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RecruitingLast updated: 26 May 2026

ATNM-400: Evaluating a targeted radiotherapy (called ATNM-400) in people with metastatic castration resistant prostate cancer (mCRPC)Phase 1 trial of a novel HER3 antibody-targeted radiotherapy (ATNM-400 [225Ac]-barecetamab-DOTA) in patients with metastatic castrate-resistant prostate cancer

Trial purpose

Medical clipboardCancer treatment

Tumor type

Urinary System Cancers Genitourinary

Age

People18+

Trial acronym

ATNM-400

Clinical summary

Summary

This study aims to understand how a new anti-cancer drug called ATNM-400 behaves in the body, to determine a safe dose range, and to assess its early signs of anti-tumour activity. ATNM-400 is also known as [²²5Ac]-barecetamab-DOTA.

Who is it for?
You may be eligible for this study if you are:

  • aged 18 years or older,
  • have been diagnosed with metastatic prostate cancer that has not responded to surgery,
  • have undergone at least one previous round of chemotherapy.

Study details
Participants who choose to enrol in this study may be invited to participate in one of three parts.

  • Part A - Participants will have a dose of [89Zr]-barecetamab-DFO injected into a vein and will then undergo PET-CT imaging.
    • [89Zr]-barecetamab-DFO is a non-therapeutic version of ATNM-400 and is used with PET/CT scans to show how it finds and attaches to the tumour, and how it moves through the body.
    • These participants will also be asked to provide blood samples for up to 6 hours after their injection.
  • Part B - Participants will be given a dose of ATNM-400 injected into a vein once every 6 weeks.
    • If participants don't experience any extreme side effects, they may have this treatment repeated up to 4 times.
    • Different groups of participants will be enrolled to assess higher doses of ATNM-400 for this part.
  • Part C - Participants will be give a dose of ATNM-400 injected into a vein once every 6 weeks.
    • If participants don't experience any extreme side effects, they may have this treatment repeated for up to 1 year.

Participants in Part B and C will also be asked to provide further blood samples while receiving ATNM-400 and to undergo additional PET-CT and possibly MR imaging.

It is hoped this research will determine if ATNM-400 anti-cancer treatment could be developed further for patients with advanced prostate cancer who have limited treatment options.

Conditions

This trial is treating people with metastatic castration-resistant prostate cancer with a positive HER3 PET/CT scan

Eligibility

Inclusion

Adults aged 18 years and older with histologically confirmed metastatic castrate-resistant prostate cancer (mCRPC) and a positive HER3 PET/CT scan. Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 1. Life expectancy greater than 6 months. Prior androgen deprivation therapy (ADT) with or without a taxane. Adequate organ function. Recovered from all prior treatment-related toxicities to less than Grade 1 severity.

Exclusion

Urinary obstruction with catheter; prior HER3-targeted radiotherapy; recent chemo / investigational drug < 28 days; severe comorbidity (CHF III/IV, active infection, hep B/C); CNS metastases unless stable; superscan on bone scan

Inclusion

  • Your cancer has spread to other parts of the body (metastatic) or has grown into nearby parts of the body (locally advanced).
  • You have had treatment but your cancer has gotten worse or has not responded to the treatment you have been given.
  • You have had a certain type of treatment or surgical procedure.

Exclusion

  • You have certain types of non-cancer medical conditions.
  • You have had certain treatments, surgical procedures or drugs.
Message

Clinical trials have complex eligibility criteria, and other criteria may apply for this trial. Ask your doctor about whether this trial could be right for you.

Participating hospitals

Recruiting hospitals

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More information

Trial Identifiers

Information on this page is partially produced from ANZCTR *. View further details about this trial on the registry via the links below:

Trial sponsor

Actinium Pharmaceuticals Australia Pty Limited

Scientific Title

Phase 1 trial of a novel HER3 antibody-targeted radiotherapy (ATNM-400 [225Ac]-barecetamab-DOTA) in patients with metastatic castrate-resistant prostate cancer

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