Abdel‐Wahab, Omar

Purpose: The discovery of MAPK/ERK pathway mutations has led to the approval of MEK-inhibitor (MEKi) cobimetinib in histiocytic neoplasms. However, the pivotal clinical trial that led to the approval of cobimetinib included only 4 patients with Langerhans cell histiocytosis (LCH). Therefore, there is a need to define outcomes with MEKi therapy in patients with LCH. We undertook a multi-center collaboration through the Adult LCH Working Group for the Histiocyte Society to address this gap in knowledge. Methods: Adults with LCH who received MEKi therapy were included from five institutions. Objective response rate (ORR) was evaluated using PET/CT criteria, and CT/MRI if PET scan was not available; response categories were categorized into complete response (CR), partial response (PR), stable disease (SD), and progressive disease (PD). Progression-free (PFS) and overall survival (OS) were calculated from the time of targeted therapy initiation. Risk organ disease was defined as liver, spleen, or bone marrow involvement. Results: 25 adults with LCH were included in this study; median age at MEKi initiation 43y (range, 18-85). Most common systems involved at diagnosis were bone (52%), pituitary (44%), and lung (36%). Risk organ involvement was observed in 7 (28%, 6 liver, 1 liver and spleen) and 2 (8%) patients had intra-axial CNS involvement. Median lines of prior therapy received were 2 (range: 1-5), and 4 (16%) patients received MEKi in first-line. MAPK/ERK pathway status was assessed via target capture next generation sequencing (NGS) in 22 (96%) cases. Amongst those who underwent NGS, alterations identified included: BRAF V600E (2/22, 9%), BRAF deletions (11/22 50%), MAP2K1 or MEK mutations (4/22, 18%), and MAPK1 or ERK2 (n=1, 5%). Overall, 5 patients also received BRAF inhibitors (4 patients as first therapy prior to MEKi and 1 concomitantly due to BRAF V600E positive melanoma). Specific MEKi agents utilized included cobimetinib (n=13) and trametinib (n=12). Among the response evaluable patients (n=23), ORR to MEKi treatment was 78% (9 CR, 9 PR, 4 SD, 1 PD). Among the 7 patients with liver involvement, responses were seen in 2 (29%) cases. ORR did not significantly differ according to mutation status among those with NGS data (78% MAPK mutated vs. 100% unmutated; p=1.0). In this subcohort, all of the 4 cases that did not respond to MEKi had liver involvement; 3 had BRAF deletions (2 SD and 1 PD), and one had MAPK1 mutation (SD). Median follow-up duration after MEKi initiation in the entire cohort was 18 months (95% CI 6 - 30). The median PFS and OS were not reached; 2-year PFS and OS were 78.1% and 79.9%, respectively (Figure 1A). The median PFS was much shorter in those with liver involvement (7 months [95% CI 0 - 14]) compared with those without liver disease (not reached [95% CI 19-not reached] P=0.047; Figure 1B). PFS did not differ significantly between MAPK pathway mutated and unmutated patients (p=0.34) Adverse events (AEs) were reported in 36% (n=9) and most commonly included rash (n=5) and fatigue (n=3). Four patients experienced grade 3-4 AEs including rash, fatigue, and thrombocytopenia. Common causes of MEKi discontinuation included AEs (n=3), progression (n=2), and drug holiday (n=2). At last follow-up, 5 patients died and 18 remained on MEKi. Death was attributable to LCH (n=3), concomitant malignancy (n=1), or unknown causes (n=1). Conclusions: In our multi-institutional study of adults with LCH, we found MEKi therapy to be highly efficacious. However, liver involvement correlated with a lack of response and worse PFS, while mutational status did not. Future studies are needed to evaluate optimum treatment for high-risk subgroups of LCH like liver disease.

