Radiolabelling an¹⁸F biologicviafacile IEDDA “click” chemistry on the GE FASTLab™ platform

Abstract

The use of biologics in positron emission tomography (PET) imaging is an important area of radiopharmaceutical development and new automated methods are required to facilitate their production. We report an...

Development of [18F]AmBF3 Tetrazine for Radiolabeling of Peptides: Preclinical Evaluation and PET Imaging of [18F]AmBF3-PEG7-Tyr3-Octreotide in an AR42J Pancreatic Carcinoma Model

“…The RCYs were low, partly due to the compromise of using the prosthetic group [ 18 F]­6 (100 nmol) in a molar excess of minimum 2:1 to the TOC precursor 14 or 15 (50 nmol) during IEDDA in order to consume the TCO-modified peptide completely to avoid having unlabeled TOC–TOC as a competitor in the final formulation. [ 18 F]­6 , [ 18 F]­14 , and [ 18 F]­15 required only a SPE cartridge purification prior to administration, rendering the method suitable for a cassette-based radiolabeling system, similar to that reported by Allott et al The loss of radioactivity could be decreased by altering the ratio of the TCO biomolecule to the radiolabeled tetrazine during IEDDA, but the biggest loss of radioactivity was attributed to [ 18 F]­fluoride escaping likely as [ 18 F]­HF in the acidic conditions already during the concentration step. This could be hypothetically resolved by employing microfluidic trapping in lieu of heat-induced evaporation for the [ 18 F]­fluoride concentration.…”

A practical guide to automating fluorine-18 PET radiochemistry using commercially available cassette-based platforms

“…We recently published the automated radiosynthesis of an 18 F-labelled biologic, recombinant interleukin-2 (Proleukin™), via the facile inverse electron demand Diels–Alder (IEDDA) “click” chemistry using the GE FASTLab™ platform. 17 In this Tutorial Account, we will use this radiochemistry as a case study to exemplify some of the methodology we have discussed herein; full experimental detail can be found in the previously published article but a summary of the radiochemistry is shown in Scheme 1. The automated radiosynthesis of [ 18 F]TTCO-IL2 is complex but serves as a good example as it covers both small molecule fluorination ( i.e.…”

“…As many (if not all) cassette-based platforms are designed to be used in [ 18 F]FDG production, the radiosynthesis of tracers by nucleophilic substitution followed by a simple hydrolysis and purification, is straightforward to automate; whereas the radiolabelling of more complex molecules like peptides and proteins, or small molecules which require multi-step post-radiolabelling assembly, can be a lot more challenging to automate, but not impossible! 17,18 Once satisfied that you can feasibly fit the entire radiosynthesis onto a single cassette, potential for cross-…”

“…A) Radiochemistry precursors for IEDDA "click" chemistry; B) an overview of the synthesis of [ 18 F] TTCO-IL2. Reaction conditions: a)[ 18 F]F − , KHCO 3 , K222, 90 °C, 6.6 min; b) aniline hydrochloride, MeCN/H 2 O, 40 °C, 10 min; c) EtOH, 10 min, RT.Adapted from a published method 17.…”

Positron Emission Tomography Probes for Imaging Cytotoxic Immune Cells

“…In addition to this, Allott et al, using click-chemistry, achieved labelling of IL-2 ( Figure 7 B) with E-2-(((4-[ 18 F]fluorobenzylidene)amino)oxy)-N-(4-(6-methyl-1,2,4,5-tetrazin-3-yl)benzyl)acetamide ([ 18 F]FBoxTz). This method allows the whole IL-2 radiolabelling process to be fully automated under GMP compatible conditions with a similar yield to the [ 18 F]SFB method [ 141 , 142 ]. Additionally, [ 18 F]FB-IL-2 was shown to specifically distinguish between unstimulated and stimulated PBMCs in various murine models [ 140 , 143 , 144 ].…”