A Phase 2 interventional study of Cyclophosphamide and Fludarabine in Pediatric Osteosarcoma, sponsored by St. Jude Children's Research Hospital. Recruiting at 1 site in United States. Open to participants aged Up to 21 Years. Per ClinicalTrials.gov, last updated 2026-11-03.
Sponsored by St. Jude Children's Research Hospital · Phase 2, Interventional, and Treatment
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:
This is a phase 2 study of SJCARB7H3-41BBL for participants with newly diagnosed high-risk metastatic osteosarcoma who received standard chemotherapy.
All participants will receive standard chemotherapy (for example methotrexate, anthracycline, platinum), local control surgery, and pulmonary metastasectomy if applicable, and this is not considered part of protocol therapy. Participants will undergo apheresis prior to standard local control surgery (about 12 weeks after diagnosis) for SJCARB7H3-41BBL manufacture and then resume standard consolidation therapy. A safety run will initiate with Regimen A. For Regimen A, eligible participants with available SJCARB7H3-41BB product will receive lymphodepletion chemotherapy 14-28 days after the completion of standard chemotherapy (31 weeks after diagnosis), followed by SJCARB7H3-41BB infusion. If Regimen A is not cleared, then Regimen B will be evaluated, where lymphodepletion and SJCARB7H3-41BB infusion occur post pulmonary metastasectomy. Following successful clearance of either regimen A or, if necessary, regimen B, then the efficacy cohort will be initiated. Participants will be followed with serial disease evaluations for 2 years from SJCARB7H3-41BB infusion prior to transfer to our institutional long-term follow-up (LTFU) protocol. The total duration from completion of standard therapy, including experimental therapy and follow-up on 3CAR4OS, is approximately 2 years.
488 studies on the registry are indexed under Osteosarcoma; 124 are open to participants now.
This study's planned enrollment of 41 is close to the median of 40 across 354 interventional studies indexed under Osteosarcoma.
Browse Osteosarcoma studies →St. Jude Children's Research Hospital is the lead sponsor of 440 studies on the registry; 102 are open to participants now.
Of its 61 completed or terminated interventional studies of FDA-regulated products, 37 (61%) have results posted.
Counted across the registry records on this site, refreshed daily.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Prior cancer therapy:
Adequate organ function as indicated by:
Laboratory values meet the following criteria:
Exclusion Criteria:
Presence of active severe infection, defined as:
Participant has received prior disease-directed therapy other than therapy with methotrexate, an anthracycline, and a platinum and local control surgery
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
A 0–100 scale of how well someone can carry out everyday activities. 100 is no complaints and no signs of illness; 70 is able to look after yourself but not to work or keep up normal activity; 50 is needing considerable help and frequent medical care.
Studies often ask for 60 or 70 and above. Your doctor gives the score.
The top of the normal range for a blood test, as set by the laboratory that runs it. Each lab prints its own range next to your result.
“≤ 2.5 × ULN” means the result can be up to two and a half times that top value.
A yellow substance made when red blood cells are broken down, which the liver clears. A high level can mean a problem with the liver or the bile ducts.
Criteria often allow more for people with Gilbert’s syndrome, a harmless inherited condition that raises bilirubin.
Two enzymes measured in a routine blood test of the liver. Higher levels can mean the liver is under strain or damaged. SGPT and SGOT are older names for ALT and AST.
Criteria usually give a limit as a multiple of the upper limit of normal (ULN), often higher when cancer has spread to the liver.
The share of blood the heart’s main pumping chamber (the left ventricle) pushes out with each beat, measured by an echocardiogram (heart ultrasound) or a MUGA scan. About 50–70% is normal.
The number of neutrophils, white blood cells that help fight infection, in a given amount of blood. Too few raises the risk of infection.
It is a count, not a percentage of the white cells. Limits are written in units that mean the same: ≥ 1.5 × 10⁹/L is ≥ 1,500 per mm³ (µL). Each lab has its own reference range.
Blood cells that help blood clot. Too few raises the risk of bleeding and bruising. A usual adult range is about 150–400 × 10⁹/L (150,000–400,000 per µL); each lab has its own reference range.
The protein in red blood cells that carries oxygen. A low level is anaemia, which can cause tiredness and breathlessness. Measured in g/dL or g/L (9 g/dL is 90 g/L).
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
A line of therapy is one course of treatment, which may combine several drugs. First-line is the first course given; second-line follows when that stops working or is not tolerated.
“Two prior lines” means two courses that count separately under the study’s rules — not simply two drugs. Ask the study team if you are unsure how yours are counted.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Karnofsky performance status (KPS)
A 0–100 scale of how well someone can carry out everyday activities. 100 is no complaints and no signs of illness; 70 is able to look after yourself but not to work or keep up normal activity; 50 is needing considerable help and frequent medical care.
