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Study Evaluating Dosimetry, Randomized Dose Optimization, Dose Escalation and Efficacy of Ac-225 Rosopatamab Tetraxetan in Participants With PSMA PET-Positive Castration-Resistant Prostate Cancer (CRPC)

  • PhasePhase 2
  • StatusRecruiting
  • Planned enrollment93 people
  • Recruiting US sites8
  • SponsorConvergent Therapeutics
  • RegistryNCT06549465

Recruitment re-checked on ClinicalTrials.gov Oct 30, 2026. Public record; not medical advice.

Study Evaluating Dosimetry, Randomized Dose Optimization, Dose Escalation and Efficacy of Ac-225 Rosopatamab Tetraxetan in Participants With PSMA PET-Positive Castration-Resistant Prostate Cancer (CRPC): a one-minute explainerNCT065494651 min

Eligibility

Who can join

The film gives the main points. The full list below is copied from the registry; the study team makes the final decision.

  • Age18 Years to no maximum
  • SexMale
  • Healthy volunteersNo

You may be able to join if

  • Progressive CRPC defined as castrate levels of testosterone and progressing by at least one of the following criteria:
  • Serum PSA progression as defined by PCWG3 (rising PSA consisting of two consecutive increases measured at least 3 weeks apart, of a rise of >25%, and with an absolute rise of 2.0 ng/mL.
  • Soft tissue progression defined as a ≥20% increase in the sum of the diameter (short axis for nodal lesions and long axis for non-nodal lesions) of all target lesions based on the smallest sum of the diameter since the previous treatment was started or the appearance of one or more new lesions by CT/magnetic resonance imaging (MRI)
  • Progression of bone disease defined by PCWG3 as evaluable disease or new bone lesions by bone scan
  • Identification of new soft tissue or bone lesions on PSMA PET imaging
  • Metastatic disease defined as either or both of the following:
  • Parts 1, 2, 3, and 4: Documented M1 disease on conventional imaging (CT/MRI of the chest/abdomen/pelvis and/or Technetium 99m [99mTc] whole-body bone scan)
  • Parts 1, 2, and 4 only: Identification of bone lesion(s), extra-pelvic soft tissue lesion(s), or visceral metastases on PSMA PET imaging with an FDA-approved imaging agent
  • PSMA PET-positive disease, defined as at least one PSMA-positive metastatic lesion and no PSMA-negative lesions
  • Progression following treatment with ADT and at least one ARSI (e.g., enzalutamide, apalutamide, darolutamide, and/or abiraterone acetate)
  • The standard of care use (in the setting of metastatic CRPC with significant burden of active bone metastases) of antiresorptive bone-targeted agents (e.g., zoledronic acid, denosumab) is required for all participants without a contraindication, for at least 4 weeks prior to administration of Ac-225 rosopatamab tetraxetan.
  • Participants with HIV are eligible if they are well-controlled (i.e, an undetectable HIV viral load (<50 copies/mL) within 6 months of enrollment and a stable ART regimen for at least 6 months prior to enrollment) and at low risk for HIV-related illness
  • Part 3 Only:
  • Prior treatment with Lu-177-PSMA-radioligand therapy
  • Prior treatment with up to only one taxane-based chemotherapy regimen is allowed

You cannot join if

  • Superscans by nuclear medicine/99mTc bone scan
  • A known malignancy that is progressing or has required active treatment within the past 3 years other than CRPC, which is expected to alter life expectancy or may interfere with CRPC disease assessment
  • Prior platinum-based chemotherapy
  • Prior PARP inhibitors (e.g., olaparib or rucaparib)
  • Prior treatment with Radium-223, Actinium-225, Strontium-89, Samarium-153, Rheunium-186, or Rhenium-188
  • Participants receiving anti-coagulants or anti-platelet drugs (e.g., aspirin or nonsteroidal anti-inflammatory drugs [NSAIDs]) who cannot discontinue use if platelet count decreases to <50,000
  • Part 2 and 4 Only:
  • Prior chemotherapy for CRPC. Prior taxane chemotherapy for HSPC is allowed if discontinued ≥1 year prior to randomization
  • Prior radiopharmaceutical therapy (e.g., Ra-223, Lu-177-PSMA-617, or Lu-177-PSMA-I&T)
  • Prior PSMA-targeted therapy, except for bispecific or CAR-T therapies
  • Part 3 Only:
  • Prior PSMA-targeted therapy (e.g., antibody-drug conjugates or CAR-T therapy), except for Lu-177-PSMA-radioligand therapy and bispecific or CAR-T therapies

