Avapritinib for advanced systemic mastocytosis.

Avapritinib, a highly selective inhibitor of KIT D816V, was approved by the Food and Drug Administration in 2021 for treatment of advanced systemic mastocytosis (AdvSM) and by the European Medicines Agency in 2022 for AdvSM after prior systemic therapy. The phase 1 EXPLORER and phase 2 PATHFINDER trials demonstrated that avapritinib can elicit complete and durable clinical responses and molecular remission of KIT D816V. Key management challenges relate to the complex mutational landscape of AdvSM, often found with an associated hematologic neoplasm.

Therapeutic modulation of KIT ligand in melanocytic disorders with implications for mast cell diseases.

KIT ligand and its associated receptor KIT serve as a master regulatory system for both melanocytes and mast cells controlling survival, migration, proliferation and activation. Blockade of this pathway results in cell depletion, while overactivation leads to mastocytosis or melanoma. Expression defects are associated with pigmentary and mast cell disorders. KIT ligand regulation is complex but efficient targeting of this system would be of significant benefit to those suffering from melanocytic or mast cell disorders. Herein, we review the known associations of this pathway with cutaneous diseases and the regulators of this system both in skin and in the more well-studied germ cell system. Exogenous agents modulating this pathway will also be presented. Ultimately, we will review potential therapeutic opportunities to help our patients with melanocytic and mast cell disease processes potentially including vitiligo, hair greying, melasma, urticaria, mastocytosis and melanoma.

Mast Cell-Targeting Therapies in Mast Cell Activation Syndromes.

PURPOSE OF REVIEW: Provide an overview of the expanding landscape of mast cell (MC)-targeting treatments in mast cell activation syndromes (MCAS). RECENT FINDINGS: Tyrosine-kinase inhibitors (TKIs) targeting wild-type and mutated KIT can efficiently induce MC depletion. Avapritinib and midostaurin can also temper IgE-mediated degranulation. Avapritinib has been recently approved by the FDA for the treatment of indolent systemic mastocytosis (ISM). Targeting activation pathways and inhibitory receptors is a promising therapeutic frontier. Recently, the anti Siglec-8 antibody lirentelimab showed promising results in ISM. MCAS is a heterogeneous disorder demanding a personalized therapeutic approach and, especially when presenting as anaphylaxis, has not been formally captured as outcome in prospective clinical trials with TKI. Long-term safety of TKI needs to be addressed. New drugs under investigation in diseases in which non-neoplastic MCs play a pivotal role can provide important inputs to identify new efficient and safe treatments for MCAS.

Drug-induced mast cell eradication: A novel approach to treat mast cell activation disorders?

Mast cell (MC) activation is a key event in allergic reactions, other inflammatory states, and MC activation syndromes. MC-stabilizing agents, mediator-targeting drugs, and drugs interfering with mediator effects are often prescribed for these patients. However, the clinical efficacy of these drugs varies depending on the numbers of involved MCs and the underlying pathology. One straightforward approach would be to eradicate the primary target cell. To date however, no MC-eradicating treatment approach has been developed for patients with MC activation disorders. Nevertheless, recent data suggest that long-term treatment with agents effectively inhibiting KIT function results in the virtual eradication of tissue MCs and a sustained decrease in serum tryptase levels. In many of these patients, MC depletion is associated with a substantial improvement in mediator-induced symptoms. In patients with an underlying KIT D816V-positive mastocytosis, such MC eradication requires an effective inhibitor of KIT D816V, such as avapritinib. However, the use of KIT inhibitors must be balanced against their potential side effects. Here we discuss MC-eradicating strategies in various disease models, the feasibility of this approach, available clinical data, and future prospects for the use of KIT-targeting drugs in MC activation disorders.

Hereditary alpha-tryptasemia in 101 patients with mast cell activation-related symptomatology including anaphylaxis.

