ClinicalTrials.gg
RecruitingNCT04996875Updated Sep 15, 2026

(Apex) Bezuclastinib in Patients With Advanced Systemic Mastocytosis

A Phase 2 interventional study of bezuclastinib in Advanced Systemic Mastocytosis (AdvSM), SM With an Associated Hematologic Neoplasm (SM-AHN) and Mast Cell Leukemia (MCL), sponsored by Cogent Biosciences, Inc.. Recruiting at 42 sites in 14 countries. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-09-15.

Primary conditionLeukemia, Mast-CellRegistry: Mastocytosis, SystemicReclassifiedWhy we changed it
Registry
Mastocytosis, Systemic — the first condition term the registry derived for this study.
ClinicalTrials.gg
Leukemia, Mast-Cell
Why
  1. The study's listed conditions name Leukemia, Mast-Cell, a narrower term within Mastocytosis, Systemic.
Confidence
High: the new condition is named in the study's own listed conditions. Of 351 hand-checked studies reclassified this way, 68% were exactly right and 84% in the right disease family; the registry's first term was right for 5% (measured 2026-10-21). How we classify →
Wrong?
Tell us the study's main condition →

Sponsored by Cogent Biosciences, Inc. · Phase 2, Interventional, and Treatment

From the registry’s dates

  • Started Nov 2021; still recruiting 5 years later.
Phase
Phase 2
Study type
Interventional
Enrollment
140
Allocation
Not applicable
Ages
18 Years and older
Sex
All
01

Study summary

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).

02

Conditions studied

  • Advanced Systemic Mastocytosis (AdvSM)
  • SM With an Associated Hematologic Neoplasm (SM-AHN)
  • Mast Cell Leukemia (MCL)
  • Aggressive Systemic Mastocytosis (ASM)

Keywords

  • Mastocytosis
  • Systemic Mastocytosis
  • Advanced Mastocytosis
  • Aggressive Mastocytosis
  • Hematologic Neoplasms
  • Mast Cell
  • Mast Cell Leukemia
  • Soft Tissue Neoplasms
  • Neoplasms by site
  • Skin Diseases
  • Immune Complex Diseases
  • Immune System Diseases
  • Hypersensitivity
  • Hematologic Diseases
  • Leukemia
  • Myeloid Leukemia
  • Acute Myeloid Leukemia
  • SM with Associated Hematologic Neoplasm
  • AdvSM
  • ASM
  • SM-AHN
  • MCL
  • Neoplasm
  • D816V
  • KIT D816V
  • AML
  • bezuclastinib
  • CGT9486
  • CGT
  • PLX
  • Connective Tissue Neoplasms
  • Urticaria Pigmentosa
  • High-risk myelodysplastic syndrome
  • Chronic myelomonocytic leukemia
  • Myeloproliferative neoplasm
  • High-risk myeloid neoplasm
  • High-risk MDS
  • MPN
  • High-risk MPN
  • Accelerated phase MPN
  • CMML
03

In context

Leukemia, Mast-Cell Reclassified

60 studies on the registry are indexed under Leukemia, Mast-Cell; 5 are open to participants now.

This study's planned enrollment of 140 is above the median of 50 across 38 interventional studies indexed under Leukemia, Mast-Cell.

Browse Leukemia, Mast-Cell studies →

Lead sponsor

Cogent Biosciences, Inc. is the lead sponsor of 14 studies on the registry; 6 are open to participants now.

