Precursor ALL Research Articles

SH2B3 inactivation through CN-LOH 12q is uniquely associated with B-cell precursor ALL with iAMP21 or other chromosome 21 gain

In more than 30% of B-cell precursor acute lymphoblastic leukaemia (B-ALL), chromosome 21 sequence is overrepresented through aneuploidy or structural rearrangements, exemplified by intrachromosomal amplification of chromosome 21 (iAMP21). Although frequent, the mechanisms by which these abnormalities promote B-ALL remain obscure. Intriguingly, we found copy number neutral loss of heterozygosity (CN-LOH) of 12q was recurrent in iAMP21-ALL, but never observed in B-ALL without some form of chromosome 21 gain. As a consequence of CN-LOH 12q, mutations or deletions of the adaptor protein, SH2B3, were converted to homozygosity. In patients without CN-LOH 12q, bi-allelic abnormalities of SH2B3 occurred, but only in iAMP21-ALL, giving an overall incidence of 18% in this sub-type. Review of published data confirmed a tight association between overrepresentation of chromosome 21 and both CN-LOH 12q and SH2B3 abnormalities in B-ALL. Despite relatively small patient numbers, preliminary analysis linked 12q abnormalities to poor outcome in iAMP21-ALL (p = 0.03). Homology modelling of a leukaemia-associated SH2 domain mutation and in vitro analysis of patient-derived xenograft cells implicated the JAK/STAT pathway as one likely target for SH2B3 tumour suppressor activity in iAMP21-ALL.

FxCycle™ Based Ploidy Correlates with Cytogenetic Ploidy in B-Cell Acute Lymphoblastic Leukemia and Is Able to Detect the Aneuploid Minimal Residual Disease Clone.

Flow cytometry (FCM) is a simple, sensitive, and specific technique that can potentially determine DNA ploidy in B-cell precursor ALL (BCP-ALL) and is complementary to cytogenetics. A prospective FCM DNA ploidy analysis using FxCycle™ Violet (assay sensitivity 0.01%) was done in 125 consecutive new cases of BCP-ALL (90 cases <15 years of age) and compared with corresponding cytogenetic ploidy (karyotyping and/or FISH) data wherever available. This assay was also subsequently evaluated for detection of residual aneuploid clone in few BCP-ALL cases. Of the total 125 BCP-ALL cases evaluated, flow ploidy analysis revealed diploidy (DI 0.96-1.05) in 44.8% (n = 56), low-hyperdiploidy (DI 1.06 to 1.15) in 13.6% (n = 17), high-hyperdiploidy (DI 1.16-1.39) in 32.8% (n = 41) and near-tetraploidy (DI ≥ 1.80) in 2.4% (n = 3) cases. The high risk sub-group of low-hypodiploidy (DI 0.70 to 0.88)/near-triploidy (DI 1.40 to 1.79) constituted 5.6% (n = 7) cases while there was only one case with haploidy (DI 0.58). Overall, high concordance of 90.4% (n = 113) was noted between the combined cytogenetics ploidy and FCM ploidy. Of the total discordant cases (n = 12), the maximum discordance was seen in the low-hyperdiploid DI subgroup (n = 10), which included seven cases with low DNA index high hyperdiploidy (LDI-HHD). FCM DNA ploidy assay was able to detect the residual clone in all six MRD positive aneuploid cases evaluated. FxCycle™ based DNA ploidy ascertains strong correlation with cytogenetic profiles and yields complementary information that can be used by the cytogenetics laboratories or otherwise. © 2019 International Clinical Cytometry Society.

Validation of the United Kingdom copy-number alteration classifier in 3239 children with B-cell precursor ALL

AbstractOutcomes for children with acute lymphoblastic leukemia are generally excellent, one of the most impressive success stories in the treatment of cancer. However, identifying children with more challenging cases early in the process is of high significance. The International BFM Study Group examines and validates one such system, the United Kingdom Copy Number alteration classifier, in a manuscript with great promise to help guide future therapies.

CDKN2B downregulation and other genetic characteristics in T-acute lymphoblastic leukemia

We identified principal genetic alterations in 97.1% (99/102) of patients with T-acute lymphoblastic leukemia (T-ALL) using integrative genetic analyses, including massive parallel sequencing and multiplex ligation-dependent probe amplification (MLPA). A total of 133 mutations were identified in the following genes in descending order: NOTCH1 (66.7%), FBXW7 (19.6%), PHF6 (15.7%), RUNX1 (12.7%), NRAS (10.8%), and DNMT3A (9.8%). Copy number alterations were most frequently detected in CDKN2B, CDKN2A, and genes on 9p21.3 in T-ALL (45.1%). Gene expression data demonstrated the downregulation of CDKN2B in most cases of T-ALL, whereas CDKN2A downregulation was mainly restricted to deletions. Additional quantitative methylation analysis demonstrated that CDKN2B downregulation stemmed from deletion and hypermethylation. Analysis of 64 patients with CDKN2B hypermethylation indicated an association with an older age of onset and early T cell precursor ALL, which involved very early arrest of T cell differentiation. Genes associated with methylation and myeloid neoplasms, including DNMT3A and NRAS, were more commonly mutated in T-ALL with CDKN2B hypermethylation. In particular, a CDKN2B biallelic deletion or high methylation level (≥45%), the age of onset, and the GATA3 and SH2B3 mutations were factors associated with a poor prognosis. This study clarifies that one of the most important genetic events in T-ALL, namely, CDKN2B downregulation, occurs mechanistically via deletion and hypermethylation. Different susceptible genetic backgrounds exist based on the CDKN2B downregulation mechanism.

