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

Actinium (NYSE: ATNM) announced three abstracts at SNMMI 2026 (May 30–June 2, Los Angeles) presenting preclinical data for ATNM-400 and radiochemistry optimization.

Rhea-AI Summary

Actinium (NYSE: ATNM) announced three abstracts at SNMMI 2026 (May 30–June 2, Los Angeles) presenting preclinical data for ATNM-400 and radiochemistry optimization. The posters report ATNM-400 activity in KRAS-mutated NSCLC and PSMA-high/low/negative prostate cancer models and CAR optimization for 225Ac radioconjugates.

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Key Figures

Conference dates: May 30–June 2, 2026 NSCLC session time: June 2, 2026, 11:30am–12:15pm PT Prostate session time: June 2, 2026, 11:30am–12:15pm PT +5 more

Conference dates

May 30–June 2, 2026

SNMMI 2026 Annual Meeting schedule

NSCLC session time

June 2, 2026, 11:30am–12:15pm PT

ATNM-400 NSCLC abstract presentation

Prostate session time

June 2, 2026, 11:30am–12:15pm PT

ATNM-400 prostate cancer abstract presentation

Radiochemistry session time

May 31, 2026, 7:30–8:00pm PT

Chelator-to-antibody ratio optimization abstract

Radioisotope

Actinium-225 (225Ac)

Core isotope used in ATNM-400 antibody radioconjugate

Current price

$1.26

Pre-news share price in latest session

52-week range

$0.952–$1.9454

Low to high over last 52 weeks

2025 net loss

$33.9 million

Net loss reported in 2025 10-K

Historical Context

5 past events · Latest: Apr 22

5 events

1. Apr 22

   ATNM-400 pan-tumor data

   24h Move

   -10.9%

   Compelling ATNM-400 preclinical pan-tumor data at AACR 2026 across solid tumors.

2. Apr 22

   Actimab-A AML data

   24h Move

   -10.9%

   AACR 2026 data showing mutation-agnostic anti-leukemic activity and combination benefits.

3. Apr 06

   AACR abstract announcement

   24h Move

   +11.2%

   Announcement of AACR abstracts featuring new ATNM-400 and Actimab-A preclinical data.

4. Feb 17

   AACR presentation notice

   24h Move

   -2.7%

   Notice of two upcoming AACR 2026 abstracts on ATNM-400 and Actimab-A programs.

5. Dec 12

   Breast cancer data

   24h Move

   +4.1%

   SABCS 2025 ATNM-400 data showing potent activity across multiple breast cancer subtypes.

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

Key Terms

nsclc, kras, psma, chelator-to-antibody ratio, +3 more

7 terms

nsclc medical

"ATNM-400 in NSCLC: New data demonstrates ATNM-400's potential in KRAS-mutatedmodels..."

NSCLC stands for non-small cell lung cancer, which is the most common type of lung cancer. It develops in the lungs and can spread to other parts of the body, making it serious but often treatable if caught early. Understanding NSCLC helps people recognize the importance of lung health and early detection.

kras medical

"potential in KRAS-mutatedmodels supporting its development as a mutation-agnostic therapy..."

KRAS is a gene that makes a protein acting like a switch to control cell growth; certain changes (mutations) can lock that switch on and drive uncontrolled cell multiplication, which is a common cause of many cancers. Investors care because drugs or tests targeting KRAS mutations can create large markets or avoidable risks depending on trial results and regulatory decisions, much like a key product feature deciding a gadget’s commercial success.

psma medical

"spectrum of PSMA-high, PSMA-low, and PSMA-negativedisease, addressing a key limitation..."

Prostate-specific membrane antigen (PSMA) is a protein on the surface of prostate cells that becomes much more common on many prostate cancer cells, acting like a biological “flag” that helps locate or attach to tumors. Investors care because diagnostic scans and drugs that detect or bind to PSMA can improve diagnosis and treatment; success or failure of those products often has a direct financial impact on the companies developing them.

chelator-to-antibody ratio medical

"optimizing chelator-to-antibody ratio(CAR) improves tumor targeting, internalization..."

The chelator-to-antibody ratio (CAR) is the average number of small linking molecules attached to each antibody that hold a drug or radioactive payload. Think of the antibody as a carrier and the chelators as hooks that let it carry multiple “packages”; the CAR affects how potent the therapy is, how predictable and safe dosing will be, and how consistently it can be manufactured and regulated—factors that directly influence clinical success and investor risk.

radioconjugate medical

"Actinium's first-in-class Actinium-225 (225Ac) antibody radioconjugate, demonstrating its potential..."

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.

pharmacokinetics medical

"ratio(CAR) improves tumor targeting, internalization, and pharmacokinetics of 225Ac-labeledantibodies..."

