A pilot study of ruxolitinib as a front-line therapy for 12 children with secondary hemophagocytic lymphohistiocytosis

Differential effects of itacitinib, fedratinib, and ruxolitinib in mouse models of hemophagocytic lymphohistiocytosis

ABSTRACT

Hemophagocytic lymphohistiocytosis (HLH) comprises a severe hyperinflammatory phenotype driven by the overproduction of cytokines, many of which signal via the JAK/STAT pathway. Indeed, the JAK1/2 inhibitor ruxolitinib has demonstrated efficacy in preclinical studies and early-phase clinical trials in HLH. Nevertheless, concerns remain for ruxolitinib-induced cytopenias, which are postulated to result from the blockade of JAK2-dependent hematopoietic growth factors. To explore the therapeutic effects of selective JAK inhibition in mouse models of HLH, we carried out studies incorporating the JAK1 inhibitor itacitinib, JAK2 inhibitor fedratinib, and JAK1/2 inhibitor ruxolitinib. All 3 drugs were well-tolerated and at the doses tested, they suppressed interferon-gamma (IFN-γ)-induced STAT1 phosphorylation in vitro and in vivo. Itacitinib, but not fedratinib, significantly improved survival and clinical scores in CpG-induced secondary HLH. Conversely, in primary HLH, in which perforin-deficient (Prf1-/-) mice are infected with lymphocytic choriomeningitis virus (LCMV), itacitinib, and fedratinib performed suboptimally. Ruxolitinib demonstrated excellent clinical efficacy in both HLH models. RNA-sequencing of splenocytes from LCMV-infected Prf1-/- mice revealed that itacitinib targeted inflammatory and metabolic pathway genes in CD8 T cells, whereas fedratinib targeted genes regulating cell proliferation and metabolism. In monocytes, neither drug conferred major transcriptional impacts. Consistent with its superior clinical effects, ruxolitinib exerted the greatest transcriptional changes in CD8 T cells and monocytes, targeting more genes across several biologic pathways, most notably JAK-dependent proinflammatory signaling. We conclude that JAK1 inhibition is sufficient to curtail CpG-induced disease, but combined inhibition of JAK1 and JAK2 is needed to best control LCMV-induced immunopathology.

Ruxolitinib-based regimen in children with primary hemophagocytic lymphohistiocytosis

Primary hemophagocytic lymphohistiocytosis (pHLH) is a rare immune disorder and hematopoietic stem cell transplan- tation (HSCT) is the only potentially curative treatment. Given the high pre-HSCT mortality of pHLH patients reported in the HLH-2004 study (17%), more regimens to effectively control the disease and form a bridge with HSCT are needed. We conducted a retrospective study of pHLH children treated by ruxolitinib (RUX)-based regimen. Generally, patients received RUX until HSCT or unacceptable toxic side-effect. Methylprednisolone and etoposide were added sequentially when the disease was suboptimally controlled. The primary end point was 1-year overall survival. Twenty-one pHLH patients (12 previously treated and 9 previously untreated) were included with a median follow-up of 1.4 years. At last follow-up, 17 (81.0%) patients were alive with a 1-year overall survival of 90.5% (95% confidence interval: 84.1-96.9). Within the first 8 weeks, all patients had an objective response, of which 19 (90.5%) achieved complete response (CR) and two (9.5%) achieved partial response (PR) as a best response. Seventeen (81.0%) patients received HSCT, of which 13 (76.5%) had CR, three (17.6%) had PR and one (5.9%) had disease reactivation at the time of HSCT. Fifteen (88.2) patients were alive post- HSCT. Notably, eight (38.1%) patients received zero doses of etoposide, suggesting the potential of RUX-based regimen to reduce chemotherapy intensity. Patients tolerated RUX-based regimen well and the most frequently observed adverse events were hematologic adverse events. Overall, RUX-based regimen was effective and safe and could be used as a bridge to HSCT for pHLH children.

JAK Inhibitors in Cytokine Storm Syndromes

Cytokine storm syndromes (CSSs) comprise a group of severe and often fatal hyperinflammatory conditions driven by the overproduction of pro-inflammatory cytokines by activated cells of the immune system. Many of the CSS-associated cytokines mediate their downstream effects by signaling through the Janus kinases (JAKs) and signal transducers and activators of transcription (STATs). In addition, several of these cytokines are produced downstream of JAK/STAT pathway activation. Therefore, targeting JAK/STAT signaling using small molecule JAK inhibitors has become an increasingly appealing therapeutic option to dampen hyperinflammation in patients with CSSs. Application of JAK inhibitors in preclinical CSS models has shown improvements in multiple sequelae of hyperinflammation, and there is growing clinical evidence supporting the efficacy of JAK inhibition in patients with these conditions. Although generally well tolerated, JAK inhibitor use is not without potential for toxicity, especially in settings like CSSs where end-organ dysfunction is common. More prospective clinical trials incorporating JAK inhibitors, alone or in combination with other immunomodulatory therapies, are necessary to determine the optimal dosing, schedule, efficacy, and tolerability of these agents for patients experiencing CSSs.

Frequency of HLA-DR+CD38hi T cells identifies and quantifies T-cell activation in hemophagocytic lymphohistiocytosis, hyperinflammation, and immune regulatory disorders

BACKGROUND

Quantifying T-cell activation is essential for the diagnosis and evaluation of treatment response in various hyperinflammatory and immune regulatory disorders, including hemophagocytic lymphohistiocytosis. Plasma soluble IL-2 receptor (sIL-2R) is a well-established biomarker for evaluating systemic T-cell activation. However, the limited availability of sIL-2R testing could result in delayed diagnosis. Furthermore, high sIL-2R levels may not always reflect T-cell activation.

OBJECTIVES

To address these limitations, this study investigated whether cell surface markers of T-cell activation, HLA-DR, and CD38, as assessed by flow cytometry, could be used to quantify systemic T-cell activation in a variety of inflammatory disease states and examine its correlation with sIL-2R levels.

METHODS

Results for sIL-2R, CXCL9, and ferritin assays were obtained from patient's medical records. Frequency of HLA-DR+CD38high(hi) T-cells was assessed in different T-cell subsets using flow cytometry.

RESULTS

In this study's cohort, activation in total CD8+ T (r = 0.65; P < .0001) and CD4+ (r = 0.42; P < .0001) T-cell subsets significantly correlated with plasma sIL-2R levels. At the disease onset, the frequency of HLA-DR+CD38hi T cells in CD8+ T (r = 0.65, P < .0001) and CD4+ T (r = 0.77; P < .0001) effector memory (TEM) compartments correlated strongly with sIL-2R levels. Evaluation of T-cell activation markers in follow-up samples also revealed a positive correlation for both CD4+ TEM and CD8+ TEM activation with sIL-2R levels; thus, attesting its utility in initial diagnosis and in evaluating treatment response. The frequency of HLA-DR+CD38hi T-cells in the CD8+ TEM compartment also correlated with plasma CXCL9 (r = 0.42; P = .0120) and ferritin levels (r = 0.32; P = .0037).

