New preclinical data on ATNM-400, a non-PSMA-targeting antibody radioconjugate delivering Actinium-225 (Ac-225) for prostate cancer, was presented at the 4th Annual Targeted Radiopharmaceuticals Summit in San Diego.

ATNM-400 targets a protein linked to tumor progression, survival signaling, and resistance to androgen receptor pathway inhibitors (ARPI).

The data builds on earlier findings from April 2025, showing improved efficacy compared to 177Lu-PSMA-617 (Pluvicto) and 225Ac-PSMA-617 in treatment-resistant models.

When combined with enzalutamide (Xtandi), ATNM-400 achieved 40% complete cures in tumor-bearing animals. PET imaging confirmed tumor uptake up to 216 hours with rapid clearance from normal tissues, suggesting reduced off-target effects. The therapy showed efficacy in models resistant to both Pluvicto and enzalutamide, addressing unmet needs in advanced prostate cancer. Additional data is expected in the second half of 2025. While promising, these preclinical results await clinical validation to confirm safety and efficacy in humans.

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