Breast CancerPhase 1NCT07311993
Phase 1 Study of CLR 125 in Triple Negative Breast Cancer
A Phase 1 study testing Iopofosine I 131 and CLR 125 in people with Breast Cancer, run by Cellectar Biosciences, Inc. at 4 sites in United States.
Trial summary
The goal of this clinical trial is to evaluate the safety and efficacy of 3 different dose levels of CLR 125 in patients with advanced triple negative breast cancer. The main questions the study aims to answer are: What dose and regimen should be used in future trials of CLR 125 in patients with advanced triple… Read more about this study
- Who is it for?
- Ages 18 years and older
- Conditions the study is for
- Breast Cancer
- What is being tested?
- Iopofosine I 131 and CLR 125
- Type of treatment
- Injection or infusion
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 60 participants
- Where
- 4 sitesUnited States
- Study dates
- 5 Dec 2025to Jul 2029
- Phase
- Phase 1
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 years and older
- All sexes
- No healthy volunteers
- Adult, Older adult
Who may be able to join
- Unequivocal TNBC histology [ER and PR less than 10% each and HER-2 negative].
- Patients that have progressed after at least one prior standard therapeutic regimen given alone or in combination (including, but not limited, to: chemotherapy, immunotherapy, sacituzumab govitecan-hziy, trastuzumab deruxtecan).
- Patients who have received neo-adjuvant or adjuvant therapy must be at least one year from that treatment regimen.
- Patient is ≥ 18 years of age.
- ECOG performance status of 0 to 2.
- Life expectancy ≥ 6 months.
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- Patient must meet the following laboratory criteria:
- Platelets ≥ 75,000/uL [75 x 10^9/L]
- White blood cell (WBC) count ≥ 3000/uL
- Absolute neutrophil count ≥ 1500/uL
- Hemoglobin ≥ 9 g/dL
- Estimated glomerular filtration rate ≥ 30 mL/min/1.73 m2 (as reported by the local lab)
- Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤ 2.5 × upper limit of normal (ULN)
- Bilirubin < 1.5 × ULN
- At least one measurable lesion, as defined by RECIST v1.1, with longest diameter at baseline ≥ 10 mm (excluding lymph nodes, for which the short diameter must be ≥ 15 mm).
- Patients with known brain metastases must have completed any radiotherapy or systemic treatments for brain metastases prior to enrollment; by investigator assessment be considered stable with no new signs or symptoms for at least 1 month, and on a stable dose of steroids (unchanged for three weeks prior to registration or on a steroid tapering regimen).
- Patients must express willingness and ability to comply with scheduled study visits, treatment plans, laboratory tests, and other study procedures.
- Patient or their legally authorized representative must have the ability to understand and provide signed informed written consent before the initiation of any study-related procedures.
- Female patients of childbearing potential must have a negative pregnancy test within 24 hours of dosing.
- Women of childbearing potential must agree to use a highly effective method of contraception during the study and for 12 months following administration of the study drug. Highly effective methods of contraception include combined (estrogen and progestogen containing) hormonal contraceptives associated with inhibition of ovulation, progestogen-only hormonal contraception associated with inhibition of ovulation, intrauterine device, intrauterine hormone-releasing system, vasectomized partner, or sexual abstinence. Women who have undergone hysterectomy, bilateral oophorectomy, or bilateral tubal ligation, or are post-menopausal (no menses for 12 months without an alternative medical cause) are considered to be of non-childbearing potential.
- Men who are able to father a child must agree to use a condom during the study and for 12 months following administration of the study drug.
Who cannot join
- Antitumor systemic therapy or investigational therapy, within three-half-lives of the agent preceding study drug administration. NOTE: Patients participating in non-interventional clinical trials (i.e., non-drug) are allowed to participate in this trial.
- Focal radiation (including palliative radiation) to non-target lesions should be completed at least 2 weeks prior to dosing.
- For patients receiving CLR 125 after participation in the dosimetry phase, CLR 131 washout is not required prior to dosing with CLR 125.
- Prior targeted radiotherapy.
- Prior external beam radiation therapy resulting in greater than 20% of total bone marrow receiving greater than 20 Gy. For estimation purposes, the following bone marrow percentages can be used:
- Vertebral bodies: Cervical 0.5%, thoracic 1%, lumbar 2% per vertebral body
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- Hemipelvis (ilium, acetabulum, ischium): 13% per side
- Sacrum: 10%
- Skull: 12%
- Scapula: 5% per side
- Ribs: 4% per side
- Femur: 3% per side
- Ongoing Grade 2 or greater toxicities due to previous therapies, excluding alopecia, that in the opinion of investigator might be exacerbated by study treatment.