Clinical Profile of Childhood Early T cell Precursor ALL

Clinical Profile of Childhood Early T cell Precursor ALL

Health-Related Quality of Life in Adults with B-Cell Precursor Acute Lymphoblastic Leukemia and Minimal Residual Disease Treated with Blinatumomab

Background: Positive minimal residual disease (MRD) is an established prognostic marker for hematologic relapse, negative hematopoietic stem cell transplantation (HSCT) outcome, and mortality in adults with B-cell precursor acute lymphoblastic leukemia (ALL; Gökbuget N, et al. Blood. 2012;120:1868-1876). In the open-label, single-arm phase 2 BLAST study (N=116; ClinicalTrials.gov, NCT01207388), treatment with blinatumomab, a bispecific T-cell engager (BiTE®) antibody construct that redirects cytotoxic T cells to residual CD19+ blast cells, led to complete MRD response in 88 of 113 (78%) patients after cycle 1 (Gökbuget N, et al. Blood. 2018;131:1522-1531). Median overall survival was 36.5 months. Among patients with Philadelphia chromosome-negative B-cell ALL in complete MRD remission, relapse-free survival was 54% at 18months. In this analysis of the BLAST study, we assessed the health-related quality of life (HRQoL) of patients during and after treatment with blinatumomab.Methods: Eligible patients (≥18 years) had B-cell precursor ALL in first or later hematologic complete remission and persistent or recurrent MRD ≥10-3 after ≥3 blocks of intensive chemotherapy. Blinatumomab 15 μg/m2/day was administered by continuous intravenous (cIV) infusion for 4 weeks, followed by a 2-week infusion-free interval, for up to 4 cycles. Patients could receive HSCT any time after cycle 1. HRQoL was assessed using the EORTC QLQ-C30 Questionnaire at baseline, on day 29 of each treatment cycle, at the safety follow-up visit (30 days after end of treatment), and at the efficacy follow-up visits (3, 6, 9, 12, 18, and 24 months after treatment start). The questionnaire included 1 global health status scale, 5 functioning scales (physical, role, emotional, cognitive, and social functioning), 3 symptom scales (fatigue, nausea and vomiting, and pain), and 6 single-symptom items (dyspnea, insomnia, appetite loss, constipation, diarrhea, and financial difficulties). For global health status and functioning scales, a higher score indicates better HRQoL; for symptom scales/items, a lower score indicates better HRQoL. A 10-point change is often viewed as the minimum clinically important difference (MID) in EORTC QLQ-C30 (Zikos E, et al. EORTC, 2016). In this analysis, the mean (SD) and the mean (SD) change from baseline to end of cycle 1 of the scores for each scale/item was summarized at each scheduled assessment during and after blinatumomab treatment.Results: In total, 89 patients had a nonmissing baseline value and a nonmissing value of any scale on day 29 of cycle 1, and thus were evaluable for HRQoL. The patient-reported global health status and functioning scale scores were stable over time during and after blinatumomab treatment (Figure 1). Symptom-scale and single-symptom scores were similarly stable during and after treatment (not shown). Mean (SD) changes from baseline to end of cycle 1 in global health status and in physical functioning, role functioning, emotional functioning, cognitive functioning, and social functioning were 2.5 (18.5), 0.3 (12.5), -4.0 (30.0), 4.2 (20.5), -1.7 (16.2), and 10.4 (31.8), respectively (Figure 2). These results show that, after 1 cycle of blinatumomab, the change in HRQoL was minimal for most scales, with potential clinically meaningful improvements in social functioning. Similar minimal changes were observed for all symptom scales/items (not shown).Conclusions: In this population of patients with B-cell precursor ALL and MRD successfully treated with blinatumomab 15 μg/m2/day cIV for up to 4 cycles, HRQoL was maintained during and after blinatumomab treatment, which is an important result considering the potential HRQoL impact of standard chemotherapy. [Display omitted] DisclosuresZugmaier:Amgen Inc.: Consultancy, Employment, Patents & Royalties: 20170327581, 9688760, 20170122947, 9486475, 20160208001, 9192665, 20150071928, 8840888, 20140227272, 20140228316, 20130323247, 20130287774, 20130287778, 20110262440, 20100112603, 7700299, 20070037228. Bonifacio:Incyte: Consultancy; Pfizer: Consultancy; Amgen: Consultancy; Novartis: Research Funding; Bristol Myers Squibb: Consultancy. Topp:Boehringer Ingelheim: Research Funding; Regeneron Pharmaceuticals, Inc.: Honoraria, Research Funding; F. Hoffmann-La Roche Ltd: Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Research Funding. Tran:Amgen Inc.: Employment. Zhang:Amgen Inc.: Employment, Equity Ownership. Goekbuget:Kite / Gilead: Consultancy; Celgene: Consultancy; Novartis: Consultancy, Other: Travel support, Research Funding; Pfizer: Consultancy, Other: Travel support, Research Funding; Amgen: Consultancy, Other: Travel support, Research Funding.

Monitoring of the Clonal Architecture of B-Cell Precursor ALL during Induction Chemoimmunotherapy

Background:High throughput sequencing of immunoglobuline heavy chain gene rearrangements (IGH) recently demonstrated that B-cell precursor ALL (BCP-ALL) is a highly oligoclonal disease in children (Theunissen, Hematologica, 2017), however, little is known about the degree of oligoclonality in adults with BCP-ALL. Furthermore, no data exist on potential changes of the subclonal composition during therapy. Therefore, we aimed to monitor the clonal architecture of the leukemic blasts before and after Rituximab containing induction treatment in the context of the current German Multicentric Acute Lymphoblastic Leukemia (GMALL) 08/2013 trial.Materials & Methods:We identified and studied complete and incomplete immunoglobulin (IG) heavy chain rearrangements in 100ng of bone marrow (BM) DNA at diagnosis (dx) and 500ng BM DNA after Rituximab-containing induction I in 19 patients with BCP-ALL. We employed IGH-VJ FR1 and IGH-DJ NGS assays developed within the EuroClonality-NGS Consortium (www.euroclonalityngs.org), performing next generation sequencing on Illumina MiSeq. We analysed data with the ARResT/Interrogate bioinformatics platform (Bystry, Bioinformatics, 2017), which is also able to isolate and use the DN-J stem of V/DJ junctions to link clonally related rearrangements. Clones with abundance ≥5 %, and all subclones carrying the same DN-J stem as the dominant clones were considered as leukemia-associated and studied further. Employing the sequence of the DN-J stem, we could also link related complete and incomplete rearrangements, even though those are amplified in two separate PCRs.Results:At dx, 18/19 patients carried at least 1 IGH rearrangement with abundance ≥ 5%, 10 patients carried 2 or more. In all 18 patients with dominant markers detected at dx, subclones with abundance <5% carrying the same DN-J stem as the dominant clone were present, indicating oligoclonality and clonal evolution. On average, 53.1 (range 0-295) (sub)clones per DN-J stem were detected at dx, and 32.7 (range 0-238) after treatment.Next, we compared the kinetics of all (sub)clones with abundance ≥1% in at least one of the time-points. Of the 18 patients, 6 only had subclones with abundance <1%, and we did not investigate the kinetics of such subclones. In another 11 patients (Fig. 1, Pt. 1-11), all sub(clones) had the same kinetics, with no clone gaining predominance over time. In 1 patient (Fig. 1, Pt. 12), 3 (sub)clones which were present at dx disappeared and a new subclone appeared after treatment. This patient had a pro-B immunophenotype, where oligoclonality and clonal instability are well known phenomena (Szczepanski, Leukemia, 2001).Conclusions:It has recently been shown that ALL is a highly oligoclonal disease in children (Theunissen, Hematologica, 2017), and our study extends this finding to adults with BCP-ALL. We furthermore demonstrate that the subclonal composition remains stable in the majority of patient during induction chemoimmunotherapy. The fact that the response to treatment is generally consistent among different (sub)clones has important implications for MRD quantification as it reassures the usage of the dominant clonal IG gene rearrangement for MRD monitoring in ALL. However, also significant changes of the clonal composition may occur in BCP-ALL as exemplified in one patient of our cohort. Further investigations are necessary to elucidate factors that influence subclonal heterogeneity in response to treatment. [Display omitted] DisclosuresViardot:Pfizer: Consultancy, Honoraria; Gilead Kite: Consultancy, Honoraria; Roche: Consultancy, Honoraria; Amgen: Consultancy; BMS: Consultancy, Honoraria. Kneba:AbbVie: Consultancy, Honoraria; Roche: Consultancy, Honoraria. Goekbuget:Pfizer: Consultancy, Other: Travel support, Research Funding; Novartis: Consultancy, Other: Travel support, Research Funding; Kite / Gilead: Consultancy; Amgen: Consultancy, Other: Travel support, Research Funding; Celgene: Consultancy. Brüggemann:Incyte: Consultancy; PRMA: Consultancy; Regeneron: Research Funding; Affimed: Research Funding; Pfizer: Speakers Bureau; Amgen: Consultancy, Research Funding, Speakers Bureau; Roche: Speakers Bureau.

