Digoxin for reduction of circulating tumor cell cluster size in metastatic breast cancer: a proof-of-concept trial
Christian Kurzeder, Bich Doan Nguyen-Sträuli, Ilona Krol, Alexander Ring, Francesc Castro-Giner, Manuel Nüesch, Simran Asawa, Yu Wei Zhang, Selina Budinjas, Ana Gvozdenovic, Maren Vogel, Angela Köhler, Cvetka Grašič Kuhar, Fabienne D. Schwab, Viola Heinzelmann‐Schwarz, William P. Weber, Christoph Rochlitz, Denise Vorburger, Heike Frauchiger-Heuer, Isabell Witzel, Andreas Wicki, Gabriela M. Kuster, Marcus Vetter, Nicola Aceto
Abstract
Abstract The presence of circulating tumor cell (CTC) clusters is associated with disease progression and reduced survival in a variety of cancer types. In breast cancer, preclinical studies showed that inhibitors of the Na + /K + ATPase suppress CTC clusters and block metastasis. Here we conducted a prospective, open-label, proof-of-concept study in women with metastatic breast cancer, where the primary objective was to determine whether treatment with the Na + /K + ATPase inhibitor digoxin could reduce mean CTC cluster size. An analysis of nine patients treated daily with a maintenance digoxin dose (0.7–1.4 ng ml −1 serum level) revealed a mean cluster size reduction of −2.2 cells per cluster upon treatment ( P = 0.003), meeting the primary endpoint of the study. Mechanistically, transcriptome profiling of CTCs highlighted downregulation of cell–cell adhesion and cell-cycle-related genes upon treatment with digoxin, in line with its cluster-dissolution activity. No treatment-related adverse events occurred. Thus, our data provide a first-in-human proof of principle that digoxin treatment leads to a partial CTC cluster dissolution, encouraging larger follow-up studies with refined Na + /K + ATPase inhibitors and that include clinical outcome endpoints. ClinicalTrials.gov identifier: NCT03928210 .