Pharmacokinetics is the study of how a substance, such as a drug or chemical, moves through and is processed by the body over time. It tracks how it is absorbed, distributed, broken down, and eventually eliminated. For investors, understanding pharmacokinetics helps gauge the effectiveness, safety, and potential risks of new medications or treatments, which can influence a company’s success and valuation in the healthcare industry.

actinium-225 medical

"Actinium's first-in-class Actinium-225 (225Ac) antibody radioconjugate, demonstrating its potential..."

Actinium-225 is a rare, radioactive form of the metal actinium used as a microscopic radiation source in some cancer treatments; it emits very strong, short-range radiation that can destroy diseased cells when attached to a carrier drug. Investors pay attention because supply is limited and production is complex, so shortages or cost changes can directly affect the development, manufacturing and valuation of companies pursuing therapies that rely on this scarce medical “fuel.”

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– ATNM-400 in NSCLC: New data demonstrates ATNM-400's potential in KRAS-mutated
models supporting its development as a mutation-agnostic therapy in settings where
resistance to EGFR- and KRAS-targeted agents remains a major clinical challenge

– ATNM-400 in prostate cancer: New data further supports ATNM-400 as a potential
treatment option across the spectrum of PSMA-high, PSMA-low, and PSMA-negative
disease, 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-labeled
antibodies, directly supporting ATNM-400 development and reinforcing a proprietary
radiochemistry 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. Together, the data underscore Actinium's scientific leadership in next-generation alpha-emitting radioconjugates.

Sandesh Seth, Actinium's Chairman and CEO, said, "Data to be presented at SNMMI 2026 further strengthen the profile of ATNM-400 as a first-in-class, radiotherapy with broad solid tumor applicability. In NSCLC, ATNM-400 demonstrates the ability to overcome key resistance mechanisms to both EGFR and KRAS mutations that limit current targeted therapies and support its development as a mutation agnostic agent. In prostate cancer, new data demonstrate its potential in the PSMA negative setting, in addition to promising data in PSMA-high and medium settings further supporting the differentiated profile of ATNM-400. Importantly, as we head toward clinical studies with ATNM-400, we showcase our efforts to maximize ATNM-400's therapeutic index by utilizing our deep radiochemistry expertise to optimize the CAR. Together, the data to be presented support ATNM-400's growing potential as a differentiated radiotherapy across multiple high-value solid tumor indications that represent some of oncology's largest commercial opportunities."

ATNM-400 SNMMI 2026 Presentation Details

Abstract Title: ATNM-400: A First-in-Class Actinium-225 Antibody Radioconjugate Demonstrating Potent PSMA-Independent Efficacy in Prostate Cancer Models
Session: Oncology: Discovery & Translational Meet the Author Session
Date & Time: Tuesday, June 2, 2026 11:30am-12:15pm PT | Los Angeles, California

Abstract Title: ATNM-400: A First-in-Class Actinium-225 Antibody Radioconjugate Demonstrating Durable, Mutation-Agnostic Anti-Tumor Activity in Non-Small Cell Lung Cancer Models
Session: Oncology: Discovery & Translational Meet the Author Session
Date & Time: Tuesday, June 2, 2026, 11:30am-12:15pm PT | Los Angeles, California

Abstract Title: Optimizing Chelator-to-Antibody Ratio Improves Tumor Targeting and Pharmacokinetics of 225Ac-Labeled Antibodies
Session: MTA05 RPSC/CMIIT POPs and Science Pavilion Mixer
Date & Time: Sunday, May 31, 2026, 7:30-8:00pm PT | Los Angeles, California

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.

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What will Actinium (ATNM) present about ATNM-400 at SNMMI 2026?

Actinium will present preclinical posters on ATNM-400's activity in lung and prostate cancer models. According to the company, sessions include data on KRAS-mutated NSCLC and PSMA-high/low/negative prostate cancer plus radiochemistry CAR optimization supporting 225Ac conjugates.

When and where are Actinium's ATNM-400 SNMMI 2026 presentations scheduled?

Two ATNM-400 oncology posters are scheduled for Tuesday, June 2, 2026, 11:30am–12:15pm PT in Los Angeles. According to the company, an additional radiochemistry poster is set for Sunday, May 31, 2026, 7:30–8:00pm PT.

What does the SNMMI data say about ATNM-400 in KRAS-mutated NSCLC (ATNM)?

Preclinical data show ATNM-400 demonstrates mutation-agnostic anti-tumor activity in NSCLC models. According to the company, results indicate potential to overcome resistance to EGFR- and KRAS-targeted agents in these models.

How does ATNM-400 perform in prostate cancer models according to Actinium (ATNM)?

ATNM-400 showed activity across PSMA-high, PSMA-low, and PSMA-negative prostate cancer models. According to the company, the data address a limitation of PSMA-targeted therapies by demonstrating PSMA-independent efficacy in preclinical studies.

What is the significance of the chelator-to-antibody ratio (CAR) data for ATNM-400 development?

Optimizing CAR improved tumor targeting, internalization, and pharmacokinetics of 225Ac-labeled antibodies in preclinical work. According to the company, this radiochemistry capability directly supports ATNM-400 optimization and broader pipeline development.