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Iopofosine I-131

Phase 3

Waldenstrom Macroglobulinaemia | Small molecule | Oncology |Cellectar Biosciences, Inc.|Last Updated: Aug 14, 2026

Target and mechanism

ModalitySmall molecule

Also known as CLR 131, Iopofosine I 131 single dose, Iopofosine I 131 fractionated dose, Iopofosine I 131

Success Probability

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Market & Valuation

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Trial Design

RandomizedACTIVE_CONTROLLEDDMC
Total Trials1
Total Enrollment219

FDA Designations

ACCELERATED_APPROVALORPHAN_DRUGRARE_PEDIATRIC_DISEASEFAST_TRACKBREAKTHROUGH_THERAPY

Clinical trial landscape

Iopofosine I-131 · 6 trials · 24 indications

Phase 3 1Phase 2 1Phase 1 4
NCT07766421Evaluation of Iopofosine I 131 vs. R-CD in WM PatientsWaldenstrom Macroglobulinaemia
NOT YET_RECRUITING219 Analytics
PHASE3NOT YET_RECRUITING
Evaluation of Iopofosine I 131 vs. R-CD in WM Patients
Waldenstrom MacroglobulinaemiaUnlock trial analytics

Study Endpoints

Primary Endpoints

Superiority of progression free survival (PFS)
From baseline randomization through study completion of progressive disease, or death due to any reason (whichever status is recorded first).

A survival analysis will be performed comparing treatment arms using the Cox Proportional Hazard model to determine the hazard ratio, corresponding 95% CI, and p-value to determine superiority between iopofosine I 131 and R-CD.

Part A [CLOVER-1] Clinical benefit rate
84 days

Response assessment per International Uniform Response Criteria for Multiple Myeloma; Lugano Criteria for lymphoma; International Workshop on Chronic Lymphocytic Leukemia for CLL; VIth Waldenstrom's Macroglobulinemia Criteria for Response Assessment; or 2005 Response Criteria for CNS Lymphoma

Part B [CLOVER-WaM] Major Response Rate
12 months

Response assessment per criteria modified from VIth Waldenstrom's Macroglobulinemia Criteria for Response Assessment

Incidence of Treatment Related Adverse Events
up to 18 weeks

Incidence of adverse events assessed using Common Terminology Criteria for Adverse Events (CTCAE) version 5.0. Adverse Events Grading (1 = mild, 2 = moderate, 3 = severe, 4 = life threatening, and 5 = death)

Summary of Adverse Events Possibly Related to Treatment
up to 18 weeks

Adverse Events Grading (1 = mild, 2 = moderate, 3 = severe, 4 = life threatening, and 5 = death)

Dose Determination for CLR 125
57 days after initiation of last cycle (each cycle is 57 days)

Identify the recommended Phase 2 dose and regimen of CLR 125 in advanced TNBC patients

Number of adverse events related to study treatment (CLR 125)
Assessed throughout the study through 1 year following completion of treatment.

Adverse Events are graded per NCI CTCAE v5.0

Safety Evaluation of CLR 131
Assessed throughout the study to 1-year post-infusion follow-up period

Will be assessed by physical examination, performance status, vital signs, laboratory changes over time, and adverse events. Evaluations will use a nonparametric Wilcoxon Signed Rank test and a linear mixed effects modeling will be conducted to evaluate longitudinal changes.

Efficacy Evaluation for Progression Free Survival
Day 84 post-infusion follow-up period through 3 years following completion of treatment.

To determine the therapeutic activity defined as Progression Free Survival (PFS) using Kaplan Meier estimator. PFS is defined as the time from arm assignment until disease progression or death.

Number of participants with dose limiting toxicities (DLT)
up to 64 days

DLT will be assessed by physical examination, vital signs, and laboratory values

Secondary Endpoints

Major response rate (MRR)
Day 1 of Cycle 1 of dosing through the start of new antineoplastic treatment or early termination, whichever occurs first.
Overall response rate (ORR)
Day 1 of Cycle 1 of dosing until start of new antineoplastic treatment or early termination, whichever occurs first.
VGPR/CR rates
Day 1 of Cycle 1 of dosing until the start of new antineoplastic treatment or early termination, whichever occurs first.
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Study Design & Arms