ObjectiveErdheim‐Chester disease (ECD) is rare histiocytosis with a wide range of clinical manifestations. Somatic mutations are key to the pathogenesis of the disease; however, the relationship between germline genetic variants and ECD has not been examined so far. The present study aims to explore the inherited genetic component of ECD by performing the first genome‐wide association study.MethodsAfter quality controls, a cohort of 255 patients with ECD and 7,471 healthy donors was included in this study. Afterward, a logistic regression followed by in silico functional annotation was performed.ResultsA signal at the 18q12.3 genomic region was identified as a new susceptibility locus for ECD (P = 2.75 × 10−11; Odds Ratio = 2.09). This association was annotated to the SETBP1 gene, which is involved in clonal haematopoiesis. Functional annotation of this region and of the identified suggestive signals revealed additional genes that could be potentially involved in the pathogenesis of the disease.ConclusionOverall, this work demonstrates that germline genetic variants can impact on the development of ECD and suggests new pathways with a potential pathogenic role.image

AbstractSomatic mutations in isocitrate dehydrogenase (IDH) genes occur frequently in adult acute myeloid leukemia (AML) and less commonly in pediatric AML. The objective of this study was to describe the prevalence, mutational profile, and prognostic significance of IDH mutations in AML across age. Our cohort included 3141 patients aged between <1 month and 88 years treated on Children’s Cancer Group/Children’s Oncology Group (n = 1872), Southwest Oncology Group (n = 359), Eastern Cooperative Oncology Group (n = 397) trials, and in Beat AML (n = 333) and The Cancer Genome Atlas (n = 180) genomic characterization cohorts. We retrospectively analyzed patients in 4 age groups (age range, n): pediatric (0-17, 1744), adolescent/young adult (18-39, 444), intermediate-age (40-59, 640), older (≥60, 309). IDH mutations (IDHmut) were identified in 9.2% of the total cohort (n = 288; IDH1 [n = 123, 42.7%]; IDH2 [n = 165, 57.3%]) and were strongly correlated with increased age: 3.4% pediatric vs 21% older, P < .001. Outcomes were similar in IDHmut and IDH-wildtype (IDHWT) AML (event-free survival [EFS]: 35.6% vs 40.0%, P = .368; overall survival [OS]: 50.3% vs 55.4%, P = .196). IDH mutations frequently occurred with NPM1 (47.2%), DNMT3A (29.3%), and FLT3-internal tandem duplication (ITD) (22.4%) mutations. Patients with IDHmut AML with NPM1 mutation (IDHmut/NPM1mut) had significantly improved survival compared with the poor outcomes experienced by patients without (IDHmut/NPM1WT) (EFS: 55.1% vs 17.0%, P < .001; OS: 66.5% vs 35.2%, P < .001). DNTM3A or FLT3-ITD mutations in otherwise favorable IDHmut/NPM1mut AML led to inferior outcomes. Age group analysis demonstrated that IDH mutations did not abrogate the favorable prognostic impact of NPM1mut in patients aged <60 years; older patients had poor outcomes regardless of NPM1 status. These trials were registered at www.clinicaltrials.gov as #NCT00070174, #NCT00372593, #NCT01371981, #NCT00049517, and #NCT00085709.

Abstract Mutations in chromatin regulator ASXL1 are frequently identified in myeloid malignancies, in particular ∼40% of patients with chronic myelomonocytic leukemia (CMML). ASXL1 mutations are associated with poor prognosis in CMML and significantly co-occur with NRAS mutations. Here, we show that concurrent ASXL1 and NRAS mutations defined a population of CMML patients who had shorter leukemia-free survival than those with ASXL1 mutation only. Corroborating this human data, Asxl1−/− accelerated CMML progression and promoted CMML transformation to acute myeloid leukemia (AML) in NrasG12D/+ mice. NrasG12D/+;Asxl1−/− (NA) leukemia cells displayed hyperactivation of MEK/ERK signaling, increased global levels of H3K27ac, upregulation of Flt3. Moreover, we find that NA-AML cells overexpressed all the major inhibitory immune checkpoint ligands: programmed death-ligand 1 (PD-L1)/PD-L2, CD155, and CD80/CD86. Among them, overexpression of PD-L1 and CD86 correlated with upregulation of AP-1 transcription factors (TFs) in NA-AML cells. An AP-1 inhibitor or short hairpin RNAs against AP-1 TF Jun decreased PD-L1 and CD86 expression in NA-AML cells. Once NA-AML cells were transplanted into syngeneic recipients, NA-derived T cells were not detectable. Host-derived wild-type T cells overexpressed programmed cell death protein 1 (PD-1) and T-cell immunoreceptor with immunoglobulin and ITIM domains (TIGIT) receptors, leading to a predominant exhausted T-cell phenotype. Combined inhibition of MEK and BET resulted in downregulation of Flt3 and AP-1 expression, partial restoration of the immune microenvironment, enhancement of CD8 T-cell cytotoxicity, and prolonged survival in NA-AML mice. Our study suggests that combined targeted therapy and immunotherapy may be beneficial for treating secondary AML with concurrent ASXL1 and NRAS mutations.

