Actinium Pharmaceuticals Announces Oral and Poster Presentations at EANM 2026 Highlighting Broad Antitumor Activity of ATNM-400 Across Lung, Colorectal and Ovarian Cancer Models

• Oral presentation to highlight ATNM-400 antitumor activity across KRAS- and ALK-driven NSCLC models, building on earlier EGFR-mutant findings and supporting mutation-agnostic development

• Colorectal cancer data demonstrate ATNM-400's potential to enhance responses to standard-of-care therapies

• Ovarian cancer data demonstrate the durable antitumor activity of ATNM-400, including in treatment-resistant models

• Collectively, the findings support the broad potential of ATNM-400 as a differentiated targeted radiotherapy across multiple large solid tumor indications, both as monotherapy and in combination with existing treatments

NEW YORK, Oct. 16, 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 three presentations, including an oral presentation and two e-posters, highlighting preclinical data supporting ATNM-400's broad potential at the 39th Annual Congress of the European Association of Nuclear Medicine (EANM), October 17–21, 2026, in Vienna, Austria.

The presentations feature ATNM-400, the Company's first-in-class Actinium-225 (²²⁵Ac) radiotherapy, in non-small cell lung cancer (NSCLC), colorectal cancer, and ovarian cancer models. Together, the studies demonstrate preclinical antitumor activity as monotherapy and enhanced activity in combination with standard-of-care agents, supporting both approaches to development across solid tumors. These findings further expand the preclinical evidence supporting ATNM-400's potential across multiple cancer indications, complementing its ongoing clinical development in metastatic castration-resistant prostate cancer (mCRPC).

In NSCLC, ATNM-400 demonstrated antitumor activity as monotherapy and enhanced activity in combination with KRAS or ALK inhibitors, including in resistant models. These findings extend earlier EGFR-mutant results and support mutation-agnostic development both as a standalone therapy and in combination with established treatments.

In colorectal cancer, ATNM-400 demonstrated monotherapy activity in SW620 xenografts and enhanced activity when combined with bevacizumab plus oxaliplatin in HCT15 xenografts, a model with moderate target expression and limited response to the standard-of-care combination. These findings support both monotherapy development and combinations aimed at improving outcomes in poorly responsive disease.

In ovarian cancer, ATNM-400 monotherapy produced durable antitumor activity, including in bevacizumab-refractory tumors. These findings support its potential as a standalone treatment in recurrent disease, with further evaluation of ATNM-400 alone and in combination with standard-of-care therapies extending this development strategy.

"These findings build a compelling preclinical foundation for ATNM-400's pan-cancer potential and our vision to expand targeted radiotherapy across major solid tumor indications," said Sandesh Seth, Actinium's Chairman and CEO. "The high prevalence of ATNM-400's target in NSCLC, coupled with activity in KRAS- and ALK-driven models that builds on our earlier EGFR-mutant findings, supports the potential to reach a broad lung cancer population regardless of oncogenic mutation. Encouraging results in colorectal and treatment-resistant ovarian cancer models further extend this opportunity into areas of significant unmet need. Together, these data support our strategy to develop ATNM-400 as both a standalone therapy and a combination partner for established treatments, with the potential to address multiple large patient populations."

Abstract Title: ATNM-400 Elicits Durable Anti-tumor Responses in KRAS- and ALK-Driven NSCLC Models in a Mutation-Agnostic Manner Abstract Number: EPS-149 Presentation Type: Oral presentation Session: 1109 — Translational Imaging and Therapy Session Date & Time: Monday, October 19, 2026, 4:45–6:15 p.m. CEST | Vienna, Austria Location: Hall G2

Abstract Title: ATNM-400, a First-in-Class Actinium-225 Radioconjugate Improves Response to Standard-of-Care Therapeutics in Colorectal Cancer Models Abstract Number: EP-0163 Presentation Type: e-Poster

Abstract Title: ATNM-400, a First-in-Class Actinium-225 Radioconjugate Triggers Durable Antitumor Responses in Ovarian Cancer Models Abstract Number: EP-0176 Presentation Type: e-Poster

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.

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.