Bayer reports encouraging results for investigational targeted radionuclide therapy 225Ac-PSMA-Trillium in advanced metastatic prostate cancer
For UK Healthcare, Medical and Trade Media
225Ac-PSMA-Trillium (BAY 3563254) is an investigational targeted alpha therapy being developed for patients with advanced metastatic castration-resistant prostate cancer (mCRPC)
Promising data from PAnTHa, the global Phase I first-in-human, dose-escalation study were presented during the 2026 American Society of Clinical Oncology Genitourinary Cancers Symposium in San Francisco, CA, USA
Data support advancing 225Ac-PSMA-Trillium to the next phase of development
Prostate cancer is the second most common diagnosed cancer in men globally1, with median survival of less than three years among metastatic patients who have developed castration-resistance2
Bayer today announced encouraging results from the ongoing global Phase I first-in-human, dose-escalation PAnTHa study (NCT06217822) evaluating the safety, tolerability and preliminary efficacy of 225Ac-PSMA-Trillium (BAY 3563254), a targeted alpha therapy in patients with advanced metastatic mCRPC. The dose for expansion was successfully identified, with ≥80% of patients achieving a PSA50 response at the expansion dose. The new data were presented during the 2026 American Society of Clinical Oncology Genitourinary Cancers Symposium, taking place in San Francisco, CA, United States, from February 26-28, 2026. These clinical data represent the first disclosure for 225Ac-PSMA-Trillium and were selected as part of the rapid oral session focused on advanced prostate cancer research. They support advancing 225Ac-PSMA-Trillium to the next phase of clinical development.
“We are excited to see the encouraging results from the Phase I PAnTHa study demonstrating the potential of our targeted alpha therapy to advance outcomes for patients with advanced metastatic castration-resistant prostate cancer, a type of cancer with limited treatment options and poor prognosis,” said Dominik Ruettinger, M.D., Ph.D., Head of Research and Early Development for Oncology at Bayer’s Pharmaceuticals Division. “The development of 225Ac-PSMA-Trillium confirms our ongoing focus on prostate cancer treatment and our continued drive to develop precise and personalised healthcare solutions, holding the promise to shift the treatment paradigm for patients.”
“Despite progress, patients with metastatic castration-resistant prostate cancer continue to face high mortality, highlighting the urgent need for new precision therapies,” said Fred Saad, MD, FRCS, Professor and Chairman of Surgery at the University of Montreal and Director of Genitourinary Oncology at the University of Montreal Hospital Center (CHUM), Canada. “225Ac-PSMA-Trillium is a novel approach that could help address this need. The promising data support the further investigation of this molecule to provide a potentially meaningful clinical benefit for patients with mCRPC.”
225Ac-PSMA-Trillium (BAY 3563254) is an investigational TAT labeled with actinium-225 and comprising a novel PSMA (prostate-specific membrane antigen)-targeting small molecule with a customised albumin-binding moiety. The compound is designed specifically to increase uptake within the tumour, with the goal to provide a differentiated safety and efficacy profile.
Prostate cancer is the second most commonly diagnosed cancer in men globally, with median survival of less than three years among metastatic patients who have developed castration-resistance. There is an increasing unmet need to improve the outcomes of men with mCRPC.
ENDS
Note To Editors
About the PAnTHa study (NCT06217822)
PSMA-targeted Actinium-225-Trillium FiH study in Advanced mCRPC (PAnTHa), is a Phase I, open-label, first-in-human, multicentre study to evaluate safety, tolerability, pharmacokinetics, and antitumour activity of 225Ac-PSMA-Trillium (BAY 3563254) in participants with advanced mCRPC that have at least 1 PSMA-positive lesion on PSMA-PET. In the trial, patients received 225Ac-PSMA-Trillium intravenously every 6 weeks for up to 4 doses. At data cut-off, 50 patients were enrolled across four dose levels in the escalation cohort and 80% completed all four cycles of 225Ac-PSMA-Trillium (range: 75 to 150 kBq/kg; 12-13 patients/cohort).
Detailed Results from PAnTHa
No dose-limiting toxicities (DLTs) or treatment-related deaths have been observed to date. Of those patients eligible, 80% completed all four cycles of 225Ac-PSMA-Trillium. Most common treatment-emergent adverse events (TEAEs) were dry mouth, fatigue and nausea. Overall, 38% of patients had Gr ≥3 TEAEs, most commonly lymphopenia, 16% of patients had serious TEAEs and 4% of patients discontinued treatment due to TEAEs. The overall response rate per PCWG3 criteria across all doses in patients with measurable disease at baseline (n=24) was 46%, with disease control rate of 83%. Respective PSA50 and PSA90 response rates were 58% and 36% overall, and 83% and 58% at the Recommended Dose for Expansion (RDE). This was further supported by the robust decline in circulating tumour DNA (ctDNA) fraction at the RDE. Further, PSA50 responses were observed across all baseline mean Standardized Uptake Value (SUVmean) groups.
About 225Ac-PSMA-Trillium (BAY 3563254)
225Ac-PSMA-Trillium (BAY 3563254) is a trifunctional PSMA-targeting radiopharmaceutical that comprises a highly specific PSMA-targeting motif, an albumin-binding domain to optimise tumour uptake and retention, and a Macropa™ chelator complexed with the alpha-emitter actinium-225. Both in vitro and in vivo characterisation of 225Ac-PSMA-Trillium demonstrates high tumour uptake and retention. Potent antitumour efficacy has been observed in several preclinical models of prostate cancer.
PSMA-Trillium resulted from Bayer’s acquisition of PSMA Therapeutics and Noria Therapeutics in 2021 and is now under clinical investigation.
About Targeted Alpha Therapy
Targeted alpha therapy (TAT) is an emerging class of radionuclide therapy that can be used against a variety of tumours. It delivers alpha particle radiation directly to the tumour inside the body, either via its bone-seeking property or by combining alpha radionuclides, such as actinium-225, with specific targeting moieties.
Actinium-225 is an alpha particle–emitting radionuclide with a 9.9-day half-life. Alpha particles deposit highly ionising radiation over a short range. This localised delivery of the radioactive payload induces irreparable DNA double-strand breaks, often resulting in cell death. At the same time, because the energy travels a short range, damage to nearby normal tissues is much reduced.3-5
About prostate cancer
Prostate cancer is the second most commonly diagnosed cancer in men globally. Despite significant advances in the last decade, the prognosis for men with mCRPC remains poor with a median survival of about 31 months.2 Advances in imaging technologies (i.e. PSMA-PET) and their utilisation across all stages of prostate cancer will likely result in an increased number of patients diagnosed with metastatic disease earlier. Consequently, more men will be diagnosed with de novo PSMA-positive metastatic disease.
About Bayer
Bayer is a global enterprise with core competencies in the life science fields of health care and nutrition. In line with its mission, “Health for all, Hunger for none,” the company’s products and services are designed to help people and the planet thrive by supporting efforts to master the major challenges presented by a growing and aging global population. Bayer is committed to driving sustainable development and generating a positive impact with its businesses. At the same time, the Group aims to increase its earning power and create value through innovation and growth. The Bayer brand stands for trust, reliability and quality throughout the world. In fiscal 2024, the Group employed around 93,000 people and had sales of 46.6 billion euros. R&D expenses amounted to 6.2 billion euros. For more information, go to www.bayer.co.uk.
PP-3563254-GB-0002 / February 2026