Abstract Genomic classification has improved risk assignment of pediatric, but not adult B-lineage acute lymphoblastic leukemia (B-ALL). The international UKALLXII/ECOG-ACRIN E2993 (#NCT00002514) trial accrued 1229 adolescent/adult patients with BCR-ABL1− B-ALL (aged 14 to 65 years). Although 93% of patients achieved remission, 41% relapsed at a median of 13 months (range, 28 days to 12 years). Five-year overall survival (OS) was 42% (95% confidence interval, 39, 44). Transcriptome sequencing, gene expression profiling, cytogenetics, and fusion polymerase chain reaction enabled genomic subtyping of 282 patient samples, of which 264 were eligible for trial, accounting for 64.5% of E2993 patients. Among patients with outcome data, 29.5% with favorable outcomes (5-year OS 65% to 80%) were deemed standard risk (DUX4-rearranged [9.2%], ETV6-RUNX1/-like [2.3%], TCF3-PBX1 [6.9%], PAX5 P80R [4.1%], high-hyperdiploid [6.9%]); 50.2% had high-risk genotypes with 5-year OS of 0% to 27% (Ph-like [21.2%], KMT2A-AFF1 [12%], low-hypodiploid/near-haploid [14.3%], BCL2/MYC-rearranged [2.8%]); 20.3% had intermediate-risk genotypes with 5-year OS of 33% to 45% (PAX5alt [12.4%], ZNF384/-like [5.1%], MEF2D-rearranged [2.8%]). IKZF1 alterations occurred in 86% of Ph-like, and TP53 mutations in patients who were low-hypodiploid (54%) and BCL2/MYC-rearranged (33%) but were not independently associated with outcome. Of patients considered high risk based on presenting age and white blood cell count, 40% harbored subtype-defining genetic alterations associated with standard- or intermediate-risk outcomes. We identified distinct immunophenotypic features for DUX4-rearranged, PAX5 P80R, ZNF384-R/-like, and Ph-like genotypes. These data in a large adult B-ALL cohort treated with a non–risk-adapted approach on a single trial show the prognostic importance of genomic analyses, which may translate into future therapeutic benefits.

Background: Somatic mutations in the IDH genes are common in acute myeloid leukemia (AML). Mutations occur at active site arginine residues in IDH1 (R132) and IDH2 (R140, R172). IDH inhibitors, ivosidenib (IDH1) and enasidenib (IDH2), have shown improved clinical outcomes in patients with relapsed/refractory IDH-mutant AML and are approved for use in this setting, while investigations in combination with chemotherapy are underway in de novo AML. The prognostic significance of IDH mutations remains controversial. We hypothesize that refining our understanding of IDH-mutated AML will contribute to risk-adapted treatment strategies, including optimal use of IDH-targeted agents. The objective of our study was to identify characteristics that affect outcome in de novo IDH-mutated AML across the age spectrum utilizing a large cohort of patients enrolled on several pediatric and adult trials. Methods: The total cohort (N=3588) included patients age <1 month - 88 years. Pediatric and young adult (YA) patients were treated on recent CCG/COG AML trials (CCG2961, COG 03P1, 0531, 1031, N=2231) and YA/adult patients were treated on SWOG S0106 (N=396), ECOG E1900 AML trials (N=398), Beat AML (N=363), or included in the TCGA biology study (N=200; outcomes not evaluated for this group). Patients were analyzed according to three defined age groups: "younger" 0-29 years of age (N=2401), "intermediate" 30-59 years of age (N=819) and "older" 60 years of age and above (N=319). Data regarding clinical characteristics and treatment outcomes were collected and evaluated according to the standard practices of each cooperative or research groups for the respective studies. Mutational profiling was performed by targeted sequencing for patient samples from COG trials, Beat-AML, ECOG, and