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 that preclinical data highlighting the efficacy of the combination of an anti-HER3 antibody radiation conjugate (ARC) and a CD47 blocking antibody immunotherapy was presented at the American Association for Cancer Research (AACR) (Free AACR Whitepaper) (AACR 2022) annual meeting, which is being held April 8th – 13th at the Ernest N. Morial Convention Center in New Orleans, Louisiana (Press release, Actinium Pharmaceuticals, APR 11, 2022, View Source [SID1234611980]). Actinium assessed an Actinium-225 (Ac-225)-conjugated anti-HER3 antibody with magrolimab, an anti-CD47 antibody being developed by Gilead Sciences, in HER3-positive preclinical models.
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AACR Poster Highlights:
Dramatic improvement in tumor growth inhibition is observed in vivo with the Ac-225-HER3-ARC and magrolimab combination therapy compared to magrolimab alone
The combination of Ac-225-HER3-ARC and magrolimab significantly enhanced phagocytosis in HER3-positive cells compared to either single agent in vitro
Upregulation of cell surface calreticulin is observed following treatment with 225Ac-HER3-ARC in HER3-positive cell lines
Dr. Helen Kotanides, Vice President, Translational Research and Preclinical Development, said, "We hypothesize that the upregulation of the ‘eat me’ signal, calreticulin, induced by targeted radiotherapy could enhance the immunomodulatory effects of an anti-CD47 antibody, resulting in increased anti-tumor efficacy. These data presented at AACR (Free AACR Whitepaper) corroborate our previous work presented at SITC (Free SITC Whitepaper) and support our rationale in targeting both blood cancer and solid tumors with a CD47 targeted radiotherapy combination. We are highly encouraged by the remarkable improvement in anti-tumor efficacy observed with the combination of an Ac-225-HER3-ARC with magrolimab. Collectively, the in vitro and in vivo data support further investigation of this novel combination and we look forward to continuing to advance the first ever targeted radiotherapy CD47 combinations."
Sandesh Seth, Chairman and CEO of Actinium, said, "We continue to demonstrate the potential of combining targeted radiotherapy with a CD47 blocking antibody immunotherapy such as magrolimab. These results support our vision to develop more effective treatments for cancer patients through the expansion of our pipeline into solid tumors and to develop innovative targeted radiotherapy combinations with immunotherapy leveraging our strong technology platform, IP and clinical experience. We are excited to highlight these results showing the potential for adding Ac-225-HER3 ARC to CD47 antibodies to enhance the latter’s immunotherapeutic efficacy at AACR (Free AACR Whitepaper). These data along with our recent collaborations with EpicentRx and AVEO Oncology give us strong momentum towards the clinic with highly novel CD47-SIRPα combinations and HER3 targeted radiotherapies."
The full poster is available as an e-poster on the AACR (Free AACR Whitepaper) 2022 platform with details below:
AACR Poster Details
Title: Anti-HER3 radioimmunotherapy enhances the anti-tumor effects of CD47 blockade in solid tumors
Session Category: Immunology
Session Title: Immune Checkpoints
Session Date and Time: Sunday, April 10, 2022, 1:30 PM – 5:00 PM
Location: New Orleans Convention Center, Exhibit Halls D-H, Poster Section 38
Poster Board Number: 19
Permanent Abstract Number: 609
The poster will be accessible via Actinium’s website here.