Compared within Leukemia, Mast-Cell, this study's primary condition as ClinicalTrials.gg classifies it; the registry's first condition term is Mastocytosis, Systemic. The counts are of registry records indexed under each term, refreshed daily. How we classify →

04

Who can participate

Ages eligible
18 Years and older
Sexes eligible
All
Accepts healthy volunteers
No

Eligibility criteria

Key Inclusion Criteria for Main Study:

  1. Diagnosed with one of the following advanced mastocytosis diagnoses by Eligibility Committee

    1. Aggressive Systemic Mastocytosis (ASM)
    2. Systemic Mastocytosis with an Associated Hematologic Neoplasm (SM-AHN)
    3. Mast Cell Leukemia (MCL)
  2. according to modified IWG-MRT-ECNM criteria. (A subset of patients inevaluble per mIWG-MRT-ECNM will be included in the study).
  3. (0 to 3)
  4. Have clinically acceptable local laboratory screening results (clinical chemistry, hematology) within certain limits

Key Exclusion Criteria for Main Study:

  1. Persistent toxicity from previous therapy for AdvSM that has not resolved to ≤ Grade 1
  2. Associated hematologic neoplasm requiring immediate antineoplastic therapy
  3. cardiac disease
  4. Known positivity for the FIP1L1 PDGFRA fusion. Patients with eosinophilia without detectable KIT D816V mutation must demonstrate lack of PDGFRA fusion mutation prior to enrollment
  5. Seropositive for (HIV) 1 or 2, or positive for surface antigen or virus (HCV) antibody
  6. History of clinically significant bleeding event within 30 days before the first dose of study drug or need for therapeutic anticoagulation on study
  7. Diagnosed with or treated for other than the disease under study within the prior 3 years before enrollment
  8. Received any cytoreductive therapy or any agent less than 14 days, and for cladribine, interferon alpha, pegylated interferon, and any antibody therapy less than 28 days, before screening bone marrow
  9. Received hematopoietic growth factor support within 14 days before the first dose of study drug
  10. Received strong inhibitors or inducers within 14 days or 5 drug half-lives, whichever is longer, before the first dose of study drug
  11. Need for treatment with high dose

Key Inclusion Criteria for Substudy Population:

Rollover Cohort

  1. Demonstrate AHN progression requiring immediate AHN-directed therapy while receiving bezuclastinib
  2. Demonstrated clinical benefit from bezuclastinib therapy
  3. Have clinically acceptable local laboratory screening results (clinical chemistry, hematology) within certain limits

High-Risk Cohort

  1. Receiving or indicated for AHN-directed therapy.
  2. Diagnosed with one of the following pathologic diagnoses of SM-AHN:

    1. Myelodysplastic syndrome (MDS) that is high- or very high-risk
    2. Accelerated phase myeloproliferative neoplasm (MPN)
    3. MDS with excessive blasts in bone marrow or peripheral blood
    4. Chronic myelomonocytic leukemia-2 (CMML-2)
  3. Have clinically acceptable local laboratory screening results (clinical chemistry, hematology) within certain limits.

Key Exclusion Criteria for Substudy Population:

  1. Diagnosis of Philadelphia chromosome-positive malignancy
  2. Diagnosis of acute myeloid leukemia (AML)
  3. Appropriate for allogenic hematopoietic stem cell transplantation
  4. Any to selected concomitant therapy
  5. Rollover Cohort: Have not demonstrated acceptable tolerability of previous bezuclastinib therapy
  6. High-Risk Cohort: Previously treated with investigational therapy for AdvSM
  7. High-Risk Cohort: Previously treated with cytoreductive therapy and discontinued due to treatment-related toxicity
  8. High-Risk Cohort: Received any cytoreductive therapy or any investigational agent less than 14 days, and for cladribine, interferon alpha, pegylated interferon, and any antibody therapy less than 28 days, before screening or archival bone marrow biopsy
Terms in these criteria, in plain language(12)

Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.

Measurable disease

The amount of disease can be tracked with a defined measurement, so the study can see whether it shrinks or grows. It might be a tumour measured on a scan or, in some blood cancers such as myeloma, a marker measured in blood or urine.

The criteria or the study team say which measurement counts — having no tumour visible on a scan does not by itself rule you out.

ECOG performance status

A scale of how much an illness limits everyday activity. For people being assessed to join a study, scores run from 0 (fully active) to 4; lower is more active.

