First‑in‑human study of 99mTc‑labeled fucoidan, a SPECT tracer targeting P‑selectin
Reindert F. Oostveen, Kang H. Zheng, Yannick Kaiser, Nick S. Nurmohamed, Jeffrey Kroon, Tim C. de Wit, Edwin Poel, Joel Aerts, Francois Rouzet, Erik S. G. Stroes, Didier Letourneur, Hein J. Verberne, Cédric Chauvierre and Mia R. Ståhle
Background
Activation of endothelial cells and platelets in atherothrombosis is characterized by upregulation of P-selectin. As a consequence, P-selectin represents a potential target for molecular imaging to identify thrombosis at an early stage. Fucoidan is a polysaccharide ligand extracted from brown algae with nanomolar affinity for P-selectin. This first-in-human study evaluated in healthy volunteers the safety, whole-body biodistribution, and dosimetry of 99mTc-fucoidan (Good Manufacturing Practices grade). We also investigated whether we could observe binding of 99mTc-fucoidan to human thrombi ex vivo and in vivo. In ten healthy volunteers, conjugate whole-body scans were performed up to 24 h following intravenous injection of 99mTc-fucoidan (370 MBq). Moreover, 99mTc-fucoidan uptake in ex vivo human thrombi (n = 11) was measured by gamma counting. Additionally, three patients with a newly diagnosed deep vein thrombosis (DVT) were subjected to 99mTc-fucoidan SPECT/CT imaging.
Results
99mTc-fucoidan was well tolerated in all participants without any drug-related adverse events. The totalbody absorbed dose in males was comparable to females (0.012 ± 0.004 vs. 0.011 ± 0.005 mSv/MBq; p = 0.97). Gamma counting experiments demonstrated binding of tracer to ex vivo human thrombi that was 16% lower after blocking with a natural P-selectin ligand, Sialyl Lewis X. 99mTc-fucoidan demonstrated specific uptake at the thrombus site
in one out of three scanned patients with DVT.
Conclusions
99mTc-Fucoidan has a favorable biodistribution and safety profile. 99mTc-fucoidan exhibited specific binding to human thrombi in both in vivo and ex vivo settings. Nonetheless, the in vivo results do not support further clinical investigation of 99mTc-fucoidan as an imaging modality for DVT. Other clinical implementations of a technetium− 99m-labeled P-selectin tracer should be considered.