Actinium Pharmaceuticals Oral Presentation at SNMMI 2026 Highlights ATNM-400 Overcoming Resistance to All Three Approved Androgen Receptor Inhibitors and Offers Flexible, Well-Tolerated Dosing in Prostate Cancer Models

New data demonstrated ATNM-400 remains potently active in prostate cancer cells and tumors resistant to all three approved androgen receptor inhibitors (ARPIs) -enzalutamide (Xtandi®), apalutamide (Erleada®), and darolutamide (Nubeqa®)- directly targeting the point of failure for a high proportion of mCRPC patients   ATNM-400 substantially outperformed apalutamide and darolutamide in an ARPI-resistant tumor model, and in combination with either ARPI it showed durable complete responses, supporting both monotherapy and combination strategies in refractory disease similar to prior data with enzalutamide  ATNM-400 delivered superior tumor control as a single bolus or repeat dose with a consistent safety profile and minimal off-target toxicity across treatment regimens, indicating dosing flexibility and a wide therapeutic window that could de-risk clinical translation. In high PSMA expressing disease, ATNM-400 outperformed 177Lu-PSMA-617 in terms of activity and was similar to 225Ac-PSMA-617.

PRNewsWire • Jun 3, 2026

Actinium Presents New ATNM-400 Data in KRAS and EGFR Mutant Models at SNMMI 2026 Supporting a Mutation-Agnostic Opportunity In Non-Small Cell Lung Cancer

New KRAS-mutant data show ATNM-400 outperformed standard-of-care inhibitors sotorasib and adagrasib as a monotherapy. Treatment with these agents increased expression of the ATNM-400 target greater than 3.5x and enhanced their effect in combination  Additional data in the EGFR-mutant setting demonstrated powerful synergy with osimertinib due to enhanced target expression in treated animals resulting in complete tumor regression in the combination arm  The data with EGFR and KRAS mutations which account for approximately 40-50 percent of all NSCLC cases provide compelling evidence of the potential of ATNM-400 as a monotherapy or in combination with inhibitory agents against these mutations  ATNM-400 is a radioconjgate comprising an antibody coupled to Actinium-225 which causes cell death via double stranded DNA breaks independent of cellular mechanisms and offers broad potential as a mutation agnostic agent in NSCLC where its target is expressed in over 90 percent of tumors with greater expression as resistance emerges NEW YORK, June 3, 2026 /PRNewswire/ -- Actinium Pharmaceuticals, Inc. (NYSE American: ATNM) (Actinium or the Company), a pioneer in the development of targeted radiotherapies, on June 2, 2026, presented new preclinical data on ATNM-400 in non-small cell lung cancer (NSCLC) at the Society of Nuclear Medicine and Molecular Imaging (SNMMI) 2026 Annual Meeting in Los Angeles, California.

PRNewsWire • Jun 3, 2026

Actinium Pharmaceuticals Presents New Radiochemistry Data at SNMMI 2026 Demonstrating That CAR Optimization Improves Tumor Targeting and Pharmacokinetics of Actinium-225 Radioconjugates

Optimization of chelator-to-antibody ratio (CAR) is a key design parameter for next-generation radioconjugates, presenting tunable levers Actinium is utilizing to engineer more effective drug candidates Optimized CAR improved tumor targeting, internalization, and pharmacokinetics of 225Ac-labeled antibodies Lower-CAR conjugates preserved tumor targeting while reducing off-target liver and spleen uptake, supporting a wider therapeutic window that may enable higher, safer dosing Findings reinforce Actinium's proprietary radiochemistry expertise and directly support the Company's broader radioconjugate pipeline a capability that applies to every program from the platform NEW YORK, June 1, 2026 /PRNewswire/ -- Actinium Pharmaceuticals, Inc. (NYSE American: ATNM) (Actinium or the Company), a pioneer in the development of targeted radiotherapies, on May 31, 2026 presented new radiochemistry data at the Society of Nuclear Medicine and Molecular Imaging (SNMMI) 2026 Annual Meeting taking place in Los Angeles, California. The poster presented a systematic evaluation of chelator-to-antibody ratio (CAR) optimization for Actinium-225 (225Ac)-labeled antibody radioconjugates, a critical but often underappreciated design parameter that directly influences radiolabeling efficiency, antigen binding, internalization, and biodistribution.

