• Iomab-B significantly improved outcomes in TP53 positive patients with a median overall survival of 5.49 months versus 1.66 months in those not receiving Iomab-B (hazard ratio = 0.23, p-value=0.0002) in the Phase 3 SIERRA Trial
  
• The results demonstrate Iomab-B's ability to overcome the negative impact of a TP53 mutation in these patients who otherwise would have limited treatment options and dismal prognosis
  
• Five presentations include two upcoming oral presentations detailing improved outcomes in SIERRA trial patients ages 65+ and demonstration of robust engraftment with Iomab-B

NEW YORK, Feb. 23, 2024 /PRNewswire/ -- Actinium Pharmaceuticals, Inc. (NYSE AMERICAN: ATNM) (Actinium or the Company), a leader in the development of targeted radiotherapies, today highlighted results from three poster presentations at the 2024 Tandem Meetings | Transplantation & Cellular Therapy (TCT) Meetings of ASTCT^® (American Society for Transplantation and Cellular Therapy and CIBMTR^®  (Center for International Blood and Marrow Transplant Research) being held in San Antonio, Texas. The posters detailed results and findings from the Phase 3 SIERRA trial of Iomab-B (¹³¹I-Apamistamab) including; improved rates of Complete Remission (CR), durable Complete Remission (dCR) and survival in patients with a TP53 mutation, key aspects of radiopharmaceutical dosimetry as related to Iomab-B, and early results from a Phase 1 study demonstrating safety and lymphodepletion from Iomab-ACT conditioning with CD19 CAR-T therapy.

Dr. Avinash Desai, Actinium's Chief Medical Officer, said, "Patients with a TP53 mutation have a desperate need for viable treatment options to improve outcomes. As seen in the SIERRA trial, Iomab-B led bone marrow transplant can overcome the negative impact of a TP53 mutation, producing complete remissions in more than 50% of patients as well as significant durable complete remissions. This is in stark contrast to the 0% complete remission and durable complete remission rate seen in the TP53 positive patients on the control arm who received best available treatment based on physician's choice. We are excited to further highlight these important outcomes to the transplant community and look forward to presenting additional findings from the SIERRA trial in our upcoming oral presentations."

The presented Iomab-B Phase 3 SIERRA trial results and highlights include:

Response Rate by TP53 Mutational Status and Treatment

CR = Complete Remission

Improved Survival with Iomab-B

Upcoming Iomab-B Phase 3 SIERRA Trial 2024 TCT Oral Presentations:

Title: ¹³¹I-Apamistamab Improves Outcomes in Patients 65 Years and Older with Relapsed or Refractory AML

Date & Time: Saturday, February 24, 2024, at 11:45 AM

Title: Targeted Myeloablative Radiation Using ¹³¹I-Apamistamab Prior to Allogeneic Hematopoietic Cell Transplant for Patients with R/R AML Results in Robust Engraftment

Date & Time: Saturday, February 24, 2024, at 10:30 AM

In addition, Actinium presented results from its ongoing phase 1 trial using Iomab-ACT as conditioning prior to CD19 CAR-T therapy for patients with relapsed or refractory B-cell Acute Lymphoblastic Leukemia or Diffuse Large B-cell Lymphoma. Importantly, no patients (0/4) developed immune effector cell-associated neurotoxicity syndrome (ICANS) of any grade, a major safety measure of the study, as ICANS is observed in 25% or more of pts w/ R/R B-ALL and DLBCL treated with various CAR T-cell products. Iomab-ACT demonstrated transient depletion of peripheral blood lymphocytes and monocytes.  Persistence of CAR T-cells up to 8 weeks and minimal non-hematologic toxicities have been observed to date.

About the TCT Tandem Meetings

The Tandem Meetings I Transplantation & Cellular Therapy Meetings of ASTCT and CIBMTR are the combined annual meetings of the American Society for Transplantation and Cellular Therapy (ASTCT) and the Center for International Blood & Marrow Transplant Research (CIBMTR). Administrators, clinicians, data manager / clinical research professionals, fellows-in-training, investigators, laboratory technicians, MD/PhDs, nurses, nurse practitioners, pharmacists, physician assistants, and other allied health professional attendees benefit from a full scientific program that addresses the most timely issues in hematopoietic cell transplantation and cellular therapy.

About Actinium Pharmaceuticals, Inc.

Actinium develops targeted radiotherapies to meaningfully improve survival for people who have failed existing oncology therapies. Advanced pipeline candidates Iomab-B (pre-BLA & MAA (EU)), an induction and conditioning agent prior to bone marrow transplant, and Actimab-A (National Cancer Institute CRADA pivotal development path), a therapeutic agent, have demonstrated potential to extend survival outcomes for people with relapsed and refractory acute myeloid leukemia. Actinium plans to advance Iomab-B for other blood cancers and next generation conditioning candidate Iomab-ACT to improve cell and gene therapy outcomes. Actinium holds more than 220 patents and patent applications including several patents related to the manufacture of the isotope Ac-225 in a cyclotron.

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.

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