- Patients with prior or concurrent malignancy other than TNBC with the following exceptions, which must be fully treated with no evidence of disease for at least 2 years: non-melanoma skin cancers only requiring topical treatment or surgical excision; melanoma in situ; treated cervical carcinoma in situ; successfully treated prostate cancer.
- Any other concomitant serious illness or organ system dysfunction (including cardiac and pulmonary dysfunction) that in the opinion of the Investigator would either compromise patient safety or interfere with the evaluation of the safety of the test drug.
- Known history of human immunodeficiency virus or uncontrolled, serious, active infection.
- Pregnancy or breast-feeding
Trial locations and contacts
4 sites in 1 country. Contact the study team or a site near you to ask about taking part.
United States4 sites, 4 recruiting
- Recruiting
United Theranostics
Glen Burnie, Maryland, 21061
Amanda Huggins, 667-467-3669, clinicaltrial@unithera.com
Babak Saboury, MD
- Recruiting
Mayo Clinic Florida
Jacksonville, Florida, 32224
Clinical Trials Referral Office, 855-776-0015, CancerTrials@mayo.edu
Pooja Advani, MD
- Recruiting
United Theranostics
Princeton, New Jersey, 08540
Amanda Huggins, 667-467-3669, clinicaltrial@unithera.com
Munir Ghesani, MD
- Recruiting
Mayo Clinic Rochester
Rochester, Minnesota, 55905
Clinical Trials Referral Office, 855-776-0015, CancerTrials@mayo.edu
Karthik Giridhar, MD
About this study
Official title: A Phase 1b, Open-Label Parallel Study Evaluating CLR 125 in Patients With Relapsed or Refractory Triple Negative Breast Cancer
The goal of this clinical trial is to evaluate the safety and efficacy of 3 different dose levels of CLR 125 in patients with advanced triple negative breast cancer. The main questions the study aims to answer are:
- What dose and regimen should be used in future trials of CLR 125 in patients with advanced triple negative breast cancer.
- What side effects do participants have when taking CLR 125.
Read more
Participants will:
- Have CLR 125 administered via infusion 4 times each cycle; repeated every 8 weeks.
- Visit the clinic once every 3 weeks for checkups and testing.
- Report any side effects or new medications.
Some participants may also receive one dose of CLR 131 to evaluate the amount of radiation delivered to various organs and to the tumor. These participants will:
- Have 4 scans completed over 2 weeks
- Have blood drawn 6 times over 2 weeks.
Read the detailed description
This study is designed to determine the recommended dose and regimen for future trials and to evaluate the safety and tolerability of CLR 125 at the selected doses in patients with advanced triple negative breast cancer. It will also determine the antitumor activity (treatment response by RECIST v1.1) through assessment of overall response rate, progression free survival, overall survival, duration of response and duration of clinical benefit of CLR 125 in patients with advanced triple negative breast cancer.
Total body, organ, and tumor dosimetry will be assessed in a select number of patients prior to CLR 125 dosing. At the conclusion of the study, total body, organ, and tumor dosimetry will be calculated for the intended patient population, to inform future studies.
Up to 60 evaluable patients will be enrolled.
- Conditions
- Breast Cancer
- Being tested
- Iopofosine I 131, CLR 125
- Keywords
- triple negative breast cancer
- Medical subject headings
- Breast Neoplasms, Triple Negative Breast Neoplasms
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Iopofosine I 131Drug
Also called CLR 131
Investigational radiopharmaceutical product intended for IV administration.
CLR 125Drug
Investigational radiopharmaceutical product intended for IV administration.
| Study group | Role | What they receive |
|---|---|---|
| Dosimetry Phase | Other | Iopofosine I 131 (CLR 131) will be administered at 10 mCi on day 1 for approximately 15 patients for imaging purposes. Receives: Drug: Iopofosine I 131 |
| Treatment Phase: CLR 125 Arm 1 | Experimental | CLR 125 administered at 65 mCi/m2 fractionated over four doses (day 1, 2, 36, and 37) in each 8-week cycle; patient will receive up to 4 cycles. Receives: Drug: CLR 125 |
| Treatment Phase: CLR 125 Arm 2 | Experimental | CLR 125 will be administered at 125 mCi/m2 fractionated over four doses (day 1, 2, 36, and 37) in each 8-week cycle; patient will receive up to 3 cycles. Receives: Drug: CLR 125 |
| Treatment Phase: CLR 125 Arm 3 | Experimental | CLR 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. Arm 3 is no longer enrolling. Receives: Drug: CLR 125 |
| Treatment Phase: CLR 125 Arm 4 | Experimental | CLR 125 will be administered at 80 mCi/m2 fractionated over four doses (day 1, 2, 36, and 37) in each 8-week cycle; patient will receive up to 4 cycles. Receives: Drug: CLR 125 |
What is being measured
The primary outcome is the main question the study is designed to answer.