A Tumor Suppressor Role for Bank1 in B-Cell Precursor Acute Lymphoblastic Leukemia

Introduction: Since the implementation of next generation sequencing techniques, inherited mutations in malignancy-associated susceptibility genes have become of major interest, to identify high-risk individuals, even before an actual disease onset. One challenge in this regard is that germline susceptibility variants often display incomplete or reduced penetrance, which can be influenced by genetic as well as environmental factors (Martin-Lorenzo A. et al., Cancer Discov, 2015), making it even harder to assess the complete spectrum of the predisposition. Here, we aimed to elucidate the variable penetrance of a family, which harbors the inherited B-cell precursor ALL (BCP-ALL) susceptibility variant PAX5 c.547G>A (Auer F et al., Leukemia, 2014).Methods: We generated a new in vivo model, namely double transgenic Bank1+/-+Pax5+/- mice. Next generation sequencing was used to determine candidate genes influencing the variable penetrance of PAX5 c.547G>A. Pax5+/-+Bank1+/-, as well as Arf-/-+Bank1+/- mouse models were utilized to assess the tumor suppressor potential of Bank1. Murine leukemias were characterized by immune-phenotyping, whole exome sequencing (WES) as well as expression analyses.Results: In a family, harboring PAX5 c.547G>A, 5 out of 7 analyzed children were shown to be mutation carriers, while only 3 out of 5 developed BCP-ALL. In order to assess this variable penetrance further, re-analysis of the WES data revealed an additional rare variant in the B-cell scaffold protein with ankyrin repeats (BANK1) (c.120G>C; rs35978636, minor allele frequency (MAF)<0.01), with a similar transmission spectrum like the heterozygous PAX5 susceptibility variant c.547G>A (Figure 1).BANK1 is primarily expressed in B-cells where it acts as an important adaptor that is involved in B-cell receptor (BCR) induced Ca2+ mobilization from intracellular stores (Yokoyama K et al., EMBO, 2002). Importantly, single nucleotide variants (SNVs) in BANK1 could be linked to confer a susceptibility to a variety of autoimmune diseases, including Systemic Lupus Erythematosus (SLE) (Kozyrev SV et al., Nat. Genet., 2008). The identified BANK1 variant c.120G>C is located in Exon2, the IP3R binding site of BANK1, in proximity to the previously described SLE susceptibility variant c.182G>A, and results in a predicted deleterious protein structure as calculated by SIFT and PolyPhen-2.To test whether Bank1 and Pax5 heterozygosity could cooperate to promote BCP-ALL development, we crossed Bank1+/- mice on a Pax5 heterozygous background and monitored the leukemia incidence of double transgenic Bank1+/-+Pax5+/- mice. Bank1+/-+Pax5+/- mice developed BCP-ALL with clonal blast infiltration in secondary lymphoid organs and an identical leukemia phenotype (CD19-B220+IgM-) and latency like Pax5+/- mice. However, we observed an increase in BCP-ALL disease incidence of 33% compared to the Pax5+/- cohort. These results suggest that Pax5 loss promotes an aberrant B-cell precursor compartment that is susceptible for leukemic transformation, while the combination with Bank1 heterozygosity causes a susceptibility increase in the pre-leukemic population. While these results reflect the variable BCP-ALL penetrance in the human family carrying both PAX5 c.547G>A and BANK1 c.120G>C, it also underlines the multifactorial nature of the disease.Since these results suggest a tumor suppressor function of BANK1 in BCP-ALL, we next explored the effect of Bank1 loss of function on the disease phenotype in a tumor-prone mouse model lacking BCP-ALL susceptibility. Therefore, Bank1-/- mice were crossed back on a p19Arf-deficient background, to obtain the mouse cohorts Bank1+/-p19Arf-/- and Bank1-/-p19Arf-/-. The additional Bank1-deficiency promoted a shift from a T- to mainly B-cell phenotype in the resulting p19Arf-deficient tumors, further supporting a specific tumor suppressor role of Bank1 in BCP-ALL.Conclusion: Taken together, our data underline a tumor suppressor role of Bank1 in the context of BCP-ALL development and supports its involvement in the variable penetrance of BCP-ALL in a family carrying PAX5 c.547G>A. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Characteristics and Outcome of Early T Cell Precursor ALL (ETP-ALL) Patients Treated with High-Risk Spanish Pethema Protocols

