NCT06549465 · Convergent Therapeutics
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)
What this study is about
This is a three-part study evaluating the safety and effectiveness of a PSMA-directed radioantibody (rosopatamab tetraxetan, conjugated to either In-111 or Ac-225). Part 1 will consist of one administration of In-111-rosopatamab tetraxetan to characterize the biodistribution of the radioantibody to target organs and prostate cancer lesions.
View original scientific description
This is a three-part study evaluating the safety and efficacy of a PSMA-directed radioantibody (rosopatamab tetraxetan, conjugated to either In-111 or Ac-225). Part 1 will consist of one administration of In-111-rosopatamab tetraxetan to characterize the biodistribution of the radioantibody to target organs and prostate cancer lesions. Participants then will be enrolled into either Part 2 (Dose Optimization) or Part 3 (Dose Escalation and Expansion) depending on their prior treatment history.
Interventions
BIOLOGICAL
In-111 rosopatamab tetraxetan
A single dose of 148 ± 37 MBq In-111 rosopatamab tetraxetan will be administered as an IV infusion over a period of 10 minutes.
BIOLOGICAL
45 kBq/kg Ac-225 rosopatamab tetraxetan
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.
BIOLOGICAL
45 kBq/kg or equivalent fixed dose activity Ac-225 rosopatamab tetraxetan
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.
BIOLOGICAL
60 kBq/kg Ac-225 rosopatamab tetraxetan
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.
BIOLOGICAL
Single dose 22 kBq/kg or equivalent fixed dose activity Ac-225 rosopatamab tetraxetan
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.
BIOLOGICAL
Single dose 34 kBq/kg or equivalent fixed dose activity Ac-225 rosopatamab tetraxetan
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.
BIOLOGICAL
Single dose 45 kBq/kg or equivalent fixed dose activity Ac-225 rosopatamab tetraxetan
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.
BIOLOGICAL
55 kBq/kg or equivalent fixed dose activity Ac-225 rosopatamab tetraxetan
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.
BIOLOGICAL
60 kBq/kg or equivalent fixed dose activity Ac-225 rosopatamab tetraxetan
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.
Primary outcome measures
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
Time frame: 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
Time frame: Screening through Week 12
Part 2: Proportion of participants who achieve a greater than or equal to 50% decline in prostate-specific antigen (PSA50)
Time frame: 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
Time frame: Screening through Week 12
Part 3: Determine the recommended Phase 2 dose (RP2D) of Ac-225 rosopatamab tetraxetan
Time frame: 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)
Time frame: 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
Time frame: Screening through Week 12
Part 4: Determine the recommended Phase 2 dose (RP2D) of Ac-225 rosopatamab tetraxetan
Time frame: Through end of study (approximately 3 years)
Who can participate
This study lists these criteria on ClinicalTrials.gov. A study coordinator reviews eligibility during screening — this page does not determine whether you qualify.
Inclusion criteria
- 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
Exclusion criteria
- 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
Where
- San Diego, California
- Boston, Massachusetts
- St Louis, Missouri
- Omaha, Nebraska
- New York, New York
- Durham, North Carolina
- Cleveland, Ohio
Related conditions & keywords
Frequently asked questions
What is a clinical trial?
A clinical trial is a research study that tests new medical treatments, drugs, devices, or procedures to determine their safety and effectiveness. Trials are carefully designed and monitored to protect participants while advancing medical knowledge.
Is it safe to participate?
Clinical trials follow strict safety guidelines and ethical standards. Trials must be reviewed and approved, and participants are closely monitored by medical professionals throughout the study. You can withdraw at any time if you choose.
Will I be compensated?
Many clinical trials offer compensation for your time, travel expenses, and inconvenience. The specific compensation varies by study and will be discussed during the screening process. All study-related medical care is typically provided at no cost to participants.
Will I receive a placebo instead of treatment?
When effective treatment exists, participants typically receive either the standard treatment plus the study intervention, or the standard treatment plus placebo. You would not be denied effective care. Placebos are primarily used when no proven treatment is available, or in addition to standard care. Your trial consent form will clearly explain what treatments you may receive.
Can I leave a trial if I change my mind?
Absolutely. Participation in clinical trials is completely voluntary. You have the right to withdraw from the study at any time, for any reason, without penalty or loss of benefits to which you are otherwise entitled.
How long does a clinical trial last?
Trial duration varies widely depending on the study design and purpose. Some trials last just a few weeks, while others may continue for months or years. The study coordinator will provide specific timeline information during your screening call.
Data: ClinicalTrials.gov · synced Oct 2, 2026 · Source of record for eligibility and locations