SWOG; whole-genome or whole-exome sequencing for the TCGA cohort. Prevalence of IDH mutations, co-occurring mutations, and outcomes (5-year event-free survival [EFS]) were analyzed across the defined age groups. Results: The prevalence of IDH mutations among the entire cohort was 8.6% (N=276). Analysis according to mutation type demonstrated that IDH2 mutations comprised 57% (N=158) and IDH1 mutations 43% (N=118). The prevalence of IDH mutations was strongly correlated with increased age (Fig 1A); according to the age-defined cohorts was 4.0% (N=82) in younger, 15.2% (N=126) in intermediate, and 20.3% (N=65) in older patients (p<0.001). The co-occurring mutational profile demonstrated that IDH mutations commonly co-occurred with NPM1,DNMT3A, and FLT3-ITD mutations (Fig 1B). Among IDH-mutant patients, 48% (N=132) harbored dual mutations (IDHmut/NPM1mut); 11.6% (N=32) triple mutations (IDHmut/NPM1mut/DNMT3Amut), the latter particularly prevalent in intermediate-aged adults (N=27/32, 85%). Analysis of the cohort with outcome data (N=2824) demonstrated that IDHmut and IDH-WT patients experienced similar EFS of 39% vs. 40%, respectively (p=0.723). Given the favorable prognostic significance of NPM1, we subsequently analyzed outcomes of this dual mutant group and found that NPM1 mutations retained favorable prognostic impact in the context of IDH mutant patients (Fig 2A). Notably, this effect was age-dependent, as those with IDHmut/NPM1mut had a favorable EFS compared to IDHmut/NPM1-WT for younger (76% vs. 24%, p<0.001) and intermediate patients (43% vs. 15%, p=0.001, Fig 2B) but this favorable effect was lost in older patients (29% vs. 34%, p=0.456, Fig 2C). Among intermediate age patients, outcome was further stratified by DNMT3A status, and IDHmut/NPM1mut/DNMT3Amut patients experienced an inferior EFS of 25% vs. 57% in IDHmut/NPMmut (p=0.003, Fig 2D). Conclusion: Analysis of this large patient cohort provides the most comprehensive description of IDH mutations in AML across the age spectrum. We confirm age-associated prevalence of IDH mutations and frequent co-occurrence with NPM1 mutation in all ages and in further combination with DNMT3A mutation in intermediate-aged adults. We definitively demonstrate that IDH mutation status is not an independent prognostic determinant of outcome in any age group. Co-occurrence of NPM1 and IDH mutations favorably impacts outcome in patients < 60 years of age with AML, particularly in the absence of DNMT3A mutation. Our data support that IDH inhibitors may be of particular interest in older adults and in patients <60 according to co-occurring NPM1 and DNMT3A mutations. Disclosures Othus: Marck: Consultancy; Daiichi Sankyo: Consultancy; Celgene: Membership on an entity's Board of Directors or advisory committees; Glycomimetics: Membership on an entity's Board of Directors or advisory committees. Radich:Jazz: Consultancy; Novartis Pharmaceuticals Corporation: Consultancy, Research Funding; Amgen: Consultancy; Bristol-Myers Squibb: Consultancy. Abdel-Wahab:Merck: Consultancy; Janssen: Consultancy; Envisagenics Inc.: Current equity holder in private company; H3 Biomedicine Inc.: Consultancy, Research Funding. Tallman:UpToDate: Patents & Royalties; ADC Therapeutics: Research Funding; BioSight: Membership on an entity's Board of Directors or advisory committees, Research Funding; Glycomimetics: Research Funding; Rafael: Research Funding; Amgen: Research Funding; Bioline rx: Membership on an entity's Board of Directors or advisory committees; Daiichi-Sankyo: Membership on an entity's Board of Directors or advisory committees; KAHR: Membership on an entity's Board of Directors or advisory committees; Rigel: Membership on an entity's Board of Directors