▪Background:ETP-ALL was included as a provisional identity in the 2016 WHO classification of ALL. This subtype was first identified by Coustan-Smith et al. in 2009. However, this immunophenotype-based classification does not fully enclose all ETP-ALL cases identified by gene expression profile (GEP). Although early studies in small series of ETP-ALL suggested a very poor outcome for ETP ALL more recent and larger series have showed improvement in outcome treating children with a contemporary protocol based on chemotherapy schedules, or after allogeneic stem cell transplantation (allo-SCT) in adults.Aim:To investigate the clinical and biological features of ETP-ALL cases in the Spanish cohort of adult T-cell ALL (T-ALL) patients and to assess the potential impact of high-risk therapy on their outcome.Method:One hundred eighty-five adults with T-ALL treated according to two consecutive MRD-oriented high-risk adult PETHEMA protocols -ALL-HR-2003 (NCT00853008) and ALL-HR-11 (NCT01540812; still ongoing)- were included in this study. The EGIL criteria were used to define the immunologic subtype of T-ALL after central review of immunophenotype reports, and the criteria proposed by Zuurbier et al. (Zuurbier L. et al. Haematologica 2014; 99:94-102) were used to define ETP-ALL. These later criteria consist of a combination of immunophenotypic markers (absence of CD1a-/CD4-/CD8-, cut-off <10%, and expression of the stem cell marker CD34+and/or at least one myeloid marker such as CD13+or CD33+, cut-off >25%), that resemble those published by Coustan-Smith, with the advantage that include most ETP-ALL cases, as identified by GEP, avoiding the use of partial expression of CD5 marker to immuno-classify these patients.Results:Thirty-four out of 167 evaluable patients (20%) with T-ALL showed an ETP-ALL immunophenotype. Patients with ETP-ALL were older (mean 39 [SD 12] vs. 33 [12] yr; p=0.011), showed more frequently lymph node involvement (79% vs. 56%; p=0.021) and lower WBC counts at diagnosis (mean, 72 [155] vs. 97 [112] x109/L; p=0.004). At genetic level, ETP-ALL patients were associated with the absence of deletions in CDKN2A/B gene cluster (91% vs. 26%; p<0.001) (10/11 cases) and with the absence of bi-allelic deletions in TCRG gene (67% vs. 5%; p=0.001) (6/9 cases). In turn, ETP-ALL patients showed poorer response to induction therapy: 82% of ETP-ALL had poorer early cytologic response (>10% BM blasts on day+14) vs. 37% of non-ETP (p<0.001), and 23% of ETP-ALL patients did not reach CR vs. 6% non-ETP T-ALL cases (p=0.005). Flow-MRD data at CR (available in 141/167 patients) showed MRD levels ≥0.1% in 65% of ETP-ALL vs. 18% of non-ETP ALL (p<0.001), and MRD level ≥0.01% in 85% vs. 37%, respectively (p<0.001). Forty-six percent of ETP-ALL patients required a second induction treatment compared to 8% of non-ETP-ALL (p<0.001). Consequently, more ETP-ALL patients underwent allo-SCT (70% vs. 21%, p<0.001). The OS of ETP-ALL patients was poorer after censoring or not the follow-up at the time of transplant (Figures 1A and B).Conclusions:ETP-ALL accounts for 20% of adult T-ALL in the PETHEMA cohort and it is associated with a poorer initial response to treatment (lower CR rate, poorer MRD clearance) than the remaining T-ALL patients. Such poorer outcome is not overcome by allo-SCT in our series.Supported by grants from: Asociación Española Contra el Cáncer, AECC (GC16173697BIGA), Instituto Carlos III (PI14/01971 FI), 2017-SGR288 (GRC), CERCA Program from Generalitat de Catalunya, and “La Caixa” Foundation. [Display omitted] DisclosuresMontesinos:Daiichi Sankyo: Consultancy, Speakers Bureau; Novartis: Research Funding, Speakers Bureau.

CD20 Expression and Response to Rituximab Treatment in B-Cell Precursor Lymphoblastic Leukemia - Results of the GMALL 08/2013 Trial

Introduction: Treatment with Rituximab has improved the outcome for patients with B-cell precursor ALL (B-ALL) and is conventionally restricted to patients with CD20 expression on leukemic blasts above a level of 20%. However, it is not known whether this arbitrary cutoff is biologically meaningful, or if also patients with lower CD20 expression levels profit from Rituximab treatment. In addition, CD20 expression levels might differ between different compartments and can change during early treatment. Therefore, in the current German Multicentric Acute Lymphoblastic Leukemia (GMALL) 08/2013 trial Rituximab is applied to all BCR-ABL1-negative B-ALL patients during induction and early consolidation irrespective of the initial blast CD20 expression. In this study, CD20 expression on blasts at diagnosis and after a 5-day dexamethasone prephase is thoroughly characterized and correlated to MRD response after induction I including one dose of Rituximab to evaluate its impact on response to Rituximab.Methods: Comparative quantification of CD20 expression levels was performed at diagnosis (blood and bone marrow (BM)) and at the end of the prephase (blood) and correlated to minimal residual disease (MRD) response after early Rituximab treatment. Samples were subjected to the EuroFlow standardized stain, lyse and wash and instrument setting procedures (van Dongen et al., 2012) and stained with a 3-tube, 8-color panel, containing the markers CD45, CD20, CD10, CD66c, CD3, CD19, CD71, CD9, CD13+33, CD34, CD22, CD11a, and CD38. CD20 median fluorescence intensities (CD20-MFI) as well as percentages of CD20+ B-ALL blasts among all blasts (%CD20+) were measured. MRD was quantified at day 22 after induction I using real-time quantitative PCR of clonal immune gene rearrangements. MRD response after induction was defined as MRD decrease to a level below 10-4, MRD persistence as detection of quantifiable MRD ≥10-4.Results: FCM results of a total of 166 samples of 84 B-ALL patients were evaluated. CD20 expression of circulating blasts significantly increased after a 5-day prephase in common/pre-B-ALL (c/pre-B) but not in pro-B-ALL in a cohort of 36 paired peripheral blood samples (Fig. 1 A-B, n=8 pro-B-ALL, paired t-test of CD20-MFI and %CD20: p=.1016 and p=.1660, Fig. 2 A-B, n=28 c/pre-B-ALL, p=.0029 and p=0.0060). Interestingly, the increase of CD20 expression on B-ALL blasts contrasted that on mature normal B-cells, where a decrease occurred in pro-B-ALL and c/pre-B-ALL samples at day 6 (paired t-test: p=.0485 and p<.0001, respectively) (Fig.1A, 2A).In 24 paired blood/BM pre-treatment samples the percentage of CD20+ blasts was significantly higher in blood in c/pre-B-ALL (n=19: paired t-test: p=.0009), but not in pro-B-ALL (n=5: paired t-test: p=.095) (Fig. 1C, 2C). The significance levels were not consistently reached for the comparison of CD20-MFI. Nevertheless, we show that in 3/24 (12.5%) patients the percentage of CD20+ B-ALL blasts in BM did not reach the arbitrary cutoff of 20% whereas the matching diagnostic blood did.Finally, CD20 expression levels from 25 BM and 30 pre-treatment blood samples and 38 blood samples after dexamethasone prephase from 54 patients were assessed (in total 93 samples). In further calculations we correlated MRD response values after one dose of Rituximab with the CD20 expression levels on blasts. In detail, the highest measured percentage value of %CD20 per patient in the group of MRD responders was compared to the highest measured %CD20 per patient in the group of MRD persisters. CD20 expression levels were significantly lower in 33 MRD persisters compared to 21 MRD responders (Fig 3, p=.0336). The difference was mainly attributable to a high frequency of MRD persisters in pro-B-ALL compared to c/pre-B-ALL (MRD persistence in pro-B-ALL 8/9 (89%) compared to 25/45 (56%) in c/pre-B-ALL).Conclusion: We measured significant differences in CD20 expression levels on leukemic blasts (i) between pre-treatment blood and BM and (ii) between pre-treatment blood and blood after prephase in patients with c/pre-B-ALL challenging the conventional eligibility criteria for the CD20 targeted treatment. MRD responders tended to have higher CD20 expression levels compared to MRD persisters. Extension of the patient cohort is ongoing to confirm this observation. Furthermore, we will analyze the impact of 3 rituximab applications after induction phase II. [Display omitted] DisclosuresRitgen:abbvie: Research Funding; Roche: Honoraria, Research Funding. Viardot:Gilead Kite: Consultancy, Honoraria; Roche: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; BMS: Consultancy, Honoraria; Amgen: Consultancy. Kneba:Roche: Consultancy, Honoraria; AbbVie: Consultancy, Honoraria. Goekbuget:Kite / Gilead: Consultancy; Celgene: Consultancy; Novartis: Consultancy, Other: Travel support, Research Funding; Pfizer: Consultancy, Other: Travel support, Research Funding; Amgen: Consultancy, Other: Travel support, Research Funding. Brüggemann:Incyte: Consultancy; Amgen: Consultancy, Research Funding, Speakers Bureau; PRMA: Consultancy; Affimed: Research Funding; Regeneron: Research Funding; Pfizer: Speakers Bureau; Roche: Speakers Bureau.