CONCLUSIONS

This study demonstrates that flow cytometry-based direct T-cell activation assessed by HLA-DR+CD38hi T cells accurately quantifies T-cell activation and strongly correlates with sIL-2R levels across a spectrum of hyperinflammatory and immune dysregulation disorders.

An analysis of sintilimab combined with ruxolitinib as compassionate therapy for 12 adults with EBV-associated hemophagocytic lymphohistiocytosis

Epstein-Barr virus-associated hemophagocytic lymphohistiocytosis (EBV-HLH) is a severe hyperinflammatory illness that affects adults and is caused by an EBV infection. Without allogeneic hematopoietic stem cell transplantation (allo-HSCT), the overall survival of adult patients with EBV-HLH is unsatisfactory, necessitating the development of innovative therapeutic approaches. The clinical records of twelve EBV-HLH patients who received sintilimab therapy combined with ruxolitinib on a compassionate basis at the First Affiliated Hospital of Soochow University were retrospectively examined in this investigation. All the patients responded without fever, but three patients relapsed within a week. Among the nine patients achieving complete response (CR), 55.6% (5/9) maintained CR for >4.5 months, and 33.3% (3/9) relapsed following CR. Neither patients with no response (NR) nor relapsed patients were fit for allo-HSCT, and all died soon after discharge. Six patients had clinical CR with a median follow-up of 5 (4.4-14.7) months. There were no documented severe negative effects. Additional information on this innovative treatment for adult EBV-HLH is provided in our report.

Scope of JAK Inhibitors in Children: Recent Evidence and Way Forward

Over the last decade, there has been an increase in the use of targeted therapy using small molecules such as Janus kinase (JAK) inhibitors. Since the introduction of ruxolitinib, the first non-selective JAK inhibitor approved for use in myelofibrosis, many other JAK inhibitors have been tried in a wide spectrum of immune-mediated disorders. Although various trials have shown the promising efficacy of JAK inhibitors in immune-mediated inflammatory disorders (IMIDs), there is a growing concern over the major cardiovascular events and malignancies associated with the use of these molecules in older adults, particularly those over 65 years of age. In this review, we aim to discuss the immunology of the JAK-STAT pathway, the scope of use of JAK inhibitors, and their safety in paediatric practice. Here, we discuss high-quality evidence favouring the use of JAK inhibitors in children with juvenile idiopathic arthritis (JIA) who are refractory to one or more conventional/biological disease-modifying drugs, demonstrated in two randomised controlled trials (RCTs). In addition to JIA, there are reports favouring the role of JAK inhibitors in other IMIDs such as systemic-onset JIA and interferonopathies. Thus far, the existing literature suggests an acceptable safety profile for JAK inhibitors in children. With the expanding scope of JAK inhibitors in a wide range of IMIDs in children, there is a significant need for long-term close vigilance for any potential harm.

A case of T-cell-Epstein-Barr virus-haemophagocytic lymphohistiocytosis and sustained remission following ruxolitinib therapy

Objectives

Epstein-Barr virus (EBV) is a common cause of secondary haemophagocytic lymphohistiocytosis (HLH). While B cells are reservoirs for EBV, infection within T cells and NK cells in this disease can be difficult to treat.

Methods

A 19-year-old female presented with a 6-week history of coryzal symptoms on a background of Crohn's disease. On examination, she was febrile and tachycardic with mild tonsillar enlargement and splenomegaly. New trilineage cytopenias and elevation in liver enzymes were detected, with acute EBV subsequently confirmed on whole blood PCR. A diagnosis of EBV-associated HLH was supported further with elevated serum ferritin, triglycerides and soluble CD25, low fibrinogen and the presence of haemophagocytosis in the bone marrow.

Results

Corticosteroids, IVIG and rituximab were given, and anakinra was subsequently added due to ongoing fevers. EBV infection was then demonstrated within CD8⁺ T cells on EBER Flow-FISH assay. Ruxolitinib was commenced and her fevers abated on day 5, with improvement in other HLH parameters. She was discharged after a 39-day hospital admission. To date, she has remained in remission of HLH, despite developing COVID-19 infection during the convalescence phase of HLH.

Conclusion

EBV viraemia requires adequate treatment to control EBV-associated HLH as rituximab may be insufficient, and corticosteroid resistance can result in continued EBV infection in CD8⁺ T cells. This entity is known as T-cell-EBV-HLH. Ruxolitinib is a novel treatment strategy in this specific context and has several advantages, including inhibition of corticosteroid resistance to promote apoptosis of EBV-infected T cells.

Secondary haemophagocytic lymphohistiocytosis in a patient with new-onset systemic lupus erythematosus: the challenges of timely diagnosis and successful treatment

Haemophagocytic lymphohistiocytosis (HLH) is an immune-mediated disease driven by abnormal macrophage activation and regulatory cell dysfunction. HLH can be primary due to genetic mutations or secondary due to infection, malignancy or autoimmune conditions. We describe a woman in her early 30s who developed HLH while being treated for newly diagnosed systemic lupus erythematosus (SLE) complicated by lupus nephritis as well as concomitant cytomegalovirus (CMV) reactivation from a dormant infection. The trigger for this secondary form of HLH may have been either aggressive SLE and/or CMV reactivation. Despite prompt treatment with immunosuppressive therapies for SLE consisting of high-dose corticosteroids, mycophenolate mofetil, tacrolimus, etoposide for HLH and ganciclovir for CMV infection, the patient developed multiorgan failure and passed away. We demonstrate the difficulty in identifying a specific cause for secondary HLH when multiple conditions are present (SLE and CMV) and the fact that, despite aggressive treatment for both conditions, the mortality for HLH remains high.

Anakinra versus etoposide-based therapy added to high-dose steroids for the treatment of secondary hemophagocytic lymphohistiocytosis

OBJECTIVE

Hemophagocytic lymphohistiocytosis (HLH) is a rare life-threatening, hyperinflammatory syndrome usually treated with high-dose steroids (HDS), often complemented with adjunct therapies, such as etoposide (HLH-94 protocol). Anakinra has been reported to effectively treat HLH; however, has not been comparatively examined with etoposide-based therapies. We sought to evaluate the effectiveness and durability of these treatment approaches.

