Primary Hemophagocytic Lymphohistiocytosis Research Articles

Overcoming Diagnostic Challenges: A Rare Presentation of Primary Hemophagocytic Lymphohistiocytosis (HLH) in a Young Female and the Importance of Timely Recognition

Overcoming Diagnostic Challenges: A Rare Presentation of Primary Hemophagocytic Lymphohistiocytosis (HLH) in a Young Female and the Importance of Timely Recognition

Inhibition of interferon gamma impairs induction of experimental epidermolysis bullosa acquisita

Epidermolysis bullosa acquisita (EBA) is a muco-cutaneous autoimmune disease characterized and caused by autoantibodies targeting type VII collagen (COL7). The treatment of EBA is notoriously difficult, with a median time to remission of 9 months. In preclinical EBA models, we previously discovered that depletion of regulatory T cells (Treg) enhances autoantibody-induced, neutrophil-mediated inflammation and blistering. Increased EBA severity in Treg-depleted mice was accompanied by an increased cutaneous expression of interferon gamma (IFN-γ). The functional relevance of IFN-γ in EBA pathogenesis had been unknown. Given that emapalumab, an anti-IFN-γ antibody, is approved for primary hemophagocytic lymphohistiocytosis patients, we sought to assess the therapeutic potential of IFN-γ inhibition in EBA. Specifically, we evaluated if IFN-γ inhibition has modulatory effects on skin inflammation in a pre-clinical EBA model, based on the transfer of COL7 antibodies into mice. Compared to isotype control antibody, anti-IFN-γ treatment significantly reduced clinical disease manifestation in experimental EBA. Clinical improvement was associated with a reduced dermal infiltrate, especially Ly6G+ neutrophils. On the molecular level, we noted few changes. Apart from reduced CXCL1 serum concentrations, which has been demonstrated to promote skin inflammation in EBA, the expression of cytokines was unaltered in the serum and skin following IFN-γ blockade. This validates IFN-γ as a potential therapeutic target in EBA, and possibly other diseases with a similar pathogenesis, such as bullous pemphigoid and mucous membrane pemphigoid.

L-DEP regimen salvage therapy for refractory primary hemophagocytic lymphohistiocytosis triggered by Epstein-Barr virus infection in 4 children

Objective: To analyze the efficacy and safety of the L-DEP regimen (asparaginase, liposome doxorubicin, etoposide and methylprednisolone) as a salvage therapy for the refractory primary hemophagocytic lymphohistocytosis triggered by Epstein-Barr virus infection (EBV-pHLH) in children. Methods: In this retrospective case study, clinical and laboratory data before and after L-DEP regimen of 4 children diagnosed with EBV-pHLH in Beijing Children's hospital between January 2016 and June 2022 were collected, and the efficacy and safety of L-DEP regimen for the treatment of EBV-pHLH were analyzed. Results: Among 4 patients, there were 3 females and 1 male with the age ranged from 0.8 to 7.0 years. Two of them showed compound heterozygous mutations of PRF1, one with a heterozygous mutation of UNC13D, one homozygous mutation of ITK. Before the L-DEP therapy, all of them had anemia and a soaring level of soluble CD25, 3 patients had neutropenia and thrombopenia, 3 patients had a high level of ferritin, 3 patients had hypofibrinogenemia and 1 patient had hypertriglyceridemia. After receiving 1 or 2 cycles of L-DEP treatment, three achieved remission, including complete remission (1 case) and partial remission (2 cases), and the other one had no remission. The levels of blood cell counts, soluble CD25, triglyceride, fibrinogen and albumin were recovered gradually in 3 patients who got remission. All four patients underwent hematopoietic stem cell transplantation (HSCT) after L-DEP regimen, and three survived. All patients had no severe chemotherapy related complications. The main side effects were bone marrow suppression, infection and pancreatitis, which recovered after appropriate treatments, apart from one who died from severe infection after urgent HSCT. Conclusion: L-DEP regimen could be served as an effective and safe salvage treatment for refractory pediatric EBV-pHLH, and also provide an opportunity for patients to receive HSCT.

Population Pharmacokinetics of the Anti-Interferon-Gamma Monoclonal Antibody Emapalumab: An Updated Analysis.

Emapalumab is a fully human monoclonal antibody that targets free and receptor-bound interferon-gamma (IFNγ), neutralizing its biological activity. IFNγ levels differ by orders of magnitude between patients with primary hemophagocytic lymphohistiocytosis (HLH) and macrophage activation syndrome (MAS; a form of secondary HLH) in systemic juvenile idiopathic arthritis (sJIA). Therefore, this study aimed to develop a population pharmacokinetic model for emapalumab across a patient population with a wide range of total (free and emapalumab-bound) IFNγ levels using observations from patients with primary HLH or MAS in sJIA in clinical trials. Pharmacokinetic data were pooled (n = 58; 2709 observations) from studies enrolling patients administered emapalumab for primary HLH or MAS in sJIA. Patients with primary HLH were administered emapalumab 1mg/kg (potentially increasing to 3, 6, and up to 10mg/kg based on clinical response) every 3days. Patients with MAS in sJIA were administered emapalumab 6mg/kg, followed by 3mg/kg every 3days until day 15 and twice weekly until day 28. An earlier population PK model was re-parameterized using this data. The final model for emapalumab comprised a 2-compartment model with first-order elimination. Emapalumab clearance remains constant when the total IFNγ concentration (free and emapalumab-bound) is < ~ 10,000pg/ml but increases proportionally to total IFNγ concentration above this threshold. Emapalumab clearance was estimated to be 0.00218, 0.00308, 0.00623 and 0.01718 l/h at total serum IFNγ concentrations of 103, 104, 105 and 106pg/ml, respectively, with corresponding terminal half-lives of 19.2, 13.8, 7.18 and 3.12days for a 1-year-old patient weighing 10kg with primary HLH. The median terminal half-life for emapalumab in patients with MAS in sJIA was estimated to be 24.0 (range, 6.13-32.4)days, which is similar to observations in healthy volunteers. Emapalumab pharmacokinetics in patients with primary HLH and MAS in sJIA were described by a two-compartment model with fixed allometric exponents and an age-related effect. Differences in total IFNγ levels between patients with primary HLH and MAS may affect emapalumab pharmacokinetics, suggesting that each indication may require different dosing to rapidly control hyperinflammation. Clinicaltrials.gov identifiers: NCT01818492, NCT03311854 and NCT02069899.

