Actinium Pharmaceuticals Presents New Preclinical Data Demonstrating Potent Anti-Tumor Activity of ATNM-400 Across Multiple Breast Cancer Subtypes Including Hormone Receptor-Positive, Triple-Negative, and Tamoxifen- and HER2 Therapy-Resistant Breast Cancer Models at SABCS 2025

-       ATNM-400's target antigen is overexpressed in breast cancer and its expression is further increased in breast cancer cells resistant to standard of care endocrine therapy, tamoxifen and the HER2 therapy trastuzumab -       The Actinium-225 alpha-emitter payload of ATNM-400 induced irreversible double-strand DNA breaks and has the potential to produce potent localized tumor killing with reduced off-target lung toxicity that limits the use of antibody drug conjugates -       Data supports the continued development of ATNM-400 as a monotherapy or combination therapy to address multiple breast cancer subtypes with limited treatment options NEW YORK , Dec. 12, 2025 /PRNewswire/ -- Actinium Pharmaceuticals, Inc. (NYSE American: ATNM), a leader in the development of differentiated targeted radiotherapies, today announced the presentation of new preclinical data for ATNM-400, its first-in-class Actinium-225 (Ac-225) based antibody radioconjugate, at the 2025 San Antonio Breast Cancer Symposium (SABCS). The data highlight robust anti-tumor activity and a favorable tolerability profile across a broad panel of preclinical breast cancer models, including hormone receptor–positive (HR+), triple-negative breast cancer (TNBC), and tamoxifen- and trastuzumab-resistant tumors.

PRNewsWire • Dec 12, 2025

Actinium Pharmaceuticals Announces ATNM-400 Data Demonstrating Potent Efficacy in Triple-Negative Breast Cancer and Ability to Overcome Endocrine and HER2-Targeted Therapy Resistance Being Presented at the San Antonio Breast Cancer Symposium

Presentation to include new data in triple-negative disease, a breast cancer subtype with poor outcomes and limited viable treatment options ATNM-400 overcomes HER2 therapy resistance and represents a novel targeted radiotherapy with the potential to avoid off-target toxicities including ILD that constrains other therapeutic modalities such as antibody drug conjugates ATNM-400 has demonstrated the potential to overcome resistance to first-line tamoxifen endocrine therapy Data to be presented on December 11, 2025 at 5:00 PM CT NEW YORK , Dec. 1, 2025 /PRNewswire/ -- Actinium Pharmaceuticals, Inc. (NYSE American: ATNM), a leader in the development of differentiated targeted radiotherapies, today announced compelling preclinical data for ATNM-400, a first-in-class Actinium-225 (AC-225) antibody radioconjugate, in hormone receptor positive (HR+), HER2 positive (HER2+) and triple-negative breast cancer (TNBC) that will be presented at the San Antonio Breast Cancer Symposium (SABCS) being held December 10‑14, 2025 in San Antonio, Texas. The data demonstrates significant anti-tumor activity in breast cancer models resistant to standard-of-care therapies including endocrine therapy tamoxifen and HER2-targeted therapy trastuzumab (Herceptin, Roche) as well as potent tumor growth inhibition in TNBC models.

PRNewsWire • Dec 1, 2025

The Race for the Global Radiotherapy Cancer Market; Actinium Pharmaceuticals' (ATNM) Big Bet

Vancouver, Kelowna, and Delta, British Columbia--(Newsfile Corp. - November 17, 2025) - Investorideas.com, a go-to investing platform covering biotech and pharma stocks issues a snapshot looking at the radiotherapy cancer market, featuring Actinium Pharmaceuticals, Inc. (NYSE American: ATNM), a pioneer in the development of differentiated, targeted radiotherapies intended to meaningfully improve outcomes for patients with advanced cancers. Actinium is deploying its technologies, capabilities and intellectual property with approximately 250 issued and pending patents worldwide, to develop next-generation radiotherapies focused on solid tumors, hematology and conditioning for cellular therapies.

Newsfile Corp • Nov 17, 2025

Actinium Announces Superior Anti-Tumor Activity of ATNM-400 in Lung Cancer Compared to the Leading First, Second and Third-Line Approved EGFR Mutant Therapies and Mechanistic Synergy with Osimertinib at the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics

