ALBERT

Description: Langerhans cell histiocytosis (LCH) can present in several clinical forms with expected response to therapy categorized by the organ systems involved. Low Risk patients (unifocal bone, skin, or lymph nodes disease) are nearly always cured of the disease, patients with multifocal bone involvement are more likely to have relapses, and High Risk patients (involving liver, lung, spleen, or bone marrow) have only a 50% chance of cure. The etiology of LCH is unknown and controversy exists whether this is purely an immunologic dysfunction or a neoplastic disease since the Langerhans cells have been identified as a clonal proliferation. Understanding interaction of Langerhans cells (LC) with T lymphocytes and macrophages in the lesions of Langerhans cell histiocytosis (LCH) is critical to elucidating LCH pathophysiology. We have used laser capture microdissection to isolate CD1a+ LC and CD3+ T cells from frozen LCH lesions. RNA from the dissected cells was enzymatically amplified, hybridized to a cytokine/growth factor array and analyzed for quantity of gene expression after normalizing to b-actin. A complex expression profile has emerged: Gene Expression in LCH Clinical Groups Low Risk Multifocal Bone High Risk * to ***= low to high expression of a gene, VEGF:vascular endothelial growth factor, FGF: fibroblast growth factor CD1a Cytokines IL-9**, -11***, -17**, Leptin*,TGF- β IL-10**, IL-11**,TGF- β IL-9*,11*,Leptin** CD1a Growth Factors FGF-6*, VGEF*** FGF-6**, VEGF** FGF-6***, VEGF* CD3 Cytokines IL-9**, Lymphotoxin- α IL-9*,-10 IL-9*** Lymphotoxin- α** CD3 Growth Factors GM-CSF* GM-CSF** FGF-5* GM-CSF*** FGF-5** Growth factor and cytokine interactions from these LCH patients with different clinical presentations illustrates the importance of both LC and T-cells as well as the known influence of macrophages on the type of LCH. Although previous studies have shown TNF-a is an important factor, our data illustrates that other cytokines and growth factors may play critical roles, because of their relative higher gene expression when compared with TNF-a. These data will facilitate development of in vitro systems to test our hypotheses that a combination of cytokines/growth factors may be important in varying LCH clinical presentations.

Description: Key Points Whole-exome sequencing may identify specific therapeutic opportunities for patients with HLH. HLH should be conceptualized as a critical illness phenotype driven by toxic activation of immune cells from different underlying mechanisms.

Description: Key Points Germline gain-of-function mutations in STAT3 lead to lymphoproliferation and autoimmunity with prominent cytopenias. Mutations in STAT3 cause altered regulatory T cells and cytokine signaling.

