Actinium Pharmaceuticals Highlights Analysis of Pivotal Iomab-B Phase 3 SIERRA Trial Presented in Oral Session at ASH Annual Meeting

On December 4, 2018 Actinium Pharmaceuticals, Inc. (NYSE AMERICAN: ATNM) reported that additional data from an updated analysis of the pivotal Iomab-B Phase 3 SIERRA trial were highlighted last night in an oral presentation at the 60th American Society of Hematology (ASH) (Free ASH Whitepaper) Annual Meeting (Press release, Actinium Pharmaceuticals, DEC 4, 2018, View Source [SID1234531873]). The SIERRA trial is the only ongoing Phase 3 trial offering a bone marrow transplant (BMT) to patients 55 years of age or older with active, relapsed or refractory acute myeloid leukemia (AML). Data in the table below were presented in the oral session and are updated from those at the time of abstract submission. Preliminary data strongly support the feasibility and safety of re-induction and targeted conditioning with Iomab-B prior to a BMT.

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Preliminary Feasibility and Safety Data

Randomized to
Iomab-B Study Arm
(N=19)

Randomized to
Conventional Care
(N=19)

Randomized to
Conventional Care,
No Remission, and
Crossed Over (N=10)

Number of Patients
Receiving BMT after
receiving therapy

100% (18/18)

(1 patient did not
receive therapeutic
Iomab-B dose)

21% (4/19)

100% (10/10)

Blast % at
Randomization

Median: 30%

Range: 4* -74

Median: 26%

Range: 6-97

At Randomization
24% (6-70)
At Crossover 45%
(10-70)

Days to BMT

(post-randomization)

Median: 28

Range: 23-38

Median: 67

Range: 66-86

Median: 66

Range: 57-161

Days to Absolute
Neutrophil
Engraftment

Median:13

Range: 9 – 22

Not entered

Median:13

Range: 9 – 20

Days to Platelet
Engraftment

Median: 16

Range: 13 – 26

Not entered

Median:17

Range: 10 – 20

100-Day Non-
Relapse Mortality

0% (0/18)

25% (1/4 – septic
shock)

10% (1/10 – diffuse
alveolar hemorrhage)

*1 patient with 4% blasts in the marrow had circulating AML blasts

Other Key Highlights:

15 of 19 (79%) patients in the control arm failed to achieve a complete response
67% (10/15) of patients eligible for crossover successfully transplanted with Iomab-B
All patients receiving Iomab-B engrafted despite active disease with high blast count (median 30%, or median 45% for crossover patients)
Patients receiving Iomab-B received a BMT more quickly post-randomization (28 days) than patients receiving conventional care (67 days)
In the conventional care arm, there was no difference in time to BMT for patients that crossed over to Iomab-B (66 days) compared to those achieving complete remission with conventional care (67 days)
No Grade 3 or 4 Iomab-B infusion related reactions with all Iomab-B infusions completed
No non-relapse mortality in patients randomized to Iomab-B arm
Abstract #1017: Targeted Conditioning of Iomab-B (131I-anti-CD45) Prior to Allogeneic Hematopoietic Cell Transplantation Versus Conventional Care in Relapsed or Refractory Acute Myeloid Leukemia (AML): Preliminary Feasibility and Safety Results from the Prospective, Randomized Phase 3 Sierra Trial

Dr. Edward Agura, Medical Director of Bone Marrow Transplantation at Baylor University Medical Center said, "Given that more than two thirds of patients who are diagnosed with AML are 55 years of age or older, there exists a significant unmet medical need to broaden transplant access and improve outcomes for these patients. The data from the SIERRA trial thus far are highly encouraging as they demonstrate that Iomab-B can enable a potentially curative transplant in patients with active disease, including those patients with progressing disease who did not achieve a response on conventional care. The nearly universal and rapid engraftment of patients receiving Iomab-B, together with no 100-day non-relapse mortality, is particularly compelling as these results have not been achieved with conventional care."

The 150 patient SIERRA study is a multi-center randomized trial that will compare outcomes of patients who receive Iomab-B and a BMT to those patients receiving physician’s choice of salvage chemotherapy, defined as conventional care, as no standard of care exists for this patient population. AML patients with active, relapsed or refractory AML have dismal prognoses and are typically not offered curative transplant as an option. This is largely because salvage treatments have a limited ability to produce a complete remission, which is necessary prior to BMT if conventional BMT is to be successful. However, with Iomab-B targeted conditioning, a complete remission prior to starting the Iomab-B conditioning is not necessary for a successful transplant.

Dr. Mark Berger, Actinium’s Chief Medical Officer said, "We believe that Iomab-B represents a potentially disruptive modality for targeted conditioning. The preliminary data from the SIERRA trial presented at ASH (Free ASH Whitepaper) exceeded our expectations regarding feasibility and safety, which adds to the already extensive body of research and data demonstrating the utility of Iomab-B for targeted conditioning in multiple hematologic indications. With this data in hand we are highly motivated to complete the SIERRA trial, which will serve as the beachhead for our multi-target, multi-disease pipeline for targeted conditioning, where we are committed to expanding our leadership position."