METHODS

We performed a retrospective analysis of all adult patients diagnosed with secondary HLH between January 2011 and November 2022 who received anakinra and HDS, the HLH-94 protocol, HDS alone, or supportive care.

RESULTS

Thirty adult patients with secondary HLH were included. Cumulative incidence (CI) of response at 30 days was 83.3%, 60%, and 36.4% for patients treated with anakinra, the HLH-94 protocol, and HDS alone, respectively. CI of relapse at 1 year was 50%, 33.3%, and 0% with the HLH-94 protocol, HDS, and anakinra and HDS, respectively. Overall survival at 1 year was higher with anakinra and HDS compared to the HLH-94 protocol, yet was not statistically significant (77.8% vs. 33.3%; hazard ratio: 0.29; p = .25).

CONCLUSION

Treatment with anakinra and HDS in adults with secondary HLH was associated with higher response rates with longer survival compared with alternative therapies and should be further investigated in this setting.

Cellular and transcriptional impacts of Janus kinase and/or IFN-gamma inhibition in a mouse model of primary hemophagocytic lymphohistiocytosis

Background

Primary hemophagocytic lymphohistiocytosis (pHLH) is an inherited inflammatory syndrome driven by the exuberant activation of interferon-gamma (IFNg)-producing CD8 T cells. Towards this end, ruxolitinib treatment or IFNg neutralization (aIFNg) lessens immunopathology in a model of pHLH in which perforin-deficient mice (Prf1-/-) are infected with Lymphocytic Choriomeningitis virus (LCMV). However, neither agent completely eradicates inflammation. Two studies combining ruxolitinib with aIFNg report conflicting results with one demonstrating improvement and the other worsening of disease manifestations. As these studies used differing doses of drugs and varying LCMV strains, it remained unclear whether combination therapy is safe and effective.

Methods

We previously showed that a ruxolitinib dose of 90 mg/kg lessens inflammation in Prf1-/- mice infected with LCMV-Armstrong. To determine whether this dose controls inflammation induced by a different LCMV strain, we administered ruxolitinib at 90mg/kg to Prf1-/- mice infected with LCMV-WE. To elucidate the impacts of single agent versus combination therapy, Prf1-/- animals were infected with LCMV, treated or not with ruxolitinib, aIFNg or both agents, and analyzed for disease features and the transcriptional impacts of therapy within purified CD8 T cells.

Results

Ruxolitinib is well-tolerated and controls disease regardless of the viral strain used. aIFNg, administered alone or with ruxolitinib, is most effective at reversing anemia and reducing serum IFNg levels. In contrast, ruxolitinib appears better than aIFNg, and equally or more effective than combination therapy, at lessening immune cell expansion and cytokine production. Each treatment targets distinct gene expression pathways with aIFNg downregulating IFNg, IFNa, and IL-6-STAT3 pathways, and ruxolitinib downregulating IL-6-STAT3, glycolysis, and reactive oxygen species pathways. Unexpectedly, combination therapy is associated with upregulation of genes driving cell survival and proliferation.

Conclusions

Ruxolitinib is tolerated and curtails inflammation regardless of the inciting viral strain and whether it is given alone or in combination with aIFNg. When administered at the doses used in this study, the combination of ruxolitinb and aIFNg appears no better than treatment with either drug alone in lessening inflammation. Further studies are warranted to elucidate the optimal doses, schedules, and combinations of these agents for the treatment of patients with pHLH.

Cytokine nanosponges suppressing overactive macrophages and dampening systematic cytokine storm for the treatment of hemophagocytic lymphohistiocytosis

Hemophagocytic lymphohistiocytosis (HLH) is a highly fatal condition with the positive feedback loop between continued immune cell activation and cytokine storm as the core mechanism to mediate multiple organ dysfunction. Inspired by macrophage membranes harbor the receptors with special high affinity for proinflammation cytokines, lipopolysaccharide (LPS)-stimulated macrophage membrane-coated nanoparticles (LMNP) were developed to show strong sponge ability to both IFN-γ and IL-6 and suppressed overactivation of macrophages by inhibiting JAK/STAT signaling pathway both in vitro and in vivo. Besides, LMNP also efficiently alleviated HLH-related symptoms including cytopenia, hepatosplenomegaly and hepatorenal dysfunction and save the life of mouse models. Furthermore, its sponge effect also worked well for five human HLH samples in vitro. Altogether, it's firstly demonstrated that biocompatible LMNP could dampen HLH with high potential for clinical transformation, which also provided alternative insights for the treatment of other cytokine storm-mediated pathologic conditions such as COVID-19 infection and cytokine releasing syndrome during CAR-T therapy.

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LMNP functioned better as a multiple-cytokine sponging tool when compared with conventional macrophage coated nanoparticles.

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LMNP sponged inflammation cytokines and suppressed macrophage overactivation by inhibiting JAK/STAT signaling pathway.

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LMNP calmed down systematic cytokine storm and dampened HLH in HLH mice models.

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LMNP also worked well in sponging cytokines in human HLH samples which indicated high potential of clinical transformation.

Population pharmacokinetics of ruxolitinib in children with hemophagocytic lymphohistiocytosis: focus on the drug-drug interactions

PURPOSE

The optimal dose regimen of ruxolitinib (RUX) in children with hemophagocytic lymphohistiocytosis (HLH) remains to be determined. The aim was to develop and verify a population pharmacokinetic (PPK) model, and then provide references for the optimization of dose regimen of RUX in children with HLH.

METHODS

A total of 189 RUX concentrations from 32 children were included. The PPK model was established using the nonlinear mixed-effects model approach. Predictive performance and stability of the final PPK model were evaluated. The exposure of RUX in different clinical scenarios was simulated through Monte Carlo simulations.

RESULTS

A one-compartment model with first-order absorption and linear elimination was identified to describe the disposition of RUX. The absorption rate constant (K_a) in the final PPK model was 1.05 h^-1, and the apparent clearance (CL/F) and volume of distribution (V/F) were 9.80 L/h and 30.6 L, respectively. Coadministration with triazoles (TZS) and azithromycin (AZM) resulted in approximately 31.0% and 32.4% reductions in the CL/F of RUX, respectively. Multiple evaluation procedures showed satisfactory predictive performance and stability of the final model. Monte Carlo simulations showed that the exposure of RUX was significantly affected by the coadministration with TZS and/or AZM under different clinical scenarios.

CONCLUSION

For the first time, a PPK model of RUX in children with HLH was developed and evaluated. The coadministration with TZS and/or AZM were found to reduce the clearance of RUX in children. These findings could provide new insights for the precise treatment of RUX in children with HLH.

