CSF-1R Inhibitor, Axatilimab, for Prevention of Acute and Chronic GVHD After HLA-Matched Related and Unrelated Donor Allogeneic Stem Cell Transplantation (ABRAXAS)

Phase II Open-Label, Randomized-Controlled Trial of CSF-1R Inhibitor, Axatilimab, for Prevention of Acute and Chronic GVHD After HLA-Matched Related and Unrelated Donor Allogeneic Stem Cell Transplantation

This is a randomized, multisite, Phase II study designed to compare the 1-year GVHD-free survival of the control arm (no axatilimab) to the experimental arm (axatilimab) after myeloablative allogeneic HCT.

Study Overview

• Status: Not yet recruiting
• Conditions: Graft -Versus-host-disease
• Intervention / Treatment: Procedure: Hematopoietic Cell Transplantation; Drug: Cyclophosphamide; Drug: Tacrolimus; Drug: Mycophenolate Mofetil (MMF); Drug: Axatilimab

Detailed Description

This study will determine if axatilimab in combination with standard of care posttransplant cyclophosphamide + tacrolimus/mycophenolate mofetil is safe, tolerable, and efficacious as GVHD prophylaxis in a population of adult patients with hematologic malignancies receiving a first HLA-matched related or unrelated donor myeloablative allogeneic HCT.

• Study Type: Interventional
• Enrollment (Estimated): 72
• Phase: Phase 2

Contacts and Locations

• Study Contact: Name: Medical College of Wisconsin Cancer Center Clinical Trials Office; Phone Number: 8900 866-680-0505; Email: cccto@mcw.edu

Study Locations

• United States
  • Wisconsin
    • Milwaukee, Wisconsin, United States, 53226
      • Froedtert & the Medical College of Wisconsin
      • Contact: Sameem Abedin, MD; Phone Number: 414-805-4600; Email: sabedin@mcw.edu
      • Principal Investigator: Sameem Abedin, MD

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Age ≥18 years.

• Patients with a history of a hematologic malignancy with a planned myeloablative conditioning (MAC) peripheral blood allogeneic HCT.

  a. Note: Patients with acute leukemia must be in morphologic complete remission with or without hematologic recovery with ≤5% blasts in the bone marrow. Patients with Chronic Myelomonocytic Leukemia (CMML) must have a white blood cell (WBC) count ≤10,000 cells/µL and ≤5% blasts in the marrow. Patients with ≥5% blasts due to a regenerating marrow must contact the protocol chairs for review. Patients with a diagnosis of myelofibrosis require sponsor approval before enrolling.

• Patients must be receiving an allograft from a suitable HLA-matched sibling or (7/8 or 8/8) unrelated donor according to transplant center's guidelines (for selection of appropriate donor).

• The following laboratory values obtained ≤14 days prior to registration/randomization:

  1. Total bilirubin ≤1.5 x ULN or total bilirubin ≤3.0 x the Upper Limit of Normal (ULN) in the presence of Gilbert's syndrome. If total bilirubin is abnormal (≥1.5 x ULN), assess direct bilirubin. NOTE: Patients with Gilbert Syndrome and elevated baseline unconjugated (indirect) bilirubin up to 3.0 mg/dL are eligible. Gilbert syndrome should be confirmed by the presence of UGT1A1*28 variant.
  2. Alanine aminotransferase (ALT) and aspartate transaminase (AST) ≤2.5 x ULN).
  3. Calculated creatinine clearance ≥30 mL/min using the Cockcroft-Gault formula below:

Creatinine clearance for males = (140 - age)(weight in kg) /(72)(serum creatinine in mg⁄dL) Creatinine clearance for females = (140 - age)(weight in kg) (0.85) /(72)(serum creatinine in mg⁄dL)

• Negative serum pregnancy test done ≤7 days prior to registration/randomization, for persons of childbearing potential only.

• Sexually active patients and their partners must use an effective method of contraception associated with a low failure rate prior to study entry and for the duration of study participation and for at least 3 months after the last dose of study drug.

  a. Note: The following are considered effective contraceptives: oral contraceptive pill; condom plus spermicide; diaphragm plus spermicide; patient or partner surgically sterile; patient or partner more than 12 months postmenopausal; or injectable or implantable agent/device. Male patients should refrain from sperm donation and female patients should refrain from breastfeeding throughout this period.

• Ability to understand and provide written informed consent at the time of initial study enrollment. Participants who later lose decisional capacity may remain on study with consent from a legally authorized representative (LAR), as applicable.
• Willingness to provide mandatory blood and bone marrow aspirate specimens for correlative research.
• Willing to return to enrolling institution for follow-up (during the Active Monitoring Phase of the study).

Exclusion Criteria:

• Any of the following because this study involves an investigational agent whose genotoxic, mutagenic, and teratogenic effect on the developing fetus and newborn are unknown:

  1. Pregnant persons.
  2. Nursing persons.
  3. Persons of childbearing potential, and persons able to father a child, who are unwilling to employ adequate contraception.