The treatment

How it is intended to work

This is how the treatment is meant to work. Whether it helps, and how safe it is, is what this trial is testing.

actinium Ac 225 rosopatamab tetraxetan. A radioimmunoconjugate consisting of a humanized monoclonal antibody directed against prostate specific membrane antigen (PSMA) labeled with the alpha particle-emitting radioisotope actinium Ac-225, with potential antineoplastic activity. Upon administration, actinium Ac 225 rosopatamab tetraxetan binds to the extracellular domain of PSMA with high affinity, thereby delivering alpha radiation to PSMA expressing cells. PSMA, a type II membrane protein expressed in all types of prostatic tissues, is often overexpressed in tumor cells. NCI Drug Dictionary

Treatments listed in the registry

  • In-111 rosopatamab tetraxetan (Biological): A single dose of 148 ± 37 MBq In-111 rosopatamab tetraxetan will be administered as an IV infusion over a period of 10 minutes.
  • 45 kBq/kg Ac-225 rosopatamab tetraxetan (Biological): 45 kBq/kg Ac-225 rosopatamab tetraxetan will be administered as an IV infusion over a period of 10 minutes. Doses will be given two weeks apart for a total of two doses.
  • 45 kBq/kg or equivalent fixed dose activity Ac-225 rosopatamab tetraxetan (Biological): 45 kBq/kg Ac-225 rosopatamab tetraxetan will be administered as an IV infusion over a period of 10 minutes. Doses will be given two weeks apart for a total of two doses.
  • 60 kBq/kg Ac-225 rosopatamab tetraxetan (Biological): 60 kBq/kg Ac-225 rosopatamab tetraxetan will be administered as an IV infusion over a period of 10 minutes. Doses will be given two weeks apart for a total of two doses.
  • Single dose 22 kBq/kg or equivalent fixed dose activity Ac-225 rosopatamab tetraxetan (Biological): 22 kBq/kg Ac-225 rosopatamab tetraxetan will be administered as an IV infusion over a period of 10 minutes. A single dose will be given.
  • Single dose 34 kBq/kg or equivalent fixed dose activity Ac-225 rosopatamab tetraxetan (Biological): 34 kBq/kg Ac-225 rosopatamab tetraxetan will be administered as an IV infusion over a period of 10 minutes. A single dose will be given.
  • Single dose 45 kBq/kg or equivalent fixed dose activity Ac-225 rosopatamab tetraxetan (Biological): 45 kBq/kg Ac-225 rosopatamab tetraxetan will be administered as an IV infusion over a period of 10 minutes. A single dose will be given.
  • 55 kBq/kg or equivalent fixed dose activity Ac-225 rosopatamab tetraxetan (Biological): 55 kBq/kg Ac-225 rosopatamab tetraxetan will be administered as an IV infusion over a period of 10 minutes. Doses will be given two weeks apart for a total of two doses.
  • 60 kBq/kg or equivalent fixed dose activity Ac-225 rosopatamab tetraxetan (Biological): 60 kBq/kg Ac-225 rosopatamab tetraxetan will be administered as an IV infusion over a period of 10 minutes. Doses will be given two weeks apart for a total of two doses.

The study

Treatment groups

Non Randomized · Sequential · masking: None

Part 1: 148 ± 37 MBq In-111 rosopatamab tetraxetan (Experimental)

Part 2: 45 kBq/kg Ac-225 rosopatamab tetraxetan (Experimental)

Part 2: 60 kBq/kg Ac-225 rosopatamab tetraxetan (Experimental)

Part 3: Dose Escalation and Expansion (Experimental)

Participants previously treated with Lu-177-PSMA-radioligand therapy will be assigned to receive one of the three dose levels (45 kBq/kg, 55 kBq/kg, or 60 kBq/kg, or equivalent fixed dose activity) depending on the dose limiting toxicities (DLTs) observed.

