RECRUITING Phase 1 ClinicalTrials.gov

Actinium Therapy for Late-stage Aggressive Sarcomas

Sponsor: Ratio Therapeutics, Inc. • ClinicalTrials.gov ID: NCT07156565

Registry updated: 2026-08-28

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Description

The goal of this clinical trial is to learn about the safety of drug \[Ac225\]RTX-2358 and the diagnostic imaging agent \[Cu64\]LNTH-1363S. Additionally Ratio Therapeutics will learn if \[Ac225\]RTX-2358 drug is effective in treating advanced sarcoma. The main questions the study aims to answer in Phase/Part 1 of the trial are: * Is \[Ac225\]RTX-2358 tolerable or does it cause toxicities (medical problems) in patients. * What is the most tolerable dose of \[Ac225\]RTX-2358 * Does the treatment show effectiveness on advanced sarcoma Participants will: * Take drug \[Ac225\]RTX-2358 once every 8 weeks (4 cycle target; 6 cycle maximum) over a period of 12 months * Visit the clinic three times for the first week of cycle one, then once a week for the remaining 7 weeks of cycle 1 for check-ups and tests. * For cycles 2-6: patient will visit the clinic once every 2 weeks for checkups and tests * Remain in long term follow-up for a period of four additional years

Interventions

[Ac 225]RTX-2358 (Drug)
\[Ac225\]RTX-2358 will be given as an intravenous injection once every 8 weeks for up to 6 doses. Each group will receive a set administered activity level (dose) of \[Ac 225\]RTX 2358 given once every 8 weeks. The first group will received the lower dose, the second group will received the mid level dose, and the third group the highest dose. A Safety Review Committee will determine when/if it is appropriate to allow the next group to proceed.
[Cu64]LNTH-1363S (Diagnostic test)
\[Cu64\]LNTH-1363S is a investigational radioactive diagnostic imaging agent to demonstrate that the tumor expresses Fibroblast Activation Protein. An imaging test is performed after a single injection with \[Cu64\]LNTH-1363S 14-30 days before the first administration of study drug \[AC225\]RTX-2358 to confirm that the sarcoma has FAP expression.

Eligibility criteria

Inclusion Criteria: * 18 years of age or older. * History of relapsed or refractory soft tissue sarcoma. 1. Histological confirmation of sarcoma at any point since diagnosis 2. At least 1 prior treatment regimen * 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: 1. Neutrophil count ≥ 1200 µL without granulocyte colony stimulating factor 2. Platelet count ≥ 100,000 µL 3. Hemoglobin ≥ 8 g/dL 4. Total bilirubin level ≤ 1.5 × upper limit of normal (ULN). 5. Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤ 2.5 × ULN. 6. Calculated creatinine clearance ≥ 60 mL/min. 6. Coagulation parameters (prothrombin time, international normalized ratio and activated partial thromboplastin time) ≤ 1.5 × ULN 7. All patients (males and females of childbearing potential) must agree to practice 2 forms of highly effective contraceptive precautions to prevent pregnancy from the time consent is signed and throughout the trial. 8\. The patient or the patient's legal representative must be willing and able to provide written informed consent. Exclusion Criteria: * History of whole pelvic irradiation or lung irradiation. * History of radioligand therapy. * Treatment within 14 days prior to first administration with: 1. Palliative surgery or external beam radiation. 2. Approved anticancer therapy including chemotherapy or immunotherapy. 3. Any investigational therapy. 4. Any major surgery (e.g., requiring general anesthesia). * 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.

Conditions

Advanced Soft Tissue Sarcoma

Locations

UCLA — Los Angeles, California, United States
Mayo Clinic — Rochester, Minnesota, United States
Memorial Sloane Kettering Cancer Center — New York, New York, United States
Case Western — Cleveland, Ohio, United States
MD Anderson Cancer Center — Houston, Texas, United States
Princess Margaret Cancer Centre — Toronto, Ontario, Canada

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Official Source

Data sourced from ClinicalTrials.gov, a service of the U.S. National Institutes of Health.

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