Actinium Pharmaceuticals Announces New Pan-Tumor Preclinical Data for ATNM-400 in Solid Tumors and Differentiated Mechanism for Actimab-A in AML to be Presented at 2026 AACR Annual Meeting

Rhea-AI Summary

Actinium Pharmaceuticals (NYSE: ATNM) announced two AACR 2026 abstracts to be presented April 21, 2026, highlighting new preclinical data for ATNM-400 and a differentiated mechanism for Actimab-A. ATNM-400 shows pan-tumor Ac-225 radioconjugate activity; Actimab-A shows mutation-agnostic transcriptional reprogramming that may enhance AML therapy response. Posters: ATNM-400 #5824 and Actimab-A #5827 in session Radiopharmaceutical Platforms for Theranostic Precision Oncology, April 21, 2:00–5:00 PM PT, Poster Section 16.

News Market Reaction – ATNM

+11.18% 1.8x vol

7 alerts

+11.18% Session close to close

+8.2% Peak in 30 hr 27 min

$37.34M Market Cap

1.8x Rel. Volume

In the Apr 6 session, ATNM gained 11.18%, reflecting a significant positive market reaction. Argus tracked a peak move of +8.2% during that session. Our momentum scanner triggered 7 alerts that day, indicating moderate trading interest and price volatility. Trading volume was above average at 1.8x the daily average, suggesting increased trading activity.

Data tracked by StockTitan Argus on the day of publication.

Market Context

The stock surged +11.2% in the session following this news. A strong positive reaction aligns with t...

Analysis

The stock surged +11.2% in the session following this news. A strong positive reaction aligns with the company’s pattern of meaningful moves on broad platform or market-positioning news, such as the Nov 17, 2025 radiotherapy article. However, ATNM traded below its 200-day MA of 1.43 and near its 52-week low ahead of this release, so investors would monitor whether enthusiasm persists as further ATNM-400 and Actimab-A data readouts emerge in 2026.

Key Figures

AACR 2026 dates: April 17–22, 2026 Poster number ATNM-400: 5824 Poster number Actimab-A: 5827 +5 more

8 metrics

AACR 2026 dates April 17–22, 2026 American Association for Cancer Research Annual Meeting schedule

Poster number ATNM-400 5824 ATNM-400 AACR 2026 poster identifier

Poster number Actimab-A 5827 Actimab-A AACR 2026 poster identifier

Poster session time 2:00 PM–5:00 PM PT AACR 2026 poster session on April 21, 2026

Poster section Section 16 Location for both AACR 2026 posters

Board number ATNM-400 18 Board position for ATNM-400 poster

Board number Actimab-A 21 Board position for Actimab-A poster

Common shares outstanding 31,374,994 As of March 30, 2026 per 10-K

Historical Context

5 past events · Latest: Feb 17 (Positive)

Pattern 5 events

Date	Event	Sentiment	24h Move	Catalyst
Feb 17	AACR 2026 abstracts	Positive	-2.7%	Announcement of two AACR 2026 abstracts for ATNM-400 and Actimab-A.
Dec 12	Breast cancer data	Positive	+4.1%	New preclinical ATNM-400 data across multiple breast cancer subtypes at SABCS.
Dec 01	TNBC efficacy update	Positive	-0.7%	ATNM-400 data showing potent TNBC efficacy and resistance-overcoming activity.
Nov 17	Radiotherapy market piece	Positive	+14.2%	Feature on Actinium’s radiotherapy strategy and ATNM-400’s competitive preclinical profile.
Nov 04	Pan-tumor profile update	Positive	-2.2%	Preview of ATNM-400 data expanding pan-tumor profile across three solid tumors.

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

Pattern Detected

Positive R&D and platform news has produced mixed reactions, with several preclinical updates selling off but broader strategic radiotherapy coverage drawing a stronger positive response.

Recent Company History

Over the past six months, Actinium has repeatedly highlighted its Ac-225 platform and ATNM-400 pan-tumor profile across breast, prostate, and lung cancer, along with Actimab-A progress. News on detailed preclinical data and conference presentations (e.g., SABCS 2025 and AACR 2026) has sometimes led to selling, while a broader radiotherapy market article on Nov 17, 2025 coincided with a stronger gain. Today’s AACR data-preview fits this ongoing platform-building narrative.

