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

• 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

SOURCE Actinium Pharmaceuticals, Inc.