Actinium Pharmaceuticals Announces Oral Presentation at EANM 2026 Highlighting First-in-Human Phase 1 Study of ATNM-400, a Non-PSMA Targeting Radiotherapy, in Prostate Cancer

Actinium Pharmaceuticals (ATNM) will present early results from its first-in-human Phase 1 ATNM-400 prostate cancer study at EANM on October 19, 2026.

Rhea-AI Summary

Actinium Pharmaceuticals (ATNM) will present early results from its first-in-human Phase 1 ATNM-400 prostate cancer study at EANM on October 19, 2026.

The ongoing dose-escalation study involves metastatic castration-resistant prostate cancer, cancer that has spread and resists testosterone-lowering treatment. It evaluates Zirconium-89-labeled ATNM-400 for safety, distribution in the body and radiation exposure. Repeated PET scans will assess tumor uptake, distribution and clearance, with radiation-dose estimates informing dosing of the Actinium-225-labeled therapy. ATNM-400 targets an antigen other than PSMA. Actinium said the early clinical data support advancing the program, which is being developed for patients including those with low or absent PSMA and those whose disease does not respond to or progresses after PSMA-directed therapies.

Previous Clinical trial Reports

1 past event · Latest: Oct 24

Same Type 1 event

1. Oct 24

   ATNM-400 preclinical data

   24h Move

   +16.8%

   Earlier ATNM-400 preclinical findings precede the current first-in-human Phase 1 study.

24h Move is the share-price change in the day after each event; other market factors may also have contributed.

Key Terms

theranostic, mcrpc, radioconjugate, biodistribution, +1 more

5 terms

theranostic medical

"Early clinical data from the Phase 1 theranostic trial support the advancement"

A theranostic is a single medical approach or agent that combines diagnosis and treatment—using a test or imaging step to find patients likely to benefit, then delivering a targeted therapy tied to that same marker. For investors, theranostics can speed development, lower the chance of failed trials and concentrate sales on the right patients, like a smart key that both locates the correct lock and opens it, potentially improving clinical and commercial success.

mcrpc medical

"metastatic castration-resistant prostate cancer (mCRPC)"

mCRPC stands for metastatic castration‑resistant prostate cancer, a form of prostate cancer that has spread beyond the prostate and keeps progressing despite treatments that lower male hormones. It matters to investors because this stage is harder to treat, drives demand for new therapies, and often involves large, expensive clinical trials and regulatory decisions that can strongly influence a drug maker’s future revenue and stock value—think of it as a stubborn problem that creates both medical need and commercial opportunity.

radioconjugate medical

"Actinium-225 (²²⁵Ac) antibody radioconjugate targeting a non-PSMA antigen"

A radioconjugate is a medicine made by attaching a small amount of radioactive material to a targeting molecule so the radiation is delivered directly to specific cells, like a guided missile carrying a tiny explosive to a precise address. Investors care because its safety, effectiveness, manufacturing complexity, and regulatory path determine development costs, market size and reimbursement potential, affecting a company’s future revenue and risk profile.

biodistribution medical

"safety, biodistribution, and dosimetry of Zirconium-89-labeled ATNM-400"

Biodistribution is the map of where a drug, vaccine, or diagnostic agent travels and accumulates inside the body after administration. Investors care because where a product ends up affects how well it works, what side effects it may cause, and whether regulators will approve it—similar to tracking dye in a plumbing system to find leaks or blockages; unexpected destinations can raise safety, cost, and market-adoption risks.

dosimetry medical

"safety, biodistribution, and dosimetry of Zirconium-89-labeled ATNM-400"

Dosimetry is the measurement and calculation of how much ionizing radiation is absorbed by people, tissues, or devices, similar to a thermostat tracking temperature in different rooms to know where and how much heat is present. Investors should care because accurate dosimetry underpins safety, treatment effectiveness, regulatory approval, and liability for products and services that use radiation—affecting market access, costs, and commercial risk.

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• Early clinical data from the Phase 1 theranostic trial support the advancement of ATNM-400 as a non-PSMA targeted alpha therapy for metastatic castration-resistant prostate cancer (mCRPC)
  
  
• Evaluation of Zirconium-89-labeled ATNM-400 to assess safety, biodistribution, and dosimetry to inform the development of Actinium-225-labeled ATNM-400 as a targeted radiotherapy
  
  
• ATNM-400 is a first-in-class, non-PSMA targeted radiotherapy being developed to address a broad mCRPC patient population, including PSMA-low and PSMA-negative disease and patients who do not respond to or progress following PSMA-directed therapies

NEW YORK, Oct. 15, 2026 /PRNewswire/ -- Actinium Pharmaceuticals, Inc. (NYSE American: ATNM) (Actinium or the Company), a pioneer in differentiated targeted radiotherapies with the potential to transform cancer treatment, today announced that an oral presentation with early results from the first-in-human Phase 1 study of ATNM-400 in metastatic castration-resistant prostate cancer (mCRPC) will be presented at the 39th Annual Congress of the European Association of Nuclear Medicine (EANM), October 17–21, 2026, in Vienna, Austria.