Complications of complications: diagnosis and treatment of recurrent macrophage activation syndrome in a patient with well-controlled systemic juvenile idiopathic arthritis

Macrophage activation syndrome (MAS) is a subtype of haemophagocytic lymphohistiocytosis (HLH), and a well-described complication of systemic juvenile idiopathic arthritis (SJIA), triggered by disease onset or flare, infection, or some medications. Here, we report a 20-year-old man with previously well-controlled SJIA, who developed first time MAS after acute Epstein-Barr virus (EBV) infection, with MAS recurrence due to a drug reaction, '3-week sulfasalazine syndrome', secondary to prophylactic trimethoprim/sulfamethoxazole. Both episodes of MAS were minimally responsive to pulse corticosteroids. Initial EBV-driven MAS was treated with multiple doses of emapalumab prior to resolution, while MAS secondary to sulfasalazine-induced 3-week syndrome required the initiation of ruxolitinib. This case exhibits two rare but life-threatening causes of MAS/secondary HLH in a single patient and the difficulties in their diagnosis and management.

Hemophagocytic lymphohistocytosis in trisomy 21: successful treatment with interferon inhibition

BACKGROUND

Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening condition of immune dysregulation primarily driven by the cytokine interferon gamma. It can be either a genetic or acquired disorder associated with infection, malignancy, and rheumatologic disorders. Trisomy 21 can express a wide range of phenotypes which include immune dysregulation and shares inherent pathophysiology with a group of disorders termed interferonopathies. Knowledge of this overlap in seemingly unrelated conditions could provide a basis for future research, and most importantly, alternative therapeutic interventions in acute life threatening clinical scenarios. Herein, we describe two patients with trisomy 21 presenting with HLH that was refractory to conventional treatment. Both patients were successfully managed with novel interventions targeting the interferon pathway.

CASE PRESENTATION

We describe a 17-month-old male and 15-month-old female with trisomy 21 presenting with a myriad of signs and symptoms including fever, rash, cytopenias, and hyperferritinemia, both ultimately diagnosed with HLH. Each had relapsing, refractory HLH over time requiring several admissions to the hospital receiving conventional high dose corticosteroids and interleukin-1 inhibition therapy. Successful steroid-free remission was achieved after targeting interferon inhibition with emapalumab induction followed by long-term maintenance on baricitinib.

CONCLUSION

To our knowledge, these are the first reported cases of relapsed, refractory HLH in patients with trisomy 21 successfully treated with emapalumab and transitioned to a steroid-sparing regimen with oral baricitinib for maintenance therapy. Trisomy 21 autoimmunity and HLH are both thought to be driven by interferon gamma. Targeting therapy toward interferon signaling in both HLH and autoimmunity in trisomy 21 may have potential therapeutic benefits. Further investigation is needed to determine if trisomy 21 may predispose to the development of HLH given this common pathway.

A Review of Current and Emerging Therapeutic Options for Hemophagocytic Lymphohistiocytosis

Objective:

To provide an overview of clinical sequelae and emerging treatment options for hemophagocytic lymphohistiocytosis (HLH).

Data Sources:

A literature search was conducted using the search terms “hemophagocytic lymphohistiocytosis,” “hemophagocytic syndrome,” “macrophage activation syndrome,” and “treatment” on Ovid and PubMed from January 1, 2017, through September 28, 2022.

Study Selection and Data Extraction:

Relevant clinical trials, meta-analyses, case reports, review articles, package inserts, and guidelines to identify current and emerging therapeutic options for the management of HLH.

Data Synthesis:

Genetic disorders and secondary causes may trigger HLH in both children and adults. Notable improvements in the diagnosis of HLH were seen with implementation of the HLH-2004 standard diagnostic criteria; however, timely and accurate identification of HLH remain significant barriers to optimal management. Multiagent immunochemotherapy are the backbone of aggressive therapy for acutely ill patients with HLH.

Relevance to Patient Care and Clinical Practice:

The global coronavirus 2019 (COVID-19) pandemic and emerging immune effector cell therapies have served to highlight the concerns with immune dysregulation and subsequent HLH precipitation. Without prompt identification and treatment, HLH can be fatal. Historically, the clinician’s armamentarium for managing HLH was sparse, with etoposide-based protocols serving as the standard of care. Relapsed or refractory disease portends a poor prognosis and requires additional treatment options. Second- or subsequent-line options now include hematopoietic stem cell transplantation, emapalumab, alemtuzumab, anakinra, ruxolitinib, and tocilizumab.

Conclusions:

Improvements in diagnostic methods and novel immunosuppressive treatment strategies, including noncytotoxic immunochemotherapy, have transformed the therapeutic landscape. Unfortunately, many unanswered questions remain. Additional studies are required to optimize dosing, schedules, treatment sequences, and indications for novel treatment options.

Adoptive T cell therapy cures mice from active hemophagocytic lymphohistiocytosis (HLH)

Primary hemophagocytic lymphohistiocytosis (HLH) is a hyperinflammatory syndrome caused by impaired lymphocyte cytotoxicity. First-line therapeutic regimens directed against activated immune cells or secreted cytokines show limited efficacy since they do not target the underlying immunological problem: defective lymphocyte cytotoxicity causing prolonged immune stimulation. A potential rescue strategy would be the adoptive transfer of ex vivo gene-corrected autologous T cells. However, transfusion of cytotoxicity-competent T cells under conditions of hyperinflammation may cause more harm than benefit. As a proof-of-concept for adoptive T cell therapy (ATCT) under hyperinflammatory conditions, we transferred syngeneic, cytotoxicity-competent T cells into mice with virally triggered active primary HLH. ATCT with functional syngeneic trigger-specific T cells cured Jinx mice from active HLH without life-threatening side effects and protected Perforin-deficient mice from lethal HLH progression by reconstituting cytotoxicity. Cured mice were protected long-term from HLH relapses. A threshold frequency of transferred T cells with functional differentiation was identified as a predictive biomarker for long-term survival. This study is the first proof-of-concept for ATCT in active HLH.

Adult-Onset Still's Disease-A Complex Disease, a Challenging Treatment

Adult-onset Still's disease (AOSD) is a systemic inflammatory disorder with an unknown cause characterized by high-spiking fever, lymphadenopathy, hepatosplenomegaly, hyperferritinemia, and leukocytosis. The clinical course can be divided into three significant patterns, each with a different prognosis: Self-limited or monophasic, intermittent or polycyclic systemic, and chronic articular. Two criteria sets have been validated. The Yamaguchi criteria are the most generally used, although the Fautrel criteria offer the benefit of adding ferritin and glycosylated ferritin values. AOSD's pathogenesis is not yet completely understood. Chemokines and pro-inflammatory cytokines, including interferon (IFN)-γ, tumor necrosis factor α (TNFα), interleukin (IL)-1, IL-6, IL-8, and IL-18, play a crucial role in the progression of illness, resulting in the development of innovative targeted therapeutics. There are no treatment guidelines for AOSD due to its rarity, absence of controlled research, and lack of a standard definition for remission and therapy objectives. Non-steroidal anti-inflammatory drugs (NSAIDs), corticosteroids (CS), and conventional synthetic disease-modifying antirheumatic drugs (csDMARDs) are used in AOSD treatment. Biological therapy, including IL-1, IL-6, IL-18, and IL-17 inhibitors, as well as TNFα or Janus-kinases (JAKs) inhibitors, is administered to patients who do not react to CS and csDMARDs or achieve an inadequate response.

