IL-18 Armored STEAP1 CAR T Cells for the Treatment of Metastatic Castration Resistant Prostate Cancer

August 28, 2026 updated by: Fred Hutchinson Cancer Center

Phase 1 Dose-Escalation and Expansion Study of IL-18 Armored STEAP1 CAR T in Participants With mCRPC

This phase I trial tests the safety, side effects, best dose and how well giving IL-18 armored STEAP1 CAR T cells after lymphodepleting chemotherapy (with cyclophosphamide and fludarabine) works for the treatment of castration resistant prostate cancer that has spread from where it first started (primary site) to other places in the body (metastatic). Giving chemotherapy, with cyclophosphamide and fludarabine, prior to CAR T cells helps kill cancer cells in the body and prepare the body to receive the CAR T cells. Chimeric antigen receptor (CAR) T-cell therapy is a type of treatment in which a patient's T cells (a type of immune system cell) are changed in the laboratory so they will attack cancer cells. T cells are taken from a patient's blood. Then the gene for a special receptor that binds to a certain protein on the patient's cancer cells is added to the T cells in the laboratory. The special receptor is called a chimeric antigen receptor. Large numbers of the CAR T cells are grown in the laboratory and given to the patient by infusion for treatment of certain cancers. Giving IL-18 armored STEAP1 CAR T cells after lymphodepleting chemotherapy may be safe, tolerable and/or effective in treating patients with metastatic castration resistant prostate cancer.

Study Overview

Status

Not yet recruiting

Conditions

Intervention / Treatment

Detailed Description

OUTLINE:

Patients undergo leukapheresis. Patients receive cyclophosphamide intravenously (IV) and fludarabine IV on days -5 to -3. Patients receive FH-STEAP1 IL-18 CAR T cell IV on day 0. Patients may continue to receive androgen deprivation therapy per standard of care, throughout the study. Patients undergo nuclear medicine bone scan, computed tomography (CT) scan, magnetic resonance imaging (MRI) and/or positron emission tomography (PET) scan, tumor biopsy and blood sample collection throughout the study. Patients may also undergo multigated acquisition (MUGA) scan or echocardiography during screening.

After completion of study treatment, patients are followed up on day +1, +3, +7, +10, +14, +21, + 28, months 2-6, month 9, month 12, then every 6 months until year 5 then yearly until year 15.

Study Type

Interventional

Enrollment (Estimated)

20

Phase

  • Phase 1

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Locations

  • United States
    • Washington
      • Seattle, Washington, United States, 98109
        • Fred Hutch/University of Washington Cancer Consortium
        • Contact:
        • Principal Investigator:
          • Rosa Nadal Rios, MD, PhD

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • Documented, histologically confirmed adenocarcinoma of the prostate
  • Measurable disease by RECIST 1.1 criteria or bone only metastases with measurable PSA (≥ 1ng/mL)
  • Must have mCRPC with progressive disease (PD), stable disease (SD), lack of clinical benefit or intolerance to ≥ 1 line of systemic therapy, after becoming castration resistant

  • Have received the following for metastatic prostate cancer:

