Actinium Reports Superior Efficacy of ATNM-400 Over Pluvicto, Including in Pluvicto-Resistant Prostate Cancer Models at AACR Ann

Actinium Pharmaceuticals, Inc., a leader in targeted radiotherapy development, announced new preclinical results for ATNM-400 in prostate cancer models at the American Association for Cancer Research (AACR) Annual Meeting. ATNM-400 is a first-in-class, non-PSMA-targeting radiotherapy that uses the Actinium-225 (Ac-225) radioisotope. Actinium is currently evaluating ATNM-400 in prostate cancer models, both before and after treatment with Pluvicto. Pluvicto (Lu-177-PSMA-617) is a PSMA-targeted radiotherapy labeled with the beta-emitting isotope Lutetium-177 (Lu-177), approved for patients with metastatic castration-resistant prostate cancer.

ATNM-400 is a highly innovative, first-in-class prostate cancer therapy that differs from Pluvicto and most other radiotherapies in development, which typically target PSMA and focus on non-differentiated or poorly differentiated cancer cells. Instead, ATNM-400 targets a distinct non-PSMA receptor that remains highly expressed in metastatic castration-resistant prostate cancer (mCRPC), even after treatment with Pluvicto, which does not affect this receptor’s expression.

Key Results Presented:

• Results highlight ATNM-400's potential as a transformative therapeutic option for prostate cancer patients with unmet clinical needs, as expression of the target receptor for ATNM-400 persists following Pluvicto therapy, and ATNM-400 demonstrates sustained tumor control after Pluvicto stops working
• ATNM-400 showed greater tumor growth inhibition compared to Pluvicto in prostate cancer models, with 99.8% tumor growth inhibition achieved with a single 40 µCi/kg dose of ATNM-400, demonstrating the potential to be offered as an alternative option
• ATNM-400 was well tolerated with no apparent toxicities at two different dose levels, with efficient clearance from essential organs

"We are thrilled to unveil these exciting results demonstrating the transformative therapeutic potential of ATNM-400. There is a significant unmet need for a therapy that can address patients who are treated with Pluvicto and progress, which we only expect to increase following the recent approval of Pluvicto in the earlier line, pre-taxane setting. Our enthusiasm for ATNM-400 was validated by the significant interest this data received at AACR, and we look forward to validating the potential of this exciting radiotherapy candidate as we advance its development with additional data expected later this year," stated Sandesh Seth, Actinium's Chairman and CEO.