BACKGROUND: Hereditary alpha-tryptasemia (HαT) is an autosomal dominant genetic trait characterized by multiple copies of the alpha-tryptase gene at the TPSAB1 locus. Previously described symptomatology involves multiple organ systems and anaphylaxis. The spectrum of mast cell activation symptoms is unknown, as is its association with specific genotypes. OBJECTIVE: To describe clinical, laboratory, and genetic characteristics of patients referred for the evaluation of mast cell activation-related symptoms and genotype-confirmed HαT. METHODS: We retrospectively describe clinical characteristics, baseline tryptase, and tryptase genotype in 101 patients. Patients were referred for mast cell activation-related symptoms and underwent genotyping to confirm diagnosis of HαT. RESULTS: Of 101 patients, 80% were female with average tryptase of 17.2 ng/mL. Tryptase was less than 11.4 ng/mL in 8.9% and greater than 20 ng/mL in 22.3% (range 6.2-51.3 ng/mL). KIT D816V mutation was negative in all subjects tested. 2α:3ß was the most common genotype but did not correlate with tryptase levels. Unprovoked anaphylaxis was noted in 57% of the subjects with heterogeneous genotypes. Most common symptoms include gastrointestinal, cutaneous, psychiatric, pulmonary, cardiovascular, and neurologic. A total of 85% of patients were taking H1- or H2-antihistamines with partial symptom relief. Omalizumab was effective at suppressing anaphylaxis or urticaria in 94% of the patients. CONCLUSION: HαT encompasses a broad range of baseline tryptase and should be considered in patients with symptoms of mast cell activation and tryptase levels greater than 6.2 ng/mL. Patients may present with complex symptomatology including cutaneous, gastrointestinal, neurologic, and psychiatric symptoms and anaphylaxis, some of which respond to omalizumab.

Safe administration of chemotherapy in mast cell activation syndrome.

INTRODUCTION: Mast Cell Activation Syndrome (MCAS) is an immunogenic disorder typically presenting with episodic multi-organ symptoms, caused by the inappropriate and aberrant release of mast cell mediators. Symptoms may be severe, including anaphylaxis and often occur in response to specific triggers which include many drugs and potentially chemotherapeutic agents. The administration of adjuvant chemotherapy and radiotherapy in endometrial cancer significantly reduces the risk of reoccurrence in patients with high risk disease. Currently there is no evidence or case reports to guide the safe administration of chemotherapy in MCAS patients. CASE REPORT: We present the case of a 59-year-old lady with stage 3 A grade 2 endometroid endometrial cancer who underwent successful surgical management. She then received 4 cycles of adjuvant chemotherapy in the form of carboplatin and paclitaxel. This case describes a staged approach to chemotherapy administration and the utilisation of a carboplatin desensitization regimen to reduce the risk of immediate and delayed hypersensitivity sequalae.Management & outcome: Utilising an enhanced pre-medication strategy and a staged approach to chemotherapy administration, she was able to complete adjuvant treatment without any serious complications. At the date of censoring (May 2020) she has not shown any evidence of disease re-occurrence.Discussion & conclusion: Administering chemotherapy to patients with any mast cell disorder remains challenging. We hope that this case may provide the framework for safer chemotherapy administration for any patients at high risk of serious hypersensitivity sequalae in endometrial cancer and beyond.

Effect of a Cytoprotective Dose of Dehydroleucodine, Xanthatin, and 3-Benzyloxymethyl-5H-furan-2-one on Gastric Mucosal Lesions Induced by Mast Cell Activation.

The aim of this study was to determine whether the lactones dehydroleucodine, xanthatin and 3-benzyloxymethyl-5H-furan-2-one, would be effective in an animal model of gastric ulcer induced by mast cell activation. Rats were divided into ten groups. Treatments were repeated for four days. The degree of gastric erosion was assessed with a scoring system and histological preparations. Gastric mast cell morphology was analyzed by histological procedures. Serum serotonin levels were determined as markers of mast cell activation. Statistical analyses were done using ANOVA and Tukey-Kramer test. We demonstrated that the repeated administration of compound 48/80 results in extensive mucosal lesions in the gastric mucosa and that such lesions occurred in association with mast cell degranulation and a significant increase of serum serotonin. We showed that these lesions were prevented by dehydroleucodine, xanthatin, and 3-benzyloxymethyl-5H-furan-2-one and that this effect was similar to that obtained with sodium cromoglycate. In conclusion, the results of the present study indicate that the optimal gastric cytoprotective dose of dehydroleucodine, xanthatin, and 3-benzyloxymethyl-5H-furan-2-one is efficacious in an animal model of gastric ulcer induced by mast cell activation. Our findings suggest that these lactones could be valuable tools for designing novel therapeutic agents for digestive disorders associated with inappropriate mast cell activation.

