On April 18, 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 that results from the Phase 3 SIERRA trial of Iomab-B were presented in an oral presentation at the 50th Annual European Bone Marrow Transplant Society Meeting (EBMT) held in Glasgow, Scotland on April 14-17 (Press release, Actinium Pharmaceuticals, APR 18, 2024, View Source [SID1234642164]). The results showed that an Iomab-B led bone marrow transplant (BMT) results in higher rates of remissions and durable Complete Remission (dCR), which is the primary endpoint of the SIERRA trial, as well as significant improvement in overall survival in TP53 positive patients. Iomab-B is a targeted radiotherapeutic comprised of an anti-CD45 monoclonal antibody with the Iodine-131 radioisotope payload. The Phase 3 SIERRA trial enrolled 153 patients age 55 and above with active relapsed or refractory acute myeloid leukemia (AML) and compared outcomes of patients receiving Iomab-B BMT to those of patients receiving physician’s choice of care in the control arm. In total, 24% (37/153) of the patients enrolled on SIERRA had a TP53 mutation, which is associated with limited treatment options and poor outcomes.
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Data highlighted in the ASH (Free ASH Whitepaper) oral presentation, which can be accessed on the investor relations page of Actinium’s website, included:
Response rates by TP53 Mutation Status:
Iomab-B & Crossover
Control Arm
TP53 Positive
N=27
N=10
CR
55.56% (15/27)
0 %
dCR
14.81% (4/27)
0 %
TP53 Wildtype
N=93
N=23
CR
58.06% (54/93)
17.39% (4/23)
dCR
16.13% (15/93)
0 %
Overall Survival in Patients with a TP53 Mutation:
Iomab-B & Crossover
Control Arm
Median OS
5.49 months
1.66 months
Number of Patients
27
10
Hazard Ratio
0.23
p-value
0.0002
Median OS was 6.37 months in TP53 negative patients receiving Iomab-B and 5.72 months for TP53 positive patients demonstrating Iomab-B’s ability to overcome TP53 gene mutations.
Dr. Hannah Choe, Assistant Professor of Medicine at Ohio State University and SIERRA trial investigator, commented, "TP53 mutations are associated with very poor outcomes due to resistance to anti-leukemic therapies with patients rarely offered access to potentially curative transplantation. The SIERRA trial showed that Iomab-B was well tolerated and can enable unprecedented access to transplant in this patient population and induce high complete remission rates despite active, relapsed/refractory disease and a TP53 mutation. These results were very well received at EBMT and demonstrate the novelty and safety of a CD45-directed antibody radiation conjugate. More importantly, we see that these response rates translated into improved overall survival, overcoming the increased risk associated with TP53 mutation while no other viable treatment options exist. We are excited for Iomab-B’s potential use and safety for disease control in patients with a TP53 mutation."
About the EBMT Annual Meeting
The Annual Meeting of the EBMT is attended by more than 5,500 participants, including physicians, nurses, data managers, statisticians, quality managers, cell therapists, paediatricians, pharmacists, psychologists, psychiatrists and psychoanalysts, transplant coordinators, lab scientists, trainees, and patients. This important congress ensures and encourages dialogues and information exchange, education and scientific productivity.
The full annual meeting program is available online at: