A Phase 1 interventional study of CLR 131 in Pediatric Solid Tumor, Pediatric Lymphoma and Pediatric Brain Tumor, sponsored by Cellectar Biosciences, Inc.. Active, not recruiting at 8 sites in 3 countries. Open to participants aged 2 Years to 25 Years. Per ClinicalTrials.gov, last updated 2026-10-01.
Sponsored by Cellectar Biosciences, Inc. · Phase 1, Interventional, and Treatment
The study evaluates CLR 131 in children, adolescents, and young adults with relapsed or refractory malignant solid tumors and lymphoma and recurrent or refractory malignant brain tumors for which there are no standard treatment options with curative potential.
Even with standard, highly toxic multimodality therapies and salvage regimen, most pediatric patients with primary metastatic or relapsed solid tumors are confronted with a poor prognosis. For these patients there is currently no accepted successful treatment regimen. There is a need for new drugs, including targeted radiopharmaceuticals, preferably with cancer-specific uptake and broad applicability for these rare pediatric malignancies.
CLR 131 is a radioiodinated therapeutic that exploits the selective uptake and retention of phospholipid ethers (PLEs) by malignant cells. Cellectar Biosciences' novel cancer-targeted small-molecule compound (CLR1404) is radiolabeled with the isotope iodine-131 (I-131). CLR 131 has demonstrated tumor selective uptake across numerous adult and pediatric cancer cell types. Therapeutic efficacy has been demonstrated in various pediatric and adult-type cancer xenograft models, confirming the ability of CLR 131 to target tumors.
Based on the critical unmet medical need for effective agents with novel mechanisms of action in relapsed pediatric cancers and initial preclinical and clinical experience with radioiodinated CLR1404, Cellectar Biosciences has chosen to assess CLR 131 in a phase 1 pediatric trial.
675 studies on the registry are indexed under Neuroblastoma; 127 are open to participants now.
This study's planned enrollment of 30 is close to the median of 32 across 507 interventional studies indexed under Neuroblastoma.
Browse Neuroblastoma studies →Cellectar Biosciences, Inc. is the lead sponsor of 13 studies on the registry; 2 are open to participants now.
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.
All Patients
Patients with Pediatric Solid Tumor or Lymphoma
Patients with Recurrent or Refractory Brain Tumors
Exclusion Criteria:
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.
Relapsed: the illness came back after treatment had worked. Refractory: it did not respond to treatment, or stopped responding while still on it.
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.
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 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.
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).
GFR (glomerular filtration rate) is how much blood the kidneys filter each minute. It is usually estimated from a blood test — eGFR, by formulas such as CKD-EPI or MDRD — and some studies ask for it to be measured directly instead. Usually given in mL/min/1.73 m².
Check the method, the units and the minimum the study states. A value of 90 or above is in the normal-or-high range, but kidney damage can show in other tests too.
How quickly the kidneys clear creatinine, a waste product, from the blood. A study may estimate it from a blood test with age, weight and sex (often by the Cockcroft–Gault formula), or measure it using blood and urine collected over a set time. Given in mL/min; higher is better.
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 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.
Stem cell (bone marrow) transplants. Allogeneic uses cells from a donor; autologous uses your own cells, collected earlier and given back.
The amount of disease can be tracked with a defined measurement, so the study can see whether it shrinks or grows. It might be a tumour measured on a scan or, in some blood cancers such as myeloma, a marker measured in blood or urine.
The criteria or the study team say which measurement counts — having no tumour visible on a scan does not by itself rule you out.
Cancer deposits in the brain from a cancer that started elsewhere in the body (CNS metastases include the spinal cord).
Studies differ: some leave out any brain metastases, some accept ones treated and stable for some weeks. Check what this study allows.
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.
Cancer that has spread from where it began to other parts of the body. “Metastatic” cancer is cancer that has spread this way.
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.
A planned gap after a treatment, so that its effects can lessen before the study treatment or a study assessment. Ask the study team and the doctor who prescribed it before changing any medicine.
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.
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.
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.
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.
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.