Part 4: Dose Escalation and Expansion (Experimental)

Participants will initially receive two doses of the Part 2 selected dose level, followed by a single third dose of Ac-225 rosopatamab tetraxetan approximately 12 weeks after the completion of the Part 2 fractionated dosing regimen. Participants will be assigned to receive one of the three dose levels (22 kBq/kg, 34 kBq/kg, or 45 kBq/kg, or equivalent fixed dose activity) depending on the dose limiting toxicities (DLTs) observed.

Goals

What the study measures

Main goals

  • Part 1: Visual evaluation on whole body planar scans (days 1 and 4) with comparison to reference scans for the presence of radiolabeled rosopatamab textraxetan in organs of interest (e.g., liver, circulation, spleen) to determine biodistribution (Day 1 and Day 4)
  • Part 2: Incidence of Adverse Events (AEs) and Serious Adverse Events (SAEs) overall, by severity, and leading to discontinuation of study intervention (Screening through Week 12)
  • Part 2: Proportion of participants who achieve a greater than or equal to 50% decline in prostate-specific antigen (PSA50) (Through end of study (approximately 3 years) or until PSA progression as defined by PCWG3 criteria)
  • Part 3: Incidence of Adverse Events (AEs) and Serious Adverse Events (SAEs) overall, by severity, and leading to discontinuation of study intervention (Screening through Week 12)
  • Part 3: Determine the recommended Phase 2 dose (RP2D) of Ac-225 rosopatamab tetraxetan (Day 1 through 6 weeks)
  • Part 3 (Participants treated at RP2D): Proportion of participants who achieve a greater than or equal to 50% decline in prostate-specific antigen (PSA50) (Through end of study (approximately 3 years) or until PSA progression as defined by PCWG3 criteria)
  • Part 4: Incidence of AEs and SAEs overall, by severity, by relationship to study drug, and leading to discontinuation of study intervention (Screening through Week 12)
  • Part 4: Determine the recommended Phase 2 dose (RP2D) of Ac-225 rosopatamab tetraxetan (Through end of study (approximately 3 years))

Other goals

  • Part 2: Determine the clearance of rosopatamab tetraxetan and Ac-225 rosopatamab tetraxetan via measurement of whole blood and serum levels at specified serial timepoints
  • Part 2: Radioactivity levels of Ac-225 rosopatamab tetraxetan
  • Part 2: Radiation dosimetry of Ac-225 rosopatamab tetraxetan: Absorbed radiation dose (expressed as Gy/MBq) in normal organs
  • Part 2: Biochemical progression-free survival (bPFS) as assessed by the Prostate Cancer Working Group 3 (PCWG3)
  • Part 3: Proportion of participants who achieve PSA50
  • Part 3: Determine the clearance of rosopatamab tetraxetan and Ac-225 rosopatamab tetraxetan from the circulation via measurement in the serum at specified serial timepoints
  • Part 3: Radioactivity levels of Ac-225 rosopatamab tetraxetan
  • Part 4: Proportion of participants who achieve PSA50
  • Part 4: Biochemical progression-free survival (bPFS) as assessed by the Prostate Cancer Working Group 3 (PCWG3)

Planned enrollment: 93 (estimated).

Where

Recruiting US sites

  • University of California San Diego, San Diego, California
  • Dana-Farber Cancer Institute, Boston, Massachusetts
  • X Cancer Omaha / Urology Cancer Center, Omaha, Nebraska
  • Laura & Isaac Perlmutter Cancer Center, New York, New York
  • Memorial Sloan Kettering Cancer Center, New York, New York
  • New York Presbyterian/Weill Cornell Medical Center, New York, New York
  • Duke University Medical Center, Durham, North Carolina
  • The Cleveland Clinic Foundation, Cleveland, Ohio

Site status as of Oct 30, 2026. Check the live record before contacting a site.

Sources

Where this comes from

Registry record reviewed as fetched Oct 30, 2026, last updated by the sponsor Oct 1, 2026. Public record; not medical advice.

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