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Blood & Immune

Systemic Mastocytosis (SM) Clinical Trials and Treatments

Also called SM, Mast Cell Disease, Systemic Mast Cell Disorder

Systemic Mastocytosis results from clonal proliferation of mast cells due to activating mutations, most commonly KIT D816V, leading to accumulation of abnormal mast cells in bone marrow, lymphoid tissues, skin, and other organs. Mast cells produce numerous mediators including histamine, tryptase, heparin, and various cytokines that cause symptoms upon release.

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About Systemic Mastocytosis

Systemic Mastocytosis results from clonal proliferation of mast cells due to activating mutations, most commonly KIT D816V, leading to accumulation of abnormal mast cells in bone marrow, lymphoid tissues, skin, and other organs. Mast cells produce numerous mediators including histamine, tryptase, heparin, and various cytokines that cause symptoms upon release.

The disease is classified into several subtypes: indolent systemic mastocytosis (ISM), smoldering systemic mastocytosis (SSM), systemic mastocytosis with associated hematologic neoplasm (SM-AHN), aggressive systemic mastocytosis (ASM), and mast cell leukemia (MCL), with widely varying prognosis and management. Symptoms result from both mast cell accumulation and mediator release.

Mediator-related symptoms include flushing, pruritus (itching), abdominal symptoms, and anaphylaxis. Mast cell accumulation contributes to bone marrow dysfunction with cytopenias, osteoporosis, organomegaly, and tissue infiltration. Risk factors for mediator release include food additives, medications, insect stings, stress, and heat. Many patients develop myelodysplastic syndrome or acute myeloid leukemia as a complication.

Common Symptoms of Systemic Mastocytosis

Recognizing the signs of Systemic Mastocytosis early can lead to faster diagnosis and better outcomes. Symptoms may vary in severity from person to person. If you or a loved one are experiencing any of the following, consider speaking with a specialist.

  • Flushing and itching, especially with triggers like heat or food
  • Abdominal pain, diarrhea, and malabsorption
  • Bone pain and osteoporosis
  • Anaphylactic reactions with throat tightness and hypotension
  • Headaches and cognitive difficulties
  • Hepatomegaly and splenomegaly

Who Systemic Mastocytosis Affects

Systemic Mastocytosis can present at any age, from childhood to elderly, though adult onset is most common. It affects males and females roughly equally. The disease occurs across all racial and ethnic groups.

The KIT D816V mutation, present in approximately 90% of adult cases, is typically somatically acquired and not inherited. Some pediatric cases with different KIT mutations or other genetic alterations have different clinical courses.

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Help Paying for Systemic Mastocytosis Treatment

Charity funds and drugmaker programs for Systemic Mastocytosis, checked at the source. Pick your insurance to see what fits.

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  • From a charity · Blood Cancer United (formerly The Leukemia & Lymphoma Society)
    Acute Myeloid Leukemia Co-Pay Fund (covered diagnoses include Mastocytosis) fund
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    Pays for: Insurance premiums and treatment-related copays, deductibles and coinsurance, up to $4,000 per year. Requires health insurance (any kind).

Status as each foundation showed it on September 28, 2026.

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Side Effect Explorer

Real-world side effect reports from the FDA Adverse Event Reporting System (FAERS). Includes both FDA-approved drugs and investigational therapies from active clinical trials. Click any drug to see what patients reported.

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Genetic Testing

Genetic testing can confirm a diagnosis, guide treatment decisions, and identify family members who may be at risk.

The KIT gene page lists every condition Orphanet links to the gene and the open trials that name it.

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Trusted Systemic Mastocytosis Resources

Reputable organizations and medical references for learning more about Systemic Mastocytosis, including disease registries, foundation resources, and clinical guidelines.

FDA decision ahead
The FDA is due to decide on Bezuclastinib (Cogent Biosciences) for Nonadvanced systemic mastocytosis by December 30, 2026. Selective KIT D816V inhibitor for the most common form of systemic mastocytosis.
See all upcoming rare disease FDA decisions →

Active Clinical Trials for Systemic Mastocytosis

Use this Systemic Mastocytosis clinical trial finder to see the 11 studies recruiting patients and 2 opening soon in the United States and worldwide, with eligibility criteria in plain English. These studies play a critical role in advancing care for blood & immune conditions and may offer access to treatments not yet widely available. Each trial below is sourced directly from ClinicalTrials.gov, with eligibility criteria translated into plain English to help patients and caregivers evaluate whether a study may be a fit.