Case report: Ruxolitinib as first-line therapy for secondary hemophagocytic lymphohistiocytosis in patients with AIDS

Background

Hemophagocytic lymphohistiocytosis (HLH) is a fatal immunological syndrome resulting from excessive production of inflammatory cytokines. The conventional therapies for HLH, which are based on cytotoxic agents, are not always efficacious and safe, especially in patients with severe immunodeficiency. Ruxolitinib, a strong inhibitor of Janus kinase (JAK) 1/2, has already been evaluated as salvage and first-line therapy for HLH. Despite its promising efficacy and tolerability in the treatment of secondary HLH, the efficacy and safety of ruxolitinib in HLH patients with HIV infection remain to be investigated.

Case presentation

Two men (ages: 45 and 58 years) both presented at our hospital with a high fever. They were found to be HIV-positive with severe immunodeficiency and opportunistic infections. Their laboratory tests showed severe pancytopenia, hypofibrinogenemia, hypertriglyceridemia, and increased levels of inflammatory factors and ferritin. Hemophagocytosis was found in the bone marrow, and abdominal computed tomography or ultrasonography showed splenomegaly. Both patients were diagnosed with infection-induced HLH due to severe immunodeficiency. Given they were both highly immunocompromised, we chose ruxolitinib as a first-line treatment alternative to cytotoxic chemotherapy. Rapid remission of clinical symptoms and normalization of laboratory parameters were achieved after ruxolitinib therapy. Neither patient had any associated adverse drug reactions or other laboratory abnormalities. Both patients were eventually discharged and ruxolitinib was discontinued as their disease alleviated, and they did not show signs of relapse during the 3- and 5-month of follow-up examinations.

Conclusion

We described two cases of AIDS-related secondary HLH treated with ruxolitinib. Our cases highlight the feasibility of using ruxolitinib as a first-line therapy in patients with HIV infection and secondary HLH. Nevertheless, the safety and efficacy of this novel treatment need to be evaluated in large clinical trials in the future.

Development and application of an LC-MS/MS method for pharmacokinetic study of ruxolitinib in children with hemophagocytic lymphohistiocytosis

Ruxolitinib (RUX), a small molecule inhibitor of JAK1/JAK2, has been identified as the possible novel targeted agent for the treatment of hemophagocytic lymphohistiocytosis (HLH). However, due to the lack of randomized clinical trials (RCTs), it is extremely difficult to determine the effective therapeutic dose for RUX in HLH patients, especially in pediatric patients. At the same time, the clinical response of pediatric patients to RUX varies greatly among individuals according to several case reports. Therefore, it is imperative to investigate the pharmacokinetic and pharmacodynamic characteristics of RUX in HLH children, and this must be based on a satisfactory method to determine the concentration of RUX. Owing to several limits of published analytical methods, herein, we describe a novel liquid chromatography tandem mass spectrometry (LC-MS/MS) method for monitoring RUX in children's plasma samples. The protein precipitation method using methanol was used for sample cleanup. The analytes were separated by gradient elution in which 2.0 mM ammonium acetate in distilled water and acetonitrile were used as mobile phases. In the positive electrospray ionization (ESI+) mode, the m/z 307.1 → 186.0 and 316.1 → 185.9 ion pair transitions of RUX and RUX-d9 were used for the qualitative and quantitative analysis, respectively. The calibration curves of RUX were linear in the concentration range from 0.5 to 400 ng mL^-1. The intra- and inter-batch precision, accuracy, recovery, dilution completeness, and stability of this method were all within acceptable standards, and no matrix effects or residues were found. This method was successfully applied to the clinical pharmacokinetic study of RUX in 32 children with HLH. The pharmacokinetic parameters of HLH children after a single dose of RUX and the steady state plasma concentration after multiple administrations were proposed through this method. Most importantly, it was found that the age and serum creatinine (SCr) of children with HLH had a significant and complex impact on the in vivo process of RUX after the single as well as multiple administrations of RUX.

Plasma Exosomal Proteomic Pattern of Epstein-Barr Virus-Associated Hemophagocytic Lymphohistiocytosis

Epstein-Barr virus (EBV)-associated hemophagocytic lymphohistiocytosis (EBV-HLH) is a life-threatening syndrome, which is caused by EBV infection that is usually refractory to treatment and shows relapse. The development of new biomarkers for the early diagnosis and clinical treatment of EBV-HLH is urgently needed. Exosomes have been shown to mediate various biological processes and are ideal non-invasive biomarkers. Here, we present the differential plasma exosomal proteome of a patient with EBV-HLH before vs. during treatment and with that of his healthy twin brother. A tandem mass tag-labeled LC-MS technique was employed for proteomic detection. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses indicated that differential proteomic profiles were related to virus infection, coagulopathy, nervous system dysfunction, imbalance of immune response, and abnormal liver function. The candidate biomarkers were first identified in the patient’s plasma exosomes at different treatment and follow-up time points. Then, 14 additional EBV-HLH exosome samples were used to verify six differentially expressed proteins. The upregulation of C-reactive protein, moesin, galectin three-binding protein, and heat shock cognate 71 kDa protein and the downregulation of plasminogen and fibronectin 1 could serve as potential biomarkers of EBV-HLH. This plasma exosomal proteomic analysis provides new insights into the diagnostic and therapeutic biomarkers of EBV-HLH.

Progress in Biological Therapies for Adult-Onset Still’s Disease

Adult-onset Still’s disease (AOSD) is a rare multifactorial autoinflammatory disorder of unknown etiology, characterized by an excessive release of cytokines triggered by dysregulated inflammation and articular and systemic manifestations. The clinical spectrum of AOSD ranges from self-limiting forms with mild symptoms to life-threatening cases and presents clinical and biological similarities with the juvenile form (sJIA). Nowadays, the advances in biologic agents no longer limit the treatment to NSAIDs, glucocorticoids, or conventional synthetic DMARDs. The blockade of IL-1 and IL-6 is effective in the treatment of systemic and articular inflammation of AOSD patients; however, novel compounds with different properties and targets are now available and others are being studied. In this review, starting from the pathogenesis of AOSD, we summarized the current and emerging biological therapies, possible effective agents for achieving AOSD control and remission.

