A Study of CBX-250 in Participants With Acute Myeloid Leukemia, High-Risk Myelodysplastic Syndrome or Chronic Myelomonocytic Leukemia

NCT ID: NCT06994676

Last Updated: 2025-09-22

Study Results

Results pending

The study team has not published outcome measurements, participant flow, or safety data for this trial yet. Check back later for updates.

Basic Information

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Recruitment Status

RECRUITING

Clinical Phase

PHASE1

Total Enrollment

72 participants

Study Classification

INTERVENTIONAL

Study Start Date

2025-07-16

Study Completion Date

2027-06-30

Brief Summary

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Study CBX-250-001 is a Phase 1, open-label, dose-escalation study of CBX-250 in participants with relapsed/refractory AML, HR-MDS and CMML. Participants aged ≥ 12 years are planned to be enrolled. CBX-250 will initially be investigated on a fixed step-up dosing schedule. CBX-250 will be administered subcutaneously in 28-day cycles, with the first study drug dose administered on Cycle 1, Day 1. Cycle 1 will consist of a priming phase over 7 days, and a target phase over 28 days. Participants will continue CBX-250 until progressive disease (PD) or unacceptable toxicity. All subsequent treatment cycles will be 28 days.

Detailed Description

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Conditions

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High-risk Myelodysplastic Syndrome Chronic Myelomonocytic Leukemia (CMML) AML - Acute Myeloid Leukemia

Study Design

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Allocation Method

NA

Intervention Model

SEQUENTIAL

Primary Study Purpose

TREATMENT

Blinding Strategy

NONE

Study Groups

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CBX-250

subcutaneous CBX-250

Group Type EXPERIMENTAL

CBX-250

Intervention Type DRUG

subcutaneous CBX-250

Interventions

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CBX-250

subcutaneous CBX-250

Intervention Type DRUG

Eligibility Criteria

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Inclusion Criteria

Participants are eligible to be included in the study only if all of the following criteria apply:

Age

1. Dose Escalation: Male or female participants aged ≥18 years.
2. Backfill Cohorts: Male or female participants aged ≥12 years for whom no curative treatment options, including transplantation, are available.

Diagnosis \& Disease Characteristics
3. Participants with histological confirmation of advanced hematologic malignancy including:

1. R/R AML, as defined by standardized criteria (e.g., European LeukemiaNet criteria \[Dohner 2022\]; after standard of care therapy. Participants with persistent leukemia after initial therapy or with recurrence of leukemia at any time after achieving a response during or after the course of treatment (including HSCT) are eligible.
2. R/R HR-MDS or very high risk MDS as per the Revised International Prognostic Scoring System (IPSS-R; Greenberg 2012) or Molecular International Prognostic Scoring System (IPPS-M, Bernard 2022) who are resistant or refractory to 4-6 cycles of hypomethylating agents (HMA; decitabine or azacitidine).
3. R/R CMML who are resistant or refractory to 4-6 cycles of hypomethylating agents (HMA; decitabine or azacitidine).
4. White blood cells must be below 25,000/µL at time of enrollment. Participants may receive cytoreduction prior to enrollment.
5. Historical documented evidence of HLA-A\*02:01 allele positivity.

Performance Level
6. ECOG PS score 0-1 (if aged ≥18 years); Karnofsky Performance Scale of ≥70 (if aged ≥16 years and \<18 years); Lansky PS of ≥70 (if aged \<16 years).

Prior Therapy
7. Any prior treatment-related toxicities resolved to ≤Grade 1 prior to enrollment, with the exception of ≤Grade 2 alopecia.
8. Radiation Therapy: At least 60 days from prior total body irradiation, craniospinal radiation and/or ≥50% radiation of the pelvis, or at least 14 days from local palliative radiation therapy (small port).
9. Stem Cell Infusion: At least 60 days must have elapsed from HSCT and at least 4 weeks (from first dose) must have elapsed from donor lymphocyte infusion without conditioning.
10. Immunotherapy: At least 42 days since prior immunotherapy, including tumor vaccines and checkpoint inhibitors, and at least 21 days since receipt of chimeric antigen receptor therapy.
11. Anti-Leukemia Therapy: At least 14 days since the completion of anti-leukemic therapy (for example, but not limited to, small molecule or cytotoxic/myelosuppressive therapy), with the following exceptions:

* Hydroxyurea for cytoreduction can be initiated without restriction related to timing of study entry. Hydroxyurea for cytoreduction can be continued concomitantly with CBX-250, with Study Responsible Physician approval.
* Intrathecal chemotherapy at the time of diagnostic lumbar puncture at least 24 hours prior to the start of CBX-250 and may continue prophylactic intrathecal chemotherapy beginning in Cycle 2, at the treating physician's discretion.
12. Hematopoietic Growth Factors: At least 7 days since the completion of therapy with short-acting hematopoietic growth factors and 14 days with long-acting growth factors.
13. Biologics (e.g. monoclonal antibody therapy): At least 28 days or 5 half-lives, whichever is shorter, have elapsed since the completion of therapy with a biologic agent. Any AE related to prior biologic treatment must be resolved to baseline severity or ≤Grade 1.
14. Steroids: At least 7 days since systemic glucocorticoid therapy, unless receiving physiologic dosing (equivalent to ≤10 mg prednisone daily) or cytoreductive therapy. Cytoreductive therapy must have approval of the Study Responsible Physician.

