Actinium Showcases Targeted Conditioning Program with 2 Oral Presentations Highlighting Iomab-B and Pivotal Phase 3 SIERRA Trial at 2021…

February 11th, 2021 8:49 am

NEW YORK, Feb. 11, 2021 /PRNewswire/ --Actinium Pharmaceuticals, Inc. (NYSE AMERICAN: ATNM) ("Actinium" or the "Company") today highlighted its presence at the 2021 Transplantation & Cellular Therapy (TCT) Annual Meeting, which is being held virtually from February 8th 12th. The TCT meeting organizes thousands of transplant professionals from over five hundred transplant centers worldwide and is a seminal event for Actinium given its focus on targeted conditioning for bone marrow transplant (BMT), CAR-T and other adoptive cell therapies and gene therapy. At TCT, Actinium's pivotal Phase 3 trial SIERRA trial for Iomab-B was featured in 2 oral presentations, as well as CME event focused on AML and BMT and in investigator interactions led by Actinium's clinical development and medical affairs teams.

Dr. Mark Berger, Actinium's Chief Medical Officer, said, "TCT is the ideal venue to showcase Actinium's Iomab-B and Iomab-ACT targeted conditioning programs given the concentrated audience of thought leaders in these fields that TCT brings together. The timing of TCT is also ideal as it follows shortly after ASH resulting in a data rich period for Actinium that drives investigator interest. This is particularly the case this year as we have built strong momentum in SIERRA following positive data from 75% enrollment featured in 2 oral presentations at ASH and now in 2 oral presentations at this year's TCT, which has driven high levels of investigator and referring physician interactions. We have coupled this with bolstered outreach efforts, which will continue beyond TCT, that have resulted in new site activation despite the advanced stage of SIERRA and robust enrollment rates that give us great confidence in completing SIERRA enrollment rapidly."

Summary data presented in TCT oral presentations include:

-100% BMT and engraftment rate for patients receiving a therapeutic dose of Iomab-B compared to 18% of patients receiving physician's choice of salvage therapy on the control arm- 79% of all patients enrolled on SIERRA were able to proceed to BMT despite being a patient population not considered eligible for BMT with standard approaches-Iomab-B delivers high amounts of targeted radiation to the bone marrow with minimal impact on other organs resulting in lower rates and severity of adverse events

TCT Oral Presentation: Targeted Radioimmunotherapy with Anti-CD45 Iodine (131I) Apamistamab [Iomab-B] in Older Patients with Active, Relapsed or Refractory (R/R) Acute Myeloid Leukemia Results in Successful and Timely Engraftment Not Related to the Radiation Dose Delivered

Phase 3 SIERRA 75% Enrollment Results

Baseline Characteristics

Iomab-B Arm(N=56)

Conventional Care (CC) Arm(N=57)

Age (yrs, median, range)

63 (55-77)

65 (55-77)

Cytogenetic and Molecular Risk1, 2

Favorable: 4%Intermediate: 35%

Adverse: 61%

Favorable: 5%

Intermediate: 32%

Adverse: 63%

% TransplantedIntent-to-Treat Group

88% (49/56)

18% (10/57)

64% (30/47)


Underwent Iomab-B based Conditioning and HCT (N=49)3

Achieved CR and received standard of care HCT (N=10)

Randomized to Conventional Care and Crossed Over to Iomab-B with HCT (N=30)4

Cross-over Rate



Received Therapeutic Dose of Iomab-B (N=30)

Transplanted (N=30)

64% (30/47)

% Transplanted

100% (49/49)

18% (10/57)

100% (30/30)

% Marrow Blast @ randomization (median, range)

29% (4-95)5

20% (5-97)

28% (6-87)

Days to ANC Engraftment

14 (9-22)6

17 (13-83)7

14 (10-37)8

Days to Platelet Engraftment

18 (4-39)6

22 (8-35)7

19 (1-38)8

Days to HCT (Post Randomization)

30 (23-60)

67 (52-104)

62 (36-100)9

Myeloablative Dose Delivered to Bone Marrow

14.7 (4.6-32) Gv


15.5 (6.3-42) Gv

592 (313-1013) mCi

646 (354-1027) mCi

100-day non-Relapse Transplant-Related Mortality


(2/45 Evaluable)


(2/10 Evaluable)


(3/28 Evaluable)

1) Iomab-B arm: data unavailable (4) and patient was excluded (1)

2) Per NCCN guidelines version 3. 2020

3) No therapy dose (7) due to: declining KPS (4), Infusion reaction (1), unfavorable biodistribution (1), post- randomization eligibility (1). Two (2) did not receive DI and five (5) received DI without proceeding to TI.

4) Thirteen (13) patients ineligible for crossover due to: hospice care/progression (4), declined/ineligible for HCT (5), died pre-crossover (4). Additionally, four (4) patients were eligible for crossover and did not receive Iomab-B due to declining KPS.

5) One (1) patient with 4% blasts in the marrow had circulating AML blasts

6) ANC engraftment data not available (4), platelet engraftment data not available (7)

7) ANC and platelet engraftment data not available (1)

8) ANC engraftment data not available (1), platelet engraftment data not available (2)

9) One (1) patient at 161 days had delayed transplant due to infection & respiratory failure, received Iomab & transplant when stable, not included in range

TCT Oral Presentation: Myeloablative Targeted Conditioning with Anti-CD45 Iodine (131I) Apamistamab [Iomab-B] Spares the GI Tract and Has Low Incidence of Severe Mucositis, Febrile Neutropenia and Sepsis in the Prospective, Randomized Phase 3 Sierra Trial for Patients with Relapsed or Refractory Acute Myeloid Leukemia (AML)

Adverse Event

Iomab-B Arm (N=56)

Conventional Care Arm (N=57)

Received Iomab-B/HCT


Achieved CR and received Std HCT (N=10)

No CR Crossed over to Iomab-B/HCT (N=30)


% (N)

4.2 (2)*

30.0 (3)

23.3 (7)

Febrile Neutropenia Gr 3-4

% (N)

41.7 (20)

50.0 (5)

40.0 (12)

Mucositis Gr 3-4

% (N)

10.4 (5)

30.0 (3)

16.7 (5)

Day +100 Non-Relapse Mortality3


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Actinium Showcases Targeted Conditioning Program with 2 Oral Presentations Highlighting Iomab-B and Pivotal Phase 3 SIERRA Trial at 2021...

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