Somatic mutations in FAS pathway increase hemophagocytic lymphohistiocytosis risk in patients with T- and/or NK-cell lymphoma

AbstractAlthough significant progress has been made in understanding the genetic basis of primary hemophagocytic lymphohistiocytosis (HLH), the pathogenesis of secondary HLH, the more prevalent form, remains unclear. Among the various conditions giving rise to secondary HLH, HLH in patients with lymphoma (HLH-L) accounts for a substantial proportion. In this study, we investigated the role of somatic mutations in the pathogenesis of HLH-L in a cohort of patients with T- and/or natural killer–cell lymphoma. We identified a 3-time higher frequency of mutations in FAS pathway in patients with HLH-L. Patients harboring these mutations had a 5-time increased HLH-L risk. These mutations were independently associated with inferior outcome. Hence, our study demonstrates the association between somatic mutations in FAS pathway and HLH-L. Further studies are warranted on the mechanistic role of these mutations in HLH-L.

Real-world treatment patterns and outcomes in patients with primary hemophagocytic lymphohistiocytosis treated with emapalumab

AbstractHemophagocytic lymphohistiocytosis (HLH) is a rare, life-threatening, hyperinflammatory syndrome. Emapalumab, a fully human monoclonal antibody that neutralizes the proinflammatory cytokine interferon gamma, is approved in the United States to treat primary HLH (pHLH) in patients with refractory, recurrent, or progressive disease, or intolerance with conventional HLH treatments. REAL-HLH, a retrospective study, conducted across 33 US hospitals, evaluated real-world treatment patterns and outcomes in patients treated with ≥1 dose of emapalumab between 20 November 2018 and 31 October 2021. In total, 46 patients met the pHLH classification criteria. Median age at diagnosis was 1.0 year (range, 0.3-21.0). Emapalumab was initiated for treating refractory (19/46), recurrent (14/46), or progressive (7/46) pHLH. At initiation, 15 of 46 patients were in the intensive care unit, and 35 of 46 had received prior HLH-related therapies. Emapalumab treatment resulted in normalization of key laboratory parameters, including chemokine ligand 9 (24/33, 72.7%), ferritin (20/45, 44.4%), fibrinogen (37/38, 97.4%), platelets (39/46, 84.8%), and absolute neutrophil count (40/45, 88.9%). Forty-two (91.3%) patients were considered eligible for transplant. Pretransplant survival was 38 of 42 (90.5%). Thirty-one (73.8%) transplant-eligible patients proceeded to transplant, and 23 of 31 (74.2%) of those who received transplant were alive at the end of the follow-up period. Twelve-month survival probability from emapalumab initiation for the entire cohort (N = 46) was 73.1%. There were no discontinuations because of adverse events. In conclusion, results from the REAL-HLH study, which describes treatment patterns, effectiveness, and outcomes in patients with pHLH treated with emapalumab in real-world settings, are consistent with the emapalumab pivotal phase 2/3 pHLH trial.

Outcome of primary hemophagocytic lymphohistiocytosis: a report on 143 patients from the Italian Registry.

Primary hemophagocytic lymphohistiocytosis (pHLH) is a severe, life-threatening hyperinflammatory syndrome caused by defects in genes of the granule-dependent cytotoxic pathway. Here we investigated the clinical presentation and outcome in a large cohort of 143 patients with pHLH diagnosed in the last 15 years and enrolled in the Italian registry. The median age at diagnosis was 12 months (IQR 2-81), and ninety-two patients (64%) fulfilled the HLH-2004 criteria. Out of 111 patients who received first-line combined therapy (HLH-94, HLH-2004, Euro-HIT protocols), 65 (59%) achieved complete response (CR) and 21 (19%) partial response (PR). Thereafter, 33 patients (30%) reactivated, and 92 (64%) received HSCT, 78 of whom (85%) survived and were alive at a median follow-up from diagnosis of 67 months. Thirty-six patients (25%) died before HSCT and 14 (10%) after. Overall, 93 patients (65%) were alive after a median follow-up of 30 months. Unadjusted predictors of non-response were age.

Inflamed-HLH, MAS, or something else?

Hemophagocytic lymphohistiocytosis (HLH) is a syndrome of excessive and maladaptive inflammation. Primary HLH is most frequently encountered in young children, and, without timely recognition and therapy, can lead to multiorgan failure and death. It is most often diagnosed using the HLH-2004 criteria and by identifying pathological mutations. However, the HLH-2004 criteria are not specific for HLH, and patients can easily fulfill these diagnostic criteria in other proinflammatory states in which HLH-therapy would not be indicated, including hematologic malignancies, infections, and rheumatologic disease. Therefore, great care must be taken to ensure that the specific disease associated with features of HLH is accurately recognized, as consequences of improper treatment can be catastrophic. We propose a diagnostic pathway for patients for whom HLH is on the differential (visual abstract). Importantly, in situations in which the initial diagnostic workup is equivocal or unrevealing, reevaluation for occult malignancy, infection, or rheumatologic disease would be prudent, as occult presentations may be missed on primary evaluation. Temporizing medications can be used in critically ill patients while awaiting secondary evaluation. By using this framework, clinicians will be able to more reliably discern primary HLH from other pro-inflammatory states and thus provide timely, appropriate disease-specific therapy.