Outcomes of Pediatric Patients with Acute Leukemia Following Adult Unrelated Donor Transplant: The Impact of Donor KIR Gene Content and KIR Ligand Matching

Abstract In patients with acute leukemia, relapse remains one of the most frequent causes of treatment failure after allogeneic transplantation (allo-HCT). Early after transplant, natural killer (NK) cells predominate and thus, they have been implicated in graft vs. leukemia (GVL) reactions after allo-HCT. Killer Ig Receptors (KIR) are a family of 15 distinct genes that both positively and negatively regulate NK cell function. Individuals vary in the number of genes that they possess within their genome and thus, may vary in their GVL capacity. Accordingly, numerous studies have investigated the association of donor KIR gene content (B/x vs. A/A), KIR B gene score (neutral, better, best), KIR composite score (taking into account CenB/x and TelA/A gene status) and KIR ligand mismatching in the setting of allo-HCT. These studies have largely focused on adult transplant recipients, yielding variable outcomes. However, pediatric patients may differ from adult transplant recipients in a variety of ways including differential sensitivity of leukemic blasts to NK cytotoxicity, distinct cytogenetic changes, the higher propensity to receive myeloablative conditioning and an earlier adoption of minimal residual disease-driven timing of transplantation. The purpose of this analysis was to investigate the impact of KIR gene content and KIR ligand mismatching on outcomes of children transplanted with acute lymphoblastic and acute myeloid leukemia (ALL and AML, respectively), reported to CIBMTR. The study cohort included pediatric patients (0-&lt;19 years, n=716), who received a first HLA 7-8/8 matched, unmanipulated allo-HCT from an adult donor for either B precursor ALL (n=372) or AML (n=344), where donor KIR typing was available. The time period studied was from 1995-2016. For ALL and AML patients, most (95% and 86%) received myeloablative conditioning, without in vivo T cell depletion (79% and 70%). GVHD prophylaxis was with calcineurin inhibitor + MTX+/- serotherapy (79% and 76%) or calcineurin inhibitor + MMF +/- serotherapy (13% and 17%). Median follow up was 59 and 54 months for ALL and AML, respectively. The cumulative incidence of relapse for ALL and AML at 3 years was 22% (18-26%) and 33% (28-39%) and the disease free survival 58% (53-63%) and 48% (43-54%), respectively. The primary endpoints of the analysis were the impact of KIR gene content on relapse and disease free survival (DFS). Other secondary endpoints included acute GVHD, treatment related mortality and overall survival. Considering the various KIR models (Bx vs AA, KIR B gene content, and the KIR composite score (i.e., Tel A/A, Cen B) and KIR ligand matching, there was no significant association with the primary (relapse or DFS) or secondary endpoints in multivariate analysis when taking into account relevant covariates. Likewise, similar results were obtained when considering AML and ALL separately. Lastly, a subgroup analysis considering just patients who received in vivo T cell depletion also showed a lack of correlation between KIR genes and transplant outcomes. Collectively, these studies do not support the selection of an unmanipulated adult URD based on KIR gene content in pediatric AML or ALL transplant recipients. Disclosures Fleischhauer: GENDX: Research Funding. Fleischhauer:GENDX: Research Funding. Lee:Merck, Sharp, and Dohme: Consultancy; Courier Therapeutics: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; CytoSen Therapeutics: Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Research Funding. Paczesny:Viracor IBT Laboratories: Patents &amp; Royalties. Lee:Kadmon: Research Funding; Amgen: Consultancy, Research Funding; Incyte: Consultancy; Mallinckrodt: Honoraria; Pfizer: Consultancy; Takeda: Research Funding; Onyx: Research Funding.