PRNewsWire • Jun 1, 2026

Actinium Appoints Accomplished Oncology Expert Steffen Heeger MD, MSc as Chief Medical Officer to Drive Rejuvenated Pipeline Development

Proven Chief Medical Officer at several publicly listed and clinical-stage oncology companies with successful track record developing multiple modalities including radiotherapies from preclinical through global approvals across hematologic malignancies and solid tumors Played a leading role in clinical development and worldwide approvals of Erbitux® at Merck KGaA leading to its blockbuster status Led clinical development as CMO of NBE Therapeutics which was acquired by Boehringer Ingelheim for $1.4 billion, and most recently CMO of radiotherapy company Full-Life Technologies Timely key hire with Dr. Heeger's operational rigor and clinical expertise expected to elevate development of Actimab-A, ATNM-400, and Iomab-ACT as Actinium advances toward key data readouts and expanded clinical trials in 2H:2026 NEW YORK, June 1, 2026 /PRNewswire/ -- Actinium Pharmaceuticals, Inc. (NYSE AMERICAN: ATNM) (Actinium or the Company), a pioneer in the development of targeted radiotherapies, today announced the appointment of Steffen Heeger, MD, MSc, as Chief Medical Officer. Dr. Heeger brings a rare combination of radiotherapy expertise, global oncology drug development leadership, and public-company experience.

PRNewsWire • Jun 1, 2026

Actinium Pharmaceuticals Receives Two Patent Allowances Spanning Its Actimab-A and Iomab-ACT Programs

Together the allowances deepen protection across two priority franchises and reinforce a patent estate of approximately 250 issued and pending patents and patent applications worldwide NEW YORK, May 29, 2026 /PRNewswire/ -- Actinium Pharmaceuticals, Inc. (NYSE American: ATNM) (Actinium or the Company), a leader in the development of targeted radiotherapies, today announced that the Canadian Intellectual Property Office (CIPO) has issued Notices of Allowance for two patent applications spanning the Company's Actimab-A and Iomab-ACT programs. The allowances broaden Actinium's intellectual property protection across both hematologic malignancies and next-generation conditioning for gene-edited cell-based therapies in Canada, an important market within the Company's growing global patent estate.

PRNewsWire • May 29, 2026

Actinium Pharmaceuticals to Present ATNM-400 Program Update at SNMMI 2026 Conference on May 31-June 2 and Provides NYSE American Listing Standards Notice

NEW YORK, May 29, 2026 /PRNewswire/ -- Actinium Pharmaceuticals, Inc. (NYSE American: ATNM) (Actinium or the Company), a leader in the development of targeted radiotherapies, today announced it will provide a program update on its first-in-class Actinium-225 (225Ac) antibody radioconjugate, ATNM-400, highlighting new data that will be showcased across three presentations at the Society of Nuclear Medicine and Molecular Imaging (SNMMI) 2026 Annual Meeting, taking place May 30-June 2, 2026, in Los Angeles, California. Two of the presentations showcase ATNM-400's differentiated profile across prostate cancer and non-small cell lung cancer (NSCLC), while a third demonstrates the importance of radioconjugate optimization for radiotherapies in the context of the Company's pipeline candidates.

PRNewsWire • May 29, 2026

NorthStar and QSA Global Announce Multi-Year Strategic Partnership to Strengthen Actinium-225 Supply Chain for Targeted Alpha Therapies

BURLINGTON, Mass. & BELOIT, Wis.--(BUSINESS WIRE)--Partnership combines NorthStar's commercial-scale radioisotope production capabilities with QSA Global's expertise in management of Radium-226.

Business Wire • May 27, 2026

Actinium Pharmaceuticals Announces Three SNMMI 2026 Presentations Highlighting Differentiated Profile of ATNM-400 Across Lung and Prostate Cancer and Radioconjugate Optimization

– ATNM-400 in NSCLC: New data demonstrates ATNM-400's potential in KRAS-mutatedmodels supporting its development as a mutation-agnostic therapy in settings whereresistance to EGFR- and KRAS-targeted agents remains a major clinical challenge – ATNM-400 in prostate cancer: New data further supports ATNM-400 as a potentialtreatment option across the spectrum of PSMA-high, PSMA-low, and PSMA-negativedisease, addressing a key limitation of PSMA-targeted therapies  – Radioconjugation platform: New data demonstrates that optimizing chelator-to-antibody ratio(CAR) improves tumor targeting, internalization, and pharmacokinetics of 225Ac-labeledantibodies, directly supporting ATNM-400 development and reinforcing a proprietaryradiochemistry capability that underpins Actinium's broader pipeline NEW YORK, May 6, 2026 /PRNewswire/ -- Actinium Pharmaceuticals, Inc. (NYSE American: ATNM) (Actinium or the Company), a pioneer in the development of targeted radiotherapies, today announced the upcoming presentation of three abstracts at the Society of Nuclear Medicine and Molecular Imaging (SNMMI) 2026 Annual Meeting, taking place May 30-June 2, 2026, in Los Angeles, California. The presentations include two posters on ATNM-400, Actinium's first-in-class Actinium-225 (225Ac) antibody radioconjugate, demonstrating its potential in prostate cancer and non-small cell lung cancer (NSCLC), as well as a third poster presenting preclinical radiochemistry data on chelator-to-antibody ratio (CAR) optimization that underpins ATNM-400 development.

