ACTINIUM PHARMACEUTICALS: Actinium Highlights Actimab-A and Venetoclax Synergies Observed in New Studies Presented at AACR

Actinium Pharmaceuticals issued the following announcement on April 3.

Actinium Pharmaceuticals, Inc. (NYSE AMERICAN: ATNM) highlighted data from its poster presentation at the AACR or American Association of Cancer Research annual Meeting 2019 demonstrating that the targeted radiation delivered by Actimab-A to CD33 expressing cells can deplete MCL-1 levels in tumor cells, thereby removing a mechanism of resistance and rendering them more susceptible to venetoclax. Further, the induction of direct AML cell death via double-stranded DNA breaks by Actimab-A provides a second mechanism for enhancing synergistic potency with venetoclax. Actimab-A is an ARC or Antibody Radiation Conjugate comprised of the anti-CD33 monoclonal antibody lintuzumab and the potent alpha-particle emitting radioisotope Ac-225 or Actinium-225. Venetoclax is a BCL-2 or B-Cell Lymphoma 2 inhibitor that is jointly developed and marketed by AbbVie and Genentech and is approved for patients with AML or Acute Myeloid Leukemia, Chronic Lymphocytic Leukemia, and Small Lymphocytic Leukemia. The poster can be viewed on Actinium's website here.

Highlight's of Actinium's poster presentation are as follows:

Actimab-A treatment of venetoclax resistant AML cells led to a decrease in MCL-1 levels. MCL-1 is a protein in the BCL-2 family of anti-apoptotic proteins, which is overexpressed in relapsed or refractory AML cells and has been shown to mediate resistance to venetoclax.

The same Actimab-A treatment reduced BCL-XL. BCL-XL is another protein in the BCL-2 family and also been proposed to mediate resistance to venetoclax.

Additional studies demonstrated that Actimab-A produced double-stranded DNA breaks in two cell lines resistance to venetoclax.

At all dose levels and time points, Actimab-A significantly increased double-stranded DNA breaks compared to cells treated with lintuzumab alone.

In a venetoclax resistant AML in vivo tumor model, statistically significant reduction in tumor size was observed in animals receiving the combination of Actimab-A and venetoclax compared to venetoclax alone.

At evaluation on day 38, complete responses were reported in 3 of 5 animals receiving the combination of Actimab-A and venetoclax while no animals receiving venetoclax alone achieved a complete response at any time point.

100% survival at day 40 was observed in cohorts receiving Actimab-A and venetoclax while no animals treated with venetoclax alone survived beyond day 30.

Dr. Dale Ludwig, Actinium's Chief Scientific Officer, said, "The results of these studies further our enthusiasm for the combination of Actimab-A and venetoclax. Expanding on our previous in vitro work, it is validating to observe multiple synergies derived from Actimab-A's unique targeted radiation mechanism of action including MCL-1 reduction. Given the role this protein plays in AML cell resistance to venetoclax, it is exciting to see its depletion with Actimab-A, resulting in increased cell death and tumor control in these studies. We are also excited to demonstrate that Actimab-A causes double-stranded DNA breaks for which there is no known resistance or repair mechanism. It is important to note that these findings were observed in cell lines and xenograft animal models based on venetoclax resistant cell lines. These data further support the advancement of the combination of Actimab-A and Venetoclax into clinical trials as we are doing with two distinct clinical trials."

Actinium has filed a patent on the combination of a targeted alpha-emitting therapeutic such as Actimab-A together with a BCL-2 inhibitor, which includes venetoclax, as a method to treat cancer. Actinium has initiated a Phase 1/2 trial that is studying Actimab-A in combination with venetoclax for patients with relapsed or refractory AML and is planning a Phase 1/2 trial that will study Actimab-A and venetoclax with a hypomethylating agent also for patients with relapsed or refractory AML, which is expected to be initiated in the first half of 2019.

Sandesh Seth, Actinium's Chairman and CEO, said, "As we advance towards the clinic with our second Actimab-A venetoclax combination trial, it is encouraging to see multiple synergies in robust pre-clinical models. With many patients not responding to or having limited duration of their responses with venetoclax treatment, these important findings together with our extensive clinical data with Actimab-A will be beneficial to the advancement of our two combination trials. This work also showcases Actinium's integration of our research and development and clinical development efforts that can result in rapid translation to the clinic. With a robust intellectual property portfolio around our AWE technology platform, we see a multitude of opportunities to leverage targeted radiation via our ARC's in combination with other therapeutic modalities to generate potential therapies for patients with high unmet medical needs that are underserved by current therapeutic approaches."

Original source can be found here.

Source: Actinium Pharmaceuticals

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