Actinium Pharmaceuticals Inc. (NYSE American: ATNM) presented preclinical data on ATNM-400 for non-small cell lung cancer at the Society of Nuclear Medicine and Molecular Imaging 2026 Annual Meeting on June 2.

The data showed ATNM-400 demonstrated activity in both KRAS and EGFR mutant lung cancer models. In KRAS-mutant studies, ATNM-400 outperformed standard treatments sotorasib and adagrasib when used alone. The standard treatments increased expression of ATNM-400's target by more than 3.5-fold and enhanced effectiveness when combined with ATNM-400.

In EGFR-mutant models, ATNM-400 combined with osimertinib resulted in complete tumor regression in treated animals. ATNM-400 achieved 75% tumor growth inhibition as a single treatment compared to 40% for osimertinib alone, while the combination reached 107% inhibition.

ATNM-400 is a radioconjugate that combines an antibody with Actinium-225, which causes cell death through DNA breaks independent of cellular mechanisms. According to the company, the target is expressed in over 90% of non-small cell lung cancer tumors.

EGFR and KRAS mutations account for approximately 40-50% of all non-small cell lung cancer cases. The company states this represents a potential mutation-agnostic approach rather than targeting specific mutations.

"The consistency of activity we have now demonstrated across both EGFR- and KRAS-driven NSCLC supports our vision for ATNM-400 as a potential mutation-agnostic backbone therapy," said Sandesh Seth, Actinium's Chairman and CEO.

The studies were conducted in cell lines and animal models. The company has not announced plans for human clinical trials based on this data.