Studies often ask for 60 or 70 and above. Your doctor gives the score.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
ULN (upper limit of normal)
The top of the normal range for a blood test, as set by the laboratory that runs it. Each lab prints its own range next to your result.
“≤ 2.5 × ULN” means the result can be up to two and a half times that top value.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Bilirubin
A yellow substance made when red blood cells are broken down, which the liver clears. A high level can mean a problem with the liver or the bile ducts.
Criteria often allow more for people with Gilbert’s syndrome, a harmless inherited condition that raises bilirubin.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
ALT and AST (liver enzymes)
Two enzymes measured in a routine blood test of the liver. Higher levels can mean the liver is under strain or damaged. SGPT and SGOT are older names for ALT and AST.
Criteria usually give a limit as a multiple of the upper limit of normal (ULN), often higher when cancer has spread to the liver.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
LVEF (left ventricular ejection fraction)
The share of blood the heart’s main pumping chamber (the left ventricle) pushes out with each beat, measured by an echocardiogram (heart ultrasound) or a MUGA scan. About 50–70% is normal.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Absolute neutrophil count (ANC)
The number of neutrophils, white blood cells that help fight infection, in a given amount of blood. Too few raises the risk of infection.
It is a count, not a percentage of the white cells. Limits are written in units that mean the same: ≥ 1.5 × 10⁹/L is ≥ 1,500 per mm³ (µL). Each lab has its own reference range.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Platelets
Blood cells that help blood clot. Too few raises the risk of bleeding and bruising. A usual adult range is about 150–400 × 10⁹/L (150,000–400,000 per µL); each lab has its own reference range.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hemoglobin (Hb)
The protein in red blood cells that carries oxygen. A low level is anaemia, which can cause tiredness and breathlessness. Measured in g/dL or g/L (9 g/dL is 90 g/L).
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Corticosteroids (steroids)
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Clinically significant
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Line of therapy
A line of therapy is one course of treatment, which may combine several drugs. First-line is the first course given; second-line follows when that stops working or is not tolerated.
“Two prior lines” means two courses that count separately under the study’s rules — not simply two drugs. Ask the study team if you are unsure how yours are counted.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
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
IV
IV
IV prior to and again at 3, 6, and 9 hours following each dose of cyclophosphamide.
IV collection
1X107 CAR+ T cells/kg
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 frame: Time from SJCARB7H3-41BBL infusion to time of first event, followed up to 24-months post-infusion
Overall survival (OS), defined as time from SJCARB7H3-41BBL cell infusion to all-cause mortality.
Event-free participants will be censored at the time of last follow-up. OS will be reported similarly to the EFS endpoint on the same participant subset.
Time frame: 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.
This outcome measure will be descriptively summarized for the overall participant group and by regimen (if more than 1 regimen is evaluated) for each regimen-related toxicity. Evaluable participants include those who receive SJCARB7H3\_41BBL and remain on protocol therapy through at least 28 days post-infusion or experience a related unacceptable toxicity.
Time frame: 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
This outcome measure will be descriptively summarized for the overall participant group and by regimen (if more than 1 regimen is evaluated) for participants who undergo apheresis and remain on protocol therapy through the end of standard therapy.
Time frame: Time of SJCARB7H3-41BBL infusion
Plan to share: Yes — Individual participant de-identified datasets containing the variables analyzed in the published article will be made available (related to the study primary or secondary objectives contained in the publication). Supporting documents such as the protocol, statistical analyses plan, and informed consent are available through the CTG website for the specific study. Data used to generate the published article will be made available at the time of article publication. Investigators who seek access to individual level de-identified data will contact the computing team in the Department of Biostatistics (ClinTrialDataRequest@stjude.org) who will respond to the data request.
Supporting information: Study protocol, Statistical analysis plan, Informed consent form
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.
Started Aug 2026 (actual). Primary completion is estimated for Dec 2034, 100 months after the start.
Of 72 non-industry phase 2 interventional studies under Osteosarcoma, half reached primary completion within 66 months of starting (the median), counting those still running; a quarter within 41 and three quarters within 94. This study's planned 100 months is above that.
Counting every sponsor, half of 76 studies reached it within 65 months; a quarter within 40 and three quarters within 94.
Start moved once since we started tracking on Sep 25, 2026: Sep 2026 → Aug 2026, on Nov 3, 2026.
Earlier changes are on the record history on ClinicalTrials.gov ↗
How these figures are worked out, and which studies are left out of them.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
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Studies of the drugs tested here: Cyclophosphamide · Fludarabine · Mesna
St. Jude Children's Research Hospital →