Key Terms

ac-225, radioconjugate, mutation-agnostic, transcriptional reprogramming, +4 more

8 terms

ac-225 medical

"first-in-class Ac-225 radioconjugate with broad pan-tumor efficacy"

Ac-225 (actinium-225) is a rare radioactive isotope used as the active payload in targeted alpha therapy, a cancer treatment that delivers very powerful, short-range radiation directly to tumor cells. For investors, Ac-225 matters because its scarce, complex manufacturing and strict regulatory handling act like a critical ingredient in a drug supply chain—shortages or production hurdles can delay trials, raise costs and materially affect the commercial prospects and valuation of companies developing such therapies.

radioconjugate medical

"first-in-class Ac-225 radioconjugate with broad pan-tumor efficacy"

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.

mutation-agnostic medical

"Actimab-A demonstrates mutation-agnostic efficacy and a novel mechanism"

A mutation-agnostic therapy or diagnostic works regardless of specific genetic changes in a disease-causing organism or tumor, meaning it targets a feature common across many variants rather than one particular mutation. For investors, this implies a broader potential market, lower risk that effectiveness will be lost when new variants emerge, and a clearer path to sustained sales and regulatory value—like a universal key that fits many locks instead of one custom-made key.

transcriptional reprogramming medical

"Actimab-A's newly identified mechanism of transcriptional reprogramming provides important insight"

Transcriptional reprogramming is the process of changing which genes are turned on or off inside a cell, altering the cell’s behavior and identity. For investors, it matters because therapies or products that reliably reprogram gene activity can shift disease outcomes or create new treatment pathways—akin to changing a machine’s settings to make it run differently—which can drive clinical value, regulatory interest, and commercial opportunity.

radiopharmaceutical medical

"session Radiopharmaceutical Platforms for Theranostic Precision Oncology"

A radiopharmaceutical is a special type of medicine that contains a small amount of radioactive material, used primarily for medical imaging or treatment. It can be thought of as a tiny, targeted signal that helps doctors see inside the body or deliver therapy directly to affected areas. For investors, understanding radiopharmaceuticals is important because they represent a growing field within healthcare, driven by advancements in diagnostics and personalized treatments.

theranostic medical

"Radiopharmaceutical Platforms for Theranostic Precision Oncology"

A theranostic is a single medical approach or agent that combines diagnosis and treatment—using a test or imaging step to find patients likely to benefit, then delivering a targeted therapy tied to that same marker. For investors, theranostics can speed development, lower the chance of failed trials and concentrate sales on the right patients, like a smart key that both locates the correct lock and opens it, potentially improving clinical and commercial success.

acute myeloid leukemia medical

"Actimab-A in AML to be Presented at 2026 AACR Annual Meeting"

A fast‑moving blood cancer that starts in the bone marrow and crowd out healthy blood cell production, leaving the body short of normal red cells, white cells and platelets. It matters to investors because the disease creates urgent medical need, drives demand for new diagnostics and treatments, and so clinical trial results, regulatory decisions and drug pricing can rapidly change the commercial prospects and valuation of companies working on therapies.

hematologic malignancies medical

"across both solid tumors and hematologic malignancies"

Hematologic malignancies are types of cancers that start in the blood or the organs responsible for blood production, like the bone marrow and lymph nodes. They matter because they can disrupt normal blood functions, leading to issues like weakness, infections, or abnormal growths, and often require specialized treatments.

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• New data underscoring the potential of ATNM-400 as a first-in-class Ac-225 radioconjugate with broad pan-tumor efficacy across multiple solid tumor models
   
• Actimab-A demonstrates mutation-agnostic efficacy and a novel mechanism that enhances response to standard AML therapies
   
• Multiple data catalysts for ATNM-400 and Actimab-A in 2026; and posters for each to be presented on April 21, 2026 at AACR 2026 in San Diego, CA

NEW YORK, April 6, 2026 /PRNewswire/ -- Actinium Pharmaceuticals, Inc. (NYSE American: ATNM) (Actinium or the Company), a pioneer in the development of targeted radiotherapies, today announced the publication of two abstracts that will be presented at the American Association for Cancer Research (AACR) Annual Meeting 2026, taking place April 17–22, 2026, in San Diego, California.

