BACKGROUND Philadelphia chromosome–like acute lymphoblastic leukemia (Ph-like ALL) is characterized by a gene-expression profile similar to that of BCR–ABL1–positive ALL, alterations of lymphoid transcription factor genes, and a poor outcome. The frequency and spectrum of genetic alterations in Ph-like ALL and its responsiveness to tyrosine kinase inhibition are undefined, especially in adolescents and adults. METHODS We performed genomic profiling of 1725 patients with precursor B-cell ALL and detailed genomic analysis of 154 patients with Ph-like ALL. We examined the functional effects of fusion proteins and the efficacy of tyrosine kinase inhibitors in mouse pre-B cells and xenografts of human Ph-like ALL. RESULTS Ph-like ALL increased in frequency from 10% among children with standard-risk ALL to 27% among young adults with ALL and was associated with a poor outcome. Kinase-activating alterations were identified in 91% of patients with Ph-like ALL; rearrangements involving ABL1, ABL2, CRLF2, CSF1R, EPOR, JAK2, NTRK3, PDGFRB, PTK2B, TSLP, or TYK2 and sequence mutations involving FLT3, IL7R, or SH2B3 were most common. Expression of ABL1, ABL2, CSF1R, JAK2, and PDGFRB fusions resulted in cytokine-independent proliferation and activation of phosphorylated STAT5. Cell lines and human leukemic cells expressing ABL1, ABL2, CSF1R, and PDGFRB fusions were sensitive in vitro to dasatinib, EPOR and JAK2 rearrangements were sensitive to ruxolitinib, and the ETV6–NTRK3 fusion was sensitive to crizotinib. CONCLUSIONS Ph-like ALL was found to be characterized by a range of genomic alterations that activate a limited number of signaling pathways, all of which may be amenable to inhibition with approved tyrosine kinase inhibitors. Trials identifying Ph-like ALL are needed to assess whether adding tyrosine kinase inhibitors to current therapy will improve the survival of patients with this type of leukemia. (Funded by the American Lebanese Syrian Associated Charities and others.)

Background Inotuzumab ozogamicin, an anti-CD22 antibody conjugated to calicheamicin, is active in acute lymphoblastic leukemia. Methods In this phase 3 trial, adults with relapsed/refractory acute lymphoblastic leukemia were randomized to inotuzumab ozogamicin or standard intensive chemotherapy. Primary endpoints were complete remission and overall survival. Results Primary intent-to-treat (ITT) analysis of complete remission included the first 218 (inotuzumab ozogamicin, n=109; standard, n=109) of 326 patients randomized. Complete remission rate was significantly better with inotuzumab ozogamicin (80.7% [95% CI, 72%–88%] vs 29.4% [21%–39%]; P<0.001), as was minimal residual disease (MRD)-negativity among responders (78.4% [68%–87%] vs 28.1% [14%–47%]; P<0.001); remission duration was longer (median, 4.6 [3.9–5.4] vs 3.1 [1.4–4.9] months; hazard ratio=0.55 [0.31–0.96], P=0.034). More patients proceeded to transplant with inotuzumab ozogamicin (41%) versus standard (11%; P<0.001). In the ITT survival analysis (n=326), progression-free survival was significantly longer with inotuzumab ozogamicin vs standard (HR, 0.45 [97.5% CI, 0.34–0.61]; P<0.001; median, 5.0 [95% CI, 3.7–5.6] vs 1.8 [1.5–2.2] months). The overall survival HR was 0.77 (97.5% CI, 0.58–1.03); P=0.04; median was 7.7 (95% CI, 6.0–9.2) vs 6.7 (4.9–8.3) months. 2-year overall survival rate was 23% (95% CI, 16%–30%) vs 10% (5%–16%). In the safety population, the most frequent nonhematologic inotuzumab ozogamicin treatment-emergent grade ≥3 adverse events were liver-related. Any grade veno-occlusive liver disease occurred in 15 (11%) patients receiving inotuzumab ozogamicin. Conclusion Patients receiving inotuzumab ozogamicin versus standard care achieved higher response, MRD-negativity rates, and prolonged progression-free survival and overall survival. Veno-occlusive disease was a major non-hematologic toxicity.

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Recent genomic studies have identified chromosomal rearrangements defining new subtypes of B-progenitor acute lymphoblastic leukemia (B-ALL), however many cases lack a known initiating genetic alteration. Using integrated genomic analysis of 1,988 childhood and adult cases, we describe a revised taxonomy of B-ALL, incorporating 23 subtypes defined by chromosomal rearrangements, sequence mutations, or heterogeneous genomic alterations, many of which show marked variation in prevalence according to age. Two subtypes have frequent alterations of the B lymphoid transcription factor gene PAX5. One, PAX5alt (7.4%), has diverse PAX5 alterations (rearrangements, intragenic amplifications or mutations), and a second subtype is defined by PAX5 p.Pro80Arg and biallelic PAX5 alterations. We show that p.Pro80Arg impairs B lymphoid development and promotes the development of B-ALL with biallelic Pax5 alteration in vivo. These results demonstrate the utility of transcriptome sequencing to classify B-ALL and reinforce the central role of PAX5 as a checkpoint in B lymphoid maturation and leukemogenesis.

The classification of myeloid neoplasms and acute leukemias was last updated in 2016 within a collaboration between the World Health Organization (WHO), the Society for Hematopathology, and the European Association for Haematopathology. This collaboration was primarily based on input from a clinical advisory committees (CAC) composed of pathologists, hematologists, oncologists, geneticists, and bioinformaticians from around the world. The recent advances in our understanding of the biology of hematologic malignancies, the experience with the use of the 2016 WHO classification in clinical practice, and the results of clinical trials have indicated the need for further revising and updating the classification. As a continuation of this CAC-based process, the authors, a group with expertise in the clinical, pathologic and genetic aspects of these disorders, developed the International Consensus Classification (ICC) of myeloid neoplasms and acute leukemias. Using a multiparameter approach, the main objective of the consensus process was the definition of real disease entities, including the introduction of new entities and refined criteria for existing diagnostic categories, based on accumulated data. The ICC is aimed at facilitating diagnosis and prognostication of these neoplasms, improving treatment of affected patients, and allowing the design of innovative clinical trials.