-  ATNM-400 exhibits superior efficacy with 3-5x greater tumor growth inhibition compared to front line therapy osimertinib (EGFR TKI TAGRISSO®), second line therapy Dato-DXd (Trop-2 ADC DATROWAY®) and third line therapy amivantamab (EGFR-cMET bispecific RYBREVANT®) -  Combination of ATNM-400 and osimertinib resulted in complete tumor regression in 100% of tumor bearing animals; synergistic mechanism supported by increased ATNM-400 target antigen expression after EGFR inhibition with osimertinib -  Improved progression free survival has been demonstrated clinically with the combination of osimertinib and external beam radiotherapy providing strong rationale for a combination with targeted alpha-therapy -  Data validates the multi-tumor potential of ATNM-400 in multiple disease and treatment settings that support several blockbuster drugs NEW YORK , Oct. 27, 2025 /PRNewswire/ -- Actinium Pharmaceuticals, Inc. (NYSE AMERICAN: ATNM) (Actinium or the Company), a pioneer in the development of differentiated targeted radiotherapies, today announced the presentation of the first ever preclinical data of ATNM-400 in non-small cell lung cancer (NSCLC). ATNM-400 a novel, multi-indication first-in-class antibody radioconjugate armed with the potent alpha-emitter Actinium-225 (Ac-225) is Actinium's lead solid tumor program, which is also being studied in prostate cancer.

PRNewsWire • Oct 27, 2025

Actinium Pharmaceuticals Presents New Data Demonstrating Potent and Durable Efficacy of ATNM-400, a First-in-Class Multi-Tumor Actinium-225 Radiotherapy, at the 32nd Annual Prostate Cancer Foundation Scientific Retreat

- ATNM-400 targets a novel, non-PSMA antigen implicated in disease biology withcontinued expression following androgen receptor pathway inhibitor (ARPI) therapy and 177Lu-PSMA-617 therapy, enabling potent activity independent of PSMA expression - ATNM-400 demonstrated superior efficacy over PSMA-targeted radioligand therapy(177Lu-PSMA-617 and 225Ac-PSMA-617) with enhanced tumor control and prolonged survival in low-PSMA and treatment-resistant models - Demonstrated durable anti-tumor responses, exceeding those achieved with the ARPI enzalutamide - Combination of ATNM-400 with enzalutamide achieved complete tumor regressionin 40% of prostate cancer-bearing animals, demonstrating strong mechanistic synergy with AR pathway inhibition NEW YORK , Oct. 24, 2025 /PRNewswire/ -- Actinium Pharmaceuticals, Inc. (NYSE AMERICAN: ATNM) (Actinium or the Company), a pioneer in the development of differentiated targeted radiotherapies, today highlighted new preclinical data for ATNM-400, its novel, first-in-class antibody radioconjugate armed with the potent alpha-emitter Actinium-225 (Ac-225) at the 32nd Annual Prostate Cancer Foundation (PCF) Scientific Retreat being held October 23 – 25, 2025 in Carlsbad, CA.  ATNM-400, which targets a non-PSMA antigen associated with prostate cancer progression and treatment resistance, demonstrated superior tumor control and improved overall survival compared with the active agents in key standard-of-care therapies including enzalutamide (the active agent in Xtandi®, Astellas/Pfizer) and 177Lu-PSMA-617 (the active agent in Pluvicto®, Novartis), as well as 225Ac-PSMA-617 across multiple preclinical prostate cancer models.

PRNewsWire • Oct 24, 2025

Actinium Pharmaceuticals to Unveil the Multi-Tumor Potential of ATNM-400, a First-in-Class Actinium-225 Radiotherapy, with Data in Non-Small Cell Lung Cancer at the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics

ATNM-400 is advancing as a first-in-class, multi-tumor Actinium-225 radiotherapy candidate with activity across prostate and lung cancers, two of the largest cancer indications globally New preclinical findings demonstrate ATNM-400 overcomes resistance to the EGFR inhibitor osimertinib in EGFR-mutated NSCLC, addressing a major unmet clinical need NEW YORK , Oct. 13, 2025 /PRNewswire/ -- Actinium Pharmaceuticals, Inc. (NYSE AMERICAN: ATNM), a leader in the development of differentiated targeted radiotherapies, today announced that the first-ever preclinical data from its ATNM-400 program in non-small cell lung cancer (NSCLC) has been accepted for presentation at the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics being held October 22 – 26, 2025, at the Hynes Convention Center in Boston, Massachusetts. ATNM-400 is a highly innovative, first-in-class, Actinium-225 (Ac-225) antibody radioconjugate with preclinical data in both prostate cancer and NSCLC.

PRNewsWire • Oct 13, 2025

Actinium to Present ATNM-400 Preclinical Data Highlighting Durable Tumor Control and Ability to Overcome Resistance to Standard-of-Care Prostate Cancer Therapies at the 32nd Annual Prostate Cancer Foundation Scientific Retreat

