On February 23, 2024 Actinium Pharmaceuticals, Inc. (NYSE AMERICAN: ATNM) (Actinium or the Company), a leader in the development of targeted radiotherapies, reported 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 (Press release, Actinium Pharmaceuticals, FEB 23, 2024, View Source [SID1234640423]). 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.

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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

Iomab-B + Crossover

Conventional Care

TP53 Positive

CR

Durable CR

N=27

N=15

N=4

55.56%

14.81%

N=10

N=0

N=0

0%

0%

TP53 Wildtype

CR

Durable CR

N=93

N=54

N=15

58.06%

16.13%

N=23

N=4

N=0

17.39%

0%

CR = Complete Remission

Improved Survival with Iomab-B

Iomab-B + Crossover

Conventional Care

N=27

N=10

Median Overall Survival

(95% CI)

5.49

(3.94, 8.25)

1.66

(0.99,2.96)

Hazard Ratio

(95% CI)

0.23

(0.1., 0.52)

p-value (log-rank)

0.0002

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.22211111111