PRNewsWire • May 6, 2026

Actinium Pharmaceuticals, Inc. Announces Compelling Pan-Tumor Data for ATNM-400 Demonstrating Broad Efficacy Across Prostate, Lung, and Breast Cancer Models at the 2026 American Association of Cancer Research Annual Meeting

ATNM-400 demonstrates pan-tumor activity across prostate, lung, and breast cancer models, supporting multi-indication development potential In prostate cancer, ATNM-400 demonstrates efficacy across both high PSMA-expressing and, importantly, low PSMA-expressing prostate cancer models, unlike many PSMA-targeted radioligand therapies that work only in PSMA-high settings In EGFR-mutant non-small cell lung cancer, ATNM-400 demonstrates greater tumor growth inhibition than osimertinib (a tyrosine kinase inhibitor) plus chemotherapy and outperforms the approved Trop-2 ADC Dato-DXd (DATROWAY®), the EGFR-cMET bispecific antibody amivantamab (RYBREVANT®) and the experimental EGFR-HER3 ADC izalontamab brengitecan, supporting potential use across first-, second-, and third-line treatment settings In breast cancer, new head-to-head data shows ATNM-400 achieves efficacy comparable to the approved HER2-ADC trastuzumab deruxtecan (ENHERTU®) in trastuzumab-resistant models, with durable tumor control observed after treatment discontinuation - extending the Company's prior SABCS 2025 data and supporting potential for less frequent dosing of ATNM-400 compared to ADCs ATNM-400 is well tolerated, with no in vivo toxicities observed at efficacious doses, providing a favorable therapeutic index that supports monotherapy and combination development NEW YORK, April 22, 2026 /PRNewswire/ -- Actinium Pharmaceuticals, Inc. (NYSE AMERICAN: ATNM) (Actinium or the Company), a pioneer in the development of targeted radiotherapies, today announced preclinical results for ATNM-400 across prostate, lung, and breast cancer models presented at the American Association for Cancer Research (AACR) Annual Meeting in San Diego, CA. ATNM-400 is a novel, first-in-class targeted radiotherapy utilizing the Actinium-225 (Ac-225) radioisotope that targets a non-PSMA membrane antigen overexpressed in advanced and therapy-refractory solid tumors across multiple oncology indications.

PRNewsWire • Apr 22, 2026

Actinium Highlights Transcriptional Reprogramming as a Key Mechanism Underpinning Mutation-Agnostic Activity of Actimab-A in AML at the 2026 American Association of Cancer Research Annual Meeting

Actimab-A combinations enhanced in vivo AML cell killing across multiple preclinical models, independent of mutation status, when combined with standard-of-care targeted and non-targeted therapies including revumenib (menin-KMT2A inhibitor), gilteritinib (FLT3 inhibitor), and azacitidine (hypomethylating agent) - three pillars of modern AML treatment - supporting its potential role as a universal combination backbone Transcriptional reprogramming identified as a central mechanism showing that Actimab-A combinations don't just add cytotoxicity, they reprogram AML cells from proliferation toward differentiation and apoptosis, providing the mechanistic basis for deeper, more durable MRD-negative responses and reinforcing Actimab-A's role as a universal combination backbone across AML Robust cytotoxicity observed in primary AML patient samples across key mutations (FLT3, KMT2A, NPM1, IDH1, IDH2, or TP53), reinforcing Actimab-A's potential as a mutation-agnostic backbone therapy, complementing the manageable safety profile of Actimab-A observed across prior clinical trials in over 150 AML patients NEW YORK, April 22, 2026 /PRNewswire/ -- Actinium Pharmaceuticals, Inc. (NYSE AMERICAN: ATNM) (Actinium or the Company), a pioneer in the development of targeted radiotherapies, today highlighted data presented at the American Association for Cancer Research (AACR) Annual Meeting supporting transcriptional reprogramming as a central mechanism driving the mutation-agnostic anti-leukemic activity of Actimab-A (lintuzumab-Ac225) in acute myeloid leukemia (AML). Preclinical translational data demonstrated that lintuzumab-Ac225 delivers potent cytotoxic activity across AML models harboring common mutations, including FLT3, NPM1, KMT2A, and TP53, as well as in primary patient samples.

PRNewsWire • Apr 22, 2026