title: A DOTA based bisphosphonate with an albumin binding moiety for delayed body clearance for bone targeting.
abstract: Radiolabeled bisphosphonates are commonly used in the diagnosis and therapy of bone metastases. Blood clearance of bisphosphonates is usually fast and only 30%-50% of the injected activity is retained in the skeleton, while most of the activity is excreted by the urinary tract. A longer blood circulation may enhance accumulation of bisphosphonate compounds in bone metastases. Therefore, a chemically modified macrocyclic bisphosphonate derivative with an additional human albumin binding entity was synthesized and pharmacokinetics of its complex was evaluated. The DOTA-bisphosphonate conjugate BPAMD was compared against the novel DOTAGA-derived albumin-binding bisphosphonate DOTAGA(428-d-Lys)MBP(L1). The ligands were labeled with68Ga(III) and were evaluated in in vitro binding studies to hydroxyapatite (HA) as well as to human serum albumin. The compounds were finally compared in in vivo PET and ex vivo organ distribution studies in small animals over 6h. Binding studies revealed a consistent affinity of both bisphosphonate tracers to HA. Small animal PET and ex vivo organ distribution studies showed longer blood retention of [68Ga]L1. [68Ga]BPAMD is initially more efficiently bound to the bone but skeletal accumulation of the modified compound and [68Ga]BPAMD equalized at 6h p.i. Ratios of femur epiphyseal plate to ordinary bone showed to be more favorable for [68Ga]L1 than for [68Ga]BPAMD due to the longer circulation time of the new tracer. Thus, the chemical modification of BPAMD toward an albumin-binding bisphosphonate, L1, resulted in a novel PET tracer which conserves advantages of both functional groups within one and the same molecule. The properties of this new diagnostic tracer are expected to be preserved in177Lu therapeutic agent with the same ligand (a theranostic pair).
authors: Institute of Nuclear Chemistry, Johannes-Gutenberg-University Mainz, Germany.
authors: Marian
authors: M
authors: Meckel
authors: Department of Inorganic Chemistry, Charles University, Prague, Czech Republic.
authors: Vojtěch
authors: V
authors: Kubíček
authors: Department of Inorganic Chemistry, Charles University, Prague, Czech Republic.
authors: Petr
authors: P
authors: Hermann
authors: Department of Nuclear Medicine, University Hospital, Mainz, Germany.
authors: Matthias
authors: M
authors: Miederer
authors: Institute of Nuclear Chemistry, Johannes-Gutenberg-University Mainz, Germany.
authors: Frank
authors: F
authors: Rösch
mesh_terms: D000327:Adsorption; D000818:Animals; D001842:Bone and Bones / Q000000981:diagnostic imaging / Q000378:metabolism*; D004164:Diphosphonates / Q000737:chemistry* / Q000378:metabolism* / Q000493:pharmacokinetics; D017886:Durapatite / Q000737:chemistry; D005710:Gallium Radioisotopes; D006573:Heterocyclic Compounds, 1-Ring / Q000737:chemistry*; D006801:Humans; D008297:Male; D049268:Positron-Emission Tomography; D051381:Rats; D017208:Rats, Wistar; D012709:Serum Albumin / Q000378:metabolism*; D014018:Tissue Distribution
chemical_list: D004164:Diphosphonates; D005710:Gallium Radioisotopes; D006573:Heterocyclic Compounds, 1-Ring; D012709:Serum Albumin; C071349:1,4,7,10-tetraazacyclododecane- 1,4,7,10-tetraacetic acid; D017886:Durapatite
keywords: (68)Ga; Albumin-binder; Bisphosphonate; Bone metastases; DOTA; PET