Benzinga | Jun 15, 2021 08:46AM EDT

Actinium Pharmaceuticals Says Safety Data Highlighting Low Rates Of Adverse Events And Non-Relapse Transplant Related Mortality In Patients Receiving Lomab-B Presented At 2021 SNMMI Virtual Conference

Actinium Pharmaceuticals, Inc. (NYSE:ATNM) ("Actinium") today highlighted safety data from its ongoing pivotal Phase 3 SIERRA trial of Iomab-B in patients with relapsed or refractory Acute Myeloid Leukemia (r/r AML) were presented at the 2021 Society of Nuclear Medicine and Molecular Imaging (SNMMI) Annual Meeting held virtually July 11th -- 14th. The presentation highlighted Iomab-B's targeting ability and corresponding safety data from 113 patients, representing 75% of patient enrollment on the SIERRA trial.

Iomab-B targets CD45, an antigen expressed on leukemia and lymphoma cancer cells and immune cells including bone marrow stem cells but not on cells outside of the blood forming or hematopoietic system. This allows high amounts of radiation to be delivered to the bone marrow via Iomab-B while sparing critical organs. As a result, statistically significant lower rates of sepsis were reported as well as lower rates of febrile neutropenia, mucositis and non-relapse transplant related mortality in patients receiving Iomab-B and bone marrow transplant (BMT) compared to patients that received salvage therapy and a BMT. In addition, patients who crossed over to receive Iomab-B and went to BMT after receiving salvage therapy but not achieving a complete response also had lower rates of sepsis, febrile neutropenia, mucositis and non-relapse transplant related mortality.

Dr. Mark Berger, Actinium's Chief Medical Officer, commented, "Relapsed and refractory AML in older patients is a particularly challenging disease to treat. Patients are heavily pretreated making their disease resistant to most standard therapies and often have comorbidities that limit treatment options, particularly bone marrow transplant. It is highly encouraging to us that in the SIERRA trial thus far, Iomab-B has enabled all patients receiving a therapeutic dose to proceed to BMT, the only curative treatment option for this patient population. Importantly, Iomab-B has been well tolerated and we are elated with the safety data from 75% of patient enrollment in the SIERRA trial. Given the targeted nature of Iomab-B, we can spare non-targeted organs like GI tract and deliver higher amounts of radiation to the bone marrow, the target organ. We are thrilled to be able to highlight results of the SIERRA trial through 75% of patient enrollment at SNMMI and look forward to future opportunities to present topline data from the full study."

SNMMI Presentation Title: Low Incidence Rates of Mucositis, Febrile Neutropenia or Sepsis in the Prospective, Randomized Phase 3 SIERRA Trial for Patients with Relapsed or Refractory Acute Myeloid Leukemia with Target Delivery of Anti-CD45 Iodine (131I) Apamistamab [Iomab-B]



Presenter: Neeta Pandit-Paskar, MD, Memorial Sloan Kettering Cancer Center

SNMMI Presentation Highlights:

Received No CR Crossed over to Achieved CR and Iomab-B/HCT (N=Iomab-B/HCT (N=30)2 received Std HCT (N=Adverse Event 49)1 10) % (N) % (N) % (N)

Sepsis 4 (2) 23 (7) 30 (3)

Febrile Neutropenia 42 (20) 40 (12) 50 (5) Gr 3-4

Mucositis Gr 3-4 10.4 (5) 17 (5) 30 (3)



Day +100 2/45 3/28 2/10 Non-Relapse Mortality3 (4.4) (10.7) (20)



1 Adverse Event data available for 46 of 47 evaluable patients

2 Adverse Event data available for 27 of 30 evaluable patients

3 Iomab-B arm: 4 patients unevaluable. Conventional Care Arm: 4 patients unevaluable

No. of Radiation dose delivered toRadiation dose to GI tract.Patient Group Patientsthe Marrow. Median Median

Iomab-B 49 14.6 Gy 2.8 Gy