An Extension Study of Bomedemstat (IMG-7289/MK-3543) in Participants With Myeloproliferative Neoplasms (IMG-7289-CTP-202/MK-3543-005)

A Multi-Center, Open Label, Extension Study Evaluating the Safety and Efficacy of Bomedemstat for the Treatment of Patients With Myeloproliferative Neoplasms (MPNs) Enrolled in a Prior Bomedemstat Clinical Study

This is a multi-center, open-label extension study to assess the long-term safety and efficacy of bomedemstat administered orally once daily in participants with a Myeloproliferative Neoplasm (MPN) who participated in a prior bomedemstat study such as, but not limited to, IMG-7289-CTP-102/MK-3543-002 (NCT03136185) and IMG-7289-CTP-201/MK-3543-003 (NCT04254978) (referred to hereafter as 'feeder studies').

Study Overview

• Status: Completed
• Conditions: Primary Myelofibrosis; Thrombocythemia, Essential
• Intervention / Treatment: Drug: Bomedemstat

• Study Type: Interventional
• Enrollment (Actual): 81
• Phase: Phase 2

Contacts and Locations

Study Locations

• Australia
  • New South Wales
    • Camperdown, New South Wales, Australia, 2050
      • Royal Prince Alfred Hospital
    • Saint Leonards, New South Wales, Australia, 2065
      • Royal North Shore Hospital
  • Queensland
    • Southport, Queensland, Australia, 4215
      • Gold Coast Hospital and Health Service
  • South Australia
    • Adelaide, South Australia, Australia, 5000
      • Royal Adelaide Hospital
• Germany
  • Essen, Germany, 45147
    • Universittsklinikum Essen
• Hong Kong
  • Hong Kong, Hong Kong
    • Queen Mary Hospital
• Italy
  • Alessandria, Italy, 15121
    • Azienda Ospedaliera SS. Antonio
  • Florence, Italy, 50134
    • Azienda Ospedaliero-Universitaria Careggi - S.O.D. Ematologia (CRIMM)
  • Pavia, Italy, 27100
    • Azienda Ospedaliero Universitaria di Bologna
  • VA
    • Varese, VA, Italy, 2100
      • Ospedale di Circolo-a Fondazione Macchi
• New Zealand
  • Aukland
    • Papatoetoe, Aukland, New Zealand, 2025
      • Middlemore Clinical Trials
    • Takapuna, Aukland, New Zealand, 0622
      • Waitemata District Health Board
• United Kingdom
  • London, United Kingdom, NW1 12G
    • University College London Hospitals NHS Foundation Trust
  • London, United Kingdom, SE1 9RT
    • Guy's and Saint Thomas' NHS Foundation Trus
• United States
  • Florida
    • Miami, Florida, United States, 33136
      • University Of Miami Leonard M. Miller
  • Michigan
    • Ann Arbor, Michigan, United States, 48109
      • University of Michigan
  • Ohio
    • Cleveland, Ohio, United States, 44195
      • Cleveland Clinic Foundation
  • Pennsylvania
    • Pittsburgh, Pennsylvania, United States, 15232
      • UMPC Hillman Cancer Center
  • Washington
    • Seattle, Washington, United States, 98109
      • Fred Hutchinson Cancer Center

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

Inclusion Criteria include, but are not limited to:

• Has completed at least one Treatment Period (TP) in a prior bomedemstat Myeloproliferative Neoplasms (MPN) protocol (such as, but not limited to, IMG-7289-CTP-102/MK-3543-002 (NCT03136185) and IMG-7289-CTP-201/MK-3543-003) (NCT04254978).
• In the estimation of the Investigator, the risk-benefit favors continued dosing with bomedemstat.

