Actinium Pharmaceuticals Announces ASH 2026 Abstract Highlighting Long-Term Results of Actimab-A in Combination with CLAG-M in Relapsed or Refractory AML

• Results report the safety of combining targeted alpha therapy with CLAG-M for patients with relapsed or refractory acute myeloid leukemia

• Long-term follow-up evaluates bone marrow recovery and potential delayed kidney and liver toxicities following Actimab-A plus intensive salvage chemotherapy

• Findings support development of Actimab-A as a potential mutation-agnostic AML backbone, building on prior clinical activity following venetoclax failure and in TP53-mutated disease

NEW YORK, Nov. 4, 2026 /PRNewswire/ -- Actinium Pharmaceuticals, Inc. (NYSE American: ATNM) (Actinium or the Company), a pioneer in differentiated targeted radiotherapies with the potential to transform cancer treatment, today announced the release of an abstract for the 2026 American Society of Hematology (ASH) Annual Meeting and Exposition evaluating long-term safety and tolerability of Actimab-A (lintuzumab-Ac225) in combination with CLAG-M intensive salvage chemotherapy in patients with relapsed or refractory acute myeloid leukemia (AML).

The abstract presents follow-up from a Phase 1 study of Actimab-A plus CLAG-M, with a focused analysis of blood count recovery and potential delayed kidney and liver toxicities among patients who survived at least three months after treatment. These safety findings complement efficacy data previously presented at ASH 2022, which reported estimated one-year and two-year overall survival of 59% and 32%, respectively, in patients previously treated with venetoclax and 51% and 19%, respectively, in patients with TP53 mutated AML. Together, these observations support further evaluation of Actimab-A as a potential mutation agnostic therapeutic backbone for CD33-positive AML, including in difficult-to-treat populations, while addressing the importance of recovery and the ability to proceed to allogeneic hematopoietic cell transplantation.

"These long-term safety findings support our strategy to advance Actimab-A as a potential mutation-agnostic therapeutic backbone for AML," said Sandesh Seth, Actinium's Chairman and CEO. "The previously reported clinical activity of Actimab-A plus CLAG-M, including in patients whose disease has failed venetoclax-based therapy and those with TP53 mutations, reinforces its potential to address difficult-to-treat disease. Together with the long-term safety follow-up, these observations support further clinical evaluation of Actimab-A in combination regimens, with the goal of improving outcomes and expanding treatment options for patients with resistant disease and limited therapeutic alternatives."

Abstract Title: Long-Term Safety and Tolerability after Intensive Salvage therapy with CLAG-M for Relapsed/Refractory AML Session Title: 616. Acute Myeloid Leukemias: Investigational Drug and Cellular Therapies: Poster I Presenting Author: Sameem Abedin, MD, Medical College of Wisconsin Location: Ernest N. Morial Convention Center, Hall F Date: Sunday, December 13, 2026 Time: 6:00 PM – 8:00 PM

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 HER3, an 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.

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.