Emapalumab, a Fully Human Anti-Interferon Gamma Monoclonal Antibody, in Pediatric Patients with Primary Hemophagocytic Lymphohistiocytosis: Long-Term Follow-up of a Phase 2/3 Study

Background: Primary hemophagocytic lymphohistiocytosis (pHLH) is a rare, life-threatening genetically heterogeneous, autosomal recessive disorder, characterized by immune dysregulation and hyperinflammation. Acute treatment of pHLH has traditionally involved immunochemotherapy with glucocorticoids and etoposide to suppress hyperinflammation and facilitate the patient undergoing allogeneic hematopoietic stem cell transplantation (HSCT), the only potentially curative therapy. Emapalumab, a fully human immunoglobulin G1 anti-interferon-γ (IFNγ) monoclonal antibody, binds free and receptor-bound IFNγ, neutralizing its biologic activity. Emapalumab has demonstrated efficacy in patients with pHLH and has a favorable safety profile with no increase in the risk of adverse events (AEs), including infections, with increasing drug exposure prior to patients undergoing HSCT. Objective: To monitor the long-term safety and efficacy of emapalumab in patients with pHLH, including the period after undergoing HSCT. Methods: Long-term follow-up study (NCT02069899) of patients with pHLH who had received ≥1 dose of emapalumab in a multicenter, single-arm, open-label phase 2/3 clinical trial who were followed for 1 year after HSCT or last administration of emapalumab in the parent study (NCT01818492). Patients received emapalumab for 4 to 8 weeks in the parent study, which included a 4-week short-term follow-up period, during which patients could have undergone HSCT. Treatment with emapalumab could continue according to the parent study protocol during follow-up, if a favorable benefit/risk assessment was established. Any concomitant treatment ongoing at the time of study entry was continued as considered necessary by the investigators. Endpoints included safety, 1-year survival, and HSCT outcomes. Results: Overall, 37/45 patients who participated in the phase 2/3 study entered long-term follow-up, with 24 patients (64.9%) completing the study; 13 patients (35.1%) withdrew from the study, most commonly because of AEs (6 patients [46.2%]) and withdrawal of informed consent (2 patients [15.4%]). All patients had ≥1 concomitant medications including systemic corticosteroids and ≥1 systemic antimicrobial. Emapalumab treatment continued during long-term follow-up for 22 patients (59.5%). All patients experienced at least one AE during follow-up ( Table), most commonly infections or infestations (27 patients [73.0%] reported an infection AE). Most AEs were mild or moderate in intensity. Four patients (10.8%) had study drug-related AEs. Overall, 56.8% of patients experienced at least one severe AE. 28 patients (75.7%) experienced at least 1 serious AE (SAE), but only 1 patient (2.7%) had a treatment-related SAE (Coombs positive hemolytic anemia). Infusion-related reactions of rash were observed in 2 patients (5.4%), but these reactions were temporary and resolved without treatment. No patients experienced AEs leading to study drug discontinuation. Nine patients died during the study (4 prior to HSCT conditioning and 5 during the post-conditioning period). No study drug-related deaths were reported. 28 (75.7%) patients were alive at last observation or 1 year after last emapalumab dose and 33 (89.2%) survived to undergo HSCT or until 1 year after last emapalumab dose (whichever came first). 29 patients (78.4%) underwent HSCT, including 18 during long-term follow-up. 24 of the 29 (82.8%) patients who underwent HSCT were alive at last observation or 1 year after last emapalumab dose. Sustained engraftment was achieved in 23 patients (79.3%; 95% confidence interval, 61.6-90.2%). During the follow-up period, 6 patients (20.7%; 95% confidence interval [CI], 9.8-38.4%) experienced primary or secondary graft failure after undergoing HSCT and 7 patients (24.1%; 95% CI, 1.2-42.1%) had acute or chronic graft-versus-host disease. At the 12-months post-transplant visit, 25/26 (96.2%) patients maintained a complete response, while 1 (3.8%) patient was reported to have maintained a partial response. No pHLH reactivation was reported during the study. Conclusions: The long-term outcomes for patients with pHLH treated with emapalumab are consistent with observations made during a phase 2/3 study. A favorable safety profile was maintained, and a high proportion of patients received HSCT and achieved long-term survival.

Real-World Treatment Patterns and Outcomes Among Patients with Primary Hemophagocytic Lymphohistiocytosis with and without Infection at Diagnosis and Treated with Emapalumab: The Real-HLH Study

Background: Primary hemophagocytic lymphohistiocytosis (pHLH), a rare, life-threatening, hyperinflammatory syndrome, characteristically shows overproduction of interferon gamma (IFNγ). Since FDA approval of emapalumab for refractory, recurrent, or progressive pHLH or intolerance with conventional therapy, there are limited real-world data on its use. The REAL-HLH study assessed real-world treatment patterns and outcomes among patients treated with emapalumab. Emapalumab treatment patterns and outcomes in the real world among patients with pHLH with or without infection at HLH diagnosis are presented. Methods: Data were extracted via a retrospective medical chart review of patients with pHLH treated with ≥1 dose of emapalumab between Nov. 20, 2018, and Oct. 31, 2021, across 33 US hospitals from time of emapalumab initiation to end of data availability, death, or study end (Dec. 31, 2021). Data are presented as summary statistics and comparisons using χ 2 tests. Results: Forty-six of 105 enrolled patients met the pHLH classification criteria; 25/46 (54.3%) had infection at diagnosis with viral infections being most common (18/25; 72.0%). Baseline characteristics are provided in Table 1. The median (range) times from HLH diagnosis to emapalumab initiation and treatment duration with emapalumab for the 2 groups are provided in Table 2. Median (range) starting, maximum single, and cumulative administered dose of emapalumab for the 2 groups are provided in Table 2. Overall survival rates from emapalumab initiation for patients with (18/25; 72.0%) and without infection (16/21;76.2%) were comparable; p=0.747. A greater proportion of eligible patients without infection (15/19; 78.9%) received hematopoietic stem cell transplantation (HSCT) compared with those with infection (16/23; 69.6%), but the difference was not statistically significant (p=0.491). Conclusion: This is the first study to report real-world treatment patterns with emapalumab across a diverse patient population with pHLH with or without infection at diagnosis. Over 54% of the patients with pHLH presented with infection at diagnosis. The infection status at diagnosis did not affect the overall survival rate and the proportion of patients proceeding to HSCT after emapalumab treatment.