A study of Ruxolitinib-response-based stratified treatment for pediatric hemophagocytic lymphohistiocytosis

Hemophagocytic lymphohistiocytosis (HLH) is a lethal disorder characterized by hyperinflammation. Recently, ruxolitinib, targeting key cytokines in HLH, has shown promise for HLH treatment. However, there is a lack of robust clinical trials evaluating its efficacy, especially its utility as a front-line therapy. In this study (www.chictr.org.cn, ChiCTR2000031702), we designed ruxolitinib as a first-line agent for pediatric HLH and stratified the treatment based on its early response. Fifty-two newly diagnosed patients were enrolled. The overall response rate (ORR) of ruxolitinib monotherapy (day-28) was 69.2% (36/52), with 42.3% (22/52) achieving sustained complete remission (CR). All responders achieved their first response to ruxolitinib within 3-days. The response to ruxolitinib was significantly associated with the underlying etiology at enrollment (p=0.009). EBV-HLH patients were most sensitive to ruxolitinib, with an ORR of 87.5% (58.3% in CR). After ruxolitinib therapy, 57.7% (30/52) of the patients entered intensive therapy with additional chemotherapy. Among them, 53.3% (16/30) patients achieved CR, and 46.7% (14/30) patients dominated by chronic active Epstein Barr virus infection-associated HLH (CAEBV-HLH) developed refractory HLH by week-8. The median interval to additional treatment since first ruxolitinib administration was 6-days (range, 3-25). Altogether, 73.1% (38/52) of the enrolled patients achieved CR after treatment overall. The 12-month overall survival for all patients was 86.4% (95%CI, 77.1%-95.7%). Ruxolitinib had low toxicity and was well tolerated compared to intensive chemotherapy. Our study provides clinical evidence for ruxolitinib as a front-line agent for pediatric HLH. The efficacy was particularly exemplified with stratified regiment based on the early differential response to ruxolitinib. This study was registered in the Chinese Clinical Trials Registry Platform (http://www.chictr.org.cn/) as ChiCTR2000031702.

Malignancy-associated haemophagocytic lymphohistiocytosis

Haemophagocytic lymphohistiocytosis (HLH) is an inflammatory syndrome that can occur with cancer (malignancy-associated HLH) or with immune-activating therapies for cancer. Patients with lymphoma appear to be at particularly high risk for malignancy-associated HLH. The familial form of HLH is characterised by uncontrolled activation of macrophages and cytotoxic T cells, which can be identified by genetics or specific immune markers. However, the pathophysiology of malignancy-associated HLH is not well understood, and distinguishing pathological immune activation from the laboratory and clinical abnormalities seen in cancer and cancer treatment is challenging. Emerging diagnostic tools, such as serum cytokine or chemokine concentrations, flow cytometry, and other functional measures, are discussed. Mortality remains high with current approaches. Targeted therapy, including blockade of specific cytokines such as IL-1, IL-6, and IFNγ, and inhibition of the JAK-STAT pathways might improve outcomes for some patients. Finally, we discuss a framework for thinking of malignancy-associated HLH within a larger umbrella concept of cytokine storm syndrome.

Die hämophagozytische Lymphohistiozytose bei kritisch kranken Patienten

Bei der hämophagozytischen Lymphohistiozytose (HLH) handelt es sich um ein Hyperinflammationssyndrom bedingt durch aberrant aktivierte Makrophagen und T‑Zellen. Beim Erwachsenen ist in erster Linie die erworbene Form anzutreffen. Häufige Auslöser sind Infektionen, Malignome und Autoimmunerkrankungen. Zuletzt wurden zudem zunehmend Fälle berichtet, in denen das Auftreten im Zusammenhang mit stattgehabten Immuntherapien zu sehen war. Auf der Intensivstation ist die HLH aufgrund des ähnlichen klinischen Erscheinungsbilds oft schwer von der Sepsis abzugrenzen. Zum Teil liegen beide zeitgleich vor. Die frühzeitige Diagnosestellung und Einleitung einer adäquaten immunsuppressiven Therapie ist für den weiteren Verlauf und die Prognose der HLH essenziell. Deshalb muss bei kritisch kranken Patienten mit persistierendem Fieber und entsprechenden Symptomen (z. B. Splenomegalie, neurologische Auffälligkeiten) oder Laborveränderungen (z. B. erhöhter Ferritinwert, Zytopenie von 2 oder 3 Zellreihen, erhöhte Transaminasen) das Vorliegen einer HLH in Betracht gezogen werden. Die Diagnose wird mithilfe der HLH-2004-Kriterien gestellt. Mit dem HScore kann die Wahrscheinlichkeit des Vorliegens einer HLH berechnet werden. Hochdosierte Kortikosteroide stellen den Grundpfeiler der HLH-Therapie dar. Je nach Auslöser werden Etoposid, Immunglobuline, Anakinra oder weitere Medikamente ergänzt. Der Verlauf hängt neben einem frühzeitigen Behandlungsbeginn vom Auslöser sowie dem Ansprechen auf die Therapie ab. Insgesamt ist die Prognose der HLH trotz maximaler intensivmedizinischer Behandlung ungünstig und sie ist mit einer hohen Letalität assoziiert.

Interfering with interferons: targeting the JAK-STAT pathway in complications of systemic juvenile idiopathic arthritis (SJIA)

Systemic JIA (SJIA) is distinguished from other forms of JIA by the prevalence of the severe, life-threatening complications macrophage activation syndrome (SJIA-MAS) and lung disease (SJIA-LD). Alternative therapeutics are urgently needed, as disease pathogenesis diverges from what is observed in SJIA, and currently available biologics are insufficient. SJIA-MAS, defined by a cytokine storm and dysregulated proliferation of T-lymphocytes, and SJIA-LD which presents with lymphocytic interstitial inflammation and pulmonary alveolar proteinosis, are both thought to be driven by IFNs, in particular the type II IFN-γ. Involvement of IFNs and a possible crosstalk of type I IFNs with existing biologics indicate a distinct role for the JAK-STAT signalling pathway in the pathogenesis of SJIA-MAS and SJIA-LD. Here, we review this role of JAK-STATs and IFNs in SJIA complications and discuss how new insights of ongoing research are shaping future therapeutic advances in the form of JAK inhibitors and antibodies targeting IFNs.