Exclusion Criteria:

Exclusion Criteria include, but are not limited to:

• Ongoing participation in another investigational study (except observational studies).
• A history of non-compliance in a prior bomedemstat study (excluding dose suspensions that were medically warranted).
• Current use of a prohibited medication (e.g., romiplostim).
• Medical, psychiatric, cognitive, or other conditions that, in the Investigator's opinion, compromise the patient's safety, ability to give informed consent, or comply with the trial protocol.
• Is pregnant or breastfeeding or plan to become pregnant or breastfeed during the study.
• Women of childbearing potential (WOCBP) and fertile men unwilling to agree to use an approved method of contraception from time of enrollment until 14 days after last bomedemstat dose.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Bomedemstat; All participants will receive bomedemstat via oral capsule daily for 169 days with additional treatment continuing in patients deriving clinical benefit.	Drug: Bomedemstat; Capsule (oral); Other Names: IMG-7289; MK-3543

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Percentage of Participants Who Experience an Adverse Event (AE)	An AE is any undesirable physical, psychological or behavioral effect experienced by a participant during participation in an investigational study, in conjunction with the use of the drug or biologic, whether or not product-related. This includes any clinically significant abnormalities in vital signs and lab values, untoward signs or symptoms experienced by the participant from the time of first dose with bomedemstat under this protocol until completion of the study. The percentage of participants who experienced an AE is presented.	Up to ~32 months
Percentage of Participants Who Discontinue Study Intervention Due to an AE	An AE is any undesirable physical, psychological or behavioral effect experienced by a participant during participation in an investigational study, in conjunction with the use of the drug or biologic, whether or not product-related. This includes any clinically significant abnormalities in vital signs and lab values, untoward signs or symptoms experienced by the participant from the time of first dose with bomedemstat under this protocol until completion of the study. The percentage of participants who discontinued study intervention due to an AE is presented.	Up to ~32 months
Mean Spleen Volume Reduction Based on Spleen Volume Measured by MRI in Participants With MF.	Mean Spleen volume reduction (mL) in participants with MF as measured by central laboratory imaging analysis of MRI (or CT where applicable) approximately every 48 weeks. Per protocol only participants with MF were analyzed for this outcome measure. The change in spleen volume from baseline is presented.	Baseline and Days 169, 339, 509, 679, 849 and 924
Percentage of Participants With ET Who Achieve a Reduction of Platelet Counts to <= 400 K/uL (400 x 10^9/L) in the Absence of New Thromboembolic Events	Blood samples were taken at designated time points to determine platelet count. Percentage of participants with ET who achieve a reduction of platelet counts to <= 400 K/uL (400 x 10^9/L) in the absence of new thromboembolic events is presented.	Baseline and Days 29, 57, 85, 113, 141, 169, 198, 226, 254, 282, 310, 338, 367, 395, 423, 451, 479, 507, 536, 564, 592, 620, and 648