    • At least two lines of Food and Drug Administration (FDA)-approved therapies with at least one being a second-generation androgen receptor signaling inhibitor.
    • Targeted therapies for which they are eligible in the metastatic setting unless the patient has contraindications to receiving those medications, the agents are not available to the patient or the patient declines to receive these drugs due to personal preference
  • Castrate levels of testosterone (< 50 ng/dL) with or without the use of androgen deprivation therapy
  • 18 years or older at the time of enrollment
  • Capable of understanding and providing written informed consent
  • Fertile male participants and their female partners must be willing to use an effective contraceptive method before, during, and for at least 4 months after the FH-STEAP1 IL-18 CAR T cell infusion
  • Participants will be permitted to receive radiation therapy for palliative purposes throughout the study period, except during the 2-week period prior to undergoing leukapheresis
  • Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1
  • Serum creatinine ≤ 1.5 x upper limit of normal (ULN) or estimated creatinine clearance > 50 mL/min as calculated using the Cockcroft-Gault formula and not dialysis dependent
  • Total bilirubin ≤ 1.5 x ULN. Participants with suspected Gilbert syndrome may be included if total bilirubin (bili) > 3 mg/dL but no other evidence of hepatic dysfunction
  • Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) < 5 x ULN
  • ≤ grade 1 dyspnea and oxygen saturation (SaO2) ≥ 92% on ambient air. If pulmonary function tests (PFTs) are performed based on the clinical judgement of the treating physician, participants with forced expiratory volume at 1 second (FEVI) ≥ 50% of predicted and carbon monoxide diffusing capability (DLCO) (adjusted for lung volume) of ≥ 40% of predicted will be eligible
  • All participants ≥ 60 years of age are required to have left ventricular ejection fraction (LVEF) evaluation performed within 1 year prior to lymphodepletion chemotherapy. LVEF may be established with an echocardiogram or MUGA scan, and left ejection fraction must be ≥ 45%
  • Absolute neutrophil count (ANC) > 1500 cells/ mm^3
  • Hemoglobin ≥ 9g g/dL
  • Platelets > 100,000 per mm^3

Exclusion Criteria:

  • Expecting to conceive or father children for the duration of the trial through 4 months after T cell infusion
  • Patients that require immediate therapy due to mass effect or spinal cord compression
  • Active autoimmune disease: Participants with active autoimmune disease requiring chronic immunosuppressive therapy are excluded. Case by case exemptions are possible with approval by principal investigator (PI)
  • Corticosteroid therapy at a dose equivalent of > 10 mg of prednisone per day (or equivalent). Pulsed corticosteroid use for disease control is acceptable
  • Concurrent use of other investigational anti-cancer agents except for androgen deprivation therapy

  • Uncontrolled concurrent illness: Participants may not have uncontrolled respiratory, endocrine, renal, gastrointestinal, genitourinary or systemic infection. There are exceptions to this criterion:

    • HIV positive participants on highly active antiretroviral therapy (HAART) with a CD4 count > 500 cells/mm^3 are considered controlled, as are individuals with a history of hepatitis C who have successfully completed antiviral therapy with an undetectable viral load, and those with hepatitis B who have hepatitis well controlled on medication;
    • Patients who have recent history of cerebrovascular accident, transient ischemic attack should be cleared by the neurology service before enrolling this study
    • Patients who have recent history of coronary artery disease or cardiac arrhythmia should be cleared by the cardiology service before enrolling this study. Case by case exemptions are possible with approval by PI
  • Participants with brain metastasis
  • Active treatment for prior immune related adverse event to any immunotherapy: Participants receiving ongoing treatment for prior serious immune-related adverse events are excluded, with exception of hormone supplementation or corticosteroid therapy at equivalent of > 10 mg prednisone (or equivalent) per day, unless otherwise approved by PI
  • Patients with a second malignancy in addition to their prostate cancer are not eligible if the second malignancy has required systemic treatment within the past 4 years or is not in complete remission. There are exceptions to this criterion: successfully treated non-metastatic basal cell and squamous cell skin carcinoma
  • Other medical, social, or psychiatric factor that interferes with medical appropriateness and/or ability to comply with study, as determined by the PI
  • Known allergic reactions to any of the components of study treatments
  • Participants who do not have a reasonable standard-of-care bridging therapy option available, as determined by the treating medical oncologist, to maintain disease control should clinically significant disease progression or worsening symptoms occur during the screening and T-cell manufacturing period

