18FDG-labeled LIKKPF: a PET tracer for apoptosis imaging

Design, Synthesis, Radiolabeling, and Biologic Evaluation of Three 18F-FDG-Radiolabeled Targeting Peptides for the Imaging of Apoptosis

“…The synthesis and cleavage processes of the reference peptide, Aoe-LIKKPF, were described in detail in the literature. [20][21][22] Synthesis of LIKKP-Cl-F, which was functionalized with aminooxy, Aoa-LIKKP-Cl-F ( Fig. 1A), was done as follows: 0.5 mg Wang resin was swelled, and 4-6 equivalent (eq) of N-a-Fmoc protected amino acids (Fmoc-D-Phe (4-Cl)-OH) were first attached to the resin with 2 eq hexafluorophosphate azabenzotriazole tetramethyl uranium (HATU) and 3 eq of diisopropylethylamine (DIPEA) as coupling reagents.…”

“…Coupling of Aoa to the last amino acid was done with 2 eq of HATU, 3 eq of DIPEA, and 2 eq Eei-Aoa-NHS (N-(1-ethoxyethyidene)-2-aminooxyacetic acid N-hydroxysuccinimidyl) in dry DMF. 21 The completeness of the coupling reaction was checked by Kaiser test. The cleavage of peptide from resin was carried out using cocktail of trifluoroacetic acid (TFA)/triisobutylsilane (TIS)/H 2 O (95:2.5:2.5) for 45 min.…”

“…Radiolabeling of aminooxy functionalized peptides with 18 F-FDG was carried out with a modification to the procedure reported previously 21,26 (Fig. 2).…”

“…The biologic properties of radiolabeled peptides were assessed in vitro and in vivo. [20][21][22] LIKKPF showed less affinity for PS compared to original phage display. To improve the affinity of LIKKPF for PS, the authors developed three new analogs based on the hydrophobic, steric, and electronic properties of peptides.…”

“…23,24 Recently, the authors described the radiolabeling of LIKKPF with 18 F-FDG as a prosthetic group. 21 The new analogs were functionalized with aminooxy (Aoe) and radiolabeled with 18 F-FDG. 25 In this study, they reported development, synthesis, radiolabeling with 18 F-FDG, and biologic evaluation of three new analogs of LIKKPF in vitro and in vivo.…”