Actinium Pharmaceuticals Announces ATNM-400 a Novel Non-PSMA Targeting First in Class Prostate Cancer Radiotherapy Leveraging Actinium-225
Rhea-AI Summary
Actinium Pharmaceuticals (NYSE: ATNM) has unveiled ATNM-400, a groundbreaking non-PSMA targeting radiotherapy for prostate cancer using Actinium-225. Initial preclinical data showed remarkable results with 99.8% tumor growth inhibition at 40 µCi/kg and 68.5% at 20 µCi/kg from a single dose.
The therapy demonstrated selective tumor accumulation for up to 144 hours with minimal uptake in healthy tissues. ATNM-400 differentiates itself from Novartis's Pluvicto by targeting a different marker than PSMA and utilizing the more potent alpha-particle emitter Ac-225, potentially resulting in fewer off-target effects.
The company will present initial data at the AACR Annual Meeting (April 25-30, 2025), including results from Pluvicto-resistant prostate cancer models. The presentation will showcase findings from in vitro and in vivo studies, biodistribution imaging, and efficacy analyses at various dose levels.
Positive
- Achieved 99.8% tumor growth inhibition with single dose at 40 µCi/kg
- Demonstrated selective tumor accumulation for up to 144 hours with minimal healthy tissue uptake
- Potential to treat Pluvicto-resistant prostate cancer cases
- Targets different marker than PSMA, potentially reducing common side effects like xerostomia
Negative
- Still in preclinical stage, requiring extensive clinical trials before potential commercialization
- Will compete with established treatment Pluvicto ($1.39B sales in 2024)
News Market Reaction – ATNM
In the trading session that priced this news, ATNM gained 1.07%, reflecting a mild positive market reaction.
Data tracked by StockTitan Argus on the day of publication.
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- ATNM-400 accumulated in tumors for up to 144 hours and showed minimal uptake in healthy tissues in prostate cancer xenograft model
- Initial ATNM-400 preclinical data to be presented at AACR including results in Pluvicto resistant prostate cancer models
Sandesh Seth, Actinium's Chairman and CEO, said, "The current era of radiotherapy is built on the clinical and commercial success of Pluvicto in prostate cancer. The field is now looking to address patients that do not respond or progress after Pluvicto therapy. We believe ATNM-400 can address this high unmet need and we are incredibly excited by our data to date. As anticipated, we have seen robust tumor control and ATNM-400 has shown to be well tolerated in preclinical studies, which we believe is due to the precise and potent cell-killing of Ac-225. We are also highly excited by the results of our biodistribution studies that showed selective tumor uptake with minimal uptake in normal tissues. By focusing on a non-PSMA target, we also believe ATNM-400 has the potential to address some of the toxicities reported with Pluvicto and other PSMA targeting radiotherapies such as xerostomia. We are eager to present our ATNM-400 data at AACR and to continue to advance this highly novel prostate cancer candidate."
Highlights from the abstract include:
- ATNM-400 selectively binds to prostate cancer cells, undergoes rapid internalization, and induces dose-dependent cytotoxicity
- In prostate cancer xenograft mouse models, ATNM-400 accumulated in tumors for up to 144 hours, while showing minimal uptake in normal tissues
- Small animal SPECT/CT imaging with Indium-111-labeled antibody confirmed selective tumor accumulation and clearance from healthy tissues
- A single dose of ATNM-400 achieved
68.5% tumor growth inhibition at 20 µCi/kg and99.8% at 40 µCi/kg, with all doses being well tolerated
ATNM-400 AACR Presentation Details
Title: ATNM-400 is a novel Actinium-225 antibody radioconjugate with strong efficacy in preclinical models of prostate cancer
Abstract Number: 578
Session: PO.ET08.01 - Theranostics and Radiotheranostics
Date & Time: April 27, 2025 – 2:00 pm – 5:00 pm
About Actinium Pharmaceuticals, Inc.
Actinium is a pioneer in the development of targeted radiotherapies intended to meaningfully improve patient outcomes. Actinium is advancing its lead product candidate Actimab-A, a CD33 targeting therapeutic, as potential backbone therapy in acute myeloid leukemia (AML) and other myeloid malignancies leveraging the mutation agnostic alpha-emitter radioisotope payload Actinium-225 (Ac-225). Actimab-A has demonstrated potential activity in relapsed and refractory acute myeloid leukemia (r/r AML) patients in combination with the chemotherapy CLAG-M including high rates of Complete Remissions (CR) and measurable residual disease (MRD) negativity leading to improved survival outcomes and is being advanced to a pivotal Phase 2/3 trial. In addition, Actinium is engaged with the National Cancer Institute (NCI) under the Cooperative Research and Development Agreement (CRADA) for development of Actimab-A in AML and other myeloid malignancies. The first clinical trial under the CRADA will evaluate the triplet combination comprised of Actimab-A, Venetoclax (Abbvie/Roche) an oral Bcl-2 inhibitor and ASTX-727 (Taiho Oncology, an Otsuka holdings company) a novel oral hypomethylating agent (HMA) in frontline acute myeloid leukemia (AML) patients. Additionally, Actinium is developing Actimab-A as a potential pan tumor therapy in combination with PD-1 checkpoint inhibitors including KEYTRUDA® and OPDIVO® by depleting myeloid derived suppressor cells (MDSCs), which represents a potential multi-billion-dollar addressable market. Iomab-ACT, Actinium's next generation conditioning candidate, is being developed with the goal of improving patient access and outcomes for potentially curative cell and gene therapies. Iomab-B is an induction and conditioning agent prior to bone marrow transplant in patients with r/r AML, which Actinium is seeking a potential strategic partner for the
For more information, please visit: https://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.