On April 11, 2022 Actinium Pharmaceuticals, Inc. (NYSE AMERICAN: ATNM) ("Actinium" or the "Company"), a leader in the development of targeted radiotherapies for patients with unmet needs, reported positive results from preclinical studies evaluating an anti-HER3 antibody, conjugated with an Actinium-225 (Ac-225) radioisotope payload, for targeting HER3-positive non-small cell lung cancer (NSCLC) cells (Press release, Actinium Pharmaceuticals, APR 11, 2022, View Source [SID1234611981]). These data were presented at the American Association of Cancer Research (AACR 2022) annual meeting, which is being held April 8th – 13th at the Ernest N. Morial Convention Center in New Orleans, Louisiana.

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AACR Poster Highlights:

Ac-225-HER3 antibody radio conjugate (ARC) eliminated HER3-postive tumors in an in vivo animal model of human non-small cell lung cancer (NSCLC) at multiple dose levels with increased survival
A dose-dependent cytotoxic effect against HER3 expressing cells was observed in vitro with the Ac-225-HER3-ARC
Biodistribution data demonstrates accumulation of the Ac-225-HER3-ARC in HER3 expressing tumors in the in vivo model of NSCLC
Conjugation of Ac-225 to the HER3 antibody did not affect the antibody’s targeting properties as determined by binding to HER3 expressing cells
Dr. Helen Kotanides, Vice President, Translational Research and Preclinical Development, stated, "HER3 is a well-validated target that is overexpressed in a number of cancers and associated with poor survival in breast, ovarian, lung, gastric and prostate cancer. It is also upregulated in response to HER1 and HER2 targeted therapies as part of acquired resistance against these EGFR therapies. These data show that arming a HER3-targeting agent with Actinium-225 results in potent anti-tumor agent, which improved survival in our NSCLC models. These data support our goal of developing a HER3 targeted radiotherapy for use in a patient population in need of new treatments and give us great excitement for our ongoing collaboration with AVEO centered around HER3."

Sandesh Seth, Chairman and CEO of Actinium, stated, "We are excited to continue to demonstrate Actinium’s enhanced R&D capabilities and commitment to developing potent radiotherapies targeting solid tumors. We look forward to sharing these data, which show the efficacy for our novel approach of conjugating Actinium-225 to a HER3 antibody at AACR (Free AACR Whitepaper) 2022. The development of Ac-225-HER3-ARC, a product of our validated Antibody Warhead Enabling (AWE) technology platform, represents a departure from conventional HER3-targeting approaches, such as naked antibodies and antibody drug conjugates, that are currently being explored for this tumor antigen. These exciting data highlight Actinium’s leadership in developing novel targeted radiotherapy approaches for treating cancers having high unmet needs."

The full poster is available as an e-poster on the AACR (Free AACR Whitepaper) 2022 platform and will be presented in-person at the conference with details below:

AACR Poster Details

Title: Targeting HER3 receptor positive cancers with a novel anti-HER3 antibody radioconjugate (ARC)
Session Category: Experimental and Molecular Therapeutics
Session Title: Preclinical Radiotherapeutics
Session Date and Time: Tuesday, April 12, 2022, 1:30 PM – 5:00 PM
Location: New Orleans Convention Center, Exhibit Halls D-H, Poster Section 25
Poster Board Number: 4
Permanent Abstract Number: 3306

The poster will be accessible via Actinium’s website here.