GFR and eGFR (kidney filtering)
GFR (glomerular filtration rate) is how much blood the kidneys filter each minute. It is usually estimated from a blood test — eGFR, by formulas such as CKD-EPI or MDRD — and some studies ask for it to be measured directly instead. Usually given in mL/min/1.73 m².
Check the method, the units and the minimum the study states. A value of 90 or above is in the normal-or-high range, but kidney damage can show in other tests too.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Creatinine clearance (CrCl)
How quickly the kidneys clear creatinine, a waste product, from the blood. A study may estimate it from a blood test with age, weight and sex (often by the Cockcroft–Gault formula), or measure it using blood and urine collected over a set time. Given in mL/min; higher is better.
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.
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.
Allogeneic and autologous transplant
Stem cell (bone marrow) transplants. Allogeneic uses cells from a donor; autologous uses your own cells, collected earlier and given back.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Measurable disease
The amount of disease can be tracked with a defined measurement, so the study can see whether it shrinks or grows. It might be a tumour measured on a scan or, in some blood cancers such as myeloma, a marker measured in blood or urine.
The criteria or the study team say which measurement counts — having no tumour visible on a scan does not by itself rule you out.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Brain metastases
Cancer deposits in the brain from a cancer that started elsewhere in the body (CNS metastases include the spinal cord).
Studies differ: some leave out any brain metastases, some accept ones treated and stable for some weeks. Check what this study allows.
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.
Metastases
Cancer that has spread from where it began to other parts of the body. “Metastatic” cancer is cancer that has spread this way.
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.
Washout period
A planned gap after a treatment, so that its effects can lessen before the study treatment or a study assessment. Ask the study team and the doctor who prescribed it before changing any medicine.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
CLR 131 intravenous administration
Drug: CLR 131
IV dose of CLR 131, increased/decreased by dose level; single or fractionated dose
Also known as: I-131-CLR1404
Number of participants with dose limiting toxicities (DLT)
DLT will be assessed by physical examination, vital signs, and laboratory values
Time frame: up to 64 days
Identification of recommended phase 2 dose of CLR 131 in children, adolescents, and young adults
Dose and regimen to be used in Phase 2 trials of CLR 131 in children, adolescents, and young adults
Time frame: until non-tolerated dose is defined; dose escalation decision made upon review of data from a complete cohort (85 days after all subjects in cohort have received infusion)
Determination of preliminary antitumor activity of CLR 131 in children, adolescents, and young adults
Response assessment per applicable criteria (e.g., Neuroblastoma Response Criteria (modified); RECIST 1.1; positron emission tomography response criteria in solid tumors (PERCIST); RANO)
Time frame: through Day 85
Determination of therapeutic activity of CLR 131 in children, adolescents, and young adults
Assessment via 131-I/CLR 131 SPECT/CT scans
Time frame: up to 22 days post initial infusion
Determination of event free survival following CLR 131 infusion in children, adolescents, and young adults
Time from first infusion of CLR 131 until progression or recurrence of disease
Time frame: 1 month to 5 years
Determination of overall survival following CLR 131 infusion in children, adolescents, and young adults
Time from first infusion of CLR 131 until death due to any reason
Time frame: 1 month to 5 years
Determine dosimetry of CLR 131 in children, adolescents, and young adults
Assessment of dosimetry via whole body planar imaging
Time frame: up to 15 days post initial infusion
Plan to share: No
No publications or documents are linked to this record.
Started Apr 2019 (actual). Primary completion is estimated for Jun 2027, 98 months after the start.
Of 86 phase 1 interventional studies under Neuroblastoma, half reached primary completion within 83 months of starting (the median), counting those still running; a quarter within 60 and three quarters within 114. This study's planned 98 months is above that.
Since we started tracking on Sep 25, 2026, the dates moved once, on Oct 1, 2026: primary completion Aug 2026 → Jun 2027 and completion Feb 2027 → Dec 2027.
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 ↗
This study is active, not recruiting, as verified in Sep 2026. You cannot join it, but the record below documents what was studied.
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Studies of the drug tested here: CLR1404
Cellectar Biosciences, Inc.