AllocationRANDOMIZED
MaskingNONE
ModelPARALLEL
PurposeTREATMENT

Treatment Arms

ArmTypeDescription
Iopofosine I 131EXPERIMENTALIopofosine I 131
R-CDACTIVE_COMPARATORRituximab, cyclophosphamide, dexamethasone
Iopofosine I 131, intravenous administration WMEXPERIMENTALIopofosine I 131 in Waldenstroms Macroglobulinemia
Iopofosine I 131, intravenous administration MMEXPERIMENTALIopofosine I 131 in Multiple Myeloma
Iopofosine I 131, intravenous administration CNS LymphomaEXPERIMENTALIopofosine I 131 in Central Nervous System Lymphoma
Iopofosine I 131 intravenous administration NHL [CLOSED]EXPERIMENTALIopofosine I 131 in Chronic Lymphocytic Leukemia / Small Lymphocytic Lymphoma, Mantle Cell Lymphoma, Marginal Zone Lymphoma, and Diffuse Large B-Cell Lymphoma
CLR 131 Dose EscalationEXPERIMENTALEnrollment will start at dose level 1 (first 4 participants). Participants will receive 2 doses of CLR 131 intravenously with the first dose on day 1 followed by the second dose on day 8. Dose Level -1 (de-escalation dose, if toxicities warrant) = 12.5 mCi/m\^2 Dose Level 1 (beginning dose) = 15.6 mCi/m\^2 Dose Level 2 (escalation dose) = 18.75 mCi/m\^2 Dose escalation will proceed with no limiting toxicities at each level (maximum of 8 participants at each dose level). With maximum tolerated dose confirmed, an expansion phase will proceed.
Dosimetry PhaseOTHERIopofosine I 131 (CLR 131) will be administered at 10 mCi on day 1 for approximately 15 patients for imaging purposes.
Treatment Phase: CLR 125 Arm 1EXPERIMENTALCLR 125 administered at 65 mCi/m2 fractionated over four doses (day 1, 2, 8, and 9) in each 8-week cycle; patient will receive up to 4 cycles.
Treatment Phase: CLR 125 Arm 2EXPERIMENTALCLR 125 will be administered at 125 mCi/m2 fractionated over four doses (day 1, 2, 8, and 9) in each 8-week cycle; patient will receive up to 3 cycles.
Treatment Phase: CLR 125 Arm 3EXPERIMENTALCLR 125 will be administered at 190 mCi/m2 fractionated over four doses (day 1, 2, 8, and 9) in each 8-week cycle; patient will receive up to 2 cycles.
Pediatric High-Grade Glioma PatientsEXPERIMENTALTwo dosing cohorts will be explored; patients in the first arm will receive two doses, 20 mCi/m2 each, separated by 14 days for two cycles, with a third optional cycle. Patients in the second arm will receive two doses, 10 mCi/m2 each, separated by 14 days for three cycles with a fourth optional cycle.
CLR 131EXPERIMENTALCLR 131 intravenous administration

Interventions

NameTypeDescription
Iopofosine I 131DRUGFractionated dose
Rituximab (active comparator)DRUGRituximab
CyclophosphamateDRUGCyclophosphamide
DexamethasoneDRUGDexamethasone
Iopofosine I 131 single doseDRUGRadiopharmaceutical
Iopofosine I 131 multiple doseDRUGRadiopharmaceutical
Iopofosine I 131 fractionated doseDRUGRadiopharmaceutical
CLR 131DRUGCLR 131 is a radiopharmaceutical dosed intravenously over a period of approximately 30 minutes, dose will be based on total body surface area calculated from actual body weight and height
CLR 125DRUGInvestigational radiopharmaceutical product intended for IV administration.
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Eligibility Criteria

Age Range18 Years to N/A
SexALL
Healthy VolunteersNo

Inclusion Criteria: * Histologically and serologically confirmed diagnosis of WM. * Received at least one prior therapy for WM. * Received treatment with a BTKi (including covalent BTKi or non-covalent BTKi). * Symptomatic disease progression requiring therapy. Specifically, participant must meet o...

Countries:United StatesAustraliaBrazilCzechiaFinlandFranceGreeceIsraelSpainTurkey (Türkiye)United KingdomCanada
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Recent Changes (Last 90 Days)

LOWAug 14, 2026NCT07766421NEW_TRIAL: changed
LOWAug 14, 2026NCT07766421NEW_TRIAL: changed

Frequently asked questions about Iopofosine I-131

What is Iopofosine I 131 used for?

Iopofosine I 131 is an investigational small molecule being developed for oncology indications, including Waldenstrom macroglobulinaemia (also spelled Waldenstrom macroglobulinemia) and breast cancer. It is currently in clinical development for these conditions, with trials evaluating its use in B-cell malignancies and triple negative breast cancer.

Who makes Iopofosine I 131?

Iopofosine I 131 is being developed by Cellectar Biosciences, Inc., a biopharmaceutical company traded on the NASDAQ under the ticker symbol CLRB. The company is conducting clinical trials to evaluate the drug's safety and efficacy in various oncology indications.

What phase is Iopofosine I 131 in?

Iopofosine I 131 is in clinical development across multiple phases. A Phase 1 study is recruiting for triple negative breast cancer, a Phase 2 study (CLOVER-1) is active but not recruiting for B-cell malignancies, and a Phase 3 study is not yet recruiting for Waldenstrom macroglobulinaemia. The drug is investigational and not yet approved.

What clinical trials is Iopofosine I 131 in?

Iopofosine I 131 is being evaluated in several trials. NCT02952508 is a Phase 2 study in select B-cell malignancies with expansion in Waldenstrom macroglobulinemia. NCT07311993 is a Phase 1 study in triple negative breast cancer. NCT07766421 is a Phase 3 study comparing Iopofosine I 131 to R-CD in Waldenstrom macroglobulinaemia patients.

Is Iopofosine I 131 the same as CLR 125?

No, Iopofosine I 131 is not the same as CLR 125. Iopofosine I 131 is being studied in B-cell malignancies and Waldenstrom macroglobulinaemia, while CLR 125 is a separate investigational drug being evaluated in a Phase 1 study for triple negative breast cancer (NCT07311993). Both are developed by Cellectar Biosciences.

What FDA designations has Iopofosine I 131 received?

Iopofosine I 131 has received several FDA designations, including accelerated approval, orphan drug, rare pediatric disease, fast track, and breakthrough therapy. These designations are intended to expedite the development and review of the drug for serious or life-threatening conditions.