The oral presentation will highlight the ongoing first-in-human Phase 1 dose-escalation study of ATNM-400 in mCRPC. ATNM-400 is a first-in-class Actinium-225 (²²⁵Ac) antibody radioconjugate targeting a non-PSMA antigen implicated in tumor survival and treatment resistance. The study will characterize the safety, biodistribution, and dosimetry of Zirconium-89-labeled ATNM-400. Serial PET imaging will assess its tumor uptake, distribution, and clearance, with dosimetry estimates informing therapeutic ²²⁵Ac-ATNM-400 dosing.

"These first clinical data from ATNM-400 mark an important milestone for Actinium and for prostate cancer treatment beyond PSMA," said Sandesh Seth, Actinium's Chairman and CEO. "As a first-in-class radiotherapeutic targeting an antigen implicated in tumor survival and treatment resistance, ATNM-400 has the potential to serve the broad mCRPC population, including patients with PSMA-low or PSMA-negative disease and those who do not respond to or progress after PSMA-directed therapies. These initial findings mark an important milestone for ATNM-400 and our Actinium-225 development program."

ATNM-400 EANM 2026 Presentation Details

Abstract Title: First-In-Human Phase 1 Study of ATNM-400, Actinium-225 Antibody Radioconjugate, in Metastatic Castration-Resistant Prostate Cancer (mCRPC)
Abstract Number: OP-525
Presentation Type: Oral presentation
Session: 1111 — Theranostics Track: Prostate Cancer Therapy II
Session Date & Time: Monday, October 19, 2026, 4:45–6:15 p.m. CEST | Vienna, Austria
Location: Hall G1

About Actinium Pharmaceuticals, Inc.

Actinium is a pioneer in targeted radiotherapies designed to improve outcomes for patients with cancer. The company employs a biology-driven approach to develop differentiated radiopharmaceuticals for solid tumors and hematologic malignancies. Its mission is to transform cancer treatment through innovative radioconjugates that maximize therapeutic efficacy while minimizing toxicity to healthy tissue by combining expertise in tumor biology, translational medicine, and radiochemistry. Since inception, Actinium has focused on developing innovative radiotherapies. Its pipeline reflects this strategy across three areas: (1) solid tumor therapeutics including ATNM-400 and Actimab-A with pan-tumor potential; (2) Actimab-A as a therapeutic backbone for acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) in collaboration with the National Cancer Institute (NCI); and (3) targeted conditioning agents including Iomab-B for bone marrow transplant and Iomab-ACT for cell and gene therapy conditioning. ATNM-400 targets a novel antigen distinct from PSMA and has demonstrated preclinical activity across metastatic castration-resistant prostate cancer (mCRPC), non-small cell lung cancer (NSCLC), and breast cancer. Actimab-A has shown improved survival in relapsed/refractory AML with CLAG-M and is advancing toward a Phase 2/3 trial, with additional development ongoing through a CRADA with the NCI. Actinium is also advancing preclinical solid tumor programs and holds ~250 patents and patent applications, including intellectual property related to cyclotron-based production of Ac-225. For more information, please visit www.actiniumpharma.com.

Forward-Looking Statements

This press release may contain projections or other "forward-looking statements" within the meaning of the "safe-harbor" provisions of the private securities litigation reform act of 1995 regarding future events or the future financial performance of the Company which the Company undertakes no obligation to update. These statements are based on management's current expectations and are subject to risks and uncertainties that may cause actual results to differ materially from the anticipated or estimated future results, including the risks and uncertainties associated with preliminary study results varying from final results, estimates of potential markets for drugs under development, clinical trials, actions by the FDA and other governmental agencies, regulatory clearances, responses to regulatory matters, the market demand for and acceptance of Actinium's products and services, performance of clinical research organizations and other risks detailed from time to time in Actinium's filings with the Securities and Exchange Commission (the "SEC"), including without limitation its most recent annual report on form 10-K, subsequent quarterly reports on Forms 10-Q and Forms 8-K, each as amended and supplemented from time to time.

Investors: investorrelations@actiniumpharma.com

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SOURCE Actinium Pharmaceuticals, Inc.