PR Newswire·Jun 3, 2026, 7:25 AM ET

Actinium Pharmaceuticals Oral Presentation at SNMMI 2026 Highlights ATNM-400 Overcoming Resistance to All Three Approved Androgen Receptor Inhibitors and Offers Flexible, Well-Tolerated Dosing in Prostate Cancer Models

ATNM-400 demonstrated potent activity against prostate cancer cells and tumors resistant to all three approved androgen receptor inhibitors: enzalutamide, apalutamide, and darolutamide.
In ARPI-resistant tumor models, ATNM-400 achieved 94% tumor growth inhibition as a monotherapy, significantly outperforming apalutamide (32%) and darolutamide (5%).
Combination therapy with apalutamide or darolutamide resulted in durable complete responses in at least 57% of mice, with 107% tumor growth inhibition.
The drug matched or exceeded the efficacy of PSMA-targeted therapies (177Lu-PSMA-617 and 225Ac-PSMA-617) across high-, low-, and negative-PSMA models while using roughly one-thousandth the radioactivity of 177Lu-PSMA-617.
ATNM-400 targets a non-PSMA antigen, meaning it is not expected to cause xerostomia, a common side effect of PSMA-directed therapies due to salivary gland expression.
Clinical translation is supported by a consistent safety profile, minimal off-target toxicity, and dosing flexibility across single-bolus and repeat-dose regimens.
Actinium Pharmaceuticals estimates an addressable market of over 100,000 patients annually in the mCRPC setting who have exhausted ARPI therapy or are ineligible for PSMA-directed treatment.
The data was presented at the SNMMI 2026 Annual Meeting in Los Angeles on June 2, 2026, by Actinium Pharmaceuticals.