NCT07779798 · Crossbow Therapeutics, Inc.
A Phase 1, Open-Label, Dose-Escalation Study to Evaluate Safety, Tolerability, and Clinical Activity of CBX-663 in Participants With Relapsed or Refractory Myeloid Malignancies, Advanced Solid Tumors, or Recurrent or Progressive Glioblastoma.
(TelOscope)
What this study is about
This is a Phase 1, where both patients and doctors know the treatment given, gradually increasing doses study of CBX-663 in participants with R/R AML, MDS or CMML (group of participants A), advanced solid tumors (group of participants B), or recurrent or progressive GBM (group of participants C) (collectively called 'indication cohorts'). Participants aged ≥18 years are planned to be enrolled.
View original scientific description
This is a Phase 1, open-label, dose-escalation study of CBX-663 in participants with R/R AML, MDS or CMML (Cohort A), advanced solid tumors (Cohort B), or recurrent or progressive GBM (Cohort C) (collectively called 'indication cohorts'). Participants aged ≥18 years are planned to be enrolled. CBX-663 will initially be investigated on a fixed dosing schedule. CBX-663 will be administered intravenously (IV) on Cycle 1 Day 1 (C1D1) and then once weekly (QW) in 21-day cycles. Participants will continue treatment with CBX-663 until unacceptable toxicity, progressive disease, withdrawal of consent, or lack of clinical benefit.
Interventions
DRUG
CBX-663
Intravenous (I.V.) CBX-663
Primary outcome measures
Recommended Phase 2 Dose (RP2D)
Time frame: Until the end of study (approximately 24 months)
To determine the RP2D.
To determine safety and tolerability of CBX-663; Dose Limiting Toxicities (DLTs), Treatment-Emergent Adverse Events (TEAEs) and Treatment-Related Adverse Events (TRAEs).
Time frame: From enrollment through 30 days following end of treatment.
Frequency and type of dose-limiting toxicities (DLT), Frequency, duration, and severity of treatment-emergent adverse events (TEAEs), treatment-related AEs (TRAEs), and serious adverse events (SAEs), Frequency and severity of cytokine release syndrome (CRS) adverse events (AEs), Withdrawal from the study, drug discontinuations, drug interruptions, or dose reductions due to adverse events Incidence/shifts of clinical laboratory abnormalities
To assess the PK of CBX-663: AUC0-t
Time frame: Approximately 1 year.
Area under the plasma concentration-time curve from time 0 to time of last measurable concentration (AUC0-t) of CBX-663 and relevant metabolites.
To assess the PK of CBX-663: Cmax
Time frame: Approximately 1 year.
Maximum plasma concentration (Cmax) of CBX-663 and relevant metabolites.
To assess the PK of CBX-663: Tmax
Time frame: Approximately 1 year.
Time to observed maximum plasma concentration of CBX-663 and relevant metabolites
To assess the PK of CBX-663: Ctau
Time frame: Approximately 1 year.
CBX-663 drug concentration at the end of the dosing interval.
To assess the PK of CBX-663: T½
Time frame: Approximately 1 year.
Terminal elimination half-life of CBX-663.
To assess the PK of CBX-663: Degree of accumulation
Time frame: Approximately 1 year.
Degree of CBX-663 accumulation in the blood stream and body.
To assess the preliminary anti-leukemic activity of CBX-663 in participants with R/R AML (Cohort A):
Time frame: From enrollment through 30 days following end of treatment
Objective response rate (ORR), complete response (CR), CR with partial hematologic recovery (CRh), CR with incomplete hematologic recovery (CRi) (Dohner, 2022) CR rate (CR+CRh) CRc Rate (CR+ CRh + CRi)
To assess the preliminary anti-leukemic activity of CBX-663 in participants with R/R CMML (Cohort A)
Time frame: From enrollment through 30 days following end of treatment.
Response criteria for CMML: evaluated per IWG 2015 (Savona, 2015) in adults with endpoints including CR, PR, complete cytogenetic remission, marrow response and clinical benefit as appropriate
To assess the preliminary anti-leukemic activity of CBX-663 in participants with R/R MDS (Cohort A):
Time frame: From enrollment through 30 days following end of treatment.
Best Overall Response (BOR) as defined by MDS/MPN International Working Group (IWG) 2023 (Zeidan, 2023) for Higher-Risk MDS and IWG 2018 (Platzbecker, 2019) for Lower-Risk MDS
To assess the preliminary anti-leukemic activity of CBX-663 in participants in Cohort A: Duration of Response (DoR)
Time frame: From enrollment through 30 days following end of treatment.
