Actinium Pharmaceuticals Inc (ATNM)

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Actinium Presents Interim Data from Actimab-A CLAG-M Phase 1 Combination Trial at the 62nd American Society of Hematology Annual Meeting

- 100% remission rate in the third dose cohort of 0.75 µCi/kg of Actimab-A (lintuzumab-225Ac) and standard regimen of CLAG-M.

- 70% of patients achieving remission were MRD negative with remissions and MRD negativity reported in all dose cohorts.

https://ir.actiniumpharma.com/press-releases/detail/380

NEW YORK, Dec. 7, 2020 /PRNewswire/ -- Actinium Pharmaceuticals, Inc. (NYSE AMERICAN: ATNM) ("Actinium" or the "Company") today announced that interim data from its ongoing Actimab-A CLAG-M Phase 1 combination trial in relapsed or refractory Acute Myeloid Leukemia (AML) were presented at the 62nd American Society of Hematology (ASH) annual meeting.

ASH Oral Presentation: A Phase I study of Lintuzumab Ac225 in Combination with CLAG-M Chemotherapy in Relapsed/Refractory AML

In the third and planned final dose cohort of Actimab-A CLAG-M, 100% of evaluable patients achieved remission. The trial, which is being conducted at the Medical College of Wisconsin (MCW), is advancing to a fourth dose cohort of 1.0 µCi/kg. Across the first three cohorts, 67% (10/15) patients treated with 0.25, 0.50 and 0.75 µCi/kg of Actimab-A and the standard regimen of CLAG-M achieved a Complete Remission (CR) or Complete Remission with inadequate hematopoietic recovery (CRi). Further, 83% of patients (10/12) who received 3 or fewer prior lines of treatment achieved CR or CRi. Notably, 70% of CR/CRi patients were MRD (Measurable Residual Disease) negative indicating a deep remission with no detectable disease. MRD negativity is defined as ≤0.1% AML cells. These results, which include subtherapeutic doses of Actimab-A in the first two dose cohorts, represent a marked improvement over CLAG-M treatment alone (ORR: 55%, MRD negativity: 39%) implying potential mechanistic synergy. This novel Phase 1 combination trial is for patients with relapsed or refractory acute myeloid leukemia (R/R AML) age 18 and above deemed medically fit for cytotoxic chemotherapy.

Dr. Mark Berger, Actinium's Chief Medical Officer, said, "We look forward to continuing our work with the investigators at MCW in the Actimab-A CLAG-M combination trial. Thus far we remain thrilled with the high rates of remission, MRD negativity and transplant in this trial, which highlights the potential this combination may have for patients with R/R AML. It is exciting to see the profile of this combination emerge not only for therapeutic purposes but also for its potential as a bridge to transplant as noted by the investigators at MCW. Our CD33 program is focused on exploring the synergistic effects of Actimab-A with other therapeutic modalities and evaluating these combinations as potential backbone therapies in R/R AML."

About Actinium's CD33 Program

Actinium's CD33 program is evaluating the clinical utility of Actimab-A, an Antibody Radiation Conjugate (ARC) comprised of the anti-CD33 mAb lintuzumab linked to the potent alpha-emitting radioisotope Actinium-225 or Ac-225. CD33 is expressed in the majority of patients with AML and myelodysplastic syndrome, or MDS, as well as patients with multiple myeloma. The CD33 development program is driven by data from over one hundred treated patients, including a Phase 1/2 trial where Actimab-A produced a remission rate as high as 69% as a single agent. This clinical data is shaping a two-pronged approach for the CD33 program, where at low doses the Company is exploring its use for therapeutic purposes in combination with other modalities and at high doses for use for targeted conditioning prior to bone marrow transplant. Actinium currently has multiple clinical trials ongoing including the Phase 1 Actimab-A CLAG-M and Phase 1/2 Actimab-A venetoclax combination trials and is exploring additional CD33 ARC combinations with other therapeutic modalities such as chemotherapy, targeted agents or immunotherapy.