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

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

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Treatment (chemotherapy, FH-STEAP1 IL-18 CAR T cells)
Patients undergo leukapheresis. Patients receive cyclophosphamide intravenously (IV) and fludarabine IV on days -5 to -3. Patients receive FH-STEAP1 IL-18 CAR T cell IV on day 0. Patients may continue to receive androgen deprivation therapy per standard of care, throughout the study. Patients undergo nuclear medicine bone scan, CT scan, MRI and/or PET scan, tumor biopsy and blood sample collection throughout the study. Patients may also undergo MUGA scan or echocardiography during screening.
Procedure: Magnetic Resonance Imaging
Undergo MRI
Other Names:
  • MRI
  • Magnetic Resonance
  • Magnetic Resonance Imaging Scan
  • Medical Imaging, Magnetic Resonance / Nuclear Magnetic Resonance
  • MR
  • MR Imaging
  • MRI Scan
  • NMR Imaging
  • NMRI
  • Nuclear Magnetic Resonance Imaging
  • Magnetic Resonance Imaging (MRI)
  • sMRI
  • Magnetic resonance imaging (procedure)
  • MRIs
  • Structural MRI
Procedure: Biospecimen Collection
Undergo blood sample collection
Other Names:
  • Biological Sample Collection
  • Biospecimen Collected
  • Specimen Collection
  • Sample Collection
Drug: Cyclophosphamide
Given IV
Other Names:
  • Cytoxan
  • CTX
  • (-)-Cyclophosphamide
  • 2H-1,3,2-Oxazaphosphorine, 2-[bis(2-chloroethyl)amino]tetrahydro-, 2-oxide, monohydrate
  • Carloxan
  • Ciclofosfamida
  • Ciclofosfamide
  • Cicloxal
  • Clafen
  • Claphene
  • CP monohydrate
  • CYCLO-cell
  • Cycloblastin
  • Cycloblastine
  • Cyclophospham
  • Cyclophosphamid monohydrate
  • Cyclophosphamide Monohydrate
  • Cyclophosphamidum
  • Cyclophosphan
  • Cyclophosphane
  • Cyclophosphanum
  • Cyclostin
  • Cyclostine
  • Cytophosphan
  • Cytophosphane
  • Fosfaseron
  • Genoxal
  • Genuxal
  • Ledoxina
  • Mitoxan
  • Neosar
  • Revimmune
  • Syklofosfamid
  • WR- 138719
  • Asta B 518
  • B-518
  • WR-138719
  • B 518
  • B518
  • WR 138719
  • WR138719
  • Frindovyx
Drug: Fludarabine
Given IV
Other Names:
  • Fluradosa
Procedure: Leukapheresis
Undergo leukapheresis
Other Names:
  • Leukocytopheresis
  • Therapeutic Leukopheresis
  • Leukocyte Adsorptive Apheresis
  • White Blood Cell Reduction Apheresis
Procedure: Positron Emission Tomography
Undergo PET scan
Other Names:
  • Medical Imaging, Positron Emission Tomography
  • PET
  • PET Scan
  • Positron Emission Tomography Scan
  • Positron-Emission Tomography
  • PT
  • Positron emission tomography (procedure)
Procedure: Computed Tomography
Undergo CT scan
Other Names:
  • CT
  • CAT
  • CAT Scan
  • Computed Axial Tomography
  • Computerized Axial Tomography
  • Computerized Tomography
  • CT Scan
  • tomography
  • Computerized axial tomography (procedure)
  • Computerized Tomography (CT) scan
  • Diagnostic CAT Scan
  • Diagnostic CAT Scan Service Type
Procedure: Multigated Acquisition Scan
Undergo MUGA scan
Other Names:
  • Blood Pool Scan
  • Equilibrium Radionuclide Angiography
  • Gated Blood Pool Imaging
  • MUGA
  • Radionuclide Ventriculography
  • RNVG
  • SYMA Scanning
  • Synchronized Multigated Acquisition Scanning
  • MUGA Scan
  • Multi-Gated Acquisition Scan
  • Radionuclide Ventriculogram Scan
  • Gated Heart Pool Scan
  • RNV Scan
Procedure: Biopsy Procedure
Undergo tumor biopsy
Other Names:
  • Bx
  • BIOPSY_TYPE
Procedure: Echocardiography Test
Undergo echocardiography
Other Names:
  • Echocardiography
  • EC
Biological: FH-STEAP1 IL-18 CAR T cells
Given FH-STEAP1 IL-18 CAR T cells IV
Other Names:
  • Drug Monotherapy
  • Single Agent Treatment
  • Single Drug Therapy
Drug: Antiandrogen Therapy
Receive standard of care androgen deprivation therapy
Other Names:
  • ADT
  • Androgen Deprivation Therapy
  • Anti-androgen Therapy
  • Anti-androgen Treatment
  • Antiandrogen Treatment
  • Hormone Deprivation Therapy
  • Hormone-Deprivation Therapy
Procedure: Bone Scan
Undergo nuclear medicine bone scan
Other Names:
  • Bone Scintigraphy

