A Phase 1 interventional study of SC-CAR.GPC3xIL15.21 CAR T cells in Solid Tumor (Excluding CNS), Liver Cell Carcinoma and Malignant Rhabdoid Tumor, sponsored by Seattle Children's Hospital. Recruiting at 1 site in United States. Open to participants aged 1 Year to 26 Years. Per ClinicalTrials.gov, last updated 2026-02-17.
Sponsored by Seattle Children's Hospital · Phase 1, Interventional, and Treatment
This Phase 1, open-label, non-randomized study will enroll pediatric and young adult subjects with relapsed or refractory non-central nervous system (CNS) malignant solid tumors expressing glypican-3 (GPC3) to examine the safety, feasibility, and efficacy of administering T cell products derived from peripheral blood mononuclear cells (PBMC) that have been genetically modified to co-express a GPC3-specific chimeric antigen receptor (CAR), interleukin (IL)-15 and IL-21 as well as the inducible caspase 9 (iC9) suicide gene (SC-CAR.GPC3xIL15.21 T cells).
A child or young adult meeting all eligibility criteria and meeting none of the exclusion criteria will have a blood sample collected, which will be used to bioengineer the CAR T cells targeting their tumor.
Study Overview
This study is testing a different treatment which uses the body's own immune system to recognize and kill the cancer cells, called chimeric antigen receptor (CAR) T cells. Some solid tumors express a specific type of molecule called glypican-3 or GPC3. We are able to insert a new gene (a piece of DNA that contains a set of instructions for the body) into T cells which are a type of immune system cell. This is how we make CAR T cells: We will insert a gene that will program the CAR T cell to recognize GPC3 to make GPC3-CAR T cells. To make GPC3-CAR T cells more effective against tumor cells, we also added two genes called IL15 and IL21 which help CAR T cells grow better and stay in the blood longer. We think that this will kill tumors better. When we did this in the laboratory, we found that this mixture of GPC3-CAR, IL15, and IL21 in T cells killed tumor cells better when compared with GPC3-CAR T cells that did not have IL15 and IL21. This research study will use these cells (named GPC3xIL15.21) to treat patients with solid tumors that express GPC3 on their surface. The GPC3xIL15.21 CAR T cells are an investigational product and have not been approved by the Food and Drug Administration.
We also wanted to make sure that we could stop the GPC3xIL15.21 CAR T cells from growing in the blood if there are any bad or severe side effects. To do so, we inserted a gene called iCasp9 into the GPC3xIL15.21 CAR T cells. This allows us to eliminate the GPC3xIL15.21 CAR T cells in the blood when we give a medicine called AP1903 (also known as rimiducid). Rimiducid is an experimental medicine that has been tested in humans, with no known bad side effects. We only intend to use this medicine to get rid of the GPC3xIL15.21 CAR T cells if you develop dangerous side effects. Approximately 21 people will participate in this study.
Treatment plan
We would first confirm that the participant tumor expresses GPC3. Upon confirmation, a maximum of approximately 6 tablespoons (or 90 mL) of blood will be drawn and sent to Seattle Children's Therapeutics (SCTx) to make the CAR T cells.
After the CAR T cells are made and treatment eligibility has been verified, participants will come to Seattle Children's Hospital for treatment and close monitoring for about one month. Participants will be given lymphodepleting chemotherapy for 3 days, using cyclophosphamide and fludarabine to make room for the CAR T cells, followed by CAR T cell infusion IV.
This is a dose escalation study, which means that the investigators do not know the highest safe dose of CAR T cells. The dose each patient gets depends on how many participants get the agent before that patient and how they react. Since the treatment is experimental, what is likely to happen at any dose is not known.
All of the treatments will be given at Seattle Children's Hospital.
After treatment, participants will be monitored closely for a month to monitor for side effects and response to treatment. After this month, participants would continue to be followed for 15 years after they receive your CAR T cells, with visits becoming less frequent the longer it has been since CAR T cell infusion.
3,648 studies on the registry are indexed under Carcinoma, Hepatocellular; 1,061 are open to participants now.
This study's planned enrollment of 21 is below the median of 54 across 2,618 interventional studies indexed under Carcinoma, Hepatocellular.
Browse Carcinoma, Hepatocellular studies →Seattle Children's Hospital is the lead sponsor of 215 studies on the registry; 44 are open to participants now.
Counted across the registry records on this site, refreshed daily.
Procurement Eligibility
Inclusion Criteria:
For patients with hepatocellular carcinoma only:
Exclusion Criteria:
History of reactions to murine protein-containing products OR presence of human anti-mouse antibody (HAMA) prior to enrollment for patients who have received prior therapy with murine antibodies.
Inclusion Criteria:
For patients with hepatocellular carcinoma only:
Exclusion Criteria:
History of hypersensitivity reactions to murine protein-containing products OR presence of human anti-mouse antibody (HAMA) prior to enrollment for patients who have received prior therapy with murine antibodies.
within 30 days prior to enrollment
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.