-   ATNM-400 targets a highly differentiated, non-PSMA antigen associated with the development and progression of prostate cancer, exhibiting potent therapeutic activity independent of PSMA expression levels -   Extended follow-up in prostate cancer models demonstrated durable anti-tumor responses with ATNM-400, exceeding those achieved with the androgen receptor pathway inhibitor (ARPI), enzalutamide NEW YORK , Oct. 13, 2025 /PRNewswire/ -- Actinium Pharmaceuticals, Inc. (NYSE AMERICAN: ATNM) (Actinium or the Company), a pioneer in the development of differentiated targeted radiotherapies, today announced that compelling preclinical data for ATNM-400, its novel, first-in-class antibody radioconjugate armed with the potent alpha-emitter Actinium-225 (Ac-225), has been accepted for presentation at the 32nd Annual Prostate Cancer Foundation (PCF) Scientific Retreat being held on October 23 – 25, 2025 in Carlsbad, CA. The presentation will highlight ATNM-400's ability to induce robust, durable anti-tumor activity in metastatic castration-resistant prostate cancer (mCRPC) models, including tumors resistant to standard-of-care therapies such as the androgen receptor pathway inhibitor (ARPI), enzalutamide (Xtandi®, Astellas/Pfizer) and the PSMA-targeted therapy, 177Lu-PSMA-617 (active agent in Pluvicto®, Novartis) as well as superior efficacy compared to 225Ac-PSMA-617.

PRNewsWire • Oct 13, 2025

Is Actinium Pharmaceuticals (ATNM) Stock Outpacing Its Medical Peers This Year?

Here is how Actinium Pharmaceuticals (ATNM) and Avadel (AVDL) have performed compared to their sector so far this year.

Zacks Investment Research • Sep 2, 2025

Actinium Presents Data Supporting Paradigm Changing Potential of ATNM-400 in Prostate Cancer Demonstrating Its Superior Efficacy and Improved Survival in Treatment Resistant Tumor Models versus Pluvicto and ARPI Therapy, and Also Enhanced Efficacy in Combination with ARPI Therapy at the 4th Annual Targeted Radiopharmaceuticals Summit

-     ATNM-400 demonstrates robust efficacy in prostate cancer tumor models with acquired resistance to Pluvicto ® and enzalutamide, follow-up continues -     ATNM-400 significantly improved survival compared to the approved prostate cancer treatment Pluvicto ®, the first blockbuster radiotherapy -     In combination with enzalutamide, an approved ARPI therapy, ATNM-400 produced enhanced efficacy with 40% of prostate cancer tumor-bearing animals achieving complete cures NEW YORK , July 31, 2025 /PRNewswire/ -- Actinium Pharmaceuticals, Inc. (NYSE AMERICAN: ATNM) (Actinium or the Company), a pioneer in the development of targeted radiotherapies, today reported additional preclinical data supporting its ATNM-400 radiotherapy prostate cancer candidate at the 4th Annual Targeted Radiopharmaceuticals Summit (TRP) being held July 29 – 31, 2025 in San Diego, CA. ATNM-400 is a novel, first-in-class targeted radiotherapy designed to deliver potent Actinium-225 (Ac-225), an alpha-emitter radioisotope, to prostate cancer cells by targeting a non-Prostate Specific Membrane Antigen (PSMA), disease-driving protein overexpressed in advanced and treatment-resistant disease.

PRNewsWire • Jul 31, 2025

Actinium Highlights Expanded Data Set for ATNM-400 in Prostate Cancer Demonstrating Superior Efficacy to Enzalutamide and Ability to Overcome Resistance to ARPI Therapy and PSMA-Ac-225/Lu-177 Labelled Radiotherapy at the Society of Nuclear Medicine & Molecular Imaging Annual Meeting

-  ATNM-400 shows; superior prostate cancer cell killing compared to androgen receptor inhibitor Xtandi® (enzalutamide), the ability to overcome Xtandi resistance, and activity in combination -  ATNM-400 is more efficacious than both Pluvicto® (177-Lu-PSMA-617) and Ac-225-PSMA-617 targeted radiotherapy in prostate cancer in vitro and in vivo models and overcome resistance in prostate cancer tumors that failed Pluvicto® therapy -  ATNM-400's target is highly differentiated from PSMA as it is implicated in disease biology, contributing to disease progression, faster progression to castration resistance and poorer survival outcomes with target expression reported following androgen receptor inhibitor and PSMA radiotherapy -  Data further supports ATNM-400's potential to address critical gaps in prostate cancer treatment as a monotherapy or in sequence with other therapeutic modalities NEW YORK , June 23, 2025 /PRNewswire/ -- Actinium Pharmaceuticals, Inc. (NYSE AMERICAN: ATNM) (Actinium or the Company), a pioneer in the development of targeted radiotherapies, today reported new preclinical data from its first-in-class, non-PSMA targeting radiotherapy prostate cancer candidate ATNM-400, that leverages the potent alpha-particle emitter Actinium-225 (Ac-225) isotope, at the Society of Nuclear Medicine & Molecular Imaging (SNMMI) annual meeting being held June 21 st – 24th, 2025, in New Orleans, Louisiana. The data presented at SNMMI showed ATNM-400 has superior potency compared Xtandi® (enzalutamide) and is highly efficacious in Xtandi® resistant prostate models.

PRNewsWire • Jun 23, 2025