Actinium Pharmaceuticals Announces Three ASH 2026 Abstracts Highlighting Iomab-ACT Clinical Results in CAR T-Cell Therapy and Sickle Cell Disease

• The three abstracts strengthen the clinical foundation for Iomab-ACT's development as a targeted conditioning platform for cellular and gene therapies across cancer and nonmalignant diseases
• Phase 1b/2 trial evaluates targeted immune conditioning with Iomab-ACT before standard commercial CD19-directed CAR T-cell therapy
• Memorial Sloan Kettering Cancer Center study demonstrates promise of Iomab-ACT as targeted conditioning agent before CAR T-cell therapy, with a focus on CAR T-cell expansion, immune cell depletion and treatment-related toxicities
• Clinical experience in severe sickle cell disease evaluates Iomab-ACT-based conditioning to support donor engraftment without conventional chemotherapy

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 three abstracts for the 68th American Society of Hematology (ASH) Annual Meeting and Exposition. The abstracts highlight clinical findings and continued development of Iomab-ACT, the Company's investigational CD45-targeted radioimmunotherapy, as a conditioning approach before CAR T-cell therapy and allogeneic stem cell transplantation for severe sickle cell disease.

The abstracts include results from the Memorial Sloan Kettering Cancer Center study of Iomab-ACT before investigational CD19-directed CAR T-cell therapy, preliminary results from the Iomab-ACT-based conditioning regimen for severe sickle cell disease, and a Phase 1b/2 study evaluating Iomab-ACT before standard commercial CD19-directed CAR T-cell therapy. Together, these studies explore the potential of targeted radiation to prepare patients for cellular therapies while reducing reliance on conventional chemotherapy conditioning.

Sandesh Seth, Actinium's Chairman and CEO, stated, "These ASH presentations mark an important step in the development of our Iomab-ACT CD45-targeted radiotherapy conditioning program. Iomab-ACT is a highly differentiated conditioning agent designed to prepare patients for cellular and gene therapies through targeted radiation rather than conventional chemotherapy. Building on the promising initial clinical experience with investigational CD19-directed CAR T-cell therapy, we are excited by the opportunity to evaluate Iomab-ACT with commercial CAR T-cell therapies. The clinical experience in severe sickle cell disease further highlights its potential beyond cancer. Together, these studies support our goal of establishing Iomab-ACT as a universal targeted conditioning regimen for cellular and gene therapies."

Iomab-ACT ASH 2026 Presentation Details

Abstract Title: First Preliminary Results of Anti-CD45 ¹³¹I-Radioimmunotherapy (Iomab-ACT) as Nonmyeloablative Conditioning for HLA-Matched Sibling Allogeneic Stem Cell Transplantation in Severe Sickle Cell Disease (SCD)
Session Title: 721. Allogeneic Transplantation: Conditioning Regimens, Engraftment, and Acute Toxicities: Poster II
Presenting Author: Markus Y. Mapara, Columbia University Irving Medical Center
Location: Ernest N. Morial Convention Center, Hall F
Date: Sunday, December 13, 2026
Time: 6:00 PM – 8:00 PM

Abstract Title: Low-dose ¹³¹I apamistamab prior to adoptive cellular therapy (Iomab-ACT) for relapsed/refractory DLBCL and B-cell ALL serves as a promising means of lymphodepletion while preventing severe CRS and neurologic toxicity
Lead Author: Mark Geyer, Memorial Sloan Kettering Cancer Center

Abstract Title: Precision CD45-directed ¹³¹I radioimmunotherapy immune conditioning before CD19-directed CAR T-cell therapy for lymphoid malignancies: the phase 1b/2 IOMAB-ACT trial
Lead Author: Farrukh T. Awan, UT Southwestern Medical Center

About Iomab-ACT

Iomab-ACT is an investigational CD45-targeted antibody radioconjugate combining apamistamab with iodine-131. It is being studied as a targeted conditioning approach before cellular therapies, including CAR T-cell therapy and allogeneic stem cell transplantation. By delivering radiation to CD45-expressing hematopoietic and immune cells, Iomab-ACT is designed to prepare the host immune environment for subsequent cellular therapy. Its safety and efficacy remain under clinical investigation.

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.

Investor Contact

Peter (PJ) Kelleher
LifeSci Advisors
pkelleher@lifesciadvisors.com
(617) 430-7579

SOURCE Actinium Pharmaceuticals, Inc.