• Any of the following current or prior therapies:

  1. Patients receiving a cord blood transplant.
  2. Patients undergoing a T-cell depleted allogeneic transplantation (using ex vivo CD34 selection, or with serotherapy [antithymocyte globulin or alemtuzumab]).
  3. Patients undergoing a second allogeneic transplant (after a previous allogeneic transplant).
  4. Pre-planned treatment with JAK1/JAK2 inhibitor after transplant.
  5. Previous exposure to axatilimab.
  6. Receiving an investigational treatment ≤28 days prior to registration/randomization.
  7. Major surgery ≤3 weeks prior to registration/randomization.
  8. Chemotherapy ≤2 weeks prior to registration/randomization unless chemotherapy is part of the pre-transplant conditioning.
  9. Radiation therapy ≤2 weeks prior to registration/randomization unless radiation is part of the pre-transplant conditioning.
  10. Planned use of Donor Lymphocyte Infusion (DLI) therapy.
  11. Exception: Use of maintenance regimens as routine clinical care will be permitted but must be declared prior to registration/randomization. The trial does not restrict subsequent treatment after meeting the GFS endpoint.
• Active central nervous system (CNS) involvement by malignant cells.
• Leukemia involvement in the CNS ≤4 weeks of registration for patients with a history of prior CNS leukemia involvement (i.e., leukemic blasts previously detected in the cerebral spinal fluid).
• History of acute or chronic pancreatitis.
• History of myositis.
• Co-morbid systemic illnesses or other severe concurrent disease which, in the judgment of the investigator, would make the patient inappropriate for entry into this study or interfere significantly with the proper assessment of safety and toxicity of the prescribed regimens.

• Patients with active hepatitis B or C.

  a. Patients with a history of hepatitis B or C are allowed if HBV DNA or HCV RNA are undetectable.

• Any known infection with human immunodeficiency virus (HIV), HTLV-1.
• Uncontrolled bacterial, viral, or fungal infections (currently taking medication and with progression or no clinical improvement) at the time of registration/randomization.
• Psychiatric illness/social situations that would limit compliance with study requirements.
• Diagnosed with another malignancy (other than malignancy for which transplant was performed) ≤ 3 years of registration/randomization, unless previously treated with curative intent and approved by PI (e.g., but not limited to completely resected basal cell, squamous cell, or ductal carcinoma in situ, or low-risk prostate cancer after curative resection or on watchful waiting). In patients with transformed disease (e.g. aggressive lymphoma evolving from CLL, or acute leukemia from MDS), the original hematological disorder is not considered an exclusion. Cancer treated with curative intent <3 years previously will not be allowed unless approved by any of the Study Chairs.
• History of myocardial infarction ≤6 months, or New York Heart Association (NYHA) Class III or IV heart failure, uncontrolled angina, severe uncontrolled ventricular arrhythmias, or electrocardiographic evidence of acute ischemia.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: None (Open Label)