HLH Secondary to Influenza

Introduction Hemophagocytic lymphohistiocytosis (HLH) is a pathological condition characterized by excessive inflammation and tissue damage resulting from an aberrant immune system response. HLH can be classified into two distinct categories: primary HLH and secondary HLH. Secondary hemophagocytic lymphohistiocytosis (HLH) is an acquired condition that can be precipitated by various infections, malignancies, or rheumatological disorders. Herein, we present a rare case of HLH secondary to influenza B infection. Case Presentation A 37-year-old who routinely vapes and smokes cannabis presented to the emergency department with subjective fevers, body pains, fatigue, productive cough, shortness of breath, nausea, non-bloody, non-bilious vomiting, and watery diarrhea for one week. He was tachypneic, tachycardic, and febrile (101.1 F). He had loud bibasilar crackles on auscultation. Hb 14.8, total WBC 2.2, platelets 170, AKI with serum creatinine 1.9, and transaminitis with AST/ALT/ALP 130/56/122 U/L were the patient's initial lab results. Rapid influenza, strep, and COVID-19 antigen tests were negative. He exhibits hypoxemia with pH 7.46, pCO2 32.5, pO2 52.1, HCO3 22.9, and FIO2 40%. Urinalysis showed nonsignificant. CRP was 8.3 mg/dL. Negative procalcitonin. chest x-ray and ct showed bilateral diffuse patchy airspace infiltration, suggesting infectious process with mild pleaural effusion. In the critical care unit, he received Antibiotics and inhaled therapy for acute hypoxic respiratory failure with severe ARDS. After deteriorating, he was intubated. The respiratory pathogen panel detected Influenza B. Blood cultures and remaining pneumonia workup were negative. The lab results suggested HLH (table 1). Autoimmune tests were negative. Oseltamivir was given for 5 days. Repeat chest x-rays showed stable pulmonary infiltrates in the right middle and lower lobes, but the patient decompensated clinically with increasing ventilator requirements and dyssynchrony despite heavy sedation, paralytics, and proning and was transferred to a different hospital for ECMO evaluation on day 12. Discussion Primary and secondary HLH: Secondary HLH is caused by infections, malignancies, or rheumatological illnesses, while primary HLH is hereditary. The mortality outcome of HLH is extremely dependent on early detection and treatment 1. Due to the rarity of this disease entity, difficult diagnostic criteria, and concern for alternate diagnoses, internists may be less aware of it. Further complicating the diagnosis is the fact that the first bone marrow biopsy may not always show hemophagocytosis 2. This is why it is important to be cognizant of this diagnosis and it's diagnostic criteria. Our patient was suspected of HLH based on HScore for reactive hemophagocytic syndrome and the newest updated HLH diagnostic criteria (5 of 8 criteria should be met) 6. EBV is the most common viral infection which can cause HLH. CMV, Parvo, HSV, and H1N1 are other infections. HLH-Influenza B connection is poorly documented 7 Only one case of HLH induced by influenza B in a healthy patient was found in literature. To our knowledge, Our 38-year-old patient is the second known case of secondary HLH secondary to Influenza B in a healthy patient. Influenza B seldom causes HLH. This connection in adulthood is poorly researched. Patients with influenza virus infections have significant intestinal apoptosis and reactive hemophagocytic activity in bone marrow, lungs, and liver3. Influenza variants reduce CD8+ T cell cytotoxicity and perforin expression, likely causing HLH syndrome 4. A study suggests that virus-associated hemophagocytic syndrome (VAHS) is a common consequence of severe 2009 influenza A (H1N1) infection and contributes to multiorgan failure and mortality. 9 (36%) of 25 severely ill patients with confirmed 2009 influenza A (H1N1) infection developed VAHS, and 8 (89%) died 5. Conclusion: We present this case to raise awareness among physicians regarding the potential occurrence of hemophagocytic lymphohistiocytosis (HLH) as a complication in adult patients who present with influenza B virus infection accompanied by fever and pancytopenia. The aim is to emphasize the importance of considering HLH as a differential diagnosis in order to facilitate timely identification and initiation of appropriate treatment for this condition.

Exposure-safety relationship for patients with primary hemophagocytic lymphohistiocytosis treated with emapalumab.

Primary hemophagocytic lymphohistiocytosis (pHLH) is an immune-mediated, hyperinflammatory disorder. Interferon-γ (IFNγ) plays a key role in the pathophysiology of pHLH. Emapalumab, a fully human, anti-IFNγ monoclonal antibody neutralizes both free and receptor-bound IFNγ. However, inhibiting IFNγ-mediated signaling could result in immune dysfunction and immunosuppression. This exploratory exposure-safety analysis investigated the relationship between emapalumab and the incidence of adverse events in patients with pHLH. Increased exposure to emapalumab was not associated with an increased predicted risk of severe adverse events, infection, or infusion-related reactions. Emapalumab was associated with a favorable and manageable safety profile across all assessed doses and treatment durations.

