Actinium Pharmaceuticals Appoints Radiopharmaceutical Industry Veteran Sean Maenpaa as Senior Vice President, Business Development

– Brings more than 20 years of oncology business development and commercial leadership, including senior roles across the radiopharmaceutical sector at Bayer, Clovis Oncology, Telix Pharmaceuticals and BWXT Medical

– Will lead partnering, licensing and strategic transactions across Actinium's targeted radiotherapy pipeline

NEW YORK, Oct. 16, 2026 /PRNewswire/ -- Actinium Pharmaceuticals, Inc. (NYSE American: ATNM) ("Actinium" or the "Company"), a pioneer in the development of targeted radiotherapies, today announced the appointment of Sean Maenpaa as Senior Vice President, Business Development, effective October 12, 2026. Mr. Maenpaa will lead the Company's business development activities, including out-licensing, partnering and collaboration transactions, in-licensing opportunities, and broader corporate development strategy.

Mr. Maenpaa joins Actinium with more than two decades of experience in oncology business development, strategic marketing and commercial leadership at global pharmaceutical companies and high-growth radiopharmaceutical innovators. His significant experience with radiopharmaceuticals spans both alpha- and beta-emitting radiotherapies, diagnostic PET imaging agents, and the supply of medical isotopes, a combination of experience that is rare in the industry.

Sandesh Seth, Actinium's Chairman and CEO, said, "Sean is one of the few executives in our industry who has worked across every part of the radiopharmaceutical value chain, from isotope supply and manufacturing to alpha and beta therapy strategy, commercial launches and partnering. His background in AML and myeloid malignancies at Novartis and Celgene, his alpha-therapy experience at Bayer, and his solid tumor focused business development leadership at Clovis and Telix are directly relevant for our strategic priorities. As interest from large pharma in targeted radiotherapies, and in particular early-stage assets, continues to accelerate, Sean's relationships and deal experience will be instrumental as we work to unlock the value of our pipeline through partnerships."

Mr. Maenpaa said, "Actinium has built one of the deepest bodies of expertise with Actinium-225 (Ac-225) and targeted radiotherapy in the industry, with a pipeline spanning hematologic malignancies and solid tumors. Radiopharmaceuticals have become one of the most active areas for strategic transactions in oncology, and I believe Actinium's assets, clinical data and Ac-225 know-how position the Company very well. I look forward to working with the team to build partnerships that maximize the value of the platform."

Sean was previously Managing Director of Maenpaa Consulting LLC, where he provided strategic product planning and business development support for private equity and investment banks focused primarily on oncology radiopharmaceutical product development. Before launching his consultancy, he served as Vice President, Commercial, at BWXT Medical, overseeing business development and sales for more than $120 million in medical radioisotope supplies. Earlier, as Vice President, Global Commercial, at Telix Pharmaceuticals, Sean played a pivotal role in building a uro-oncology franchise. His leadership helped drive global sales of ILLUCCIX® to $320 million and supported a life-cycle plan in prostate cancer. He also supported early U.S. launch strategies for ZIRCAIX® (TLX-250-Px), a novel renal cell carcinoma imaging agent, and the development of Lutetium-177 rosopatamab tetraxetan (TLX-591), a radioligand therapy for advanced prostate cancer. As Head of Business Development and Global Commercialization at Clovis Oncology, Sean led business development and licensing initiatives and contributed to the successful divestment of Lutetium-177 FAP2286 to Novartis. Previously, at Bayer AG, he managed a portfolio of thorium alpha radioligand therapies and supported the acquisition of Ac-225 PSMA Trillium Macropa from Ratio Therapeutics.

Earlier in his career, at Novartis as Senior Director, Early Commercial, he led commercial strategy for a 12-asset hematology pipeline in AML, MDS, NHL and Multiple Myeloma and also served as commercial and business development lead on all licensing option deals. He began his career in commercial roles at Celgene, where he was part of the U.S. and European launches of Revlimid® in Multiple Myeloma and MDS.

Mr. Maenpaa holds an MBA from the University of Sheffield and a BSc in Pharmacology from the University of Liverpool in the UK.

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, and is being evaluated in a first-in-human Phase 1 study in mCRPC. 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 the Company's ability to retain key personnel, the Company's ability to identify, negotiate and complete business development, partnering, licensing or other strategic transactions on favorable terms or at all, 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.

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