To assess the duration of response (DoR) of CBX-663.
To assess the preliminary anti-leukemic activity of CBX-663 in participants in Cohort A: Time to Response (TTR)
Time frame: From enrollment through 30 days following end of treatment.
To assess the time to response (TTR) of CBX-663.
To assess the preliminary anti-leukemic activity of CBX-663 in participants with R/R AML, MDS or CMML (Cohort A): CRminimal residual disease (MRD)- rate for participants with CRc.
Time frame: From enrollment through 30 days following end of treatment.
To assess the CRminimal residual disease (MRD)- rate for participants with CRc of CBX-663.
To assess the preliminary anti-leukemic activity of CBX-663 in Cohort A: Hematologic Improvement (HI)
Time frame: From enrollment through 30 days following end of treatment.
HI defined as: * Not meeting criteria for CR (or CR equivalent) or CRuni or CRL * HIerythroid (HI-E) * HIplatelets (HI-P) * HIneutrophils (HI-N)
To assess the preliminary anti-leukemic activity of CBX-663 in Cohort A: Transfusion Independence
Time frame: From enrollment through 30 days following end of treatment.
Transfusion independence defined as any transfusion-free period lasting for at least 56 consecutive days, during which the participant is either on CBX-663 therapy or after cessation of CBX-663 therapy but prior to the start of new therapy.
To assess the preliminary anti-leukemic activity of CBX-663 in Cohort A: Transfusion burden reduction
Time frame: From enrollment through 30 days following end of treatment.
To assess the transfusion burden reduction of CBX-663.
To assess the preliminary anti-leukemic activity of CBX-663 in Cohort A: Rate of leukemic transformation
Time frame: From enrollment through 30 days following end of treatment.
To assess the rate of leukemic transformation of CBX-663.
To assess the preliminary anti-leukemic activity of CBX-663 in Cohort A: Event free survival (EFS)
Time frame: From enrollment through 30 days following end of treatment.
To assess the Event free survival (EFS) of CBX-663.
To assess the preliminary anti-leukemic activity of CBX-663 in Cohort A: Overall Survival (OS)
Time frame: From enrollment through 30 days following end of treatment.
To assess the Overall Survival (OS) of CBX-663.
To assess the preliminary anti-tumor activity of CBX-663 in Cohort B based on Investigator assessment using Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1 criteria: Overall Response Rate (ORR)
Time frame: From enrollment through 30 days following the end of treatment.
To assess overall response rate (ORR) of CBX-663.
To assess the preliminary anti-tumor activity of CBX-663 in Cohort B based on Investigator assessment using Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1 criteria: Duration of Response (DoR)
Time frame: From enrollment through 30 days following end of treatment.
To assess duration of response of CBX-663.
To assess the preliminary anti-tumor activity of CBX-663 in Cohort B based on Investigator assessment using Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1 criteria: Time to Response (TTR)
Time frame: From enrollment through 30 days following end of treatment.
To assess time to response (TTR) of CBX-663.
To assess the preliminary anti-tumor activity of CBX-663 in Cohort B based on Investigator assessment using Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1 criteria: Disease Control Rate (DCR)
Time frame: From enrollment through 30 days following end of treatment.
To assess disease control rate (DCR) of CBX-663.
To assess the preliminary anti-tumor activity of CBX-663 in Cohort B based on Investigator assessment using Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1 criteria: Progression Free Survival (PFS)
Time frame: From enrollment through 30 days following end of treatment.
To assess progression free survival (PFS) of CBX-663.
To assess the preliminary anti-tumor activity of CBX-663 in Cohort B based on Investigator assessment using Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1 criteria: Overall Survival (OS)
Time frame: From enrollment through 30 days following end of treatment.
To assess overall survival (OS) of CBX-663.
To assess the preliminary anti-tumor activity of CBX-663 in participants with recurrent/progressive GBM (Cohort C): Overall Response Rate (ORR)
Time frame: From enrollment through 30 days following the end of treatment.
To assess the overall response rate (ORR) per Response Assessment in Neuro-Oncology (RANO) Criteria 2.0 (Wen 2023) and iRANO
To assess the preliminary anti-tumor activity of CBX-663 in Cohort C: Duration of Response (DoR)
Time frame: From enrollment through 30 days following end of treatment.
To assess duration of response (DoR) of CBX-663.