Number of Arms

3

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Safety Run-in; An early safety analysis will be performed after the first 6 evaluable patients have been accrued to Dose Level 1 of the study and observed for four cycles of axatilimab (Cycles 1-4). Accrual will be temporarily halted while these patients are evaluated. If 2 or more of the first 6 patients experience a significant toxicity, then the protocol may be amended and the dose of axatilimab may be de-escalated to Dose Level -1.	Procedure: Hematopoietic Cell Transplantation; Subjects will receive a first HLA-matched related or (7/8 or 8/8) unrelated donor myeloablative allogeneic HCT.; Drug: Cyclophosphamide; Cyclophosphamide will be given on Day +3 and Day +4 per institutional practices, at a dose of 50 mg/kg IBW. Cyclophosphamide will be given as an IV infusion over 1-2 hours (depending on volume), or according to institutional standards.; Other Names: Cytoxan; Neosar; cytophosphane; Drug: Tacrolimus; Tacrolimus will be given per institutional practices, starting on Day +5. Subsequent dosing will be based on blood levels per institutional guidelines with a suggested range of 5-12 ng/mL.; Drug: Mycophenolate Mofetil (MMF); Mycophenolate mofetil (MMF) will be given per institutional practices, at a dose of 15 mg/kg three times daily (TID; based upon actual body weight) with the maximum total daily dose not to exceed 3 grams (1g TID, IV or PO). MMF prophylaxis will start Day +5 and continue until Day +35 post-transplant, at which time it should be discontinued (no taper necessary).; Drug: Axatilimab; The dose is dependent on the results of the safety run-in. The starting dose of the safety run-in is 0.3 mg/kg (maximum of 35 mg). If Dose Level 1 has an unacceptable level of toxicity (≥2 patients having significant toxicity), then axatilimab may be de-escalated to 0.2 mg/kg (maximum of 23 mg).; Other Names: Niktimvo; axatilimab-csfr
Experimental: Axatilimab Treatment; Starts 35 (±5) days from stem cell transplant; Dosing will occur every 14 days for a maximum of 12 cycles.	Procedure: Hematopoietic Cell Transplantation; Subjects will receive a first HLA-matched related or (7/8 or 8/8) unrelated donor myeloablative allogeneic HCT.; Drug: Cyclophosphamide; Cyclophosphamide will be given on Day +3 and Day +4 per institutional practices, at a dose of 50 mg/kg IBW. Cyclophosphamide will be given as an IV infusion over 1-2 hours (depending on volume), or according to institutional standards.; Other Names: Cytoxan; Neosar; cytophosphane; Drug: Tacrolimus; Tacrolimus will be given per institutional practices, starting on Day +5. Subsequent dosing will be based on blood levels per institutional guidelines with a suggested range of 5-12 ng/mL.; Drug: Mycophenolate Mofetil (MMF); Mycophenolate mofetil (MMF) will be given per institutional practices, at a dose of 15 mg/kg three times daily (TID; based upon actual body weight) with the maximum total daily dose not to exceed 3 grams (1g TID, IV or PO). MMF prophylaxis will start Day +5 and continue until Day +35 post-transplant, at which time it should be discontinued (no taper necessary).; Drug: Axatilimab; The dose is dependent on the results of the safety run-in. The starting dose of the safety run-in is 0.3 mg/kg (maximum of 35 mg). If Dose Level 1 has an unacceptable level of toxicity (≥2 patients having significant toxicity), then axatilimab may be de-escalated to 0.2 mg/kg (maximum of 23 mg).; Other Names: Niktimvo; axatilimab-csfr
Experimental: No Axatilimab Treatment; Starts 35 (±5) days from stem cell transplant.	Procedure: Hematopoietic Cell Transplantation; Subjects will receive a first HLA-matched related or (7/8 or 8/8) unrelated donor myeloablative allogeneic HCT.; Drug: Cyclophosphamide; Cyclophosphamide will be given on Day +3 and Day +4 per institutional practices, at a dose of 50 mg/kg IBW. Cyclophosphamide will be given as an IV infusion over 1-2 hours (depending on volume), or according to institutional standards.; Other Names: Cytoxan; Neosar; cytophosphane; Drug: Tacrolimus; Tacrolimus will be given per institutional practices, starting on Day +5. Subsequent dosing will be based on blood levels per institutional guidelines with a suggested range of 5-12 ng/mL.; Drug: Mycophenolate Mofetil (MMF); Mycophenolate mofetil (MMF) will be given per institutional practices, at a dose of 15 mg/kg three times daily (TID; based upon actual body weight) with the maximum total daily dose not to exceed 3 grams (1g TID, IV or PO). MMF prophylaxis will start Day +5 and continue until Day +35 post-transplant, at which time it should be discontinued (no taper necessary).

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
GVHD-free survival	A patient will be considered a success for 1-year GVHD-free survival if they are alive without Grade 3 or 4 acute GVHD or systemic immunosuppression requiring chronic GVHD at one year post transplant. Death, Grade 3 or 4 acute GVHD, and immunosuppression-requiring chronic GVHD (of any severity) prior to 1 year will be considered as events.	1 Year Post HCT

Collaborators and Investigators

• Sponsor: Medical College of Wisconsin
• Investigators: Principal Investigator: Sameem Abedin, MD, Medical College of Wisconsin; Study Chair: Mehdi Hamadani, MD, Medical College of Wisconsin

Study record dates

Study Major Dates

• Study Start (Estimated): November 1, 2026
• Primary Completion (Estimated): November 1, 2031
• Study Completion (Estimated): November 1, 2031

Study Registration Dates

• First Submitted: September 3, 2026
• First Submitted That Met QC Criteria: September 3, 2026
• First Posted (Actual): September 8, 2026

Study Record Updates

• Last Update Posted (Actual): September 8, 2026
• Last Update Submitted That Met QC Criteria: September 3, 2026
• Last Verified: September 1, 2026

More Information

Terms related to this study

• Keywords: hematologic malignancy; myeloablative allogeneic hematopoietic cell transplantation
• Additional Relevant MeSH Terms: Neoplasms by Site; Neoplasms; Immune System Diseases; Hematologic Diseases; Hemic and Lymphatic Diseases; Hematologic Neoplasms; Graft vs Host Disease; Organic Chemicals; Therapeutics; Fatty Acids; Lipids; Surgical Procedures, Operative; Hydrocarbons; Acids, Acyclic; Carboxylic Acids; Transplantation; Macrolides; Lactones; Phosphoramide Mustards; Nitrogen Mustard Compounds; Mustard Compounds; Hydrocarbons, Halogenated; Phosphoramides; Organophosphorus Compounds; Cell Transplantation; Cell- and Tissue-Based Therapy; Biological Therapy; Caproates; Cyclophosphamide; Mycophenolic Acid; Tacrolimus; Stem Cell Transplantation; axatilimab
• Other Study ID Numbers: IIT-HAMADANI-ABRAXAS

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

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