Synthesis of [Cu]DOTA-ADIBON-Ala-PEG-A20FMDV2 via copper-free click chemistry for PET imaging of integrin αβ.

Catalyst-free click reactions are effective chemical tools for synthesis of radiometal-based radiopharmaceuticals offering advantages towards preparation of non-toxic agents with high specific activity. In the present study the radiotracer [Cu]DOTA-ADIBON-Ala-PEG-A20FMDV2, [Cu] 3, was synthesized for positron emission tomography imaging of integrin αβ expressing tumors via a strain-promoted click reaction using both a 'pre-click' and 'post-click' approaches. The radiotracer, prepared in >99 % radiochemical yield, was evaluated in vitro (64.6 ± 2.8 % binding to αβ-positive cells vs. <5 % to αβ-negative cells) and in vivo (αβ-positive tumor uptake: 1.52 ± 0.16 % ID/g, 24 h p.i.). While the high initial renal uptake (76.2 ± 10.7 % ID/g at 1 h p.i.) was comparable to a previously reported radiotracer, [Cu]DOTA-PEG-A20FMDV2, [Cu] 3 showed notably improved renal clearance (11.3 ± 2.5 % ID/g at 24 h p.i.). Thus, the introduction of a chelator-strained alkyne system resulted in improved pharmacokinetics for the present radiotracer, highlighting the attractive prospects of strain-promoted click-based preparations in the construction of radiometalated bioconjugates for targeted molecular imaging and therapy. [ABSTRACT FROM AUTHOR]