Herombopag, a Second Generation Thrombopoietin-Receptor Agonist, Stimulates Platelet Engraftment after Haploidentical Allogeneic Hematopoietic Stem Cell Transplantation

Introduction: The delayed platelet engraftment is a common complication in allogeneic hematopoietic stem cell transplantation (allo-HSCT), which elevates treatment-related mortality and impairs quality of life. Although some studies reported that platelet engraftment after allo-HSCT was promoted by thrombopoietin-receptor agonists (TPO-RAs), the recommended detailed TPO-RA administration is still lacking. This prospective, single-center, investigator-initiated pilot study aims to explore the efficacy and safety of herombopag, a second-generation TPO-RA, to stimulate platelet engraftment in haploidentical allo-HSCT (haplo-HSCT). Methods: A total of 36 patients (median age 38; range 15-59 years) with anaplastic anemia, myelodysplastic syndrome, acute leukemia, granulocytic sarcoma, or primary hemophagocytic lymphohistiocytosis were enrolled between November 2021 and June 2023. All patients received haplo-HSCT and post-transplant cyclophosphamide for acute graft-versus-host disease (aGVHD) prophylaxis. Patients received herombopag from day+5 post-HSCT until platelet&amp;gt;100,000/µL, disease progression, intolerable toxicity, or withdrawal of informed consent. The dose of herombopag was 5 mg/day initially and reduced to 2.5 mg/day when platelet&amp;gt;75,000/µL. Complete platelet engraftment (CPE) was defined as a platelet count exceeding 50,000/μl for seven consecutive days without transfusion. Partial platelet engraftment (PPE) was defined as a platelet count exceeding 20,000/μl for seven consecutive days without transfusion. The objective response included both CPE and PPE. The primary endpoint was the 21-day cumulative incidence and 28-day cumulative incidence of CPE and objective response after haplo-HSCT. The secondary endpoints were time to CPE, time to objective response, platelet transfusion units, aGVHD, relapse, non-relapse mortality, and safety. Results: The patients received herombopag treatment for a median of 15 days. The 21-day cumulative incidence of CPE was 55.6%, and that of objective response was 77.8%. The 28-day cumulative incidence of CPE was 69.4%, and that of objective response was 80.6%. The median time to objective response was 20.5 (95%CI 17-27) days. The median time to CPE was 23 (95%CI 10-33) days. The mean units of platelet transfusions required within 30 days after HSCT was 6.7. The median follow-up time was 12.1 months. The one-year overall survival rate was 85.3% (95%CI 72.8%-99.8%). Two patients died of aGVHD and two patients died of lung infection. Four Patients (11.1%) experienced molecular relapse. The cumulative incidence of grade III-IV aGVHD was 16.7%. Furthermore, cytomegalovirus reactivation occurred in 13 patients (36.1%). The most common herombopag-related adverse events were hypomagnesemia (61.1%), increased GGT (52.8%), increased ALT (38.9%), and increased bilirubin (19.4%). No grade III/IV adverse events were observed. Conclusion: Herombopag significantly stimulates platelet engraftment in haplo-HSCT patients and has a favorable safety profile. Further research with a larger sample size and longer follow-up period is required to confirm its optimal use.

Myelodysplastic Syndrome Associated Hemophagocytic Lymphohistiocytosis: A Retrospective Study of 15 Cases in a Single Center

Introduction: Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening disorder characterized by excessive cytokine secretion, resulting in hyperinflammation and multiorgan dysfunction. It is classified into primary HLH, which is mainly caused by genetic defects, and secondary HLH, triggered by various underlying conditions. Malignancy-associated HLH (M-HLH) is a secondary form commonly observed in patients with hematological malignancies, such as lymphomas, T/NK-cell disorders, acute leukemias, lymphoproliferative diseases, and myelodysplastic syndrome (MDS). M-HLH can occur in up to 1% of patients with hematologic malignancies, with lymphoma being the most frequently associated malignancy. HLH initiated by MDS is a rare entity with only a few cases reported, leading to limited knowledge regarding its pathogenesis, diagnosis and optimal treatment strategies. Methods: In this retrospective study, we analyzed a consecutive series of MDS-HLH patients admitted to our center between March 1, 2019, and March 1, 2023. Bio-clinical data related with MDS and HLH were collected at diagnosis of MDS-HLH. Additional observational indicators encompassed the following: basic clinical characteristics of the patients (age at onset, gender, duration of MDS prior to HLH), correlation between the onset of HLH and MDS, treatment and response, and genetic defects associated with HLH and MDS. MDS risk classification was according to the Revised International Prognosis Scoring System (IPSS-R) and the WHO classification-based Prognosis Scoring System, while patients were categorized into two groups as higher-risk and lower-risk MDS-HLH group. The follow-up period started at the time of MDS-HLH diagnosis and ended at the date of death or last examination. Overall survival (OS) was calculated from the time of HLH diagnosis to the date of death from any cause. Results: A total of 15 patients diagnosed with MDS-HLH were included in the study, with a median age of 66 years (range, 33-83 years). The majority of patients (10/15, 67%) were over 60 years old. All patients exhibited typical features of aggressive HLH: fever, cytopenia and elevated serum ferritin in all patients, hepatomegaly/splenomegaly in 87% (13/15), hypofibrinogenemia/hypertriglyceridemia in 73% (11/15), hemophagocytosis in 73% (11/15), low NK-cell activity in 21% (3/14), and elevated levels of sCD25 in 93% of patients (14/15). Additionally, four patients (27%) had concurrent Epstein-Barr virus (EBV) infection. Further analysis comparing the lower-risk and higher-risk MDS-HLH groups revealed interesting findings. In the lower-risk group, all patients developed HLH concurrently with the diagnosis of MDS. However, in the higher-risk group, the majority of patients (6/8, 62.5%) experienced HLH onset during MDS progression or relapse (p=0.014). Among the 15 patients, 8 patients (53.3%) achieved remission of HLH. During the study period, 8 deaths occurred, all directly attributed to HLH or its complications. The majority of deaths (75%, 6/8) occurred within the first two months after HLH diagnosis. The median overall survival was 12.3 weeks (95%CI, 1.1-23.5). Patients who achieved complete or partial response had significantly prolonged overall survival compared to those who did not respond to treatment (p=0.002). In the multivariate analysis of prognosis, the remission status of HLH was the only factor which was significantly associated with survival (p=0.018, Exp(B)=0.003). Conclusion: This is the first comprehensive study focusing specifically on MDS-HLH, providing valuable insights into the clinical characteristics, treatment outcomes, and prognosis of MDS-HLH. The findings emphasize the need of considering revision of diagnostic criteria specially for MDS-HLH. The pathogenesis of HLH in MDS-HLH differs based on the risk classification of MDS, with higher-risk cases driven by malignancy and lower-risk cases associated with immune dysfunction. The prognosis of MDS-HLH is generally poor. Achieving remission of HLH is crucial for improving the prognosis of MDS-HLH patients. Conventional chemotherapy regimens, including etoposide, have shown limited efficacy and safety in this context. Chemotherapy-free regimens should be preferred considering the features of ineffective hematopoiesis in MDS. The role of EBV infection in MDS-HLH development should be recognized.