Adequate Organ Function Requirements within 10 Days of Treatment Initiation
15. Estimated glomerular filtration rate ≥ 45 mL/min/1.73 m2 based on local institutional practice for age-appropriate determination (eg, Schwartz formula for pediatric participants or Cockcroft-Gault formula for adults).

1. Participants ≥18 years: glomerular filtration rate ≥45 mL/min
2. Participants \<18 years: ≥45 mL/min x (participant's body surface area m2/1.73) • Adequate liver function defined as:

* Total bilirubin \<1.5 × the upper limit of normal (ULN) for age or normal conjugated bilirubin, or total bilirubin ≤ 3.0 x ULN with direct bilirubin within normal range in participants with well documented Gilbert's syndrome or hemolysis or who require regular blood transfusions.
* Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) \<3 × ULN (unless attributed to leukemic involvement with discussion with the Study Responsible Physician).

Sex and Contraceptive/Barrier Requirements
16. If a female of childbearing potential, willing to use a highly effective method of contraception or double barrier method from the time of enrollment through 120 days following the last study drug dose.
17. If male of childbearing potential, agrees to use barrier contraception from the time of enrollment through 120 days following the last study drug dose.

Informed Consent
18. Participant or participant's health care proxy is able and willing to provide written informed consent and able to follow study instructions.

Exclusion Criteria

Participants are excluded from the study if any of the following criteria apply:

Diagnosis

1. Previous CTSG targeted therapy or treatment with any pMHC T-cell engager.
2. Isolated extramedullary relapse.
3. Active central nervous system (CNS) disease. Participants with prior CNS history can be enrolled if the participant has a negative lumbar puncture following completion of intrathecal chemotherapy).

Infection
4. Known HIV infection.
5. Active hepatitis B infection (participants with documented clearance following treatment are allowed).
6. Active hepatitis C infection (participants with documented clearance following treatment are allowed).

Pregnancy and Breastfeeding
7. Pregnant or nursing women: Negative serum pregnancy tests are required during Screening and a negative serum or urine pregnancy test is required within 72 hours prior to receiving the first study drug administration, in females of childbearing potential. If the urine test is positive or cannot be confirmed as negative, a serum pregnancy test will be required.

Concurrent Conditions
8. Cardiac Disease:

* Any of the following within the 6 months prior to study entry: myocardial infarction, uncontrolled/unstable angina, congestive heart failure (New York Heart Association Classification Class \>II), life-threatening, uncontrolled arrhythmia, cerebrovascular accident, or transient ischemic attack.
* QTc using Fridericia's correction (QTcF) \>480 msec
9. Graft-Versus-Host Disease (GVHD): Active acute or chronic GVHD requiring systemic treatment with immunosuppressive medication. Participants may be on physiological doses of steroids.
10. Concurrent malignancy in the previous 2 years with the exception of basal cell carcinoma of the skin, squamous cell carcinoma of the skin, or carcinoma in situ (eg, breast carcinoma, cervical cancer in situ, melanoma in situ) treated with potentially curative therapy. Concurrent malignancy must be in CR or no evidence of disease (NED) during this timeframe.
11. History of or any concurrent condition, therapy, or laboratory abnormality that in the Investigator's opinion might confound the results of the study, interfere with the participant's participation for the full duration of the study, or is not in the best interest of the participant to participate.

Concomitant Medications and Interventions
12. Any commercially available or investigational anti-leukemic therapy other than CBX-250, with the following exceptions:

• Intrathecal chemotherapy for CNS prophylaxis is permitted after C1 is complete, at the treating physician's discretion.
13. Participation in another therapeutic interventional clinical study in which an investigational agent was administered within 14 days or 5-halflives, whichever is shorter, of starting CBX-250. Participants may continue with non-interventional follow-up from previous clinical studies.
14. Any concurrent systemic treatment to prevent GVHD. Topical treatments for GVHD are permitted.
15. Known allergy or sensitivity to study drug, including excipients.
Minimum Eligible Age

12 Years

Eligible Sex

ALL

Accepts Healthy Volunteers

No

Sponsors

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Crossbow Therapeutics, Inc.

INDUSTRY

Sponsor Role lead

Responsible Party

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Responsibility Role SPONSOR

Principal Investigators

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Briggs Morrison, MD

Role: STUDY_CHAIR

Crossbow Therapeutics, Inc.

Locations

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City of Hope

Duarte, California, United States

Site Status RECRUITING

Moffitt Cancer Center

Tampa, Florida, United States

Site Status RECRUITING

Washington University in St. Louis

St Louis, Missouri, United States

Site Status RECRUITING

Memorial Sloan Kettering Cancer Center

New York, New York, United States

Site Status RECRUITING

Sarah Cannon Cancer Institute

Nashville, Tennessee, United States

Site Status RECRUITING

Vanderbilt University Medical Center

Nashville, Tennessee, United States

Site Status RECRUITING

MD Anderson Cancer Center

Houston, Texas, United States

Site Status RECRUITING

Countries

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United States

Central Contacts

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Rachel Ghiraldi

Role: CONTACT

857-301-6432

Facility Contacts

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Mariah Santoscoy

Role: primary

626-218-2927

Morgan Swanner

Role: primary

314-454-8304

Eytan Stein, MD

Role: primary

askSARAH

Role: primary

844-482-4812

Somedeb Ball, MD

Role: primary

615-322-8973

Ghayas Issa, MD

Role: primary

713-745-6798

Other Identifiers

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CBX-250-001

Identifier Type: -

Identifier Source: org_study_id

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