion of TRBV11-2 chains with high junctional and CDR3 diversity. Moreover, the CDR3 sequences of TRBV11-2 clones shift away from SARS-CoV-2 specific T cell clones, resulting in distorted TCR repertoires. In conclusion, our study reports that CDR3-independent expansion of TRBV11-2+ cells, lacking SARS-CoV-2 specificity, defines MIS-C in children.

Clinically Applicable Assessment of Tisagenlecleucel CAR T Cell Treatment by Digital Droplet PCR for Copy Number Variant Assessment.

Chimeric antigen receptor (CAR) T cell therapy is an innovative immunotherapy for treating cancers in both children and adults with proven utility in numerous clinical trials. Significantly, some CAR T cell therapies have now been approved by relevant national regulatory bodies across numerous countries for clinical therapeutic use outside of clinical trials. One such recently licensed product is tisagenlecleucel, a CAR T therapy approved for the treatment of B-cell acute lymphoblastic leukemia (B-ALL) using autologous T cells from the patient. The genetically engineered T cells target a protein called CD19, common to B cells, through a CAR incorporating a 4-1BB costimulatory domain to improve response. Since tisagenlecleucel is now a standard of care treatment for B-ALL, it is clinically essential to be able to accurately monitor these CAR T cells in patients. Assessment of the copy number variant (CNV) of the CAR T cell products allows this within a clinically acceptable timeframe for optimal patient benefit. However, no standardized method with high reproducibility and efficiency has been described within a routine clinical laboratory setting. Here, we demonstrated a novel digital droplet PCR (ddPCR)-based methodology for the study of CNV (ddPCR-CNV) in 4-1BB CD19-specific CAR T cells with universal applicability across clinical diagnostic laboratories.

Identification of a c-MYB-directed therapeutic for acute myeloid leukemia.

A significant proportion of patients suffering from acute myeloid leukemia (AML) cannot be cured by conventional chemotherapy, relapsed disease being a common problem. Molecular targeting of essential oncogenic mediators is an attractive approach to improving outcomes for this disease. The hematopoietic transcription factor c-MYB has been revealed as a central component of complexes maintaining aberrant gene expression programs in AML. We have previously screened the Connectivity Map database to identify mebendazole as an anti-AML therapeutic targeting c-MYB. In the present study we demonstrate that another hit from this screen, the steroidal lactone withaferin A (WFA), induces rapid ablation of c-MYB protein and consequent inhibition of c-MYB target gene expression, loss of leukemia cell viability, reduced colony formation and impaired disease progression. Although WFA has been reported to have pleiotropic anti-cancer effects, we demonstrate that its anti-AML activity depends on c-MYB modulation and can be partially reversed by a stabilized c-MYB mutant. c-MYB ablation results from disrupted HSP/HSC70 chaperone protein homeostasis in leukemia cells following induction of proteotoxicity and the unfolded protein response by WFA. The widespread use of WFA in traditional medicines throughout the world indicates that it represents a promising candidate for repurposing into AML therapy.

Single-cell transcriptomics reveals a distinct developmental state of KMT2A-rearranged infant B-cell acute lymphoblastic leukemia.

KMT2A-rearranged infant ALL is an aggressive childhood leukemia with poor prognosis. Here, we investigated the developmental state of KMT2A-rearranged infant B-cell acute lymphoblastic leukemia (B-ALL) using bulk messenger RNA (mRNA) meta-analysis and examination of single lymphoblast transcriptomes against a developing bone marrow reference. KMT2A-rearranged infant B-ALL was uniquely dominated by an early lymphocyte precursor (ELP) state, whereas less adverse NUTM1-rearranged infant ALL demonstrated signals of later developing B cells, in line with most other childhood B-ALLs. We compared infant lymphoblasts with ELP cells and revealed that the cancer harbored hybrid myeloid-lymphoid features, including nonphysiological antigen combinations potentially targetable to achieve cancer specificity. We validated surface coexpression of exemplar combinations by flow cytometry. Through analysis of shared mutations in separate leukemias from a child with infant KMT2A-rearranged B-ALL relapsing as AML, we established that KMT2A rearrangement occurred in very early development, before hematopoietic specification, emphasizing that cell of origin cannot be inferred from the transcriptional state.

Rare Sequences Make Sense of CAR T-cell Therapy Outcomes.

In this issue, Pulsipher and colleagues used next-generation sequencing to detect leukemia-specific sequences following tisagenlecleucel therapy of acute lymphoblastic leukemia. A challenge for the field currently is to identify which patients will have therapy failure and to do so early enough to allow planning for further treatment, for example, stem cell transplantation. Detection of disease below the standard detection level for this technique (less than one per million cells) at day 28 was associated with poorer outcomes and potentially therefore could be used to identify those that might benefit from adjunctive therapies.See related article by Pulsipher et al., p. 66.

High-throughput sequencing of peripheral blood for minimal residual disease monitoring in childhood precursor B-cell acute lymphoblastic leukemia: A prospective feasibility study.

BACKGROUND: Minimal residual disease (MRD) measured on end-of-induction bone marrow (BM) is the most important biomarker for guiding therapy in pediatric acute lymphoblastic leukemia (ALL). Due to limited sensitivity of current approaches, peripheral blood (PB) is not a reliable source for identifying patients needing treatment changes. We sought to determine if high-throughput sequencing (HTS) (next-generation sequencing) of rearranged immunoglobulin and T-cell receptor genes can overcome this and be used to measure MRD in PB. PROCEDURE: We employed a quantitative HTS approach to accurately measure MRD from one million cell equivalents of DNA from 17 PB samples collected at day 29 after induction therapy in patients with precursor B-cell ALL. We compared these results to the gold-standard real-time PCR result obtained from their paired BM samples, median follow-up 49 months. RESULTS: With the increased sensitivity, detecting up to one abnormal cell in a million normal cells, we were able to detect MRD in the PB by HTS in all those patients requiring treatment intensification (MRD ≥ 0.005% in BM). CONCLUSION: This is proof of principle that using the increased sensitivity of HTS, PB can be used to measure MRD and stratify children with ALL. The method is cost effective, rapid, accurate, and reproducible, with inherent advantages in children. Importantly, increasing the frequency testing by PB as opposed to intermittent BM sampling may allow extension of the dynamic range of MRD, giving a more complete picture of the kinetics of disease remission while improving relapse prediction and speed of detection.

A human fetal liver-derived infant MLL-AF4 acute lymphoblastic leukemia model reveals a distinct fetal gene expression program.

Although 90% of children with acute lymphoblastic leukemia (ALL) are now cured, the prognosis for infant-ALL remains dismal. Infant-ALL is usually caused by a single genetic hit that arises in utero: an MLL/KMT2A gene rearrangement (MLL-r). This is sufficient to induce a uniquely aggressive and treatment-refractory leukemia compared to older children. The reasons for disparate outcomes in patients of different ages with identical driver mutations are unknown. Using the most common MLL-r in infant-ALL, MLL-AF4, as a disease model, we show that fetal-specific gene expression programs are maintained in MLL-AF4 infant-ALL but not in MLL-AF4 childhood-ALL. We use CRISPR-Cas9 gene editing of primary human fetal liver hematopoietic cells to produce a t(4;11)/MLL-AF4 translocation, which replicates the clinical features of infant-ALL and drives infant-ALL-specific and fetal-specific gene expression programs. These data support the hypothesis that fetal-specific gene expression programs cooperate with MLL-AF4 to initiate and maintain the distinct biology of infant-ALL.