Novartis reports early anti-tumor signal for actinium prostate cancer drug

Novartis said an experimental actinium-based prostate cancer drug showed an early anti-tumor signal in a 101-patient study, including among men who had already been treated with Pluvicto. In that group, 52.5% saw prostate-specific antigen levels fall by at least half, a result that matters because PSA is one of the main ways doctors track whether prostate cancer is active and responding to treatment.

The finding is encouraging, but it is not proof that the drug will extend survival or earn approval. PSA responses can suggest a treatment is hitting its target, yet larger studies must still show that the benefit lasts, that tumors stop growing on scans, and that the therapy can improve outcomes without unacceptable toxicity. That is the line Novartis now has to cross with its next-generation radiopharmaceutical program.

The company’s pipeline lists AAA817, also called 225Ac-PSMA-617, as a phase 3 program in metastatic castration-resistant prostate cancer, with a lead indication in the post-lutetium setting. Novartis says the study is designed to test whether 225Ac-PSMA-617, combined with an androgen receptor pathway inhibitor, can improve radiographic progression-free survival against standard-of-care options that include changing the ARPI, chemotherapy, or continuing with [177Lu]Lu-PSMA-617. The distinction is important: actinium-based radiopharma uses a different radioactive payload aimed at the same PSMA target, which could matter for patients whose disease has already moved past Pluvicto.

The timing also fits Novartis’ broader commercial strategy. In its 2025 annual report, the company said it was scaling its radioligand therapy platform and expanding its delivery network for Pluvicto, its established prostate cancer radiopharmaceutical. The Food and Drug Administration widened Pluvicto’s U.S. indication on March 28, 2025, to include PSMA-positive metastatic castration-resistant prostate cancer patients previously treated with an androgen receptor pathway inhibitor and considered appropriate to delay chemotherapy, enlarging the market Novartis already leads. Novartis also signed a long-term actinium supply agreement with Niowave in February 2026, signaling that it is preparing the manufacturing base it would need if AAA817 advances.

For patients with hard-to-treat disease, the promise is obvious: another targeted option after the current radiopharmaceutical begins to fail. For Novartis, the question is whether early PSA declines can translate into durable clinical benefit in a field where the bar for proof remains high.