The Lymphocyte Subsets Activation Profiles in Peripheral Blood May Contribute to the Diagnosis of Natural Killer/T-Cell Lymphoma-Associated Hemophagocytic Lymphohistiocytosis

The lymphocyte subsets activation profiles in peripheral blood may contribute to the diagnosis of natural killer/T-cell lymphoma-associated hemophagocytic lymphohistiocytosis Background: Hemophagocytic lymphohistiocytosis (HLH) is a rampant and potentially fatal systemic hyperinflammation characterized by dysfunction of macrophages and cytotoxic T cells. Natural killer/T-cell lymphoma (NKTCL) has been reported to be one of the most common etiologies of HLH among hematologic neoplasms. Although, the diagnosis of natural killer/T-cell lymphoma-associated hemophagocytic lymphohistiocytosis (NK/T-LAHS) refers to the HLH-2004 diagnostic guidelines for primary HLH, most of them are based on non-specific clinical features. Identification of the immunophenotype characteristics is important for the diagnosis of NK/T-LAHS. In this study, we investigated the lymphocyte subsets activation profiles of peripheral blood mononuclear cells (PBMC) from NKTCL patients, and preliminarily screened molecular marker with potential diagnostic value for NK/T-LAHS. Methods: This study retrospectively collected peripheral blood samples from 58 patients diagnosed with NKTCL in Sun Yat-sen University Cancer Center from September 2020 to December 2022. Among them, 29 patients had HLH at the time of enrollment, and peripheral blood samples from 10 healthy people were collected as the control group. NKTCL was diagnosed according to the 2016 WHO classification of malignant lymphoma. All HLH patients met HLH-2004 diagnostic criteria and primary HLH was excluded. Flow cytometric staining of PBMC was performed on BD Fortessa according to the manufacturer's instructions. All samples were analyzed by Flowjo（V10）software. The ROC curve was drawn according to the percentage of lymphocyte subsets to determine the optimal cutoff threshold. RStudio 4.2.1 was used to calculate the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and likelihood ratio (LR) of the related indicators. Graphpad prism 8.0.1 and SPSS 26.0 (IBM) was used for drawing and statistical analysis. All statistical tests were two-sided, and p＜0.05 were considered statistically significant. Results:The median age of 58 patients was 41 (range, 18-83) years old, and 10 patients (17.2%) had poor performance status (ECOG PS≥2). Forty-two patients (72.4%) were stage III-IV, and 26 patients (44.8%) had PINK-E score≥3. Firstly, we compared the immune cell activation profiles between healthy donors, NKTCL patients with or without HLH. We observed that the proportion of functionally activated T cells, NK cells, NKT cells that expressed CD86, CD69, or HLADR was significantly higher than healthy donors ( p＜0.05), except for CD86+NK cell levels was no significance between the three groups (Figure1). In addition, the percentage of CD86+NK/T cells, CD69+NK cells, HLADR+NK cells and HLADR+NKT cells were significantly higher than NKTCL patients without HLH and healthy controls( p＜0.05), and no significant difference of these immune cells subsets between those non-HLH patients and healthy controls was observed (Figure1). Based on the significance of these lymphocyte subsets in NKTCL patients with and without HLH, we evaluated the diagnostic value of CD86+NKT cells, CD69+NK cells, HLADR+NK cells, and HLADR+NKT cells in NK/T-LAHS patients by ROC analysis to determine the optimal diagnostic threshold. We observed that HLADR+NK &amp;gt; 15.9% could better distinguish NK/T-LAHS from non-HLH patients, with a sensitivity of 0.759 (95%CI: 0.603-0.914) and specificity of 0.828(95%CI:0.690-0.965), and the AUC was 0.775 (95%CI:0.647-0.904) (Table 1). HLADR+NK cells may have potential application value for the diagnosis of NK/T-LAHS. Conclusions: These activated T cells, NK cells, and NKT cells that express functional activation markers was increased in NK/T-LAHS patients. Among them, HLADR+NK &amp;gt; 15.9% could better distinguish NK/T-LAHS from NKTCL patients without HLH and healthy donors, which may be a potential biomarker for the diagnosis of NK/T-LAHS patients and contribute to better management.