Omalizumab in the treatment of adult patients with mastocytosis: A systematic review.

BACKGROUND: Mastocytosis is associated with mast cell (MC) mediator-related symptoms for which limited therapies are available. OBJECTIVE: Our aim was to assess the efficacy and safety of omalizumab in the treatment of MC mediator-related symptoms in adult patients with mastocytosis. RESULTS: We identified one multi-centre retrospective cohort study (39 patients), one retrospective cohort study (13 patients), 4 case series and 10 case reports. No published controlled randomized study was identified. We included 69 patients (13 patients with cutaneous mastocytosis and 56 with systemic mastocytosis). The mean age was 48 years. Omalizumab maintenance dose was 300 mg for the majority of patients. The mean duration of treatment was 17 months. Treatment led to a tolerability of venom immunotherapy and to a complete resolution of severe reactions in all patients with post-honeybee sting anaphylaxis. Complete resolution of idiopathic anaphylaxis episodes was noted in 84% of the patients. Complete resolution of palpitations, gastrointestinal, cutaneous, neuropsychiatric, respiratory and musculoskeletal symptoms was observed at a rate of 43%, 29%, 27%, 11%, 9% and 0%, respectively. Efficacy was maintained for the entire duration of the treatment in all but four responders. Adverse events were reported for 13 patients. CONCLUSIONS AND CLINICAL RELEVANCE: Omalizumab appears to prevent some life-threatening reactions associated with mastocytosis and may be a good option to treat the associated symptoms. However, the evidence relied upon is observational, uncontrolled and from a small number of patients. A randomized controlled trial is needed to better understand the place of omalizumab in mastocytosis treatment.

Activation of Siglec-7 results in inhibition of in vitro and in vivo growth of human mast cell leukemia cells.

Advanced systemic mastocytosis is a rare and still untreatable disease. Blocking antibodies against inhibitory receptors, also known as "immune checkpoints", have revolutionized anti-cancer treatment. Inhibitory receptors are expressed not only on normal immune cells, including mast cells but also on neoplastic cells. Whether activation of inhibitory receptors through monoclonal antibodies can lead to tumor growth inhibition remains mostly unknown. Here we show that the inhibitory receptor Siglec-7 is expressed by primary neoplastic mast cells in patients with systemic mastocytosis and by mast cell leukemia cell lines. Activation of Siglec-7 by anti-Siglec-7 monoclonal antibody caused phosphorylation of Src homology region 2 domain-containing phosphatase-1 (SHP-1), reduced phosphorylation of KIT and induced growth inhibition in mast cell lines. In SCID-beige mice injected with either the human mast cell line HMC-1.1 and HMC-1.2 or with Siglec-7 transduced B cell lymphoma cells, anti-Siglec-7 monoclonal antibody reduced tumor growth by a mechanism involving Siglec-7 cytoplasmic domains in "preventive" and "treatment" settings. These data demonstrate that activation of Siglec-7 on mast cell lines can inhibit their growth in vitro and in vivo. This might pave the way to additional treatment strategies for mastocytosis.

COVID-19 and Multisystem Inflammatory Syndrome, or is it Mast Cell Activation Syndrome?

COVID-19 derives from infection with Coronavirus [severe acute respiratory syndrome (SARS)-CoV-2] and is associated with high morbidity and mortality due to release of a storm of pro-inflammatory cytokines and thrombogenic agents resulting in destruction of the lungs. Many reports indicate that a considerable number of patients who are positive for SARS-CoV-2 are asymptomatic or have mild symptoms. However, increasing evidence suggests that many such patients who either recovered from or had mild symptoms after COVID-19 exhibit diffuse, multiorgan, symptoms months after the infection. These symptoms include malaise, myalgias, chest tightness, brain fog and other neuropsychiatric symptoms that were originally reported in children and named Multisystem Inflammatory Syndrome (MIS-C). Now the US Center for Disease Control (CDC) announced the recognition of a similar condition in adults, named Multisystem Inflammatory Syndrome (MIS-A). The symptoms characterizing these conditions are very similar to those associated with Mast Cell Activation Syndrome (MCAS, US ICD-110 code D89.42-idiopathic mast cell activation syndrome). Hence, the possibility of MCAS should be evaluated in any patient with MIS and/or multisystem inflammatory symptoms. In either case, these syndromes should be addressed with liposomal formulation (in olive pomace oil) of the flavone luteolin (e.g. PureLut® or FibroProtek®) together with the antihistamine rupatadine, which also has anti-platelet activating factor (PAF) activity and inhibits mast cells that have been implicated in the pathogenesis of cytokine storms in COVID-19.