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 study doctor’s estimate of how long someone is likely to live. Criteria use it so that people can stay in the study long enough for it to answer its question.
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 score of how well the liver works in people with liver disease such as cirrhosis: class A is mild, B moderate and C severe.
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
The human immunodeficiency virus, which weakens the immune system.
Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.
Hepatitis B is a virus that infects the liver. These are separate tests: HBsAg positive usually means a current infection (a recent vaccination can briefly cause it too); total anti-HBc (HBcAb) positive means an infection now or in the past; HBV DNA measures how much virus is in the blood.
Some studies accept a past infection if HBV DNA is undetectable, sometimes with antiviral medicine during the study. Check what this study allows.
Hepatitis C is a virus that infects the liver. An HCV antibody test can stay positive after an infection has cleared (and is occasionally positive without one); an HCV RNA test shows whether the virus is there now.
After treatment, hepatitis C counts as cured when HCV RNA is still undetectable 12 weeks or more after the treatment ended. Studies often accept people cured this way.
Relapsed: the illness came back after treatment had worked. Refractory: it did not respond to treatment, or stopped responding while still on it.
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
A condition in which the immune system attacks the body’s own tissues, such as rheumatoid arthritis, lupus, psoriasis, type 1 diabetes or inflammatory bowel disease.
Immunotherapy studies often leave out active autoimmune disease, and some name exceptions, such as thyroid disease on replacement hormone. Check the exceptions this study lists.
Vaccines made with a weakened form of the germ, such as measles–mumps–rubella (MMR), chickenpox and yellow fever. They can be risky when the immune system is weakened. Flu injections are not live; the nasal flu spray is.
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.
The New York Heart Association’s four classes of how much heart failure limits physical activity.
Studies set their own limit — many outside heart failure leave out class III–IV, while heart failure studies may ask for a particular class. Check the class this study names.
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.
Life expectancy
The study doctor’s estimate of how long someone is likely to live. Criteria use it so that people can stay in the study long enough for it to answer its question.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
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.
Child-Pugh class
A score of how well the liver works in people with liver disease such as cirrhosis: class A is mild, B moderate and C severe.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hypersensitivity
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
HIV
The human immunodeficiency virus, which weakens the immune system.
Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hepatitis B tests
Hepatitis B is a virus that infects the liver. These are separate tests: HBsAg positive usually means a current infection (a recent vaccination can briefly cause it too); total anti-HBc (HBcAb) positive means an infection now or in the past; HBV DNA measures how much virus is in the blood.
Some studies accept a past infection if HBV DNA is undetectable, sometimes with antiviral medicine during the study. Check what this study allows.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hepatitis C tests
Hepatitis C is a virus that infects the liver. An HCV antibody test can stay positive after an infection has cleared (and is occasionally positive without one); an HCV RNA test shows whether the virus is there now.
After treatment, hepatitis C counts as cured when HCV RNA is still undetectable 12 weeks or more after the treatment ended. Studies often accept people cured this way.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Relapsed and refractory
Relapsed: the illness came back after treatment had worked. Refractory: it did not respond to treatment, or stopped responding while still on it.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Investigational drug or device
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Contraception
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Autoimmune disease
A condition in which the immune system attacks the body’s own tissues, such as rheumatoid arthritis, lupus, psoriasis, type 1 diabetes or inflammatory bowel disease.
Immunotherapy studies often leave out active autoimmune disease, and some name exceptions, such as thyroid disease on replacement hormone. Check the exceptions this study lists.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Live vaccines
Vaccines made with a weakened form of the germ, such as measles–mumps–rubella (MMR), chickenpox and yellow fever. They can be risky when the immune system is weakened. Flu injections are not live; the nasal flu spray is.
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.
NYHA class (heart failure)
The New York Heart Association’s four classes of how much heart failure limits physical activity.
Studies set their own limit — many outside heart failure leave out class III–IV, while heart failure studies may ask for a particular class. Check the class this study names.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Autologous SC-CAR.GPC3xIL15.21 T cell product will be infused as a single infusion.
Biological: SC-CAR.GPC3xIL15.21 CAR T cells
Autologous SC-CAR.GPC3xIL15.21 T cell products infusion
The number of successfully manufactured SC-CAR.GPC3xIL15.21 T cell products will be assessed
The number of successfully manufactured products will be measured
Time frame: 28 days
Establish the safety, defined by adverse events of SC-CAR.GPC3xIL15.21 T cells.
Type, frequency, severity, and duration of adverse events will be tabulated and summarized
Time frame: 28 days
Estimate the maximum tolerated dose (MTD) or biologically effective dose and dose limiting toxicities (DLT), and describe the full toxicity profile of SC-CAR.GPC3xIL15.21 T cells.
Type, frequency, severity, and duration of adverse events will be tabulated and summarized
Time frame: 28 days
To estimate anti-tumor responses by measuring changes in tumor burden using disease-specific evaluations following SC-CAR.GPC3xIL15.21 T cells.
Standard imaging and blood pathology will be used to determine disease response
Time frame: 42 days
Plan to share: No
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