On November 4, 2020 Actinium Pharmaceuticals, Inc. (NYSE AMERICAN: ATNM) ("Actinium") reported that data from the Phase 1 portion of the Actimab-A venetoclax Phase 1/2 combination trial, has been accepted for poster presentation at the 2020 American Society of Hematology (ASH) (Free ASH Whitepaper) annual meeting that is being held virtually December 5-8, 2020 (Press release, Actinium Pharmaceuticals, NOV 4, 2020, View Source [SID1234569870]).

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Poster Details & Highlights

Poster Title:

Lintuzumab-225Ac in Combination with Venetoclax in Relapsed/Refractory AML: Early Results of a Phase I/II Study

Publication Number:

2875

Session Name:

616. Acute Myeloid Leukemia: Novel Therapy, excluding Transplantation: Poster II

Session Date:

Monday, December 7, 2020

Presentation Time:

7:00 AM – 3:30 PM PT / 10:00 AM – 6:30 PM ET

Combining Actimab-A (225Ac lintuzumab) with venetoclax in patients with R/R AML has an acceptable initial clinical safety profile at the initial subtherapeutic dose level of 0.5 μCi/kg of Actimab-A.
A partial response was observed after a single cycle of Actimab-A and venetoclax.
Three R/R AML patients with a median age of 54 years (range 49-75) have been enrolled to date. The enrolled patients had a median of 2 therapies (2-3) and a median bone marrow blast percentage of 30% (range 20 – >60). All 3 patients had poor risk with adverse cytogenetics, and each patient has an additional high-risk marker (FLT3-ITD+, antecedent JAK2+ myelofibrosis, or TP53 mutation).
There have been no Actimab-A related dose limiting toxicities (DLT) or nonhematologic Grade 3 or greater related AEs.
Results in the first Actimab-A dose cohort are encouraging, and the trial will continue to enroll to evaluate the hypothesis that there will be clinical synergy consistent with pre-clinical results.
Dr. Mark Berger, Actinium’s Chief Medical Officer, said, "We have great excitement for this Actimab-A venetoclax combination trial and its potential for both fit and unfit patients with R/R AML. This preliminary first-in-human data is encouraging, particularly the reported patient response after a single cycle of venetoclax with a subtherapeutic dose level of Actimab-A. These initial results support the potential mechanistic synergy of Actimab-A with venetoclax and we are pleased by the progression in the clinic to the next dose level as there were no dose limiting toxicities with this combination."

Dr. Dale Ludwig, Actinium’s Chief Scientific and Technology Officer, stated, "We believe that the combination of low doses of Actimab-A with selected therapeutic modalities that together have potential mechanistic or complementary synergies is an approach that has great therapeutic potential. Therefore, it is exciting to see the hypothesized mechanistic synergy between Actimab-A and venetoclax, which we demonstrated in preclinical studies, now advancing in the clinic. Venetoclax as a single agent has produced low response rates in patients with R/R AML so we find it highly encouraging to see an initial response with a dose of Actimab-A that has shown to be subtherapeutic as a single agent. I am eager to see additional results from the first dose cohort as well as the second dose cohort to further support the therapeutic potential of Actimab-A in combination with venetoclax."

The complete abstracts are available on the ASH (Free ASH Whitepaper) website (click here).

About Actinium’s CD33 Program

Actinium’s CD33 program is evaluating the clinical utility of Actimab-A, an 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 approximately one third of patients with multiple myeloma. The CD33 development program is driven by data obtained from well over one hundred treated patients, including results from a Phase 1/2 trial that was conducted in 58 patients with newly diagnosed AML, which was completed in 2018. This clinical data, as well as the Company’s experience with Iomab-B, is shaping a two-pronged approach for the CD33 program, where at high doses the Company is exploring its use for targeted conditioning and at low doses the Company is exploring its use for therapeutic purposes as a single agent, or in combination with other modalities. There are currently multiple clinical trials ongoing studying Actimab-A including a Phase 1 combination trial with the salvage chemotherapy regimen CLAG-M, a Phase 1/2 trial in combination with venetoclax and its Actimab-MDS planned pivotal program for targeted conditioning with standard chemotherapy. In addition, Actinium is exploring additional combinations with Actimab-A and other potentially synergistic therapeutic modalities such as chemotherapy, targeted agents or immunotherapy.