To assess the preliminary anti-tumor activity of CBX-663 in Cohort C: Time to Response (TTR)
Time frame: From enrollment through 30 days following end of treatment.
To assess time to response (TTR) of CBX-663.
To assess the preliminary anti-tumor activity of CBX-663 in Cohort C: Disease Control Rate (DCR)
Time frame: From enrollment through 30 days following end of treatment.
To assess disease control rate of CBX-663.
To assess the preliminary anti-tumor activity of CBX-663 in Cohort C: Progression Free Survival (PFS)
Time frame: From enrollment through 30 days following end of treatment.
To assess progression free survival (PFS) of CBX-663.
To assess the preliminary anti-tumor activity of CBX-663 in Cohort C: Overall Survival (OS)
Time frame: From enrollment through 30 days following end of treatment.
To assess overall survival (OS) of CBX-663.
To assess the preliminary anti-tumor activity of CBX-663 in Cohort C: Changes in Corticosteroid Use
Time frame: From enrollment through 30 days following end of treatment.
To assess changes in corticosteroid use in participants with GBM.
To assess the preliminary anti-tumor activity of CBX-663 in Cohort C: Changes in neurologic function as assessed by the Neurological Assessment in Neuro-Oncology scale
Time frame: From enrollment through 30 days following end of treatment.
To assess changes in neurologic function as assessed by the Neurological Assessment in Neuro-Oncology scale in participants with GBM.
Who can participate
This study lists these criteria on ClinicalTrials.gov. A study coordinator reviews eligibility during screening — this page does not determine whether you qualify.
Inclusion criteria
- Cohort A (R/R AML, MDS or CMML) Specific Inclusion Criteria:
- R/R AML, as defined by standardized criteria (e.g., European Leukemia Net criteria (Dohner, 2022) (Arber, 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. Participants must have bone marrow blasts ≥5%.
- R/R MDS as per WHO 2022. Participants must have peripheral or bone marrow blasts \<20%, and must have exhausted locally available treatments, including treatments for actionable mutations. a. For High-Risk MDS participants, participants must be resistant to or refractory to at least 4 cycles of hypomethylating agents or have progressed or are intolerant to such agents.
- R/R dysplastic or proliferative CMML participants, participants must be resistant or refractory to 4-6 cycles of hypomethylating agents (HMA; decitabine or azacitidine).
- White blood cells must be below 25,000/µL at time of enrollment. Participants may receive cytoreduction prior to enrollment.
- Any prior treatment-related toxicities resolved to Grade ≤1 prior to enrollment, with the exception of Grade ≤2 alopecia. Cohort B (Solid Tumor) Specific Inclusion Criteria:
- Histologically or cytologically diagnosed, locally advanced (unresectable) or metastatic solid cancers that have progressed after all available standard therapy for the specific tumor type, or for which no standard therapy exists. Participants for whom standard therapies are intolerable or considered inappropriate by the Investigator are eligible.
- Measurable disease (as defined by RECIST version 1.1). Prior Therapy
- Any prior treatment-related toxicities resolved to Grade ≤1 prior to enrollment, with the exception of Grade ≤2 alopecia.
- 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.
- 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.
- Anti-Cancer Therapy: Chemotherapy or small molecule targeted therapy, either investigational or commercially approved and available, within 2 weeks or 5 half-lives (whichever is shorter) prior to the start of study drug administration.
- 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). Cohort C (Recurrent/Progressive GBM) Specific Inclusion Criteria:
- Histologically confirmed or molecularly defined diagnosis of glioblastoma (IDH-wildtype) according to WHO 2021.
- Historical documented evidence of a TERT promoter mutation.
- Radiographic evidence of recurrent or progressive disease following prior first-line radiotherapy, defined as progression per RANO 2.0 criteria, as determined by investigator assessment. Prior use of tumor-treating fields is allowed but not required (Wen, 2023).
- Measurable (at least 1 cm x 1 cm) enhancing tumor.
- Any prior treatment-related toxicities resolved to ≤Grade 1 prior to enrollment, with the exception of ≤Grade 2 alopecia and ≤Grade 2 fatigue. Inclusion Criteria for All Participants:
- Aged ≥18 years.
- Backfill Cohorts: Participants for whom no curative treatment options, including transplantation, are available.
- Historical documented evidence of HLA-A\*02:01 allele positivity.
- ECOG PS score 0-1. Adequate Organ Function Requirements within 10 Days of Treatment Initiation
- Estimated glomerular filtration rate (eGFR) ≥60 mL/min/1.73 m2 based on local institutional practice (e.g., Cockcroft-Gault formula).