Engineered Bcor Mutations Lead to Acute Lymphoblastic Leukemia of Progenitor B-1 Lymphocyte Origin in a Sensitized Background

Chromosomal translocations resulting in NUP98 fusion genes have been associated with a wide spectrum of hematologic malignancies, including MDS, AML, T-ALL, and B cell precursor (BCP) ALL. Based on gene expression profiles and murine transplantation experiments, it is thought that NUP98 fusions can confer aberrant self-renewal potential to hematopoietic cells. Approximately 90% of mice that express a NUP98-PHF23 (NP23) fusion in the hematopoietic compartment, under the control of Vav1 regulatory elements develop AML and/or T-ALL. However, approximately 10% of NP23 mice develop an aggressive acute lymphoblastic leukemia of B1-lymphocyte progenitor origin (pro B-1 ALL). Whole exome sequencing demonstrated that all NP23 pro-B1-ALL had acquired somatic frameshift mutations of the BCL6 co-repressor (Bcor) gene, and most had acquired mutations in the Jak/Stat pathway.To determine whether experimentally engineered Bcor mutations would lead to pro B-1 ALL, we used CRISPR-Cas9 to introduce Bcor indel mutations into NP23 hematopoietic stem and progenitor cells through the use of Bcor single guide RNAs (Bcor sgRNA). Recipient mice transplanted with NP23 bone marrow (BM) or fetal liver (FL) cells that had been transduced with a Bcor sgRNA developed pro B-1 ALL, characterized by a B-1 progenitor immunophenotype, clonal Igh gene rearrangement, and Bcor indel mutation, whereas control recipients did not. In addition, similar to some human BCP ALL, the Bcor sgRNA/NP23 murine pro B-1 ALL had acquired somatic mutations in Jak kinase genes.A distinct subset of pediatric BCP ALL are characterized by rearrangement and overexpression of the CRLF2 gene (designated CRLF2r); the CRLF2 gene is the receptor for thymic stromal lymphopoietin (TSLP), a cytokine that plays a role in normal progenitor B1 cell development. The NP23 pro-B1 ALL are similar to CRLF2r BCP ALL in terms of a preferential V heavy chain (VH) usage, gene expression profile, and propensity for acquired JAK/STAT pathways mutations. JAK inhibitors (ruxolitinib and tofacitinib) induced apoptosis and inhibited the growth of pro B-1 ALL cell lines established from Bcor sgRNA/NP23 recipients, at clinically achievable concentrations (10-100 nM). Taken together, these findings demonstrate that a CRISPR-induced Bcor frameshift collaborates with an NP23 transgene to predispose B-1 progenitors to leukemic transformation. These two events are unlikely to be sufficient for leukemic transformation, as we detected spontaneous Jak pathway mutations that were required for continued growth of the leukemic cells. This constellation of mutations (NP23 expression leading to increased stem cell self-renewal, Bcor frameshift leading to impaired B cell differentiation, and Jak pathway mutations leading to dysregulated proliferation) is similar to that seen in human BCP ALL patients, and suggests that the NP23/Bcor mutant mice and cell lines will be a useful model for human pro-B1 ALL. DisclosuresAplan:NIH Office of Technolgy Transfer: Employment, Patents & Royalties: NUP98-HOXD13 mice.

Acute Lymphocytic Leukemia in the Latin American Population

Introduction: An interesting epidemiological aspect of ALL is the variation between ethnic groups. Among all subtypes of leukemia Latinos have lower incidence rates. However, in remarkable contrast, ALL has a higher incidence rate in the Latino population and also carries a more dismal prognosis (Barrington-Trimis J, et al Blood 2015).The majority of reported data among Latinos either exclusively looks at B cell precursor (BCP) ALL or does not distinguish between subtypes. In this study we used the National Cancer Institute Surveillance, Epidemiology, and End Results (SEER) database to delineate the differences in incidence rates of B-ALL and T-ALL across ethnic groups in the United States.Epidemiologically, highest rates of ALL worldwide have been reported in both adult and pediatric Latino patients. However, determining who is to be considered Latino is not always straightforward. Many studies utilize self reported ethnicity and databases such as the Surveillance, Epidemiology, and End Results (SEER) Program of the National Cancer Institute (NCI) employ complex algorithms to determine ethnicity. Of note, the North American Association of Central Cancer Registries (NAACCR) Hispanic Identification Algorithm (NHIA) used by SEER includes European Spaniards but excludes South American Brazilians. This is a point of special interest due to the fact that although the overall incidence of ALL in the Brazilian population is low, the regional distribution is strikingly heterogeneous, with higher rates in regions with higher indigenous ancestry.Methods: Data from the SEER-18 database was used compare incidence rates of T-ALL and B-ALL. Patients in which ethnicity was reported were included. Due to the utilization of cytogenetics and subsequent changes in ICD coding over the years we chose to look at the most recent data reported in 2014. We compared rates in non-Hispanic Whites, Latinos (Hispanic), Blacks and Asian-Pacific Islanders (API). Age-adjusted incidence rates per 100,000 person-years were calculated.Results: AAIR of B-ALL in the Hispanic population is consistently higher than that of Non-Hispanic Whites throughout the years, ranging from 1.0-2.4 per 100,000. Blacks had the lowest incidence overall, with rates approximately one third of those found in Latinos.The distribution of ALL throughout the Americas can perhaps shed some epidemiological light on the genetic origins of ALL in Latinos. The ancestry across Latin America is mixed but historical idiosyncrasies can perhaps explain the distribution of ALL in the Americas. We reviewed the available literature and found that throughout the Americas, higher incidence rates are seen in areas of higher Native American ancestry (Fig 1).Discussion:Our finding shows that the increase of ALL among Latinos is accounted for by the high rate of B cell origin. The increased incidence of ALL in the Latino population has been linked to polymorphisms in genes such as the transcription factor GATA3 (Perez-Andreu V, Nat Genet 2013). The underlying mechanism of disease has yet to be elucidated and is likely related to BCP- ALL and, more specifically, Ph-Like ALL. This variation appears to be related to Native American ancestry. Understanding the molecular mechanism and epidemiological origins of this subset of patients with aggressive features will lead to improved treatment and overall survival in this minority healthcare disparity. DisclosuresDouer:Shire: Membership on an entity's Board of Directors or advisory committees; Gilled Sciences, Inc: Consultancy; Spectrum: Consultancy; Jazz Pharmaceuticals: Consultancy; Amgen: Membership on an entity's Board of Directors or advisory committees; Pfizer: Honoraria.

Combining Biology and Chemistry for a New Take on Chemotherapy: Antibody-Drug Conjugates in Hematologic Malignancies.