0
Fully active, no restrictions.
1
Limited in strenuous activity, but walking and able to do light work, such as housework or office work.
2
Walking and able to look after yourself, but unable to work; up and about more than half of waking hours.
3
Able to look after yourself only in part; in bed or a chair more than half of waking hours.
4
Unable to look after yourself at all; in bed or a chair all day.

Studies most often ask for 0–1 or 0–2. Your doctor gives the score; the WHO scale uses the same steps. The full scale also has 5, which records death.

Clinically significant

Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.

HIV

The human immunodeficiency virus, which weakens the immune system.

Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.

Hepatitis B tests

Hepatitis B is a virus that infects the liver. These are separate tests: HBsAg positive usually means a current infection (a recent vaccination can briefly cause it too); total anti-HBc (HBcAb) positive means an infection now or in the past; HBV DNA measures how much virus is in the blood.

Some studies accept a past infection if HBV DNA is undetectable, sometimes with antiviral medicine during the study. Check what this study allows.

Hepatitis C tests

Hepatitis C is a virus that infects the liver. An HCV antibody test can stay positive after an infection has cleared (and is occasionally positive without one); an HCV RNA test shows whether the virus is there now.

After treatment, hepatitis C counts as cured when HCV RNA is still undetectable 12 weeks or more after the treatment ended. Studies often accept people cured this way.

Cancer (malignancy)

Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.

Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.

Investigational drug or device

A drug or device being studied in a clinical trial.

It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.

Biopsy and archival tissue

A biopsy takes a small piece of tissue to examine. “Archival tissue” is a sample already taken, for example at diagnosis, and kept by the hospital.

Whether a stored sample will do depends on when it was taken, how much there is and what the study needs. Ask whether the study accepts your stored sample or needs a new biopsy.

CYP3A (CYP3A4) inhibitors and inducers

CYP3A is a group of enzymes, mainly CYP3A4, in the liver and gut that break down many medicines. Some medicines, supplements and foods (grapefruit, St John’s wort) slow them down or speed them up, which changes how much of a study drug stays in the body.

Studies list them so they can be avoided or switched; bring a list of everything you take, including supplements.

Corticosteroids (steroids)

Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.

Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.

Contraindication

A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.

05

Study design

Phase
Phase 2
Primary purpose
Treatment
Allocation
Not applicable
Intervention model
Single group
Masking
None (open label)
Enrollment
140 participants (estimated)

Study arms

  • Experimental
    bezuclastinib

    Drug: bezuclastinib

Interventions

  • Bezuclastinib is administered as tablets to be taken orally, continuously in 28-day cycles.

    Also known as: CGT9486, PLX9486

06

What researchers measure

Primary outcomes

  1. Part I: Identify clinically active and tolerable exposures of bezuclastinib in patients with AdvSM

    Time frame: 18 months

  2. Part II: - Determine efficacy of bezuclastinib as measured by mIWG Objective Response Rate (ORR) - Confirm the exposure-response relationship of bezuclastinib

    Time frame: 18 months

Secondary outcomes

  1. Pure Pathologic Response (PPR)

    Months

    Time frame: 18 months

  2. Safety of CGT9486 as assessed by incidence of Adverse Events (AEs)

    Incidence of AEs according to CTCAE version 5.0 or higher

    Time frame: 18 months

  3. To determine the effects of bezuclastinib on mutation allele burden.

    Percentage change in KIT D816V

    Time frame: 18 months

  4. To determine the effects of bezuclastinib on serum tryptase.

    Percentage change in Serum Tryptase

    Time frame: 18 months

  5. To assess the pharmacokinetics of bezuclastinib in subjects with AdvSM.

    Percentage change in plasma concentrations of bezuclastinib

    Time frame: 18 months

  6. Change from baseline in histopathologic findings in blood and bone marrow

    Percentage change in mast cell infiltration in the bone marrow and percentage change in eosinophilia and monocytosis in the blood

    Time frame: 18 months

  7. Change in spleen and liver volume by imaging

    Percentage change

    Time frame: 18 months

  8. Duration of Response (DOR)

    Months

    Time frame: 18 months

  9. Time to Response (TTR)

    Months

    Time frame: 18 months

  10. Progression Free Survival (PFS)

    Months

    Time frame: 18 Months

  11. Overall Survival (OS)

    Months

    Time frame: 18 months

07

Study locations

18 of 42 sites recruiting
  • University of Alabama at Birmingham (UAB) Hospital
    Birmingham, Alabama 35233, United States
    Active, not recruiting

    Not enrolling at this site — choose another above.