- 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 or tumor involvement with discussion with the Study Responsible Physician).
- 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.
- If male of childbearing potential, agrees to use barrier contraception from the time of enrollment through 120 days following the last study drug dose.
- Participant or participant's health care proxy is able and willing to provide written informed consent and able to follow study instructions.
Exclusion criteria
- Cohort C (Recurrent/Progressive GBM) Specific Exclusion Criteria:
- Known or suspected leptomeningeal disease are excluded, defined as radiographic evidence of leptomeningeal involvement on MRI of the brain and/or spine, or positive cerebrospinal fluid (CSF) cytology, at screening or prior to first dose.
- Tumors involving the brainstem or spinal cord are excluded, including primary tumors arising from, or metastatic lesions involving, the brainstem (midbrain, pons, or medulla) or spinal cord.
- Received prior bevacizumab or any other anti-VEGF or anti-VEGFR therapy.
- Absolute lymphocyte count \<800/uL.
- Clinically significant mass effect or midline shift. Exclusion Criteria for All Participants:
- Previous treatment with any pHLA-targeting T-cell engager.
- Isolated extramedullary relapse.
- 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. • Note: this does not apply to Cohort C GBM participants
- Known HIV infection.
- Active hepatitis B infection (participants with documented clearance following treatment are allowed).
- Active hepatitis C infection (participants with documented clearance following treatment are allowed).
- Any acute or chronic infection requiring systemic treatment
- 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.
- 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
- Graft-Versus-Host Disease (GVHD): Active GVHD.
- 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 (e.g., 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.
- Current or historical diagnosis of a gastrointestinal autoimmune or inflammatory condition, including but not limited to ulcerative colitis (UC), Crohn's disease (CD), indeterminate colitis, or microscopic colitis (collagenous or lymphocytic colitis), or a history of GI toxicity from previous therapy that, in the opinion of the investigator, should preclude study participation.
- Significant impairment of lung function requiring chronic use of ambulatory supplemental oxygen.
- Screening laboratory values or investigations that do not meet the requirements for adequate organ function.
- 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.
- Any commercially available or investigational anti-leukemic or anti-cancer therapy other than CBX 663, with the following exceptions: • Intrathecal chemotherapy for CNS prophylaxis is permitted after C1 is complete, at the treating physician's discretion.
- Participants who experienced severe, life-threatening or recurrent (≥ Grade 2) immune-mediated adverse events or infusion-related reactions including those that led to permanent discontinuation while on previous treatment with immuno-oncology agents.
- Any concurrent systemic treatment to prevent GVHD. Topical treatments for GVHD are permitted. Participants who stopped calcineurin inhibitor (CNI) prophylaxis should be off CNI for at least 4 weeks.
- Known allergy or sensitivity to study drug, including excipients.
Where
- Duarte, California
- Tampa, Florida
- Houston, Texas
- Fairfax, Virginia
Related conditions & keywords
Frequently asked questions
What is a clinical trial?
A clinical trial is a research study that tests new medical treatments, drugs, devices, or procedures to determine their safety and effectiveness. Trials are carefully designed and monitored to protect participants while advancing medical knowledge.
Is it safe to participate?
Clinical trials follow strict safety guidelines and ethical standards. Trials must be reviewed and approved, and participants are closely monitored by medical professionals throughout the study. You can withdraw at any time if you choose.
Will I be compensated?
Many clinical trials offer compensation for your time, travel expenses, and inconvenience. The specific compensation varies by study and will be discussed during the screening process. All study-related medical care is typically provided at no cost to participants.
Will I receive a placebo instead of treatment?
When effective treatment exists, participants typically receive either the standard treatment plus the study intervention, or the standard treatment plus placebo. You would not be denied effective care. Placebos are primarily used when no proven treatment is available, or in addition to standard care. Your trial consent form will clearly explain what treatments you may receive.
Can I leave a trial if I change my mind?
Absolutely. Participation in clinical trials is completely voluntary. You have the right to withdraw from the study at any time, for any reason, without penalty or loss of benefits to which you are otherwise entitled.
How long does a clinical trial last?
Trial duration varies widely depending on the study design and purpose. Some trials last just a few weeks, while others may continue for months or years. The study coordinator will provide specific timeline information during your screening call.
Data: ClinicalTrials.gov · synced Oct 21, 2026 · Source of record for eligibility and locations