Evaluating Efficacy of B7-H3-CAR T Cells Administered at the End of Upfront Map Chemotherapy in Patients With Newly Diagnosed High-Risk Osteosarcoma

NCT07428993 | Recruiting Phase 2 DMC FDA Drug

• 1 other identifier: 3CAR4OS
• Study Type: interventional
• Target: 41
• Locations: 1 country
• Sites: 1

Brief Summary

The purpose of this study is to assess the safety, feasibility, and effectiveness of a consolidative B7-H3 CAR T cell therapy in patients with newly diagnosed high-risk osteosarcoma who have undergone upfront standard chemotherapy. Primary Objectives: \- To evaluate 1-year RFS from the time of SJCARB7H3\_41BBL infusion for patients with newly diagnosed metastatic osteosarcoma who received standard chemotherapy. Secondary Objectives:

• To evaluate the OS from time of SJCARB7H3\_41BBL infusion for patients with newly diagnosed metastatic osteosarcoma who received standard chemotherapy.
• To evaluate the feasibility of delivering SJCARB7H3\_41BBL at the end of standard therapy in patients with newly diagnosed metastatic osteosarcoma.
• To describe the safety of autologous SJCARB7H3\_41BBL therapy when delivered at the end of standard therapy in patients with newly diagnosed metastatic osteosarcoma.

Conditions

Pediatric Osteosarcoma

Keywords

Osteosarcoma

Outcome Measures

Primary Outcomes (1)

• Event-free survival (EFS), defined as time from SJCARB7H3_41BBL infusion to disease relapse, progressive disease, new systemic therapy, secondary malignancy or death

  Event-free participants will be censored at the time of last follow-up. This analysis will report the Kaplan-Meier (KM) curve, along with the 12-month EFS estimate and its 80% confidence interval using the arcsine-square root transformation. Evaluable participants are those who complete standard chemotherapy, receive SJCARB7H3\_41BBL and are treated on the regimen used for the Efficacy phase.

  Time from SJCARB7H3_41BBL infusion to time of first event, followed up to 24-months post-infusion

Secondary Outcomes (3)

• Overall survival (OS), defined as time from SJCARB7H3_41BBL cell infusion to all-cause mortality.

  Time from SJCARB7H3_41BBL infusion to time of death from any cause, followed up to 24-months post-infusion

• Number of participants experiencing protocol-specified regimen-related toxicities.

  Time from SJCARB7H3_41BBL infusion up to 28 days post-infusion.

• Number of participants with successful manufacture of SJCARB7H3_41BBL cells of sufficient dose and planned product administration

  Time of SJCARB7H3_41BBL infusion

Study Arms (1)

3CAR4OS Treatment

EXPERIMENTAL

All patients will receive standard of care chemotherapy, which is not considered part of protocol therapy. Eligible patients will undergo apheresis prior to standard local control surgery for CAR T cell manufacture and then resume standard therapy. In the absence of progressive disease, eligible patients with available SJCARB7H3\_41BBL product will receive lymphodepletion chemotherapy (fludarabine/cyclophosphamide) after the completion of standard chemotherapy, followed by SJCARB7H3\_41BBL infusion. Pulmonary metastasectomy will be performed as indicated according to the standard of care and will be timed after (Regimen A) or before (Regimen B) lymphodepletion and SJCARB7H3\_41BBL infusion. Following successful clearance of either regimen A or, if necessary, regimen B, the efficacy cohort will be initiated.

Drug: Cyclophosphamide; Drug: Fludarabine; Drug: Mesna; Procedure: Apheresis; Procedure: SJCARB7H3_41BBL infusion

Interventions

Cyclophosphamide DRUG

IV

3CAR4OS Treatment

Fludarabine DRUG

IV

3CAR4OS Treatment

Mesna DRUG

IV prior to and again at 3, 6, and 9 hours following each dose of cyclophosphamide.

3CAR4OS Treatment

Apheresis PROCEDURE

IV collection

3CAR4OS Treatment

SJCARB7H3_41BBL infusion PROCEDURE

1X107 CAR+ T cells/kg

3CAR4OS Treatment

Eligibility Criteria

• Age: Up to 21 Years
• Sex: all
• Healthy Volunteers: No
• Age Groups: Child (0-17), Adult (18-64)

You may qualify if:

