Exploring the next Generation of Radiotheragnostics for metastatic Prostate Cancer
The talk will be held jointly with Prof. Dr. Dr. Damian Wild
Radioligand therapy (RLT) has emerged as an effective treatment for patients with progressive, prostate-specific membrane antigen (PSMA)-positive metastatic castration-resistant prostate cancer (mCRPC). Despite the success of RLT, approximately one-third of patients do not respond or experience early relapse. We hypothesize that suboptimal dose delivery to microscopic disease, including single and clustered circulating tumor cells (CTCs), may contribute to treatment resistance.
Our PROGNOSTICS Phase I study (NCT06343038) investigates the efficacy, safety, and dosimetry of [¹⁶¹Tb]Tb-SibuDAB—a novel PSMA-targeting radioligand developed at the Paul Scherrer Institute—in comparison with the current standard RLT. Designed to overcome the limitations of existing PSMA-targeted therapies, [¹⁶¹Tb]Tb-SibuDAB has a long blood-circulation and consequently a higher tumor uptake and delivers not only β¯-particles but also a high dose to microscopic disease through the co-emission of conversion and Auger electrons. In this ongoing Phase Ia/b trial, mCRPC patients receive test injections with [¹⁶¹Tb]Tb-SibuDAB and the current standard compound [¹⁷⁷Lu]Lu-PSMA-I&T in a randomized cross-over design to compare tumor and organ dosimetry. The results are supported by quantitative SPECT/CT imaging, liquid biopsy analyses of CTCs, and molecular marker profiling. Preliminary results from the Phase Ia study show that [¹⁶¹Tb]Tb-SibuDAB delivers more than twice the dose to tumors and exhibits a longer tumor half-life compared to [¹⁷⁷Lu]Lu-PSMA-I&T, with favorable tumor-to-organ dose ratios and no relevant adverse effects. Early Phase Ib findings from the first three-patient cohort receiving therapeutic doses (3 GBq × 4 cycles) indicate a good safety profile. The study continues to evaluate optimal dosing, efficacy markers, and personalized predictors of response, aiming to establish [¹⁶¹Tb]Tb-SibuDAB as a next-generation radioligand therapy for mCRPC. This project exemplifies how the combined expertise within the ETH Domain and its clinical partners can deepen our molecular understanding of disease and contribute to improved treatment outcomes for cancer patients in the future.
A. Chirindel1, G.P. Nicolas1, F. Westerbergh1, D. Schmid2, N. Ahmadsei1, L. McDougall1, A. Bauman8, S. Geistlich2, A. Fokkema3, M. Saini3, N.P. van der Meulen2,5, C. Müller2,7, P. Bernhardt2,6, N. Aceto3, D. Wild1, R. Schibli2,7
1 Division of Nuclear Medicine, University Hospital Basel, Switzerland
2 Center for Radiopharmaceutical Sciences, Paul Scherrer Institute (PSI), Villigen-PSI, Switzerland
3 Department of Biology, Institute of Molecular Health Sciences, ETH Zurich, Zurich, Switzerland
4 Department of Medical Radiation Sciences, Institute of Clinical Sciences, Sahlgrenska Academy at University of Gothenburg, Gothenburg, Sweden
5 Laboratory of Radiochemistry, Paul Scherrer Institute (PSI), Villigen-PSI, Switzerland
6 Department of Medical Physics and Biomedical Engineering, Sahlgrenska University Hospital, Gothenburg, Sweden
7 Department of Chemistry and Applied Biosciences, ETH Zurich, Zurich, Switzerland
8 Division of Radiopharmaceutical Chemistry, University Hospital Basel, Basel, Switzerland