Efficacy of Omalizumab in Mastocytosis: Allusive Indication Obtained from a Prospective, Double-Blind, Multicenter Study (XOLMA Study).

BACKGROUND: Patients with mastocytosis often suffer from a variety of symptoms caused by mast cell mediators where treatments remain difficult, showing various success rates. Omalizumab, a monoclonal anti-IgE antibody, has been postulated to have a positive impact on mastocytosis-associated symptoms such as flush, vertigo, gastrointestinal problems, or anaphylaxis. OBJECTIVE: To investigate the efficacy and safety of omalizumab in systemic mastocytosis. METHODS: Patients with histologically proven mastocytosis were investigated in a multicenter prospective double-blind placebo-controlled trial to receive either omalizumab or placebo, dosed according to IgE and body weight. The primary endpoint was change in the AFIRMM activity score after 6 months of treatment. Different laboratory parameters were analyzed. RESULTS: Sixteen patients were analyzed: 7 to omalizumab and 9 to placebo (mean age 47.7 ± 13.8 vs. 45.4 ± 8.8 years; 66.6 vs. 85.7% were female; mean disease duration 10.0 ± 5.1 vs. 4.5 ± 2.9 years, respectively). After 6 months the median AFIRMM score decreased 50% from 52.0 to 26.0 in the omalizumab group versus 104.0-102.0 in the placebo group (p = 0.286); however, the difference was not significant (p = 0.941). Secondary endpoints, including the number of allergic reactions, changes in major complaints, wheal-and-flare reaction due to mechanical irritation (Darier's sign), and frequency of the use of mastocytosis-specific drugs improved in the omalizumab group, but not significantly. Adverse events like urticaria, bronchospasm, and anaphylactic shock showed no significant difference between the groups. No severe adverse events occurred. FcεRI (Fc-epsilon receptor) expression on basophils decreased after receiving omalizumab versus placebo. CONCLUSION: Omalizumab was safe and showed a tendency to improve mastocytosis-related symptoms, in particular diarrhea, dizziness, flush, and anaphylactic reactions, including the AFIRMM score and secondary endpoints; however, the difference was not significant. Due to the small study size and difference at baseline between the study groups, further studies are required to confirm our findings.

N-acetyl-L-cysteine reduces Leishmania amazonensis-induced inflammation in BALB/c mice.

BACKGROUND: Leishmaniasis is a emergent disease characterized by different clinical manifestations in both humans and dogs. Predominant clinical features of cutaneous leishmaniasis are ulcerative painless skin lesions. Several data reported that pain is associated with human and dog leishmaniasis, out with areas of painless ulcerative lesions per se. Actually, current medications used for leishmaniasis management are characterized by several side effects and, in addition, some cases of the disease are refractory to the treatment. On this background it is mandatory the identification of new and safe candidates for designing less toxic and low-cost remedies. Therefore, the search for new leishmanicidal compounds is indispensable. METHODS: In the present paper we investigated the effect of orally N-acetyl-L-cysteine (NAC) supplementation at dose of 200 mg/Kg for 10 weeks, in subcutaneous Leishmania (L). amazonensis infected BALB/c mice. And evaluating the effect of NAC on inflammatory response such as TNF-α, IL-6, IL-1ß levels, and on thermal and mechanical hyperalgesia. RESULTS: In the present paper we showed how NAC supplementation affected parameters of oxidative stress (GSH, MDA, SOD), inflammation such as cytokines levels (IL-1ß, IL-6, TNFα) and mast cell activation and consequently on induced pain, during leishmaniosis in BALB\c mice. CONCLUSIONS: The findings of our study provided the scientific data demonstrating that L. amazonensis infection induces inflammation and pain in BALB/c mice that are reversed by administration of NAC.

Massive release of the histamine-degrading enzyme diamine oxidase during severe anaphylaxis in mastocytosis patients.

