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Actinium Therapy for Advanced Sarcomas

This study is testing a new treatment called [Ac225]RTX-2358 for people with advanced soft tissue sarcoma that has come back or not responded to previous treatments. Researchers want to find out how safe [Ac225]RTX-2358 is, what dose is best, and if it can help treat the cancer. Before receiving the treatment, you'll have an imaging test using [Cu64]LNTH-1363S to confirm your tumor expresses a specific protein (Fibroblast Activation Protein). The study will enroll about 30 participants. This treatment works by immunotherapy, which helps your body's immune system fight cancer. The study's current status is unclear.

Study design
This is an open-label, Phase 1/2 study, meaning both you and your doctors will know which treatment you are receiving. It will enroll about 30 participants, with different groups receiving increasing doses of the treatment.
What's involved
You would receive [Ac225]RTX-2358 as an intravenous (IV) injection once every 8 weeks for up to 6 doses. You will also have frequent clinic visits, especially during the first week of treatment.
Compensation
Not stated in the trial record.
Follow-up
The safety of [Ac225]RTX-2358 will be evaluated for 48 weeks after treatment begins. The best dose will be determined after 8 weeks.

AI-generated from the public study record. Only the study team can confirm whether you're eligible — confirm details with them before making decisions.

NCT07156565

Actinium Therapy for Late-stage Aggressive Sarcomas

Recruiting
PHASE1Ages 18+InterventionalTreatment
Ratio Therapeutics, Inc.
~48 participants
Updated 2026-08-28 on ClinicalTrials.gov
What's tested:[Ac 225]RTX-2358[Cu64]LNTH-1363S

At a glance

Recruiting sites
6 of 6 listed sites are recruiting right now
RecruitingSuspended, closed, or not yet open
What they're measuring
Evaluate the safety (Frequency and severity of treatment emergent adverse events (TEAEs), Dose Limiting Toxicities (DLTs), serious adverse events (SAEs) and adverse events of special interest) of [Ac225-]RTX-2358
Measured over 48 weeks
+2 more outcomes measured

Conditions

Advanced Soft Tissue Sarcoma

Explore related trials

Soft Tissue SarcomaProlyl Endopeptidase FAP

Where it's being run

6 sites across 6 states
California1
Minnesota1
New York1
Ohio1
Texas1
Ontario1

Who to contact

Jacqueline Banuelos
[email protected]
310-869-7014
Email the study team

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Do you actually qualify for this trial?

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Eligibility criteria

Inclusion

18 years of age or older.
History of relapsed or refractory soft tissue sarcoma.
Measurable disease as per RECIST (v1.1) for soft tissue sarcoma that is also positive on FAPi PET/CT or PET/MRI scan.
ECOG performance status of 0 or 1.
Adequate Organ reserve and renal function as evidenced by:

Exclusion

History of whole pelvic irradiation or lung irradiation.
History of radioligand therapy.
Treatment within 14 days prior to first administration with:
Patients who are scheduled for external beam radiation therapy or radioligand therapy during the study period.
Congestive heart failure \> Class II New York Heart Association Functional Classification, current pericarditis, myocardial infarction within 6 months, or symptomatic coronary artery disease.
Patients with uncontrollable incontinence.
Unstable or clinically significant concurrent medical condition that would, in the opinion of the Investigator, jeopardize the safety of a patient and/or their compliance with the protocol.
Active infection requiring systemic antibacterial/antibiotic, antifungal, or antiviral therapy. Chronic antiviral therapy for stable viral disease can be included.
History of active fibrotic condition.
Any active malignancy other than sarcoma that requires treatment.
Stable brain metastasis is allowed but documented untreated metastases to brain or meninges are excluded.
Currently pregnant or lactating.
Known allergy to any of the study drugs or their excipients.
Inability or unwillingness to comply with any of the required imaging studies or study assessments.
History of pneumonitis, interstitial lung disease, chronic obstructive pulmonary disease (COPD) or other inflammatory/fibrotic pulmonary condition.

What this trial measures

  • Evaluate the safety (Frequency and severity of treatment emergent adverse events (TEAEs), Dose Limiting Toxicities (DLTs), serious adverse events (SAEs) and adverse events of special interest) of [Ac225-]RTX-235848 weeks

    Frequency and severity of treatment emergent adverse events (TEAEs), Dose Limiting Toxicities (DLTs), serious adverse events (SAEs) and adverse events of special interest (AESIs).

  • Evaluate the preliminary anti-tumor activity of [Ac225]RTX-2358 in patients with relapsed or refractory soft tissue sarcoma48 weeks

    Objective response rate (ORR), defined as the proportion of patient with a complete response (CR) or partial response (PR), per RECISTv1.1. Duration of response (DOR) defined as the duration of time from first date of observed response (CR or PR), to first date of disease progression or death from any cause.

  • Determine the MTD of the administered activity of [Ac-225]RTX-2358 and select the administered activity and schedule for further clinical evaluation8 weeks

    Evaluate dose levels in Phase 1 escalating group design to identify the MTD and the administered activity to be used in the expansion cohort