This review is about the antibody-drug conjugate (ADC), a form of drug delivery consisting of a monoclonal antibody, linker, and cytotoxic payload. We summarize the history of ADC development, highlighting the three FDA-approved ADCs currently available. Gemtuzumab ozogamicin is a CD33-targeted ADC linked to calicheamicin. It is approved for CD33+ AML in the first line or the relapsed or refractory (R/R) setting. Brentuximab vedotin is a CD30-targeted ADC bound to MMAE. It is approved for the treatment of certain R/R CD30+ lymphomas. Recently, it has been approved for first line therapy with chemotherapy in advanced HL. Inotuzumab ozogamicin is a CD22-directed ADC attached to calicheamicin indicated for the treatment of adults with R/R B cell precursor ALL. Three ADCs have been approved for the treatment of various hematologic malignancies. We discuss the pertinent human trials that led to FDA approval. We include our perspectives about drug resistance, toxicities, and future development.

3108 - Blockage of NG2 Antigen Synergizes in Vivo with VXL Treatment Resulting in a Delayed Relapse in a Nsg Mice-Based Preclinical Model for MLL-Rearranged BCP-ALL

MLL-rearranged (MLLr) infant B-cell precursor ALL (iMLLr-BCP-ALL) has a dismal prognosis and is associated with a pro-B/mixed phenotype, therapy refractoriness and frequent central nervous system (CNS) disease/relapse. Neuron-glial antigen 2 (NG2) is specifically expressed in MLLr leukemias and is clinically used because of its predictive value. However, its role in MLL-mediated leukemogenesis remains elusive. We previously reported in a large patient cohort that high expression of NG2 associates with poor outcome. Furthermore, we also showed that although NG2 is a malleable marker not enriching for leukemia-initiating cells, it is consistently upregulated in blasts infiltrating extramedullar hematopoietic sites and the CNS, suggesting a key role in migration. We here hypothesize that NG2 may be a therapeutic target for iMLLr-BCP-ALL. Here, we demonstrate that blocking of NG2 in vivo promotes the exit of MLLr BCP-ALL blasts from BM to PB, suggesting a role for the extracellular domain of NG2 in retaining MLLr blasts within the BM niche. When combined with standard ALL chemotherapy (Vincristine, Prednisone and L-Asp, VxL), anti-NG2 resulted in 3-fold decreased levels of minimal residual disease. Importantly, follow-up of mice in (near)-complete remission evidenced that anti-NG2 when combined with VXL significantly delayed mice relapse. Preliminary studies suggest that NG2+ blasts are more resistant than NG2- blast to Glucocorticoids. In addition, NG2 promoter has binding sites for GC receptors, and treatment with dexamethasone results in increased levels of NG2, likely reflecting a NG2-mediated mechanism to escape GC toxicity. Collectively, our data propose NG2 antigen as a therapeutic target in MLLr-B-ALL using either antibody-based or CAR T-cell-based immunotherapy.

MiR-339 Promotes Development of Stem Cell Leukemia/Lymphoma Syndrome via Downregulation of the BCL2L11 and BAX Proapoptotic Genes.

The development of myeloid and lymphoid neoplasms related to overexpression of FGFR1 kinases as a result of chromosome translocations depends on the promotion of a stem cell phenotype, suppression of terminal differentiation, and resistance to apoptosis. These phenotypes are related to the stem cell leukemia/lymphoma syndrome (SCLL), which arises through the effects of the activated FGFR1 kinase on gene transcription, which includes miRNA dysregulation. In a screen for miRNAs that are directly regulated by FGFR1, and which stimulate cell proliferation and survival, we identified miR-339-5p, which is highly upregulated in cells carrying various different chimeric kinases. Overexpression of miR-339-5p in SCLL cell types enhances cell survival and inhibition of its function leads to reduced cell viability. miR-339-5p overexpression protects cells from the consequences of FGFR1 inactivation, promoting cell-cycle progression and reduced apoptosis. Transient luciferase reporter assays and qRT-PCR detection of endogenous miR-339-5p expression in stably transduced cell lines demonstrated that BCR-FGFR1 can directly regulate miR-339-5p expression. This correlation between miR-339-5p and FGFR1 expression is also seen in primary human B-cell precursor acute lymphoblastic leukemia. In a screen to identify targets of miR-339-5p, we identified and verified the BCL2L11 and BAX genes, which can promote apoptosis. In vivo, SCLL cells forced to overexpress miR-339-5p show a more rapid onset of disease and poorer survival compared with parental cells expressing endogenous levels of miR-339-5p. Analysis of human primary B-cell precursor ALL shows a significant higher expression of miR339-5p compared with the two cohorts of CLL patient samples, suggesting direct roles in disease progression and supporting the evidence generated in mouse models of SCLL.Significance: Proapoptiotic genes that are direct targets of miR-339-5p significantly influence promotion and aggressive development of leukemia/lymphomas associated with FGFR1 overexpression. Cancer Res; 78(13); 3522-31. ©2018 AACR.

Recent Advances in the Biology and Treatment of T Cell Acute Lymphoblastic Leukemia.

This article provides an overview of the current knowledge regarding the biology and treatment of T cell acute lymphoblastic leukemia (T-ALL) and highlights the most recent findings in this field over the past 5years. Remarkable progress has been made in the genomic landscape of T-ALL over the past few years. The discovery of activating mutations of NOTCH1 and FBXW7 in a majority of patients has been a seminal observation, with several early phase clinical trials currently exploring these as potential therapeutic targets. Characterization of early T cell precursor ALL, incorporation of minimal residual disease assessment into therapeutic protocols, and use of pediatric-intensive regimens along with judicious use of allogeneic HCT have significantly improved risk stratification and treatment outcomes. Improved risk stratification and the use of novel targeted therapies based on recent genomic discoveries are expected to change the therapeutic landscape of T-ALL and hopefully improve the outcomes of this historically poor prognosis disease.