or advisory committees; Delta Fly Pharma: Membership on an entity's Board of Directors or advisory committees; Oncolyze: Membership on an entity's Board of Directors or advisory committees; Jazz Pharma: Membership on an entity's Board of Directors or advisory committees; Roche: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Abbvie: Research Funding; Cellerant: Research Funding; Orsenix: Research Funding. Atallah:Jazz: Consultancy; Genentech: Consultancy; Abbvie: Consultancy; Takeda: Consultancy, Research Funding; Pfizer: Consultancy; Novartis Pharmaceutical Corporation: Consultancy. Luger:Daiichi-Sankyo: Honoraria; Pfizer: Honoraria; Bristol-Myers Squibb: Honoraria; Acceleron: Honoraria; Agios: Honoraria; Loxo Oncology: Honoraria; Onconova: Research Funding; Kura: Research Funding; Biosight: Research Funding; Ariad: Research Funding; Hoffman La Roche: Research Funding. Levine:Novartis: Consultancy; Loxo: Current equity holder in private company, Membership on an entity's Board of Directors or advisory committees; Morphosys: Consultancy; Astellas: Consultancy; Janssen: Consultancy; Prelude Therapeutics: Research Funding; Amgen: Honoraria; Gilead: Honoraria; Lilly: Consultancy, Honoraria; Qiagen: Current equity holder in publicly-traded company, Membership on an entity's Board of Directors or advisory committees; Imago: Current equity holder in private company, Membership on an entity's Board of Directors or advisory committees; C4 Therapeutics: Current equity holder in private company, Membership on an entity's Board of Directors or advisory committees; Isoplexis: Current equity holder in private company, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Honoraria, Research Funding; Roche: Consultancy, Honoraria, Research Funding. Cooper:Celgene: Other: Spouse was an employee of Celgene (through August 2019).

Abstract Large-scale sequencing studies of hematologic malignancies have revealed notable epistasis among high-frequency mutations. One of the most striking examples of epistasis occurs for mutations in RNA splicing factors. These lesions are among the most common alterations in myeloid neoplasms and generally occur in a mutually exclusive manner, a finding attributed to their synthetic lethal interactions and/or convergent effects. Curiously, however, patients with multiple-concomitant splicing factor mutations have been observed, challenging our understanding of one of the most common examples of epistasis in hematologic malignancies. In this study, we performed bulk and single-cell analyses of patients with myeloid malignancy who were harboring ≥2 splicing factor mutations, to understand the frequency and basis for the coexistence of these mutations. Although mutations in splicing factors were strongly mutually exclusive across 4231 patients (q < .001), 0.85% harbored 2 concomitant bona fide splicing factor mutations, ∼50% of which were present in the same individual cells. However, the distribution of mutations in patients with double mutations deviated from that in those with single mutations, with selection against the most common alleles, SF3B1K700E and SRSF2P95H/L/R, and selection for less common alleles, such as SF3B1 non-K700E mutations, rare amino acid substitutions at SRSF2P95, and combined U2AF1S34/Q157 mutations. SF3B1 and SRSF2 alleles enriched in those with double-mutations had reduced effects on RNA splicing and/or binding compared with the most common alleles. Moreover, dual U2AF1 mutations occurred in cis with preservation of the wild-type allele. These data highlight allele-specific differences as critical in regulating the molecular effects of splicing factor mutations as well as their cooccurrences/exclusivities with one another.