Ruxolitinib for chronic steroid-refractory graft versus host disease: a single center experience

BACKGROUND

Chronic Graft versus Host Disease (GvHD) is a serious complication of allogeneic hematopoietic stem cell transplant that severely impacts quality of life and long-term survival. About 50-to-60 % of patients treated with steroids require a further line of therapy due to lack of sustained response. Ruxolitinib, a JAK1/2 inhibitor, has recently been approved for the treatment of acute GvHD.

METHODS

We aimed to retrospectively evaluate ruxolitinib efficacy and safety in a cohort of patients diagnosed with moderate (25 %) or severe (75 %) steroid-refractory or steroid-dependent chronic GvHD. Response evaluation was performed at three and six months.

RESULTS

Thirty-six patients received ruxolitinib after a median of three previous lines (range, r 1-11) for a median of 8.6 months (r 1-51.6). Cutaneous GvHD was the most frequent presentation. We observed an overall response of 59 % (CR 9%, PR 50 %) at three months and 62 % (CR 15 %, PR 46 %) at six months. Two patients had hematologic disease recurrence and were censored at relapse; no other permanent discontinuation due to adverse events were documented. Cutaneous, oral, genital and ocular GvHD significantly improved after treatment. 2-year overall survival and 2-year transplant related mortality were 74 % and 19 % respectively. Ruxolitinib was associated with a significant reduction of steroid dose.

CONCLUSION

Ruxolitinib was confirmed to be a safe and effective option as salvage treatment also for advanced stages of chronic GvHD. Longer follow up is needed to evaluate durability of response. Prospective analyses on larger cohorts are ongoing.

Ruxolitinib is an alternative to etoposide for patient with hemophagocytic lymphohistiocytosis complicated by acute renal injury: A case report

INTRODUCTION

Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening syndrome characterized by excessive production of inflammatory cytokines and multiple organs injury. Ruxolitinib, an oral selective JAK1/2 inhibitor, has recently shown efficacy and safety in the treatment of secondary HLH, which may be an alternative to intensive chemotherapy.

CASE REPORT

We report a case of a 2-year-old boy who presented to our institution with recurrent fever and acute renal failure. We made the diagnosis of Epstein-Barr virus related HLH based on the HLH-2004 protocol, and gave the treatment of ruxolitinib instead of etoposide.

MANAGEMENT AND OUTCOME

The patient received dexamethasone and continuous renal replacement therapy due to renal failure, but he still had fever and anuria. Given that the use of etoposide may deteriorate renal function, ruxolitinib was administered instead of etoposide. After 5 days of ruxolitinib treatment, the patient's fever was resolved and renal function also gradually recovered 14 days later.

DISCUSSION

Currently, dexamethasone, etoposide and cyclosporine A are the main drugs in HLH treatment. However, cytotoxic chemotherapy can temporally deteriorate organ damage and induce serious myelosuppression, which makes clinicians hesitate to implement these regimens. Ruxolitinib has shown efficacy in treating HLH without much toxicity in clinical trials. Thus, we suggest that ruxolitinib constitutes a treatment option for secondary HLH complicated by severe renal damage which may reduce toxic effects compared with intense chemotherapy.

The role of interferon-gamma and its signaling pathway in pediatric hematological disorders

Interferon-gamma (IFN-γ) plays a key role in the pathophysiology of hemophagocytic lymphohistiocytosis (HLH), and available evidence also points to a role in other conditions, including aplastic anemia (AA) and graft failure following allogeneic hematopoietic stem cell transplantation. Recently, the therapeutic potential of IFN-γ inhibition has been documented; emapalumab, an anti-IFN-γ monoclonal antibody, has been approved in the United States for treatment of primary HLH that is refractory, recurrent or progressive, or in patients with intolerance to conventional therapy. Moreover, ruxolitinib, an inhibitor of JAK/STAT intracellular signaling, is currently being investigated for treating HLH. In AA, IFN-γ inhibits hematopoiesis by disrupting the interaction between thrombopoietin and its receptor, c-MPL. Eltrombopag, a small-molecule agonist of c-MPL, acts at a different binding site to IFN-γ and is thus able to circumvent its inhibitory effects. Ongoing trials will elucidate the role of IFN-γ neutralization in secondary HLH and future studies could explore this strategy in controlling hyperinflammation due to CAR T cells.

Ruxolitinib in conjunction with the HLH-94 protocol for Epstein-Barr virus-related hemophagocytic lymphohistiocytosis in the intensive care unit: A case report

RATIONALE

The HLH-94 protocol is a standard induction treatment for hemophagocytic lymphohistiocytosis. However, about 30% of patients may not respond. Ruxolitinib has been clinically proven to be an effective treatment for hemophagocytic lymphohistiocytosis (HLH).

PATIENT CONCERNS

A previously healthy 14-year-old girl presented to the local hospital with a 4-day history of persistent fever and sore throat.

DIAGNOSIS

Clinical and laboratory tests revealed fever >38.5°C, hepatosplenomegaly, pancytopenia, hypertriglyceridemia, hypofibrinogenemia, hyperferritinemia, and an elevated interleukin-2 receptor level.

INTERVENTION

This patient was treated with ruxolitinib and the HLH-94 protocol.

OUTCOMES

The patient's clinical and some laboratory indices improved. Unfortunately, vital signs such as respiratory function and consciousness did not improve.

LESSONS

This case report highlights the effect of using ruxolitinib in conjunction with the HLH-94 protocol. However, safety evaluation of this regimen was not performed because critically ill patient died too fast.

The Pathogenic Role of Interferons in the Hyperinflammatory Response on Adult-Onset Still's Disease and Macrophage Activation Syndrome: Paving the Way towards New Therapeutic Targets

Adult-onset Still's disease (AOSD) is a systemic inflammatory disorder of unknown aetiology affecting young adults, which is burdened by life-threatening complications, mostly macrophage activation syndrome (MAS). Interferons (IFNs) are signalling molecules that mediate a variety of biological functions from defence against viral infections, to antitumor and immunomodulatory effects. These molecules have been classified into three major types: IFN I, IFN II, IFN III, presenting specific characteristics and functions. In this work, we reviewed the role of IFNs on AOSD and MAS, focusing on their pathogenic role in promoting the hyperinflammatory response and as new possible therapeutic targets. In fact, both preclinical and clinical observations suggested that these molecules could promote the hyperinflammatory response in MAS during AOSD. Furthermore, the positive results of inhibiting IFN-γ in primary hemophagocytic lymphohistiocytosis may provide a solid rationale to arrange further clinical studies, paving the way for reducing the high mortality rate in MAS during AOSD.