  • Mayo Clinic Arizona
    Phoenix, Arizona 85054, United States
    Recruiting
  • City of Hope Comprehensive Cancer Center
    Duarte, California 91010, United States
    Recruiting
  • UCLA Medical Center
    Los Angeles, California 90095, United States
    Recruiting
  • Stanford Cancer Institute
    Stanford, California 94305, United States
    Recruiting
  • Galiz Research
    Hialeah, Florida 33016, United States
    Withdrawn

    Not enrolling at this site — choose another above.

  • Winship Cancer Institute - Emory University
    Atlanta, Georgia 30322, United States
    Recruiting
  • Rush University Medical Center
    Chicago, Illinois 60612, United States
    Withdrawn

    Not enrolling at this site — choose another above.

  • Dana-Farber Cancer Institute
    Boston, Massachusetts 02215, United States
    Recruiting
  • Columbia University Irving Medical Center
    New York, New York 10032, United States
    Withdrawn

    Not enrolling at this site — choose another above.

  • Cleveland Clinic Taussig Cancer Center
    Cleveland, Ohio 44106, United States
    Active, not recruiting

    Not enrolling at this site — choose another above.

  • MUSC Health University Medical Center
    Charleston, South Carolina 29425, United States
    Recruiting
  • The University of Texas MD Anderson Cancer Center
    Houston, Texas 77030, United States
    Recruiting
  • Huntsman Cancer Institute - University of Utah Health
    Salt Lake City, Utah 84112, United States
    Recruiting
  • Nepean Hospital
    Kingswood, New South Wales 2747, Australia
    Recruiting
  • Gold Coast University Hospital
    Southport, Queensland 4215, Australia
    Recruiting
  • Peter MacCallum Cancer Centre
    Melbourne N., Victoria 3051, Australia
    Recruiting
  • AKH Wien, Universitatsklinikum
    Vienna, 1090, Austria
    Active, not recruiting

    Not enrolling at this site — choose another above.

  • CHU de Liege
    Liège, 4000, Belgium
    Withdrawn

    Not enrolling at this site — choose another above.

  • University of Alberta Hospital
    Edmonton, Alberta T6G 2G3, Canada
    Recruiting
  • St. Michael's Hospital - Unity Health Toronto
    Toronto, Ontario M5B 1W8, Canada
    Recruiting
  • Necker-Enfants Malades Hospital
    Paris, 75015, France
    Active, not recruiting

    Not enrolling at this site — choose another above.

  • Centre Hospitalier Universitaire (CHU) de Poitiers
    Poitiers, 86000, France
    Active, not recruiting

    Not enrolling at this site — choose another above.

  • Centre Hospitalier Universitaire (CHU) de Toulouse
    Toulouse, 31300, France
    Active, not recruiting

    Not enrolling at this site — choose another above.

  • University Hospital Aachen
    Aachen, 52074, Germany
    Active, not recruiting

    Not enrolling at this site — choose another above.

  • Universitätsklinikum Freiburg
    Freiburg im Breisgau, 79104, Germany
    Active, not recruiting

    Not enrolling at this site — choose another above.

  • UKSH Campus Lubeck
    Lübeck, 23562, Germany
    Withdrawn

    Not enrolling at this site — choose another above.

  • Universitätsklinikum Mannheim
    Mannheim, 68167, Germany
    Active, not recruiting

    Not enrolling at this site — choose another above.

  • IRCCS Azienda Ospedaliero Universitaria di Bologna
    Bologna, 40138, Italy
    Terminated

    Not enrolling at this site — choose another above.

