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Multifunctional Desferrichrome Analogues as Versatile 89Zr(IV) Chelators for ImmunoPET Probe Development
journal contribution
posted on 2017-06-30, 00:00 authored by Casey
J. Adams, Justin J. Wilson, Eszter BorosNew bifunctional hexa- and octadentate
analogues of the hydroxamate-containing
siderophore desferrichrome (DFC) have been synthesized and evaluated
as 89Zr-chelating agents for immunoPET applications. The
in vitro and in vivo inertness of these new ligands, Orn3-hx (hexadentate)
and Orn-4hx derivatives (octadentate), was compared to the gold standard
hexadentate, hydroxamate-containing chelator for 89Zr desferrioxamine
(DFO). Density functional theory was employed to model the geometries
of the resulting Zr(IV) complexes and to predict their relative stabilities
as follows: Zr(Orn4-hx) > Zr(DFC) > Zr(Orn3-hx). Transchelation
challenge
experiments of the corresponding radiochemical complexes with excess
ethylenediaminetetraacetate (EDTA) indicated complex stability in
accordance with DFT calculations. Radiolabeling of these ligands with 89Zr was quantitative (0.25 μmol of ligand, pH 7.4, room
temperature, 20 min). For antibody conjugation, the isothiocyanate
(NCS) functional group was introduced to the N terminus of Orn3-hx
and Orn-4hx. An additional trifunctional derivative that bears a silicon-rhodamine
fluorophore on the C-terminus and NCS on the N terminus was also furnished.
As proof of concept, all NCS derivatives were conjugated to the HER2-targeting
antibody, trastuzumab. Radiolabeling of immunoconjugates with 89Zr was accomplished with radiochemical yields of 16 ±
2% to 95 ± 2%. These constructs were administered to naive mice
(male, C57BL/6J, n = 4) to assess in vivo inertness,
which is inversely correlated with uptake of 89Zr in bone,
after 96 h circulation time. We found bone uptake to range from 7.0
± 2.2 to 10.7 ± 1.3% ID/g, values that compare well to the
corresponding DFO conjugate (7.1 ± 0.8% ID/g). In conclusion,
we have rationally designed linear, bifunctional and trifunctional
desferrichrome analogues suitable for the mild and inert radiolabeling
of antibodies with the radionuclide 89Zr.
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hydroxamate-containing siderophore desferrichrome96 h circulation timetrifunctional desferrichrome analoguesvivo inertnessDFCC 57BL n89 Zr-chelating agentsN terminus89 Zr desferrioxamineOrn -4hx derivativesImmunoPET Probe Development New bifunctional hexaOrn 3-hxHER 2-targeting antibodyMultifunctional Desferrichrome AnaloguesEDTAIDDFTradionuclide 89 ZrNCS89 ZrDFO
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