Description: Background Langerhans cell histiocytosis (LCH) is a heterogeneous disease whose myriad manifestations result from accumulation of Langerhans cells in a variety of organs most commonly including skin, bone, central nervous system, liver, lymph nodes, and bone marrow. The disease can affect people of any age. Treatment is primarily driven by disease extent and organ involvement and can range from focused radiation or surgery to multi-agent chemotherapy. There is a relatively high recurrence rate following complete remissions with conventional chemotherapy. In the first-time-in-human (FTIH) study of the oral pan-AKT inhibitor afuresertib (GSK2110183), in patients with hematologic malignancies, a patient with refractory multi-system LCH experienced a prolonged period (〉 3 years) of clinical benefit on 125mg oral once daily afuresertib. This observation led to the evaluation of the use of afuresertib in patients with LCH. Methods This single-arm, open-label trial was designed to evaluate the efficacy and safety of afuresertib, administered at 125 mg once daily, in adults and adolescents with relapsed/refractory LCH and adults with treatment-naïve LCH. Secondary objectives included pharmacokinetics. Diagnosis of LCH was confirmed by pathology review of archival tissue. The Histiocyte Society criteria were used for response evaluation at three and six months with safety and pharmacokinetic assessments performed at pre-specified intervals. BRAF status from archival tissue was evaluated by Sanger sequencing. Results 17 patients (16 adults, 10 females) were enrolled; median age was 38 years (15-75). 3/17 patients had isolated pulmonary disease, 1/17 had single-system multifocal-bone disease, 1/17 had single-system skin disease, and 12/17 had multi-system disease. Seven patients were treatment-naïve; 10 had relapsed/refractory disease, including the one adolescent. The most frequent (〉20% of patients) adverse events (AEs), regardless of causality, were nausea (59%), fatigue (59%), upper respiratory infection (47%), diarrhea (47%), dyspepsia (35%), bone pain (39%), asthenia (24%), memory impairment (24%), decreased appetite (24%) and vomiting (24%). Most AEs were Grade 1 or 2 in severity; no Grade 4 AEs were reported and no Grade 3 AEs occurring in more than 1 subject were reported. 6/17 (35%) had afuresertib dose modifications (interruption or reduction). Afuresertib plasma concentrations in the adult patients were similar to values seen in adult patients with other hematologic malignancies in the FTIH study. Following a single dose, the concentration-time profile in the adolescent patient was similar to adults in the FTIH study (Tmax = 3h: Cmax 229 ng/ml: AUC24 = 3893 ng*h/mL). 15 patients had archival tissues collected for BRAF testing; 13 had DNA suitable for analysis. 2/13 was BRAF V600E mutant and 11/13 were BRAF wild type. Upon evaluation of the all-treated patient population, 5/17 (29%) patients were reported as better at the three and/or six month disease assessment. Among the 5 responders, three were treatment-naïve and two had relapsed/refractory disease. The median duration on study for all patients was 214 (44-426) days. For the 5 patients who responded, the median duration on study was 372 (255-426) days. Conclusion The pharmacokinetic and safety profile of afuresertib in patients with LCH was consistent with that observed in patients with other hematologic malignancies evaluated in the FTIH study. Afuresertib was active in patients with both treatment-naïve and relapsed/refractory disease. Additional evaluation, including molecular profiling, may be warranted alone or in combination with BRAF inhibitors or established therapies for LCH to determine the optimal population of patients with LCH who might benefit from afuresertib Disclosures: Vassallo: GlaxoSmithKline: Research Funding. Oliff:GlaxoSmithKline: Employment. Morris:GlaxoSMithKline: Employment. Reedy:GlaxoSmithKline: Employment. Portnoy:GlaxoSmithKline: Stock, prior employee Other. Smith:GlaxoSmithKline: Employment, Equity Ownership. Noble:GlaxoSmithKline: Employment, stock Other. Murnane:GlaxoSmithKline: Employment, stock Other. Szabo:GlaxoSmithKline: Employment. Heaney:Novartis: Research Funding; Sanofi-Aventis: Consultancy, Research Funding; Onconova: Research Funding; Incyte: Consultancy, Research Funding.