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Participant-reported Symptom Burden Response Rate on the Myeloproliferative Neoplasm Symptom Assessment Form (MPN-SAF) Total Symptom Score (TSS)	The MPN-SAF is a questionnaire to assess symptoms including fatigue, concentration, early satiety, inactivity, night sweats, itching, bone pain, abdominal discomfort, weight loss, and fevers. Participant responses for each symptom is scored on an 11-point scale (0 = absent/as good as it can be to 10 = worst imaginable/as bad as it can be). The MPN-SAF TSS is the summation of all the individual scores on a 100-point scale. The participant-reported symptom burden response rate will be assessed as the change from baseline in the percentage of participants who achieve a ≥50% reduction to the MPN-SAF TSS.	Baseline and up to approximately 3 years
MF Participants: Objective Response Rate (ORR)	ORR is the percentage of participants with Complete Response (CR) or Partial Response (PR) per International Working Group for Myelofibrosis Research and Treatment (IWG-MRT) and European Leukemia Network (ELN) response criteria. For MF participants, CR is, in bone marrow: age-adjusted normocellularity, <5% blasts; ≤grade 1 MF AND hemoglobin (Hb) ≥100 g/L and <upper normal limit (UNL); neutrophil count ≥ 1 x 10^9/L and <UNL; platelet count ≥100 x 10^9/L and <UNL; <2% immature myeloid cells AND resolution of disease symptoms; spleen and liver not palpable; no evidence of extramedullary hematopoiesis. For MF participants, PR is all CR criteria WITH Hb ≥85 but <100 g/L and platelet count ≥50, but <100 x 10^9/L and <UNL OR WITHOUT bone marrow criteria.	Up to approximately 3 years
MF Participants: Duration of Response (DOR)	For participants who demonstrate a confirmed CR or PR, DOR is defined as the time from CR or PR to documented progressive disease (PD) or death. For MF participants, PD is the appearance of a new splenomegaly that is palpable at least 5 cm below the left costal margin (LCM) OR a ≥100% increase in palpable distance, below LCM, for baseline splenomegaly of 5-10 cm OR a 50% increase in palpable distance, below LCM, for baseline splenomegaly of >10 cm OR leukemic transformation confirmed by a bone marrow blast count of ≥20% OR a peripheral blood blast content of ≥20% associated with an absolute blast count of ≥1 x 109/L that lasts for at least 2 weeks.	Up to approximately 3 years
ET Participants: ORR	ORR is the percentage of participants with CR or PR per IWG-MRT and ELN response criteria. For ET participants, CR is durable resolution of disease-related signs, AND platelet count ≤400 x 10^9/L, WBC count <10 x 10^9/L, absence of leukoerythroblastosis, AND without signs of progressive disease, and absence of any hemorrhagic or thrombotic events, AND bone marrow histological remission. For ET participants, PR is all CR criteria WITHOUT bone marrow histological remission.	Up to approximately 3 years
ET Participants: DOR	For participants who demonstrate a confirmed CR or PR, DOR is defined as the time from CR or PR to documented PD or death. For ET participants, PD is transformation into PV, post-ET myelofibrosis, myelodysplastic syndrome, or acute leukemia.	Up to approximately 3 years
Change from Baseline in Spleen Size	Spleen size will be measured by palpation at pre-specified timepoints. The change from baseline in spleen size will be presented.	Baseline and up to approximately 3 years
Change from Baseline in the Mutant (Variant) Allele Burden	Mutant (variant) allele burden will be assessed by genetic testing of germline samples, peripheral blood, and bone marrow at pre-specified timepoints. The change from baseline in the mutant allele burden will be presented.	Baseline and up to approximately 3 years
Change from Baseline in Complete Blood Count (CBC)	CBC will include red and white blood cell (RBC and WBC) and circulating blast cell counts. Blood samples will be taken at pre-specified timepoints to determine CBC. The change from baseline in CBC will be presented.	Baseline and up to approximately 3 years
ET Participants Only: Change from Baseline in the Patient Global Impression of Change (PGIC) Score	The PGIC is a single-score questionnaire and is scored on a scale of 1 to 7. A higher score indicates a worse outcome. The changes from baseline in the PGIC score will be reported.	Baseline and up to approximately 3 years
ET Participants Only: Number of Participants who Experience a Thrombotic or Hemorrhagic Event	The number of participants who experience a thrombotic or hemorrhagic event will be reported	Baseline and up to approximately 3 years

Collaborators and Investigators

• Sponsor: Imago BioSciences, Inc., a subsidiary of Merck & Co., Inc., (Rahway, New Jersey USA)
• Investigators: Study Director: Medical Director, Merck Sharp & Dohme LLC

Publications and helpful links

Helpful Links

• Merck Clinical Trials Information

Study record dates

Study Major Dates

• Study Start (Actual): December 15, 2021
• Primary Completion (Actual): August 22, 2024
• Study Completion (Actual): August 22, 2024

Study Registration Dates

• First Submitted: August 31, 2021
• First Submitted That Met QC Criteria: January 24, 2022
• First Posted (Actual): February 4, 2022

Study Record Updates

• Last Update Posted (Actual): September 22, 2025
• Last Update Submitted That Met QC Criteria: September 17, 2025
• Last Verified: September 1, 2025

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Hematologic Diseases; Blood Coagulation Disorders; Bone Marrow Diseases; Hemorrhagic Disorders; Blood Platelet Disorders; Myeloproliferative Disorders; Hemic and Lymphatic Diseases; Thrombocytosis; Thrombocythemia, Essential; Primary Myelofibrosis; bomedemstat
• Other Study ID Numbers: IMG-7289-CTP-202; 2021-002452-37 (EudraCT Number); MK-3543-005 (Other Identifier: MSD); IMG-7289 (Other Identifier: ImagoBio)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: https://trialstransparency.msdclinicaltrials.com/pdf/ProcedureAccessClinicalTrialData.pdf

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: Yes
• Studies a U.S. FDA-regulated device product: No