Abstract Background: Novel therapies are required to improve the outcome of patients with AML. New agents are asked to demonstrate an overall survival (OS) benefit before qualifying for FDA approval. The long duration of clinical trials required in order to achieve this endpoint hampers quick evaluation of candidate therapies, including novel agents. Identification of reliable surrogate endpoints for OS in AML is needed. Here we compare the results of therapy for patients with untreated AML ages 16-60 years on the Eastern Cooperative Oncology Group 1900 trial (E1900) of induction chemotherapy followed by consolidation and autologous transplant in order to evaluate the validity of an event free survival (EFS) endpoint as a surrogate for OS. Methods:OS was measured from randomization for induction therapy to death from any cause (censored at last contact). EFS was measured from randomization to induction treatment failure, relapse after compete response (CR), or death in remission (censored at last contact). Hazard ratios (HR) were computed using Cox proportional hazards models. The association between EFS and OS was evaluated using the Kendall tau-a rank correlation for censored data. Results:There were657 patients enrolled of which 426 patients relapsed or had induction treatment failure before death or date of last contact. Median EFS and OS were 8.0 months (95% CI, 6.3 to 9.7 months) and 23.6 months (95% CI, 16.9 to 23.6 months), respectively. With a median follow-up of 80.1 months, there is a statistically significant correlation between EFS and OS (Kendall tau-a = 0.467, 95% confidence interval (CI) = (0.425, 0.510), p<0.001). This correlation was similarly significant at a median follow-up of 25.2 months (Kendall tau-a = 0.361, 95% CI (0.323, 0.400), p <0.001) when the E1900 trial was originally reported (Fernandez et al. NEJM 2009). Key findings reported based on the original OS endpoint are similar when analyzed with an EFS endpoint (Table 1). High-dose daunorubicin (90 mg/m2) (DNR 90) confers both an EFS and OS benefit in patients aged < 50 years and patients with intermediate cytogenetic risk, and does not confer an EFS or OS benefit in older patients and patients with unfavorable cytogenetic risk, on univariate analysis. Divergent results are only seen in the small subset of favorable cytogenetic risk patients, where DNR 90 conferred an OS benefit (p=0.027) without an EFS benefit (p=0.32). Both EFS and OS endpoints consistently reflect the impact of mutation status on survival. The presence of a FLT3-ITD or DNMT3A mutation has a negative impact on both EFS and OS while an IDH2 mutation has a favorable impact on EFS and OS. The presence of a NPM1 mutation confers a favorable impact on EFS and OS in patients who received DNR 90 and did not impact EFS or OS in patients receiving standard-dose daunorubicin (45 mg/m2) (DNR 45). The presence of an IDH1 mutation does not impact EFS or OS. Conclusions:The results of E1900 demonstrating superiority of DNR 90 in AML induction in patients up to age 60 are concordant when using an EFS or OS endpoint. This is true for the group as a whole as well as for subgroups for which targeted agents are in development (FLT3/IDH2 inhibitors). Further investigation of whether EFS is a reliable surrogate for OS is warranted in AML. If confirmed, its use as a primary endpoint could be adopted by regulatory agencies in order to allow more rapid completion of clinical trials in AML and bring new therapies to AML patients in a timely fashion. Table 1. Results of E1900 based on an EFS endpoint versus an OS endpoint. Subgroup N OS HR (DNR 90/DNR 45) & 95% CI Wald P EFS HR (DNR 90/DNR 45) & 95% CI Wald P DNR 45 DNR 90 Age < 50 yrs ³ 50 yrs 188 142 172 155 0.66 (0.50, 0.85) 0.81 (0.62, 1.06) 0.002 0.118 0.64 (0.50, 0.82) 0.86 (0.67, 1.10) 0.0004 0.23 Cytogenetic Favorable Intermediate Unfavorable 38 141 59 51 127 63 0.51 (0.28, 0.93) 0.68 (0.50, 0.92) 0.79 (0.54, 1.16) 0.027 0.012 0.225 0.76 (0.44, 1.31) 0.63 (0.47, 0.83) 0.72 (0.49, 1.05) 0.32 0.001 0.09 Subgroup N OS HR (MUT/WT) & 95% CI Wald P EFS HR (MUT/WT) & 95% CI Wald P FLT3-ITD WT MUT 456 147 1.62 (1.31, 2.01) <.0001 1.48 (1.21, 1.82) 0.0002 DNMT3A WT MUT 371 119 1.30 (1.03, 1.65) 0.03 1.23 (0.98, 1.54) 0.07 IDH1 WT MUT 465 36 0.88 (0.59, 1.33) 0.55 0.91 (0.62, 1.34) 0.64 IDH2 WT MUT 451 50 0.63 (0.43, 0.93) 0.02 0.68 (0.48, 0.97) 0.03 NPM1 DNR 45 DNR 90 245 257 0.84 (0.61, 1.16) 0.60 (0.41, 0.89) 0.30 0.01 0.90 (0.66, 1.22) 0.59 (0.41, 0.84) 0.49 0.004 Disclosures No relevant conflicts of interest to declare.