  • Azienda Ospedaliero Universitaria Careggi
    Florence, 50134, Italy
    Withdrawn

    Not enrolling at this site — choose another above.

  • AOU San Giovanni di Dio e Ruggi dAragonia
    Salerno, 84131, Italy
    Active, not recruiting

    Not enrolling at this site — choose another above.

  • Azienda Ospidaleira Universitaria Integrata Verona
    Verona, 37124, Italy
    Withdrawn

    Not enrolling at this site — choose another above.

  • University Medical Center Groningen
    Groningen, 9713, Netherlands
    Active, not recruiting

    Not enrolling at this site — choose another above.

  • Oslo University Hospital
    Oslo, 0450, Norway
    Active, not recruiting

    Not enrolling at this site — choose another above.

  • Public University Hospital No. 1 in Lublin
    Lublin, 20-400, Poland
    Active, not recruiting

    Not enrolling at this site — choose another above.

  • Hospital Universitario Vall d'Hebron
    Barcelona, 08740, Spain
    Active, not recruiting

    Not enrolling at this site — choose another above.

  • Institut Català d'Oncologia - Hospital Duran i Reynals
    Barcelona, 08908, Spain
    Active, not recruiting

    Not enrolling at this site — choose another above.

  • Hospital Universitario Ramón y Cajal
    Madrid, 28034, Spain
    Active, not recruiting

    Not enrolling at this site — choose another above.

  • Universitätsspital Basel
    Basel, 4031, Switzerland
    Recruiting
  • Leeds Teaching Hospitals NHS Trust
    Leeds, LS9 7TF, United Kingdom
    Recruiting
  • University College London Hospital - NHS Foundation Trust
    London, NW1 2BU, United Kingdom
    Recruiting
  • Guy's Hospital - NHS Foundation Trust
    London, SE1 9RT, United Kingdom
    Recruiting
08

References and documents

Individual participant data

Plan to share: No

No publications or documents are linked to this record.

09

Timeline

Tracking since Sep 25, 2026
ElapsedEstimatedEstimated, not yet reached

Ran from Nov 2021 to primary completion in Sep 2025, 46 months.

How these figures are worked out, and which studies are left out of them.

Registered
Jul 22, 2021
First posted
Aug 9, 2021
StartActual
Nov 9, 2021
Primary completionActual
Sep 19, 2025
CompletionEst.
Jul 2027
Results delay requested
Sep 14, 2026
Last update
Sep 15, 2026
What these dates mean
Start.
When the first participant enrolled; while estimated, when the study expects to open to recruitment.
Primary completion.
When the last participant was examined or treated to collect data for the study's main question, its primary outcome. A study that stopped early gives the date its data collection stopped.
Completion.
When the last participant's last visit took place, for every outcome, secondary ones and side effects included: the end of the study. Often later than primary completion, sometimes the same day.
Actual and Est.
Actual means the registry says the date has happened. Est. (estimated) is a date the sponsor plans or expects. It can still move, and the sponsor is expected to change it to actual once it has passed.
No changes since tracking began. The registry record was last updated on Sep 15, 2026, before this site started recording changes on Sep 25, 2026. Its history is on ClinicalTrials.gov ↗
10

Registry details

Key details

Study ID
NCT04996875
Lead sponsor
Cogent Biosciences, Inc.
Responsible party
Sponsor
First posted
Aug 9, 2021
Start date
Nov 9, 2021
Primary completion
Sep 19, 2025
Completion
Jul 2027 (estimated)
Last update
Sep 15, 2026

Study contacts

Cogent Biosciences, Inc.
Contact
ApexInfo@cogentbio.com
617-945-5576
Rachael Easton, MD, Ph.D.
study director · Cogent Biosciences, Inc.

Oversight

Data monitoring committee
Yes
FDA-regulated drug
Yes
FDA-regulated device
No
View the source record on ClinicalTrials.gov ↗

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Studies of the drug tested here: Bezuclastinib

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