Abstract LB-B16: The AKR1C3-Activated Prodrug OBI-3424 Exerts Profound In Vivo Efficacy Against Preclinical Models of T-Cell Acute Lymphoblastic Leukemia (T-ALL); a Pediatric Preclinical Testing Consortium Study

Abstract Introduction: Aldo-keto reductase family 1 member C3 (AKR1C3) belongs to a superfamily of oxidoreductases that are broadly expressed in human tissues. AKR1C3 catalyzes the reduction of a diverse group of substrates, and is expressed at high levels in several human cancers including T-ALL. We previously showed that AKR1C3 is a biomarker of T-ALL sensitivity to the hypoxia-activated pre-prodrug PR-104, which is also activated under aerobic conditions by AKR1C3 (Manesh et al, Blood, 2015;126:1193-202). Therefore, it was of interest to test the in vivo efficacy of OBI-3424 against preclinical models of T-ALL, since OBI-3424 is a highly selective prodrug that is converted by AKR1C3 to a DNA alkylating agent. Methods: ALL patient-derived xenografts (PDXs) grew in an orthotopic manner following intravenous inoculation into NSG mice. Engraftment and response to treatment were assessed by enumeration of the % human leukemic blasts in the murine peripheral blood (%huCD45+). Treatment commenced when the %huCD45+ exceeded a median of 1%, and mice received OBI-3424 (2.5 mg/kg by the intraperitoneal route once weekly x 3) or vehicle. An event was defined as the %huCD45+ exceeding 25% or leukemia-related morbidity. The Kaplan-Meier method was used to compare event-free survival (EFS) between treated (T) and control (C) groups. Stringent objective response measures were assigned to each mouse and reported as group medians (Houghton et al, PBC, 2007;49:928-40). Leukemia infiltration into the femoral bone marrow was also assessed at Day 28 following treatment initiation. OBI-3424 was provided by Threshold Pharmaceutical and is being developed by OBI Pharma, Inc. (ex-Asia) and Ascenta Pharma (Asia). Results: OBI-3424 was well tolerated, with only a 2.8% toxicity rate in the drug-treated groups. OBI-3424 induced significant differences in EFS distribution compared to control in 9 of 9 (100%) of the evaluable PDXs. T-C values ranged from 17.1 to 65.2 days (T/C 2.3-14.0), and objective responses were observed in 8 of 9 PDXs (2 complete responses, CRs; 6 maintained CRs, MCRs). A significant reduction (P&amp;lt;0.0001) in bone marrow infiltration at Day 28 was observed in 4 of 6 evaluable T-ALL PDXs. The importance of AKR1C3 in the in vivo responses of ALL PDXs to OBI-3424 was verified using a B-cell precursor ALL PDX (ALL-11) that had been lentivirally transduced to stably overexpress AKR1C3 (ALL-11/1C3) compared with empty vector control (ALL-11/EV). Mice engrafted with ALL-11/1C3 exhibited an MCR (T-C &amp;gt;37.3 days, T/C &amp;gt;3) compared with a CR for ALL-11/EV (T-C 21.1 days, T/C 2.5). Infiltration of ALL-11/1C3 cells into the murine bone marrow was significantly reduced at Day 28 in OBI-3424-treated compared with vehicle-treated mice (P&amp;lt;0.0001) but not in mice engrafted with ALL-11/EV. Conclusions: At a dose of 2.5 mg/kg, which is estimated to achieve exposure levels in mice that will be readily attainable in humans, OBI-3424 exerted profound in vivo efficacy against a broad range of T-ALL PDXs and significantly reduced leukemia infiltration in the bone marrow. Since these PDXs were derived predominantly from aggressive and fatal disease, OBI-3424 may represent a novel treatment for aggressive and chemoresistant T-ALL in an AKR1C3 biomarker-driven clinical trial. (Supported by NCI Grants CA199222 &amp; CA199000) Citation Format: Richard B. Lock, Kathryn Evans, Raymond Yung, Tara Pritchard, Beverly A. Teicher, JianXin Duan, Yuelong Guo, Stephen W. Erickson, Malcolm A. Smith. The AKR1C3-Activated Prodrug OBI-3424 Exerts Profound In Vivo Efficacy Against Preclinical Models of T-Cell Acute Lymphoblastic Leukemia (T-ALL); a Pediatric Preclinical Testing Consortium Study [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr LB-B16.

Bispecific antibodies for cancer therapy: A review.

The ability to produce monoclonal antibodies with defined and distinct specificities has resulted in a vast spectrum of therapeutic monoclonal antibodies including bispecific antibodies (BsAbs). Several types of BsAbs have been produced but the most well-known of these are trispecific antibodies (TrAbs or TrioMabs) and bispecific T cell engager antibodies (BiTE). TrAbs have two variable segments for antigen binding and an Fc component to recruit immune cells. Catumaxomab is a TrAb that has orphan drug status from the Food and Drug Administration (FDA) for EpCam positive gastric and ovarian tumors and was previously approved by the European Medicinal Agency (EMA) for the same indication. One arm of catumaxomab binds to EpCAM, the other binds to CD3 on T cells and the Fc portion recruits immune cells. Catumaxomab is no longer being produced by the manufacturer due to logistic considerations and hence not available in the European market. Blinatumomab is a BiTE that comprises of two variable segments only with one arm binding to CD19 and the other binding to CD3. Blinatumomab has been approved for relapsed or refractory B-cell precursor ALL in adults and children by the FDA. There are over 50 bispecific antibodies currently on clinical trials for various malignancies and the hope is that in the future many of these, with better understanding of principles and techniques of production, will provide treatment options for many different types of cancer.

Philadelphia Chromosome-like Acute Lymphoblastic Leukemia.

Philadelphia chromosome-like acute lymphoblastic leukemia (Ph-like ALL) is a recently described B-cell precursor ALL with a gene expression profile and a high frequency of IKZF1 gene alteration similar to that of Ph-positive ALL. Its prevalence is approximately 12% in children, 21% in adolescents (16-20 years of age), and 20% to 24% in adults older than 40 years, with a peak (27%) in young adults 21 to 39 years old. It occurs more often in male individuals and patients with Down syndrome. Ph-like ALL is overrepresented in those with Hispanic ethnicity and is associated with inherited genetic variants in GATA3 (rs3824662). It is a clinically and biologically heterogeneous subtype of B-ALL. Although most patients with Ph-like ALL have positive minimal residual disease after remission induction and poor event-free survival, approximately 40% of pediatric patients responded well to chemotherapy and can be cured with relatively low intensity of treatment. The treatment outcome correlated negatively with increasing age at presentation. Ph-like ALL is characterized by a wide range of genetic alterations that dysregulate several cytokine receptor and kinase signaling pathways, including CRLF2 rearrangement in half of the cases and translocation of nonreceptor tyrosine kinases (predominantly ABL-class and Janus kinases). Patients with ABL-class fusions respond clinically to ABL1 tyrosine kinase inhibitors, whereas mutations activating the JAK-STAT pathway are amendable to treatment with JAK inhibitors invitro or in preclinical models. Prospective studies are needed to determine if incorporation of tyrosine kinase inhibitor targeting kinase alterations into intensive chemotherapy regimens will improve outcome of patients with Ph-like ALL.