Use of the JAK Inhibitor Ruxolitinib in the Treatment of Hemophagocytic Lymphohistiocytosis

Hemophagocytic lymphohistiocytosis (HLH) is a rare hyperinflammatory syndrome driven by overactive T cells and macrophages that abundantly secrete numerous pro-inflammatory cytokines, including interferon (IFN)-gamma, interleukin (IL)-1-beta, IL-2, IL-6, IL-10, IL-18, and tumor necrosis factor (TNF). The release of these and other cytokines underlies many of the clinical and pathologic manifestations of HLH, which if left untreated, can lead to multi-organ failure and death. The advent of etoposide-based regimens, such as the Histiocyte Society HLH-94 and HLH-2004 protocols, has substantially decreased the mortality associated with HLH. Nevertheless, the 5-year survival remains low at ~60%. To improve upon these results, studies have focused on the use of novel cytokine-directed therapies to dampen inflammation in HLH. Among the agents being tested is ruxolitinib, a potent inhibitor of the Janus Kinase (JAK) and Signal Transducer and Activation of Transcription (STAT) pathway, which functions downstream of many HLH-associated cytokines. Here, we review the basic biology of HLH, including the role of cytokines in disease pathogenesis, and discuss the use of ruxolitinib in the treatment of HLH.

[Hemophagocytic lymphohistiocytosis in critically ill patients]

Bei der hämophagozytischen Lymphohistiozytose (HLH) handelt es sich um ein Hyperinflammationssyndrom bedingt durch aberrant aktivierte Makrophagen und T‑Zellen. Beim Erwachsenen ist in erster Linie die erworbene Form anzutreffen. Häufige Auslöser sind Infektionen, Malignome und Autoimmunerkrankungen. Zuletzt wurden zudem zunehmend Fälle berichtet, in denen das Auftreten im Zusammenhang mit stattgehabten Immuntherapien zu sehen war. Auf der Intensivstation ist die HLH aufgrund des ähnlichen klinischen Erscheinungsbilds oft schwer von der Sepsis abzugrenzen. Zum Teil liegen beide zeitgleich vor. Die frühzeitige Diagnosestellung und Einleitung einer adäquaten immunsuppressiven Therapie ist für den weiteren Verlauf und die Prognose der HLH essenziell. Deshalb muss bei kritisch kranken Patienten mit persistierendem Fieber und entsprechenden Symptomen (z. B. Splenomegalie, neurologische Auffälligkeiten) oder Laborveränderungen (z. B. erhöhter Ferritinwert, Zytopenie von 2 oder 3 Zellreihen, erhöhte Transaminasen) das Vorliegen einer HLH in Betracht gezogen werden. Die Diagnose wird mithilfe der HLH-2004-Kriterien gestellt. Mit dem HScore kann die Wahrscheinlichkeit des Vorliegens einer HLH berechnet werden. Hochdosierte Kortikosteroide stellen den Grundpfeiler der HLH-Therapie dar. Je nach Auslöser werden Etoposid, Immunglobuline, Anakinra oder weitere Medikamente ergänzt. Der Verlauf hängt neben einem frühzeitigen Behandlungsbeginn vom Auslöser sowie dem Ansprechen auf die Therapie ab. Insgesamt ist die Prognose der HLH trotz maximaler intensivmedizinischer Behandlung ungünstig und sie ist mit einer hohen Letalität assoziiert.

Working and safety profiles of JAK/STAT signaling inhibitors. Are these small molecules also smart?

The Janus kinase (JAK)/signal transducers and activators of transcription (STAT) pathway is an important intracellular route through which many different extracellular soluble molecules, by reaching membrane receptors, can signal the nucleus. The spectrum of soluble molecules that use the JAK/STAT pathway through their corresponding receptors is quite large (almost 50 different molecules), and includes some cytokines involved in the pathogenesis of many immune-mediated diseases. Such diseases, when left untreated, present an evident hyperactivation of JAK/STAT signaling. Therefore, given the pathogenetic role of JAK/STAT, drugs known as JAK inhibitors (JAKi), that target one or more JAKs, have been developed to counteract JAK/STAT signal hyperactivation. As some hematological malignancies present an intrinsic JAK/STAT hyperactivation due to a JAK mutation, some JAKi have also been successfully used in this context. Regulatory agencies for drug administration in different countries have already approved a few JAKi in the setting of either immune-mediated diseases or hematological malignancies. Aim of this review is to describe the physiology of intracellular JAK/STAT pathway signaling and the pathological conditions associated to its dysregulation. Then, the rationale for targeting JAK in rheumatic autoimmune diseases is discussed, along with clinical data from registration studies showing the efficacy of these drugs. Finally, the excellent safety profile of JAKi is discussed in the context of the apparent poor specificity of JAK/STAT pathway signal.

Understanding of cytokines and targeted therapy in macrophage activation syndrome

Macrophage activation syndrome (MAS) is a potentially life-threatening complication of systemic autoinflammatory/autoimmune diseases, generally systemic juvenile idiopathic arthritis and adult-onset Still's disease. It is characterized by an excessive proliferation of macrophages and T lymphocytes. Recent research revealed that cytokine storm with elevated pro-inflammatory cytokines, including IFN-γ, IL-18, and IL-6, may be central to the pathogenesis of MAS. Though the mainstream of MAS treatment remains corticosteroids and cyclosporine, targeted therapies with anti-cytokine biologics are reported to be promising for controlling systemic inflammation in MAS.

Novel Therapeutic Approaches to Familial HLH (Emapalumab in FHL)

Primary Hemophagocytic lymphohistiocytosis (pHLH) is a rare, life-threatening, hyperinflammatory disorder, characterized by uncontrolled activation of the immune system. Mutations affecting several genes coding for proteins involved in the cytotoxicity machinery of both natural killer (NK) and T cells have been found to be responsible for the development of pHLH. So far, front-line treatment, established on the results of large international trials, is based on the use of glucocorticoids, etoposide ± cyclosporine, followed by allogeneic hematopoietic stem cell transplantation (HSCT), the sole curative treatment for the genetic forms of the disease. However, despite major efforts to improve the outcome of pHLH, many patients still experience unfavorable outcomes, as well as severe toxicities; moreover, treatment-refractory or relapsing disease is a major challenge for pediatricians/hematologists. In this article, we review the epidemiology, etiology and pathophysiology of pHLH, with a particular focus on different cytokines at the origin of the disease. The central role of interferon-γ (IFNγ) in the development and maintenance of hyperinflammation is analyzed. The value of emapalumab, a novel IFNγ-neutralizing monoclonal antibody is discussed. Available data support the use of emapalumab for treatment of pHLH patients with refractory, recurrent or progressive disease, or intolerance to conventional therapy, recently, leading to FDA approval of the drug for these indications. Additional data are needed to define the role of emapalumab in front-line treatment or in combination with other drugs.