Dose Determination for CLR 125
Identify the recommended Phase 2 dose and regimen of CLR 125 in advanced TNBC patients
Measured: 57 days after initiation of last cycle (each cycle is 57 days)
Number of adverse events related to study treatment (CLR 125)
Adverse Events are graded per NCI CTCAE v5.0
Measured: Assessed throughout the study through 1 year following completion of treatment.
Secondary outcomes (5)
Efficacy Evaluation for Overall Response Rate
To determine the overall response (ORR) rate as assessed by RECIST v1.1.
Measured: 57 days after initiation of last cycle (each cycle is 57 days)
Efficacy Evaluation for Progression Free Survival
To determine the therapeutic activity defined as Progression Free Survival (PFS) using Kaplan Meier estimator.
Measured: Assessed throughout the study through 1 year following completion of treatment
Efficacy Evaluation for Overall Survival
To determine the therapeutic activity defined as Overall Survival (OS) using Kaplan Meier estimator.
Measured: Assessed throughout the study through 1 year following completion of treatment
Evaluation for Duration of Response
To determine the therapeutic activity defined as Duration of Response (DOR) using Kaplan Meier estimator.
Measured: Assessed throughout the study through 1 year following completion of treatment
Efficacy Evaluation for Duration of Clinical Benefit
To determine the therapeutic activity defined as Duration of Clinical Benefit (DOCB) using Kaplan Meier estimator.
Measured: Assessed throughout the study through 1 year following completion of treatment.
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted31 Dec 2025
- Study start5 Dec 2025
- Primary completionFeb 2028 (estimated)
- Study completionJul 2029 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Breast CancerStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase 1
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Model description
- CLR 125 is a radio-iodinated therapy comprising a core phospholipid ether (PLE) analogue radiolabeled with iodine-125. CLR 125 exploits the tumor-targeting properties of PLEs to provide targeted delivery of Auger-emitting radiation to malignant tumor cells and minimizes radiation exposure to normal tissues.
- Masking
- None (open label)
- Enrolment
- 60 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Cellectar Biosciences, Inc.
- Sponsor type
- Industry (pharma, biotech, devices)
- Responsible party
- Sponsor
- Investigators
- Jarrod Longcor, Study director, Cellectar Biosciences
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07311993
- Sponsor's protocol ID
- DCL-25-003
- Status last verified
- Oct 2026
- First submitted
- 13 Nov 2025
- Last updated
- 8 Oct 2026
- Results posted
- No
- Data monitoring committee
- Yes
- FDA-regulated drug
- Yes
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 8 Oct 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- A Phase 1b, Open-Label Parallel Study Evaluating CLR 125 in Patients With Relapsed or Refractory Triple Negative Breast Cancer
- ClinicalTrials.gov ID
- NCT07311993
- Acronym / sponsor ID
- DCL-25-003
- Conditions
- Breast Cancer
- Keywords
- triple negative breast cancer
- Phase
- Phase 1
- Study type
- Interventional
- Recruitment status
- Recruiting
- Enrolment
- 60 participants (estimated)
- Lead sponsor
- Cellectar Biosciences, Inc.Industry (pharma, biotech, devices)
- Study start
- 5 Dec 2025 (actual)
- Primary completion
- Feb 2028 (estimated)
- Study completion
- Jul 2029 (estimated)
- First posted
- 31 Dec 2025 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
The goal of this clinical trial is to evaluate the safety and efficacy of 3 different dose levels of CLR 125 in patients with advanced triple negative breast cancer. The main questions the study aims to answer are:
- What dose and regimen should be used in future trials of CLR 125 in patients with advanced triple negative breast cancer.
- What side effects do participants have when taking CLR 125.
Participants will:
- Have CLR 125 administered via infusion 4 times each cycle; repeated every 8 weeks.
- Visit the clinic once every 3 weeks for checkups and testing.
- Report any side effects or new medications.
Some participants may also receive one dose of CLR 131 to evaluate the amount of radiation delivered to various organs and to the tumor. These participants will:
- Have 4 scans completed over 2 weeks
- Have blood drawn 6 times over 2 weeks.
Detailed description
This study is designed to determine the recommended dose and regimen for future trials and to evaluate the safety and tolerability of CLR 125 at the selected doses in patients with advanced triple negative breast cancer. It will also determine the antitumor activity (treatment response by RECIST v1.1) through assessment of overall response rate, progression free survival, overall survival, duration of response and duration of clinical benefit of CLR 125 in patients with advanced triple negative breast cancer.
Total body, organ, and tumor dosimetry will be assessed in a select number of patients prior to CLR 125 dosing. At the conclusion of the study, total body, organ, and tumor dosimetry will be calculated for the intended patient population, to inform future studies.
Up to 60 evaluable patients will be enrolled.
