Actinium announces data from research on Actimab-A

Actinium Pharmaceuticals announced the first ever data demonstrating the utility of Actimab-A to depleted myeloid derived suppressor cells, or MDSCs, which are ubiquitously present within the solid tumor microenvironment as well as blood cancers. The new data were showcased in a poster presentation at the American Association for Cancer Research, or AACR, 2023 Annual Meeting, which is being held April 14 – 19 in Orlando, Florida. Highlights from the AACR poster titled, "Targeting myeloid-derived suppressor cells with actinium-225 lintuzumab, a CD33 antibody radioconjugate to enhance antitumor immunity", include: Actimab-A demonstrated efficient depletion of ex vivo human MDSCs derived from colorectal and lung cancer patient samples in vitro in addition to an in vivo humanized mouse model of Non-Small Cell Lung Cancer; Colorectal cancer blood MDSCs treated with Actimab-A were more effectively cleared compared to depletion by Mylotarg, a CD33-targeted antibody-drug conjugate, highlighting the powerful cytotoxicity and potential therapeutic benefit of radiotherapy compared to naked antibodies or ADCs; Flow cytometry data confirmed an upregulation of CD33+ MDSCs in both lung and colorectal cancer patient samples compared to healthy donor controls. Following Actimab-A treatment in mice, a specific and robust depletion of ex vivo CD33+ MDSCs was observed. These results suggest that targeted blockade of MDSC activity via treatment with Actimab-A can alleviate their pro-tumorigenic and immunosuppressive activities to bolster the efficacy of immunotherapy such as checkpoint inhibitors.