BACKGROUND: Histaminolytic activity mediated by diamine oxidase (DAO) is present in plasma after induction of severe anaphylaxis in rats, guinea pigs, and rabbits. Heparin released during mast cell degranulation in the gastrointestinal tract might liberate DAO from heparin-sensitive storage sites. DAO release during anaphylaxis has not been demonstrated in humans. METHODS: Plasma DAO, tryptase, and histamine concentrations of four severe anaphylaxis events were determined at multiple serial time points in two patients with systemic mastocytosis. The histamine degradation rates were measured in anaphylaxis samples and in pregnancy sera and plasma with comparable DAO concentrations. RESULTS: Mean DAO (132 ng/mL) and tryptase (304 ng/mL) concentrations increased 187- and 4.0-fold, respectively, over baseline values (DAO 0.7 ng/mL, tryptase 76 ng/mL) during severe anaphylaxis. Under non-anaphylaxis conditions, DAO concentrations were not elevated in 29 mastocytosis patients compared to healthy volunteers and there was no correlation between DAO and tryptase levels in mastocytosis patients. The histamine degradation rate of DAO in plasma from mastocytosis patients during anaphylaxis is severely compromised compared to DAO from pregnancy samples. CONCLUSION: During severe anaphylaxis in mastocytosis patients, DAO is likely released from heparin-sensitive gastrointestinal storage sites. The measured concentrations can degrade histamine, but DAO activity is compromised compared to pregnancy samples. For accurate histamine measurements during anaphylaxis, DAO inhibition is essential to inhibit further histamine degradation after blood withdrawal. Determination of DAO antigen levels might be of clinical value to improve the diagnosis of mast cell activation.

Management of a neonate with diffuse cutaneous mastocytosis: Case report and literature review.

Mastocytosis is an accumulation of clonal mast cells within tissues, commonly caused by mutations in the KIT proto-oncogene. This report describes the management of a neonate with diffuse cutaneous mastocytosis (DCM) caused by a rare activating KIT mutation, specifically internal tandem duplication of the Ala502Tyr503 pair on exon 9, and reviews current data regarding work-up of DCM in pediatric patients.

Successful mast-cell-targeted treatment of chronic dyspareunia, vaginitis, and dysfunctional uterine bleeding.

Dyspareunia, vaginitis and dysfunctional uterine bleeding (DUB) are common problems which, despite their polygenicity, commonly appear idiopathic and treatment-refractory. Mast cell (MC) activation syndrome (MCAS) is a newly-recognised, prevalent, chronic multisystem polymorbidity of general themes of inflammation ± allergic-type phenomena ± aberrant growth/development in assorted tissues. MCs produce significant quantities of heparin, too. As such, MCAS may underlie some cases of chronic dyspareunia, vaginitis or DUB. We report five such patients; all who responded well to MC-targeted treatment. We review aspects of MC biology and pathobiology of potential relevance to otherwise idiopathic persistent inflammatory or coagulopathic genital tract problems. Diagnostic testing for MCAS may be warranted in some patients with chronic dyspareunia, vaginitis or DUB (especially patients whose histories well fit the general profile of MCAS), and prospective therapeutic trials of MC-directed topical and/or systemic therapies may be warranted in such populations. Impact statement What is already known on this subject? Chronic, idiopathic, treatment-refractory female genital tract inflammation or bleeding are common problems for which mast cell (MC) disease, previously generally thought to consist of just rare cases of mastocytosis, and is seldom considered in the differential diagnosis. What do the results of this study add? The substantial prevalence of the newly recognised 'mast cell activation syndrome' (MCAS), featuring chronic inappropriate MC activation with little-to-no MC neoplasia, and its clinical presentation with chronic multisystem inflammation ± allergic-type phenomena ± aberrant growth/development in assorted tissues, raises the possibility that MCAS might underlie the aforementioned genital tract problems, especially in patients whose larger clinical presentations fit the MCAS profile. We report five example patients (among many more we have similarly treated) who enjoyed excellent responses to safe, inexpensive MC-targeted treatments, often given just intravaginally. What are the implications of these findings for clinical practice and/or further research? Our report identifies a potentially significant new MC-focused direction, of relevance to millions of affected women worldwide, for clinical treatment as well as for basic and clinical research, which historically has yielded major advancements disappointingly disproportionate to the scope of the affected population.

