Automated preparation of 2‐[¹⁸F]fluoropropionate labeled peptides using a flexible, multi‐stage synthesis platform (iPHASE Flexlab)

Abstract

Radiolabelled peptides are vital tools used in positron emission tomography imaging for the diagnosis of disease, drug discovery, and biomedical research. Peptides are typically labeled through conjugation to a radiolabelled prosthetic group, which usually necessitates complex, multi-step procedures, especially for fluorine-18 labeled peptides. Herein, we describe the automated synthesis and formulation of 2-[ F]fluoropropionate labeled RGD-peptides through use of the iPHASE Flexlab as an effective dual-stage radiochemical synthesis module. The fully automated preparation of the monomeric RGD-peptides, [ F]FP-GalactoRGD and [ F]FP-c(RGDy(SO )K), was accomplished in under 90 minutes with n.d.c. radiochemical yields ca. 7% from fluoride. Similarly, the automated preparation of the dimeric RGD-peptides, [ F]F-PRGD and [ F]FP-E(RGDy(SO )K) , was accomplished in under 105 minutes with n.d.c. yields ca. 4% from fluoride.

4-Nitrophenyl activated esters are superior synthons for indirect radiofluorination of biomolecules

“…13 Recently, we demonstrated the direct, one-step radiofluorination of peptides using 18 F-labelled pre-activated acylation agent 4-nitrophenyl 2-[ 18 F]fluoropropionate ([ 18 F]1). [14][15][16] A similar approach has been reported for the preparation of 2,3,5,6tetrafluorophenyl 6-[ 18 F]fluoronicotinate ([ 18 F]2) ( Fig. 1).…”

“…In comparison, the TFP esters 14 and 15 lacked the crystallinity of the PNP analogues making them less convenient to handle. Iodo-benzoates 12 and 14 were oxidized by mCPBA and converted to the corresponding (4-methoxyphenyl)-(phenyl)iodonium tosylates 16 (Fig. 4).…”

Fully automated radiosynthesis of [18F]fluoro-C-glyco-c(RGDfC): exploiting all the abilities of the AllInOne synthesizer

“…However, due to its complexity, fully or almost fully automated 18 F-labeled-peptide radiosynthesis via a prosthetic approach was only scarcely described. [33][34][35][36][37] Most of these examples have required some form of manual handling, for reformulation or final purification particularly. Indeed, multistep radiosyntheses are not easily automatable and only few synthesizers have the versatility to implement such sequence.…”

“…[ 18 F]FPyKYNE-c(RGDyK) was obtained via this semi-automated method in 12-18% decay corrected radiochemical yield in 125 minutes. More recently, Haskali et al33 described the fully automated radiosyntheses (including two HPLC purifications and reformulation) of [ 18 F]FP-GalactoRGD, [ 18 F]FP-PRGD 2 and the sulfonated versions of these peptides. The 2-[ 18 F]fluoropropionate labeled RGD-peptides were obtained via a two-pot method in 90 to 105 minutes with non-decay corrected radiochemical yields of 4 to 7%.…”

A review of approaches to 18F radiolabelling affinity peptides and proteins

“…Gallium‐68 radiochemistry lends itself more favourably to process automation due to 1‐step chelation methods, unlike the current multi‐step approaches to 18 F radiolabelling. However, the advantageous physical characteristics of 18 F (Table ) make the automation of 18 F radiolabelling approaches, a profitable endeavour …”