RecruitingPhase 1NCT07156565

Actinium Therapy for Late-stage Aggressive Sarcomas

A Seamless Phase 1/2 Open-label Study to Evaluate the Safety, Determine the Maximum Tolerated Dose of Administered Activity, and Evaluate the Efficacy of the Therapeutic Radiopharmaceutical [Ac 225]-RTX-2358 in the Treatment of Relapsed or Refractory Sarcoma

Sponsor

Ratio Therapeutics, Inc.

Enrollment

30 participants

Start Date

Nov 12, 2025

Study Type

INTERVENTIONAL

Conditions

Advanced Soft Tissue Sarcoma

Summary

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

Eligibility

Min Age: 18 Years

Plain Language Summary

Simplified for easier understanding

This study tests a targeted radiation therapy using actinium (a radioactive element) attached to a molecule that seeks out a protein called FAP on sarcoma cells. It's designed for people with advanced soft tissue sarcomas that have stopped responding to other treatments. **You may be eligible if...** - You are 18 or older - You have a confirmed diagnosis of soft tissue sarcoma that has relapsed or is no longer responding to treatment - You have received at least one prior treatment regimen - Your tumor shows up positively on a special FAPi PET scan - Your blood counts, kidney, and liver function are within acceptable ranges - Your physical performance is good (ECOG 0 or 1) **You may NOT be eligible if...** - You have had whole pelvic radiation therapy in the past - You have received radioligand therapy before - You received anticancer therapy, radiation, or surgery within the last 14 days Talk to your doctor to see if this trial is right for you.

This summary was AI-generated to explain the trial in plain language. It is not medical advice. Always discuss eligibility with your doctor before enrolling in a clinical trial.

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Interventions

DRUG[Ac 225]RTX-2358

\[Ac225\]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.

DIAGNOSTIC_TEST[Cu64]LNTH-1363S

\[Cu64\]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 13-35 days before the first administration of study drug \[AC225\]RTX-2358 to confirm that the sarcoma has FAP expression.