Description: Introduction: Langerhans Cell Histiocytosis (LCH) is an inflammatory myeloid neoplastic disorder. Patients with recurrent or refractory LCH are at increased risk of mortality and long-term morbidity. The standard of care for high-risk LCH patients who are refractory to vinblastine/prednisone or who relapse is very high dose While mostly cytarabine/cladribine. While effective, this strategy also has very high treatment-related mortality. Clofarabine is a nucleoside analog with efficacy in other myeloid malignancies. Case reports have suggest that is has activity in LCH and other histiocytic disorders at moderate doses. The purpose of this study was to report the efficacy and toxicity profile of a restrospective cohort of patients with histiocytic disorders treated with clofarabine. Methods: Medical records were retrospectively reviewed for 26 pediatric patients with histiocytic disorders who were treated with clofarabine. Twenty-one of these patients had LCH and had failed at least one prior systemic therapy, while the remaining 5 patients had other histiocytic disorders (JXG, Rosai-Dorfman disease or mixed histiocytic disease). Patients were treated for a minimum of 6 months of with clofarabine (25 mg/m2/day x 5 days every 28 days), were reassessed for response at the end of therapy and monitored for relapse or progression post-treatment. Results: All patients in this series started treatment under the age of 18 years old (median=1.5 years; range: 0.3-16.3). Patients with LCH had received a median of 3 prior treatments (range:1-5). A majority of the patients (n = 17, 65%) were received all clofarabine infusions in an outpatient clinic. The most common adverse event was fever requiring hospital admission (n = 18; 69%), followed by Grade 3 neutropenia (n = 12; 46%), and intractable nausea/vomiting (n = 7; 27%). Additional adverse events included Grade 3 anemia, Grade 2 dehydration, Grade 3 cytopenias, and Grade 3 infection. Overall survival was 100%. LCH patients who completd 6-months of clofarabine had an 85% overall response (33% complete response, 52% partial response); 10% progressed on therapy and 5% had stable disease. Relapse occurred in 5 (28%) patients with LCH after completion of treatment (median time to relapse=22 months; range: 1-42). The odds of relapse was approximately 4-times greater in LCH patients with CNS involvement (n=16) compared to those without (n=4), and also in those with high risk disease (n=5) relative to standard risk (n=10). One of the patients who experienced disease recurrence received an additional 12 cycles of clofarabine and is currently doing well with no active disease. Conclusions: Clofarabine may be an effective and relatively safe salvage therapy for LCH and other histiocytic disorders. Future prospective trials for patients with refractory histiocytic disorders will directly compare efficacy and toxicity relative to other current salvage strategies with cytotoxic nucleoside analogs or targeted inhibitors. Disclosures No relevant conflicts of interest to declare.

Description: Background: Langerhans Cell Histiocytosis (LCH) is an inflammatory myeloid neoplasia. Activating somatic mutations in MAPK pathway genes have been identified in almost all cases of LCH with BRAF-V600E as the most common somatic mutation, occurring in approximately 60% of lesions. Enforced expression of BRAF-V600E in myeloid precursors recapitulates an LCH-like phenotype in mice, supporting a central pathogenic role for MAPK activation in LCH. Given the near universal occurrence and central pathogenic role of activating MAPK pathway gene mutations in LCH, targeted inhibition of the MAPK pathway is a rationale therapeutic strategy to explore in patients with relapsed disease. Design/Methods: Medical records from 20 pediatric patients with LCH (systemic and/or LCH-associated neurodegeneration) from 12 institutions were systematically reviewed; 2 patients had disease which was mixed LCH with juvenile xanthogranuloma (JXG) and 2 patients had secondary hemophagocytic lymphohistiocytosis/macrophage activation syndrome (HLH/MAS). All patients had failed at least one prior systemic therapy and had a proven MAPK pathway somatic mutation. Response assessment was based on applicable criteria for each individual including PET (metabolic) criteria, bone marrow evaluation, brain MRI, clinical history and physical exam. Results: All patients in this series were less than 21 years old (median age at start of therapy 6.9 years; range: 0.4-20.7 years) with median disease duration of 4 years prior to start of MAPK inhibitor (range 0.07-18.4 years). Twelve patients had LCH-ND diagnosed clinically and/or by radiographic imaging, while the remaining 8 patients had systemic disease with no LCH-ND (7 with high risk organ involvement). In terms of best response, 3 patients (15%) achieved a complete response (CR) and eleven patients (55%) achieved a partial response (PR), while 3 patients (15%) only achieved stable disease (SD), and 1 patient (5%) died early on in therapy due to progressive disease (PD) complicated by secondary HLH/MAS. Of the 12 patients who had LCH-ND, none achieved a CR, but 10 (83%) had a best response of PR by either clinical or radiographic assessment. Median progression free survival (PFS) was 11.8 months (range 2-36 months), while median time to disease progression or recurrence was 4.6 months (range 1-46 months). Four of the 20 patients (20%) had a Grade 3 or 4 toxicity; 2 of these patients required dose modification in order to successfully resume therapy. Seven patients had measurable peripheral blood mononuclear cells (PBMC) or bone marrow cells with detectable BRAF-V600E mutation just prior to start of MAPK inhibitor with subsequent assessments obtained during therapy. Conclusions: MAPK pathway inhibitors may be a relatively safe salvage therapy for refractory systemic LCH and LCH-ND but the efficacy and durability of responses with this strategy remains to be delineated. Children with relapsed/refractory high-risk LCH who were at the highest risk of death from disease generally benefited from this strategy. Patients with longstanding neurodegenerative disease seem to have the least benefit from MAPK inhibitors. However, patients with relatively early onset neurodegenerative disease, especially without clinical manifestations, seem to have the greatest benefit. While the presence of persistent BRAF-V600E+ circulating cells appears to be associated with risk of relapse and type of LCH organ involvement, quantifiable changes in these levels did not consistently correlate with clinical disease activity or response (in contrast to those treated with chemotherapy). We hypothesize that inhibition of the MAPK pathway may confer clinical benefit by blocking differentiation and proliferation of lesions, but may not have cytotoxic effect on precursor cells. This is supported by the observation that MAPK regulates lesion progression by inhibiting CCR7 expression, thereby blocking emigration of LCH cells from the lesion. Persistence of BRAF-V600E+ mononuclear cells in blood and bone marrow even in patients with impressive clinical responses may underlie the high rates of eventual progression/relapse with this type of treatment. Future prospective trials of MAPK pathway inhibitors for patients with refractory LCH possibly in combination with chemotherapy will be needed in order to directly compare their efficacy and toxicity relative to other current salvage strategies. Disclosures No relevant conflicts of interest to declare.

