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Survival following relapse in children with Acute Myeloid leukemia: a report from AML-BFM and COG
(2021)
Simple Summary: Acute myeloid leukemia in children remains a difficult disease to cure despite intensive therapies that push the limits of tolerability. Though the intent of initial therapy should be the prevention of relapse, about 30% of all patients experience a relapse. Hence, relapse therapy remains critically important for survival. This retrospective analysis of two large international study groups (COG and BFM) was undertaken to describe the current survival, response rates and clinical features that predict outcomes. We demonstrate that children with relapsed AML may be cured with cytotoxic therapy followed by HSCT. High-risk features at initial diagnosis and early relapse remain prognostic for post-relapse survival. Current response criteria are not aligned with the standards of care for children, nor are the count recovery thresholds meaningful for prognosis in children with relapsed AML. Our data provide a new baseline for future treatment planning and will allow an updated stratification in upcoming studies.
Abstract: Post-relapse therapy remains critical for survival in children with acute myeloid leukemia (AML). We evaluated survival, response and prognostic variables following relapse in independent cooperative group studies conducted by COG and the population-based AML-BFM study group. BFM included 197 patients who relapsed after closure of the last I-BFM relapse trial until 2017, while COG included 852 patients who relapsed on the last Phase 3 trials (AAML0531, AAML1031). Overall survival at 5 years (OS) was 42 ± 4% (BFM) and 35 ± 2% (COG). Initial high-risk features (BFM 32 ± 6%, COG 26 ± 4%) and short time to relapse (BFM 29 ± 4%, COG 25 ± 2%) predicted diminished survival. In the BFM dataset, there was no difference in OS for patients who had a complete remission with full hematopoietic recovery (CR) following post-relapse re-induction compared to those with partial neutrophil and platelet recovery (CRp and CRi) only (52 ± 7% vs. 63 ± 10%, p = 0.39). Among 90 patients alive at last follow-up, 87 had received a post-relapse hematopoietic stem cell transplant (HSCT). OS for patients with post-relapse HSCT was 54 ± 4%. In conclusion, initial high-risk features and early relapse remain prognostic. Response assessment with full hematopoietic recovery following initial relapse therapy does not predict survival. These data indicate the need for post-relapse risk stratification in future studies of relapse therapies.
Combining LSD1 and JAK-STAT inhibition targets Down syndrome-associated myeloid leukemia at its core
(2022)
Individuals with Down syndrome (DS) are predisposed to developing acute megakaryoblastic leukemia (ML-DS) within their first years of life [1]. Although, ML-DS is associated with a favorable prognosis, children with DS often experience severe toxicities from chemotherapy [2]. This highlights the unmet need for targeted therapies with improved risk profiles in this entity.
Consequently, the aim of this study was to investigate a novel therapeutic approach specifically tailored to intervene with hallmarks of ML-DS leukemogenesis. The evolution of ML-DS occurs in a step-wise process originating from pre-malignant transient abnormal myelopoiesis (TAM) [3]. The molecular mechanisms underlying the progression from TAM to ML-DS are not fully understood. However, it was previously shown that epigenetic changes play a pivotal role in ML-DS leukemogenesis. The lysine demethylase LSD1 was identified as a crucial player in this process, as LSD1-driven gene signatures become activated in ML-DS [4]. Accordingly, RNA-sequencing analysis of pediatric acute myeloid leukemia (AML) subtypes revealed that LSD1 was highly expressed in acute megakaryoblastic leukemia (AMKL), and especially in TAM and ML-DS patients (Supplementary Fig. 1). LSD1 is essential for hematopoiesis, particularly during granulocytic and erythroid differentiation [5], and was shown to contribute to differentiation blockade in different AML subtypes [6,7,8]. Consequently, various irreversible LSD1 inhibitors have been developed, with some currently undergoing clinical trials for AML [9]. Therefore, we sought to investigate the rational use of LSD1 inhibitors in pediatric AMKL. The non-DS-AMKL cell line M-07e and the ML-DS cell line CMK were highly sensitive to irreversible LSD1 inhibition (IC50M-07e = 9.1 nM; IC50CMK = 38.8 nM; Supplementary Fig. 2A). Testing serial dilutions of the irreversible LSD1 inhibitor in non-DS-AMKL and ML-DS patient samples expanded via xenotransplantation (see Supplementary Table 1 for patient characteristics), both entities were equally sensitive to LSD1 inhibition (non-DS-AMKL: IC50#1 = 15.0 nM, IC50#2 = 2.0 nM; ML-DS: IC50#1 = 31.2 nM, IC50#2 = 17.1 nM, IC50#3 = 3.8 nM). All dose-response curves plateaued at a certain LSD1 inhibitor concentration (Supplementary Fig. 2B). The non-linear relationship between cytotoxicity and dosage points toward proliferation arrest and differentiation in response to LSD1 inhibition. In line with this, we observed myeloid differentiation upon visual inspection (Supplementary Fig. 3A) and upregulation of the myeloid markers CD86 and CD11b after 3 days of LSD1 inhibitor treatment (Supplementary Fig. 3B).
