Version 2 2021-06-04, 19:13Version 2 2021-06-04, 19:13
Version 1 2021-05-31, 07:05Version 1 2021-05-31, 07:05
journal contribution
posted on 2021-06-04, 19:13authored byAmaury Guillou, Daniel F. Earley, Simon Klingler, Eda Nisli, Laura J. Nüesch, Rachael Fay, Jason P. Holland
Most
experimental work in the space of bioconjugation chemistry
focuses on using new methods to construct covalent bonds between a
cargo molecule and a protein of interest such as a monoclonal antibody
(mAb). Bond formation is important for generating new diagnostic tools,
yet when these compounds advance to preclinical in vitro and in vivo studies, and later for translation
to the clinic, understanding the fate of potential metabolites that
arise from chemical or enzymatic degradation of the construct is important
to obtain a full picture of the pharmacokinetic performance of a new
compound. In the context of designing new bioconjugate methods for
labeling antibodies with the positron-emitting radionuclide 89Zr, we previously developed a photochemical process for making 89Zr-mAbs. Experimental studies on [89Zr]ZrDFO-PEG3-azepin-mAb constructs revealed that incorporation of the
tris-polyethylene glycol (PEG3) linker improved the aqueous
phase solubility and radiochemical conversion. However, the use of
a PEG3 linker also has an impact on the whole-body residence
time of the construct, leading to a more rapid excretion of the 89Zr activity when compared with radiotracers that lack the
PEG3 chain. In this work, we investigated the metabolic
fate of eight possible metabolites that arise from the logical disconnection
of [89Zr]ZrDFO-PEG3-azepin-mAb at bonds which
are susceptible to chemical or enzymatic cleavage. Synthesis combined
with 89Zr-radiolabeling, small-animal positron emission
tomography imaging at multiple time points from 0 to 20 h, and measurements
of the effective half-life for whole-body excretion are reported.
The conclusions are that the use of a PEG3 linker is non-innocent
in terms of its impact on enhancing the metabolism of [89Zr]ZrDFO-PEG3-azepin-mAbs. In most cases, degradation
can produce metabolites that are rapidly eliminated from the body,
thereby enhancing image contrast by reducing nonspecific accumulation
and retention of 89Zr in background organs such as the
liver, spleen, kidney, and bone.