Description: Introduction: Langerhans cell histiocytosis (LCH) is an inflammatory myeloid neoplasia characterized by lesions including pathogenic CD207+ dendritic cells among an inflammatory infiltrate, and has a median age at diagnosis of 30 months. Approximately 50% of children with LCH relapse, and 40% experience a second relapse event within two years. Sequencing studies have identified activating somatic mutations in MAPK pathway genes in ~85% of LCH lesions. Notably, LCH cases who are carriers of BRAFV600E+ experience a 2-fold increased risk of relapse. However, the role of inherited genetic effects in LCH relapse remains unknown. Therefore, we conducted a genome-wide association study (GWAS) to characterize the role of inherited genetic variants on risk of LCH relapse. Methods: LCH cases (n=117) for this discovery GWAS were recruited from Texas Children's Hospital, of which 52 patients experienced a relapse event and 65 patients did not. Genotyping was performed on the Illumina Omni5 Quad BeadChip. We tested the association between common variants (minor allele frequency 〉5%) and LCH relapse risk in PLINK. A genome-wide threshold of significance was applied at P-value

Description: Erdheim-Chester disease (ECD) is a rare histiocytosis that was recently recognized as a neoplastic disorder owing to the discovery of recurrent activating MAPK (RAS-RAF-MEK-ERK) pathway mutations. Typical findings of ECD include central diabetes insipidus, restrictive pericarditis, perinephric fibrosis, and sclerotic bone lesions. The histopathologic diagnosis of ECD is often challenging due to nonspecific inflammatory and fibrotic findings on histopathologic review of tissue specimens. Additionally, the association of ECD with unusual tissue tropism and an insidious onset often results in diagnostic errors and delays. Most patients with ECD require treatment, except for a minority of patients with minimally symptomatic single-organ disease. The first ECD consensus guidelines were published in 2014 on behalf of the physicians and researchers within the Erdheim-Chester Disease Global Alliance. With the recent molecular discoveries and the approval of the first targeted therapy (vemurafenib) for BRAF-V600–mutant ECD, there is a need for updated clinical practice guidelines to optimize the diagnosis and treatment of this disease. This document presents consensus recommendations that resulted from the International Medical Symposia on ECD in 2017 and 2019. Herein, we include the guidelines for the clinical, laboratory, histologic, and radiographic evaluation of ECD patients along with treatment recommendations based on our clinical experience and review of literature in the molecular era.