These results revealed a potent proliferation block and induction of differentiation in non-DS-AMKL and ML-DS samples, however, the therapeutic efficacy of LSD1 inhibition may be limited by its non-linear dose-response relationship. Consequently, we aimed to design a rational drug combination to increase its anti-leukemic effects. Another hallmark of ML-DS development is the acquisition of activating mutations in Janus kinases (JAK) and cytokine receptors [4], promising potent anti-leukemic effects of the combination of LSD1 inhibition and the JAK1/JAK2 inhibitor ruxolitinib, as it was previously proposed for JAK2V617F mutated myeloproliferative neoplasms, secondary AML and a CSF3Rmut/CEBPαmut AML model [10,11,12]. Accordingly, pre-treatment with 350 nM LSD1 inhibitor for 3 days followed by exposure to serial dilutions of ruxolitinib led to synergistic growth inhibition in non-DS-AMKL and ML-DS cell lines (Supplementary Fig. 4), as well as in all ML-DS patient samples (Fig. 1A). The combination of LSD1 inhibition and ruxolitinib proved to be very effective in non-DS-AMKL blasts, however, with only additive cytotoxic effects in one of the two patient samples (Fig. 1A). Drug synergy in the ML-DS samples was confirmed when calculating the Bliss synergy scores (Fig. 1B). Interestingly, samples ML-DS #1 (JAK1mut) and #2 (wild-type for JAK1, JAK2, and JAK3, Supplementary Fig. 5) showed particularly high synergy scores (ML-DS #1 synergy score = 10.4; ML-DS #2 synergy score = 15.6; Fig. 1B). Contrary, the JAK3mut patient sample ML-DS #3 (Supplementary Fig. 5) only displayed mild drug synergy between LSD1 inhibition and ruxolitinib (synergy score = 2.0; Fig. 1B). Consequently, as ruxolitinib is a JAK1/JAK2 inhibitor, synergistic anti-leukemic effects seem to depend on JAK mutational status, which must be considered in future pre-clinical and clinical testing of this drug combination for ML-DS patients.
Chimeric antigen receptor (CAR) T cell therapy is a potent new treatment option for relapsed or refractory hematologic malignancies. As the monitoring of CAR T cell kinetics can provide insights into the activity of the therapy, appropriate CAR T cell detection methods are essential. Here, we report on the comprehensive validation of a flow cytometric assay for peripheral blood CD19 CAR T cell detection. Further, a retrospective analysis (n = 30) of CAR T cell and B cell levels over time has been performed, and CAR T cell phenotypes have been characterized. Serial dilution experiments demonstrated precise and linear quantification down to 0.05% of T cells or 22 CAR T cell events. The calculated detection limit at 13 events was confirmed with CAR T cell negative control samples. Inter-method comparison with real-time PCR showed appreciable correlation. Stability testing revealed diminished CAR T cell values already one day after sample collection. While we found long-term CAR T cell detectability and B cell aplasia in most patients (12/17), some patients (5/17) experienced B cell recovery. In three of these patients the coexistence of CAR T cells and regenerating B cells was observed. Repeat CAR T cell infusions led to detectable but limited re-expansions. Comparison of CAR T cell subsets with their counterparts among all T cells showed a significantly higher percentage of effector memory T cells and a significantly lower percentage of naïve T cells and T EMRA cells among CAR T cells. In conclusion, flow cytometric CAR T cell detection is a reliable method to monitor CAR T cells if measurements start without delay and sufficient T cell counts are given.