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Treatment-related unexpected grade 3 or higher toxicity
Time Frame: Up to 28 days post infusion
Up to 28 days post infusion
Incidence of adverse events
Time Frame: Up to 28 days post infusion
Up to 28 days post infusion
Prostate cancer response
Time Frame: Up to 1 year post infusion
Assessed by Prostate Cancer Working Group 3 (PCWG3) criteria.
Up to 1 year post infusion

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Progression free survival
Time Frame: From initiation of protocol treatment to disease progression or death of any cause, up to 1 year post infusion
Will be analyzed using Kaplan-Meier method and the results will be summarized by the median with a 95% confidence interval if appropriate.
From initiation of protocol treatment to disease progression or death of any cause, up to 1 year post infusion
Overall survival
Time Frame: From initiation of protocol treatment to death of any cause, up to 1 year post infusion
Will be analyzed using Kaplan-Meier method and the results will be summarized by the median with a 95% confidence interval if appropriate.
From initiation of protocol treatment to death of any cause, up to 1 year post infusion
Objective response rate
Time Frame: Up to 1 year post infusion
Defined as complete response or partial response by Response Evaluation Criteria in Solid Tumors 1.1 criteria and PCWG 3.
Up to 1 year post infusion
Stable disease
Time Frame: Up to 1 year post infusion
Assessed by RECIST 1.1 criteria and PCWG3.
Up to 1 year post infusion
Clinical benefit
Time Frame: Up to 1 year post infusion
Defined as overall response and stable disease assessed by RECIST 1.1 criteria and PCWG3.
Up to 1 year post infusion
Overall response
Time Frame: Up to 1 year post infusion
Assessed by immune RECIST criteria.
Up to 1 year post infusion
Prostate specific antigen (PSA) response
Time Frame: From baseline, up to 15 years
Defined as ≥ 50% reductions in PSA. The estimation with an exact 95% confidence interval will be provided.
From baseline, up to 15 years

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Fred Hutchinson Cancer Center

Collaborators

PromiCell Therapeutics, Inc.

Investigators

  • Principal Investigator: Rosa Nadal Rios, MD, PhD, Fred Hutch/University of Washington Cancer Consortium

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Estimated)

October 31, 2026

Primary Completion (Estimated)

October 31, 2030

Study Completion (Estimated)

October 31, 2044

Study Registration Dates

First Submitted

August 28, 2026

First Submitted That Met QC Criteria

August 28, 2026

First Posted (Actual)

September 4, 2026

Study Record Updates

Last Update Posted (Actual)

September 4, 2026

Last Update Submitted That Met QC Criteria

August 28, 2026

Last Verified

August 1, 2026

More Information

Terms related to this study

Additional Relevant MeSH Terms

Other Study ID Numbers

  • RG1126433
  • NCI-2026-06012 (Registry Identifier: CTRP (Clinical Trial Reporting Program))
  • FH21226 (Other Identifier: Fred Hutch/University of Washington Cancer Consortium)

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

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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