The Company will present previously undisclosed data demonstrating the expanding potential of its Ac-225 radiotherapy platform across both solid tumors and hematologic malignancies. Both presentations will occur on April 21, 2026 in the session Radiopharmaceutical Platforms for Theranostic Precision Oncology.

Sandesh Seth, Actinium's Chairman and CEO, said, "These new data further validate the strength and versatility of our Ac-225 radiotherapy platform. ATNM-400 continues to show compelling pan-tumor activity, including activity in tumors resistant to current targeted therapies, supporting its potential as a first-in-class asset in large solid tumor indications. In parallel, Actimab-A's newly identified mechanism of transcriptional reprogramming provides important insight into its mutation-agnostic activity and ability to enhance standard-of-care therapies. Together, these findings reinforce our strategy to build a differentiated pipeline with multiple value-driving opportunities."

ATNM-400 AACR 2026 Presentation Details

Poster Number: 5824

Session: Radiopharmaceutical Platforms for Theranostic Precision Oncology

Date & Time: April 21, 2026 – 2:00 PM – 5:00 PM PT | Poster Section 16, Board #18

Actimab-A AACR 2026 Presentation Details

Poster Number: 5827

Session: Radiopharmaceutical Platforms for Theranostic Precision Oncology

Date & Time: April 21, 2026 – 2:00 PM – 5:00 PM PT | Poster Section 16, Board #21

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

View original content to download multimedia:https://www.prnewswire.com/news-releases/actinium-pharmaceuticals-announces-new-pan-tumor-preclinical-data-for-atnm-400-in-solid-tumors-and-differentiated-mechanism-for-actimab-a-in-aml-to-be-presented-at-2026-aacr-annual-meeting-302733914.html

SOURCE Actinium Pharmaceuticals, Inc.

FAQ

What preclinical results will Actinium (ATNM) present for ATNM-400 at AACR 2026?

ATNM will present preclinical data showing pan-tumor Ac-225 radioconjugate activity across multiple solid tumor models. According to the company, the data indicate efficacy including activity in tumors resistant to current targeted therapies, supporting ATNM-400 as a potential first-in-class asset.

How does Actimab-A's new mechanism presented by Actinium (ATNM) affect AML therapy?

Actimab-A exhibits a mutation-agnostic transcriptional reprogramming mechanism that enhances responses to standard AML therapies. According to the company, this mechanism provides insight into broader activity and potential synergy with existing standard-of-care treatments in AML patients.

When and where will Actinium (ATNM) present the AACR 2026 posters for ATNM-400 and Actimab-A?

Both posters will be presented on April 21, 2026, 2:00–5:00 PM PT in Poster Section 16 at AACR 2026 in San Diego. According to the company, ATNM-400 is Poster #5824 and Actimab-A is Poster #5827.

What is the significance of ATNM-400 being described as a first-in-class Ac-225 radioconjugate for investors in ATNM?

The designation suggests potential differentiated positioning in large solid tumor indications based on novel Ac-225 radiotherapy. According to the company, ATNM-400's pan-tumor activity could create multiple value-driving opportunities across solid tumor indications if further validated.

Will Actinium (ATNM) disclose clinical data for ATNM-400 or Actimab-A at AACR 2026?

The presentations will showcase preclinical and mechanistic data rather than new clinical trial readouts. According to the company, the abstracts reveal expanding preclinical potential and a differentiated mechanism for Actimab-A, with multiple data catalysts planned in 2026.

How can investors view Actinium's (ATNM) AACR 2026 posters and presentations?

Investors can view the posters in person at AACR on April 21, 2026, Poster Section 16; Poster #5824 and #5827. According to the company, the presentations occur in the Radiopharmaceutical Platforms session, and details are available around the conference schedule.