Compassionate Use of Emapalumab in Children with Life-Threatening Disorders: Real-World Data

Introduction: Life threatening hyperinflammation occurs in hemophagocytic lymphohistiocytosis (HLH) and during acute rejection of hematopoietic stem cell (HSC) grafts. Both conditions reflect acute activation of the immune system, in part due to overproduction of proinflammatory cytokines, particularly interferon gamma (IFNγ). Emapalumab, a fully human monoclonal antibody that binds to IFNγ, is approved by the FDA for refractory or recurrent primary HLH (pHLH) or in patients intolerant to conventional therapy. Off-label use of emapalumab has been reported for treatment of secondary HLH (sHLH) and for HSC graft rejection. The European Medicines Agency did not approve emapalumab for the treatment of HLH and many other regulatory authorities, including the Israeli Ministry of Health, have yet to approve emapalumab for clinical use. Pending such regulatory approval, emapalumab is available in Israel exclusively though the Managed Access Request Program (MAP) on a compassionate basis sponsored by Sobi (Swedish Orphan Biovitrum AB,Reg. no. 556038-9321). Experience that accumulates through on- and off-label use of emapalumab obtained via MAP enriches the knowledge base regarding the uses of this drug in the real-world clinical setting. Methods: We summarized the data of patients receiving emapalumab at our tertiary pediatric center. The medication was received after application to the MAP sponsored by Sobi International with import approval of the Israel Ministry of Health on a named-patient basis. Results: Seven patients (Pt) aged 2.5 months-17.5 years were treated with emapalumab between 3/2020-6/2023. Patients 1-5 fulfilled HLH-2004 diagnostic criteria. Indications for the use of emapalumab included treatment of HLH in a newborn with severe hepatotoxicity after treatment with the standard HLH-94 protocol (Pt. 3), treatment of acute graft rejection with recurrence of HLH in a patient with pHLH (Pt.1), secondary HSC graft failure and disease relapse in a child with pHLH (Pt. 4), sHLH with multi-organ failure (MOF) requiring extracorporeal membrane oxygenation (ECMO) (Pts 2&amp;5) and HSC primary graft rejection with suspected 2 nd rejection (Pts.6&amp;7). Table 1 summarizes the clinical characteristics of all cases. The patient outcomes were closely related to their clinical status at treatment initiation. Pt.3 was able to reach remission and successfully bridge to SCT without complications after only 4 doses of VP-16 with continuation therapy using only dexamethasone and emapalumab. Pt.4, who experienced relapsed pHLH with concomitant HSC graft loss, attained complete remission with emapalumab, dexamethasone and IVIG, facilitating a successful second HSC graft. Pt. 1 expired after initial graft failure, severe sepsis and relapse of pHLH. Pts. 2&amp;5, despite showing improvement of their HLH criteria after treatment with emapalumab, succumbed to MOF that was already present when they were referred to our center for ECMO support. Following unsuccessful emapalumab treatment for primary graft rejection, Pts. 6&amp;7 underwent successful 2 nd HSC transplants with early emapalumab treatment for suspected re-rejection. Conclusions: Emapalumab is a safe, effective, and well tolerated treatment for various HLH scenarios, and for similar hyper-inflammatory medical conditions. Administration of emapalumab early in the disease course is likely to be more effective as compared to administration of the drug when MOF has occurred or when the HSC graft has already been rejected. Since these diseases are life-threatening, eliminating delays in procurement of emapalumab is essential to expedite treatment before irreversible organ failure ensues.

Real-World Treatment Patterns and Outcomes Among Patients with Secondary Hemophagocytic Lymphohistiocytosis Treated with Emapalumab in the United States: The Real-HLH Study

Background: Hemophagocytic lymphohistiocytosis (HLH) is a rare, life-threatening, hyperinflammatory syndrome caused by the overproduction of proinflammatory cytokines, such as interferon gamma (IFNγ). Secondary HLH (sHLH) occurs in the context of an underlying disease (malignancy, rheumatologic, or metabolic disease) and/or an infection. Emapalumab is a fully human anti-IFNγ monoclonal antibody approved by the FDA in 2018 for refractory, recurrent, or progressive primary HLH (pHLH), or intolerance with conventional therapy. Since its approval, there are limited data on emapalumab use in a real-world setting. The REAL-HLH study assessed real-world treatment patterns and outcomes among patients with HLH treated with emapalumab. Methods: A retrospective medical chart review conducted across 33 US hospitals identified patients treated with ≥1 dose of emapalumab between November 20, 2018, and October 31, 2021. Data were extracted from time of emapalumab initiation to end of data availability, death, or study end (December 31, 2021). Results are presented for the subgroup of patients with sHLH treated off-label with emapalumab. Results: Overall, 105 patients were included in this chart review of which 98 (93.3%) were reportedly treated for HLH-related conditions. Of these, 51/98 (52%) did not meet the pHLH classification criteria (Table 1) and were categorized as presenting with sHLH. These patients (n=51) were grouped based on the underlying disease (i.e., rheumatologic, n=14; malignancy, n=17; and others, n=20). The “others” category comprised a miscellaneous group of patients with underlying diseases and/or HLH triggers that could not be categorized as rheumatologic or malignant disease. Median (range) age at sHLH diagnosis was 9 (0.1-39) years. Baseline demographics and clinical characteristics are presented in Table 1. More than half (32/50; 64%) of these patients were critically ill and received emapalumab in an intensive care unit. Emapalumab was primarily initiated to treat refractory (20/51; 39.2%), progressive (15/51; 29.4%), or recurrent (8/51; 15.7%) disease. The median (range) time from sHLH diagnosis to emapalumab initiation and emapalumab treatment duration are presented in Table 2. Median (range) starting, maximum single, cumulative, and number of administered doses of emapalumab are presented in Table 2. Among patients who achieved normalization of key laboratory parameters (i.e., platelets, absolute lymphocyte count, absolute neutrophil count, alanine transaminase, sCD25, ferritin, and fibrinogen [ Table 2]), the median time to first normalization of all these laboratory parameters ranged from 7-38.5 days for those with underlying rheumatologic disease; 7-38 days for those with underlying malignancy; and 7-11 days among patients in the “others” category. The 12-month survival probability following emapalumab initiation was 85.7% for patients with underlying rheumatologic disease, 23.5% for those with underlying malignancy, and 55% for patients in the “others” category. Conclusion: This is the first study to report real-world treatment patterns with emapalumab across a diverse patient population with sHLH. A phase 3 clinical trial of emapalumab in patients with sHLH/macrophage activating syndrome (MAS) and underlying rheumatologic disease is ongoing (NCT05001737).

