Actinium Pharmaceuticals Announces Three SNMMI 2026 Presentations Highlighting Differentiated Profile of ATNM-400 Across Lung and Prostate Cancer and Radioconjugate 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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News Market Reaction – ATNM
On the day this news was published, ATNM declined 1.59%, reflecting a mild negative market reaction.
Data tracked by StockTitan Argus on the day of publication.
Key Figures
Market Reality Check
Peers on Argus
ATNM is up 5% while peers show mixed moves: PDSB up 7.07%, CUE up 15.58%, GNTA down 5.8%, and
Historical Context
| Date | Event | Sentiment | Move | Catalyst |
|---|---|---|---|---|
| Apr 22 | ATNM-400 pan-tumor data | Positive | -10.9% | Compelling ATNM-400 preclinical pan-tumor data at AACR 2026 across solid tumors. |
| Apr 22 | Actimab-A AML data | Positive | -10.9% | AACR 2026 data showing mutation-agnostic anti-leukemic activity and combination benefits. |
| Apr 06 | AACR abstract announcement | Positive | +11.2% | Announcement of AACR abstracts featuring new ATNM-400 and Actimab-A preclinical data. |
| Feb 17 | AACR presentation notice | Positive | -2.7% | Notice of two upcoming AACR 2026 abstracts on ATNM-400 and Actimab-A programs. |
| Dec 12 | Breast cancer data | Positive | +4.1% | SABCS 2025 ATNM-400 data showing potent activity across multiple breast cancer subtypes. |
Preclinical and conference-focused updates have produced mixed reactions, with slightly more downside divergences than upside alignments following positive scientific news.
Over the past six months, Actinium has repeatedly highlighted its Ac-225 radioconjugate platform. On Dec 12, 2025, new ATNM-400 breast cancer data at SABCS showed potent anti-tumor activity. Multiple AACR 2026 updates on Apr 6 and Apr 22 detailed pan-tumor efficacy for ATNM-400 and mutation-agnostic activity for Actimab-A, yet share reactions were mixed, including a -10.86% move after compelling ATNM-400 data. Today’s SNMMI 2026 presentations extend this preclinical narrative into NSCLC, prostate cancer, and radiochemistry optimization.
Market Pulse Summary
This announcement expands Actinium’s ATNM-400 story with preclinical data in NSCLC and prostate cancer plus radiochemistry optimization, showcased at SNMMI 2026 from May 30–June 2, 2026. It follows prior AACR and SABCS updates demonstrating pan-tumor activity and differentiated mechanisms. Investors may track progress toward clinical studies, the timing of upcoming readouts across solid tumors and hematologic programs, and how ongoing net losses, such as the $33.9 million reported for 2025, intersect with development plans.
Key Terms
nsclc medical
kras medical
psma medical
chelator-to-antibody ratio medical
radioconjugate medical
pharmacokinetics medical
actinium-225 medical
AI-generated analysis. Not financial advice.
– 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
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 |
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 |
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 |
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.