• Participant and/or legally authorized representative has signed the Informed Consent Form for this study
• Prior cancer therapy:
• Regimen A only: Completed all planned cycles of consolidation therapy between 14-28 days prior.
• Regimen B only: has completed all planned cycles of consolidation chemotherapy at least 14 days prior and if clinically indicated, participant has undergone pulmonary metastasectomy. They must have recovered from any surgical complications with no ongoing sequelae of category 2 or higher by the Clavien-Dindo classification system and less than 6 weeks must have passed from time of pulmonary metastasectomy.
• No evidence of progressive disease since enrolled on study
• Lansky performance status score of ≥ 50 for participants \<16 years of age or Karnofsky score ≥ 50 for participants ≥ 16 years. Participants who are unable to walk because of paralysis, but who are up in a wheelchair, will be considered ambulatory for purposes of assessing performance status
• Adequate organ function as indicated by:
• Renal: Serum creatinine ≤ 1.5 X the upper limit of normal (ULN) based on enrollment eligibility table.
• Hepatic: Total bilirubin ≤ 3 times ULN for age OR conjugated bilirubin ≤ 2 mg/dL AND ALT (SGPT) ≤ 5 times ULN
• Cardiac: Shortening fraction ≥ 28% OR ejection fraction ≥ 50% as measured by echocardiogram
• Respiratory: Oxygen saturation ≥ 90% on room air without supplemental oxygen or mechanical ventilation
• Laboratory values meet the following criteria:
• Absolute Neutrophil Count (ANC) ≥ 750 cells/uL
• Platelet Count of ≥ 75,000 (can be transfused)
• Hemoglobin ≥ 7 g/dL (can be transfused)

You may not qualify if:

• Major surgical adverse event related to the primary tumor local control defined as Clavien-Dindo category 3 requiring ongoing wound care.
• Evidence of clinically significant encephalopathy/new focal neurologic deficits.
• Presence of active severe infection, defined as:
• positive blood culture within 48 hours of enrollment, OR
• fever above 38.2° C, AND clinical signs of infection within 48 hours of enrollment
• Participant has received prior disease-directed therapy other than 1st line therapy with methotrexate, an anthracycline, and a platinum and local control surgery
• Regimen B only - okay to have undergone initial pulmonary metastasectomy
• Pregnant or breastfeeding
• Presence of any condition that, in the opinion of the investigator, would prohibit the participant from undergoing treatment under this protocol

Sponsors & Collaborators

• St. Jude Children's Research Hospital: lead

Study Sites (1)

St. Jude Children's Research Hospital

Memphis, Tennessee, 38105-2794, United States

RECRUITING

Related Links

• St. Jude Children's Research Hospital
• Clinical Trials Open at St. Jude

MeSH Terms

Conditions

Osteosarcoma

Interventions

Cyclophosphamide; fludarabine; Mesna; Blood Component Removal

Condition Hierarchy (Ancestors)

Neoplasms, Bone Tissue; Neoplasms, Connective Tissue; Neoplasms, Connective and Soft Tissue; Neoplasms by Histologic Type; Neoplasms; Sarcoma

Intervention Hierarchy (Ancestors)

Phosphoramide Mustards; Nitrogen Mustard Compounds; Mustard Compounds; Hydrocarbons, Halogenated; Hydrocarbons; Organic Chemicals; Phosphoramides; Organophosphorus Compounds; Alkanesulfonates; Alkanesulfonic Acids; Alkanes; Hydrocarbons, Acyclic; Sulfhydryl Compounds; Sulfur Compounds; Sulfonic Acids; Sulfur Acids; Therapeutics

Study Officials

• Julie Park, MD

  St. Jude Children's Research Hospital

  PRINCIPAL INVESTIGATOR

Central Study Contacts

Julie Park, MD

CONTACT

888-226-4343; referralinfo@stjude.org

Judith Durrell

CONTACT

888-226-4343; referralinfo@stjude.org

Study Design

• Study Type: interventional
• Phase: phase 2
• Allocation: NA
• Masking: NONE
• Purpose: TREATMENT
• Intervention Model: SINGLE GROUP
• Sponsor Type: OTHER
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: February 5, 2026
• First Posted: February 24, 2026
• Study Start: June 1, 2026
• Primary Completion (Estimated): December 1, 2034
• Study Completion (Estimated): December 1, 2035
• Last Updated: May 19, 2026

Record last verified: 2026-05

Data Sharing

• IPD Sharing: Will share
• Shared Documents: STUDY PROTOCOL, SAP, ICF
• Time Frame: Data will be made available at the time of article publication.
• Access Criteria: Data will be provided to researchers following a formal request with the following information: full name of requestor, affiliation, data set requested, and timing of when data is needed. As an informational point, the lead statistician and study principal investigator will be informed that primary results datasets have been requested.

Locations

US (1)