Outcome of patients with primary and secondary hemophagocytic lymphohistiocytosis: A retrospective analysis from a tertiary care center.

Hemophagocytic lymphohistiocytosis (HLH) is a progressive and potentially life-threatening disorder. It is classified into primary and secondary HLH. The objective of our study was to determine the outcome of primary and secondary HLH in pediatric and adult patients based on HScore and treatment modality. We conducted a retrospective analysis done from July 2010 to June 2020. Variables analyzed included age, gender and history of death in siblings. HScore was used for disease classification while clinical and laboratory findings which were required to fulfill the HScore diagnostic criteria were also recorded. Continuous variables were summarized as median and categorical variables as frequencies and percentages. Categorical variables were compared using chi-square test and Fisher Exact test. Significance of different variables between primary and secondary HLH was calculated using independent-samples t test. A P value of < .05 was taken as significant. A total of 51 patients were included in the analysis (41 in primary and 10 in secondary HLH group). In primary HLH, 36 patients were in the pediatric age group and 12.2% had a history of death in sibling. All 41 patients had increased ferritin and decreased fibrinogen levels. The overall survival in primary HLH was 44%. In the secondary HLH group, viral infections were the most common etiology and ferritin was increased as well. The overall survival in secondary HLH was 60%. The median survival was 15 ± 4.8 months. The overall survival of both groups combined was 53%. Primary HLH should be considered in pediatric patients who present with pancytopenia and hepatosplenomegaly. In centers where genetic testing is not available, HScore along with serum ferritin and fibrinogen is a good substitute for disease classification.

Genetic and clinical characteristics of primary hemophagocytic lymphohistiocytosis in children.

To analyze the genetic variation and prognosis of primary hemophagocytic lymphohistiocytosis (pHLH) in children and the clinical features of isolated central nervous system HLH (CNS-HLH). We retrospectively analyzed the clinical and genetic data of 480 HLH children admitted to our hospital from September 2017 to September 2022. There were 66 patients (13.75%) with pHLH, and the median age was 3.21years (0.17-12.92years). Variants in UNC13D (22/66, 33.33%), PRF1 (20/66, 30.30%) and XIAP (11/66, 16.67%) were the most common. More CNS involvement was observed in pHLH patients than in secondary hemophagocytic lymphohistiocytosis (sHLH) patients (50% vs. 25.3%, P = 0.001). Eight pHLH patients had isolated CNS-HLH at onset, which progressed to systemic HLH within 10-30days to several years. Among them, five patients who underwent hematopoietic stem cell transplantation (HSCT) survived without CNS sequelae, and the three patients who did not undergo HSCT died of disease progression or recurrence. Determination of natural killer (NK) cell cytotoxicity and CD107a levels had low sensitivity and specificity in the diagnosis of pHLH, especially in patients with PRF1 and XIAP mutations. The 3-year overall survival (OS) was significantly lower in pHLH patients than in sHLH patients (74.5% ± 14.7% vs. 89.2% ± 3.53%, P = 0.021) and in patients with CNS involvement than in those without (53.8% ± 26.07% vs. 94.4% ± 10.58%, P = 0.012). There was a significant difference in OS among pHLH patients with different gene variants (P = 0.032); patients with PRF1 variants had poor 3-year OS, and patients with XIAP variants had good 3-year OS (50% ± 28.22% and 100%, respectively). pHLH patients with distinct variants have different prognoses. Isolated CNS-HLH patients are easily misdiagnosed, and HSCT may be beneficial for these patients. Determination of NK cell cytotoxicity and CD107a levels cannot precisely distinguish pHLH from sHLH.

The Role of the IL-33/ST2 Axis in CpG-Induced Macrophage Activation Syndrome.

Macrophage activation syndrome (MAS) is a fatal inflammatory condition, which is often associated with the elevation of multiple proinflammatory cytokines and multiple organ dysfunction. Previous studies have shown that ST2 contributes to T cell overactivation and plays a detrimental role in mouse models of primary hemophagocytic lymphohistiocytosis. The purpose of this study was to investigate the role of the IL-33/ST2 axis in a mouse model of MAS induced by repeated injections of cytosine-phosphate-guanine (CpG). Serum cytokines were determined using the cytometric bead array by flow cytometry. IL-33 and ST2 were detected by immunohistochemistry and real-time quantitative PCR in the liver and spleen of mice. CD3 and F4/80 in the liver were detected by immunohistochemistry. Inflammatory macrophages and effector memory T lymphocytes were detected by flow cytometry. The CpG-induced MAS model was successfully induced after repeated CpG injections, presenting with hypercytokinemia and hepatosplenomegaly. The numbers of IL-33 positive cells in the liver and spleen decreased significantly, while the expression of ST2 in the liver tended to increase in the mice with MAS. IL-33 and St2 knockout mice showed similar levels of hepatosplenomegaly, peripheral blood count, and cytokine storm when compared with wild-type (WT) mice after induction of MAS. There were also no significant differences in liver pathology (including inflammatory cell infiltration of CD3 and F4/80) and levels of splenic inflammatory macrophages and effector memory T cells between the WT and knockout mice. These results suggested that IL-33 decreased in the liver and spleen tissues of MAS mice. Further results suggest that IL-33 and St2 knockout mice have no treatment potential in CpG-induced MAS. Thus, the IL-33/ST2 axis has little effect on the prognosis of CpG-induced MAS.