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Note: Trial recruitment statuses on ClinicalTrials.gov may not immediately reflect recent FDA decisions, sponsor announcements, or enrollment changes. Always confirm a trial's current status directly with the study coordinator before making plans.

13 active trials worldwide
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RECRUITINGPHASE2, PHASE3Recently updatedNCT04910685

(HARBOR) Study to Evaluate Efficacy and Safety of BLU-263 Versus Placebo in Patients With Indolent Systemic Mastocytosis

Intervention: Elenestinib, Placebo

Sponsor: Blueprint Medicines Corporation

This is a randomized, double-blind, placebo-controlled, Phase 2/3 study comparing the efficacy and safety of elenestinib (BLU-263) + symptom directed therapy (SDT) with placebo + SDT in participants with indolent systemic mastocytosis (ISM) whose symptoms are not adequately contr...

Ages 18 Years+76 locations
Started Nov 2021Updated 6 days agoEst. Sep 2032 (~6 years)
RECRUITINGPHASE2Recently updatedNCT04996875

(Apex) Bezuclastinib in Patients With Advanced Systemic Mastocytosis

Intervention: bezuclastinib

Sponsor: Cogent Biosciences, Inc.

This is an open-label, two-part Phase 2 study investigating CGT9486 for the treatment of patients with Advanced Systemic Mastocytosis (AdvSM), including patients with Aggressive SM (ASM), SM with Associated Hematologic Neoplasm (SM-AHN), and Mast Cell Leukemia (MCL).

Ages 18 Years+42 locations
Started Nov 2021Updated 2 weeks agoEst. Sep 2025
NOT YET RECRUITINGPHASE2Recently updatedNCT07819396

Depletion of CD45RA Positive Naive T Cells for the Prevention of Graft Versus Host Disease in Older Patients Undergoing Allogeneic Hematopoietic Cell Transplantation for Acute Leukemia or Myelodysplastic Syndrome

Intervention: Allogeneic CD34+-enriched and CD45RA-depleted PBSCs, Biospecimen Collection, Bone Marrow Aspiration, Bone Marrow Biopsy, Cyclophosphamide, Fludarabine, Total-Body Irradiation

Sponsor: Fred Hutchinson Cancer Center

This phase II trial tests how well removing CD45RA positive naive T cells works to prevent graft versus host disease in older patients undergoing standard of care allogeneic hematopoietic stem cell transplantation for the treatment of acute leukemia or myelodysplastic syndrome (M...

Ages not specified1 location
Started Jan 2027Updated 2 weeks agoEst. Jun 2031 (~4y 8m)
RECRUITINGRecently updatedNCT07264959

An Observational Study in Participants With Indolent Systemic Mastocytosis (ISM)

Sponsor: Blueprint Medicines Corporation

This is a Phase 4, non-interventional, observational study to collect detailed data on the clinical characteristics, clinical outcomes and medical management of ISM in real-world settings. The study will describe the demographic and clinical characteristics of ISM participants, i...

Ages 18 Years+7 locations
Started Apr 2026Updated 3 weeks agoEst. Dec 2032 (~6y 2m)
RECRUITINGRecently updatedNCT06210698

Angioedema Biomarker Research Study

Intervention: Venipuncture

Sponsor: Foundation For Rare Disease Research

This clinical trial aims to evaluate and compare novel and commercially available diagnostic assays through blood tests for the differential diagnosis and comprehensive assessment of patients experiencing recurrent angioedema attacks, including both urticarial and non-urticarial ...

Ages 12 Years – 75 Years1 location
Started Jan 2024Updated 1 month agoEst. Jul 2027 (~10 months)
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Active trial locations34 cities in the US
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Trial Pipeline

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Data from ClinicalTrials.gov, U.S. National Library of Medicine.
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Patient Communities

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Related Blood & Immune Conditions

Other rare diseases in the blood & immune category. Patients with Systemic Mastocytosis may find relevant research, shared treatment pathways, or overlapping clinical trials among these related conditions.

Companies Developing Systemic Mastocytosis Treatments

3 pharmaceutical companies have Systemic Mastocytosis in their rare disease portfolio

Frequently Asked Questions About Systemic Mastocytosis