Study design
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- None (open label)
- Number of arms
- 5
- Model description
- CLR 125 is a radio-iodinated therapy comprising a core phospholipid ether (PLE) analogue radiolabeled with iodine-125. CLR 125 exploits the tumor-targeting properties of PLEs to provide targeted delivery of Auger-emitting radiation to malignant tumor cells and minimizes radiation exposure to normal tissues.
| Arm | Type | Receives |
|---|---|---|
| Dosimetry Phase | Other | Drug: Iopofosine I 131Iopofosine 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 1 | Experimental | Drug: CLR 125CLR 125 administered at 65 mCi/m2 fractionated over four doses (day 1, 2, 36, and 37) in each 8-week cycle; patient will receive up to 4 cycles. |
| Treatment Phase: CLR 125 Arm 2 | Experimental | Drug: CLR 125CLR 125 will be administered at 125 mCi/m2 fractionated over four doses (day 1, 2, 36, and 37) in each 8-week cycle; patient will receive up to 3 cycles. |
| Treatment Phase: CLR 125 Arm 3 | Experimental | Drug: CLR 125CLR 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. Arm 3 is no longer enrolling. |
| Treatment Phase: CLR 125 Arm 4 | Experimental | Drug: CLR 125CLR 125 will be administered at 80 mCi/m2 fractionated over four doses (day 1, 2, 36, and 37) in each 8-week cycle; patient will receive up to 4 cycles. |
Who may qualify
- Ages
- 18 years and older
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (21 listed)
- Unequivocal TNBC histology [ER and PR less than 10% each and HER-2 negative].
- Patients that have progressed after at least one prior standard therapeutic regimen given alone or in combination (including, but not limited, to: chemotherapy, immunotherapy, sacituzumab govitecan-hziy, trastuzumab deruxtecan).
- Patient is ≥ 18 years of age.
- ECOG performance status of 0 to 2.
- Life expectancy ≥ 6 months.
Key exclusion criteria (17 listed)
- Antitumor systemic therapy or investigational therapy, within three-half-lives of the agent preceding study drug administration. NOTE: Patients participating in non-interventional clinical trials (i.e., non-drug) are allowed to participate in this trial.
- Prior targeted radiotherapy.
- Prior external beam radiation therapy resulting in greater than 20% of total bone marrow receiving greater than 20 Gy. For estimation purposes, the following bone marrow percentages can be used:
- Ongoing Grade 2 or greater toxicities due to previous therapies, excluding alopecia, that in the opinion of investigator might be exacerbated by study treatment.
- Patients with prior or concurrent malignancy other than TNBC with the following exceptions, which must be fully treated with no evidence of disease for at least 2 years: non-melanoma skin cancers only requiring topical treatment or surgical excision; melanoma in situ; treated cervical carcinoma in situ; successfully treated prostate cancer.
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Iopofosine I 131Also: CLR 131Investigational radiopharmaceutical product intended for IV administration. | Drug | Dosimetry Phase |
| CLR 125Investigational radiopharmaceutical product intended for IV administration. | Drug | Treatment Phase: CLR 125 Arm 1, Treatment Phase: CLR 125 Arm 2, Treatment Phase: CLR 125 Arm 3, Treatment Phase: CLR 125 Arm 4 |
Primary outcome
Dose Determination for CLR 125
Time frame: 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)
Time frame: Assessed throughout the study through 1 year following completion of treatment.
Adverse Events are graded per NCI CTCAE v5.0
5 secondary outcomes
Efficacy Evaluation for Overall Response Rate
Time frame: 57 days after initiation of last cycle (each cycle is 57 days)
Efficacy Evaluation for Progression Free Survival
Time frame: Assessed throughout the study through 1 year following completion of treatment
Efficacy Evaluation for Overall Survival
Time frame: Assessed throughout the study through 1 year following completion of treatment
Evaluation for Duration of Response
Time frame: Assessed throughout the study through 1 year following completion of treatment
Efficacy Evaluation for Duration of Clinical Benefit
Time frame: Assessed throughout the study through 1 year following completion of treatment.
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 8 Oct 2026.
- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
Jarrod Longcor study director
Cellectar Biosciences
4 sites in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 1 study testing Iopofosine I 131 and CLR 125 in people with Breast Cancer, run by Cellectar Biosciences, Inc. at 4 sites in United States.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 21 inclusion and 17 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: looking for participants now, as of the sponsor's last update on 8 Oct 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 4 sites in United States. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this phase mean?
Phase 1 studies test a treatment in a small group of people for the first time or in a new way, mainly to check safety and find the right dose.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Kate Oliver (608-441-8120, clinical@cellectar.com), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Dose Determination for CLR 125 (time frame: 57 days after initiation of last cycle (each cycle is 57 days)). The study lists 2 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 8 Oct 2026.