Hydroxychloroquine as a novel therapeutic approach in mast cell activation diseases.

There is no therapeutic agent approved in cutaneous mastocytosis and mast cell activation syndrome. We report the efficacy of hydroxychloroquine in four patients with cutaneous mastocytosis (n = 2) and mast cell activation syndrome (n = 2). We show that this molecule reduces the long-term survival of primary human mast cells, interferes with lysosome function and leads to the accumulation of non-functional tryptase in the mast cell granules. Furthermore, hydroxychloroquine decreases the production of pro-inflammatory mediators.

Low frequency of acetyl salicylic acid hypersensitivity in mastocytosis: The results of a double-blind, placebo-controlled challenge study.

BACKGROUND: Patients with mastocytosis are at increased risk of anaphylaxis. The use of nonsteroidal anti-inflammatory drugs (NSAIDs) is often discouraged because of this reason. However, the actual prevalence and severity of NSAID-related hypersensitivity among patients with mastocytosis is unknown. METHODS: A double-blind, placebo-controlled acetylsalicylic acid (ASA) challenge up to a cumulative dose of 520 mg was performed among adult patients with mastocytosis. In addition, a retrospective search of the entire outpatient cohort was performed to obtain "real-life" data on NSAID hypersensitivity. RESULTS: Fifty patients underwent an ASA challenge. Seventy percent had indolent systemic mastocytosis, 18% had mastocytosis in the skin, and 12% had advanced mastocytosis. The ASA challenge was positive in 1 patient who developed urticaria. The additional retrospective chart review revealed that 8 of 191 patients had a history of NSAID-related hypersensitivity reaction(s), of whom 3 reported severe systemic reactions. All 8 patients had already experienced NSAID-related hypersensitivity reactions before mastocytosis was diagnosed. CONCLUSIONS: The frequency of ASA hypersensitivity was 2% in a prospective challenge study and 4.1% in a retrospective chart review of 191 patients with mastocytosis. NSAIDs can be administered safely to most patients with mastocytosis. Extra caution should be taken in patients with a history of hypersensitivity reactions to other drugs, or traditional risk factors for NSAID hypersensitivity.

[Severe Mast Cell Activation Syndrome in a 15-year-old patient with an hypermobile Ehlers-Danlos syndrome]. / Le cas clinique du mois. Syndrome d'Activation Mastocytaire sévère chez un patient de 15 ans présentant un syndrome d'Ehlers-Danlos de type hypermobile.

We report the history of a 15-year old patient with a hypermobile Ehlers-Danlos syndrome (hEDS) (his mother, his two brothers and his sister have the same phenotype as him). He suffers mainly from a severe mast cell activation syndrome (MCAS) with an overreaction of the skin to any kind of contact (water of the shower, clothes, bed sheets) but he has also fatigue, headaches, and rash. This impressive rash is exacerbated after the shower and he has the urge to rest («shower's sign¼). We describe the MCAS and its easy, fast and very effective medication management, without any significant side effects as well as its frequent association with the hEDS. We finally introduce the original term of «MASED¼ to this MCAS, associated, linked or entangled to hEDS.

Nous présentons le cas d'un jeune patient âgé de 15 ans atteint d'un syndrome d'Ehlers-Danlos (SED) de type hypermobile (sa mère, ses deux frères et sa soeur présentent le même phénotype que lui). Il présente principalement un syndrome d'activation mastocytaire (SAMA) sévère avec une atteinte démesurée au niveau de la peau exposée au simple contact (avec l'eau, les draps, les vêtements), mais également de la fatigue, des céphalées ainsi que des éruptions qui sont exacerbées après la douche avec l'envie impérieuse de se reposer (le «signe de la douche¼). Nous décrivons le SAMA, sa prise en charge médicamenteuse simple, rapide et efficace et dépourvue d'effets secondaires notables ainsi que son association fréquente au SED. Nous introduisons finalement le terme original de «SAMED¼ à ce SAMA associé, lié ou intriqué au SED.

Cladribine for mastocytosis: benefits and risks.

In this issue of Blood, Barete et al report the safety and efficacy of cladribine in 68 adult patients with mastocytosis.