On June 10, 2024 Actinium Pharmaceuticals, Inc. (NYSE AMERICAN: ATNM) (Actinium or the Company), a leader in the development of Antibody Radiation Conjugates (ARCs) and other targeted radiotherapies, reported data from multiple abstracts that were presented at the 2024 Society of Nuclear Medicine & Molecular Imaging (SNMMI) Annual Meeting being held June 8 – 11, 2024, in Toronto, Canada (Press release, Actinium Pharmaceuticals, JUN 10, 2024, View Source [SID1234644229]). The presentations featured results from the Phase 3 SIERRA trial of Iomab-B, a CD45 targeting ARC with the Iodine-131 payload, intended for conditioning to prepare patients with active relapsed or refractory acute myeloid leukemia (r/r AML) for a potentially curative bone marrow transplant (BMT). The Phase 3 SIERRA trial enrolled 153 r/r AML patients. Iomab-B achieved the primary endpoint of durable Complete Remission (dCR) with high statistical significance (p<0.0001). Additionally, Actinium’s novel linker technology was highlighted in a presentation demonstrating high tumor uptake and in vivo stability in preclinical models with significantly lower kidney and liver uptake compared to standard DOTA linkers.

Schedule your 30 min Free 1stOncology Demo!
Discover why more than 1,500 members use 1stOncology™ to excel in:

Early/Late Stage Pipeline Development - Target Scouting - Clinical Biomarkers - Indication Selection & Expansion - BD&L Contacts - Conference Reports - Combinatorial Drug Settings - Companion Diagnostics - Drug Repositioning - First-in-class Analysis - Competitive Analysis - Deals & Licensing

                  Schedule Your 30 min Free Demo!

Actinium’s Iomab-B SNMMI presentations and highlights:

Survival Outcomes and Dosimetric Analysis of Iomab-B (131I-apamistamab) Followed by Allogeneic Hematopoietic Cell Transplant for Patients with TP53 Mutated Relapsed/Refractory AML

37 patients (24%) enrolled on SIERRA had a TP53 mutation with 27 patients receiving Iomab-B (either through randomization or cross over) and 10 patients on the control arm
For patients with TP53 mutation who received Iomab-B, the median OS was 5.49 months compared to a median 1.66 months in pts who did not receive Iomab-B (HR=0.23; 95% CI [0.10, 0.52])
These results support Iomab-B’s differentiated mechanism of action to overcome the negative impact of TP53 mutation typically associated with a dismal prognosis in these patients
Exploratory Analysis of Bone Marrow Dosimetry from the Randomized Phase 3 SIERRA Trial of Iomab-B (131I-apamistamab) Prior to HCT in Relapsed/Refractory Acute Myeloid Leukemia

Iomab-B safely delivers high doses of myeloablative targeted radiation to the diseased bone marrow at greater amounts than what would be achieved with total body irradiation
Myeloablative doses were safely delivered to patients irrespective of age, performance status and other metrics
A median of 16Gy of radiation was delivered to the bone marrow while normal healthy organs received significantly less exposure, including the heart (2.6 Gy), lungs (2.5 Gy), small intestine (2.4 Gy), stomach (3.6 Gy), kidneys (4.1 Gy) and the whole body (3.3 Gy)
Mathematical Modeling of Exposure Measurements Following High-Dose Targeted Therapy Using 131I-apamistamab: Analysis From the Large Multicenter Phase III SIERRA Trial

SIERRA patients received up to 1,030 mCi (range: 300-1,030) of Iodine-131 via Iomab-B
Iomab-B is administered via a single infusion 12 days prior to BMT
Data from SIERRA show that the median time for patients to reach the release criteria was 5 days, including in patients receiving greater than 800 mCi
Actinium’s Proprietary Linker Technology SNMMI presentation and highlights:

Evaluation of novel DOTA-based linkers for improved targeted radiotherapy delivery to solid tumors

Novel linkers showed significantly lower kidney and liver uptake compared to standard DOTA linkers
SPECT/CT imaging showed high tumor uptake and in vivo stability in preclinical models
Successful design, efficient conjugation and pharmacological properties support further advancement of these novel linkers
Actinium has two wholly owned U.S. patents covering its novel bifunctional linker technology with each having a patent term extending into 2043 and a pending international patent application
Sandesh Seth, Actinium’s Chairman and CEO, said, "At this year’s SNMMI, we are proud to highlight Actinium’s broad ARC pipeline and capabilities. Building on our leadership position in hematology focused ARCs through Iomab-B and Actimab-A, we are excited to highlight the potential to treat patients with high-risk relapsed or refractory AML and overcome TP53 mutations or extensive prior therapy including Venetoclax. Hematology represents an area with potential for significant growth for the field of nuclear medicine and there is great excitement from the community around our efforts. Consistent with our vision to build a leading specialty radiotherapeutics company, we are also eager to highlight our novel linker technology for solid tumor ARCs. Finally, SNMMI provides the opportunity to showcase our proprietary Actinium-225 cyclotron-based manufacturing technology that has the potential to produce highly pure medical grade Actinium-225 at a scale and cost that is not currently achievable, which has been met with great enthusiasm given the industry emphasis on Actinium-225 supply."

About the SNMMI Annual Meeting

The SNMMI Annual Meeting is recognized as the premier educational, scientific, research, and networking event in nuclear medicine and molecular imaging. The four-day event, taking place each June, provides physicians, technologists, pharmacists, laboratory professionals, and scientists with an in-depth view of the latest research and development in the field as well as providing insights into practical applications for the clinic.