Actinium Pharmaceuticals has begun patient enrolment in its Radiolabeled Antibody Distribution In Advanced Neoplasms with Zirconium-89 (RADIANZ) trial, an imaging study supporting the development of its antibody radioconjugate (ARC) in advanced solid tumours.
The study will enrol patients who have experienced disease progression following standard-of-care treatments for advanced solid tumours, including breast, colorectal, non-small cell lung (NSCLC), ovarian, and pancreatic cancers. Preclinical activity for these indications supports pan-cancer radiotherapy, both as monotherapy and in rational combinations.
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Patients will receive scans over periods extending up to two weeks, enabling assessment of tumour uptake, retention, biodistribution, pharmacokinetics, and radiation dosimetry across various malignancies.
The imaging data are expected to support the pan-cancer therapeutic development of ²²⁵Ac-barecetamab-DOTA (ATNM-400) by assessing tumour retention alongside the nearly ten-day physical half-life of actinium-225.
ATNM-400 pairs the monoclonal antibody (mAb) barecetamab with Actinium-225, targeting human epidermal growth factor receptor 3 (HER3), an epidermal growth factor receptor protein implicated in cancer cell proliferation, survival, and treatment resistance.
The imaging protocol builds upon an ongoing first-in-human Phase I trial (ACTRN12625001362482) evaluating ATNM-400 in patients with metastatic castration-resistant prostate cancer, presented at congresses, including the European Society of Medical Oncology (ESMO) meeting 2026.
In that trial, the first three patients received 1.0µCi/kg without dose-limiting toxicities, demonstrated tumour uptake through day seven and advanced to the 1.5µCi/kg dose.
Actinium chairman and CEO Sandesh Seth said: “Dosing the first patient in RADIANZ is a major step in our pan-cancer strategy for ATNM-400. The initial clinical results we presented at EANM and the study we highlighted at ESMO established ATNM-400 in the clinic in prostate cancer.
“Our preclinical work across lung, breast, colorectal and ovarian cancer models demonstrates HER3 targeting potential beyond prostate cancer. With RADIANZ, we are now testing that potential in patients and building a clinical path for ATNM-400 across several large, treatment-resistant patient populations.”
In November 2025, Ariceum Therapeutics dosed the first patient in the SANTANA-225 Phase I/II clinical trial for 225Ac-SSO110, a treatment intended for people with Merkel cell carcinoma (MCC) and extensive-stage small cell lung cancer (ES-SCLC).
