Protoporphyrin IX (PpIX) accumulation induced by exogenous 5-aminolevulinic acid (ALA) in tumors affects the therapeutic efficacy of ALA-based photodynamic and sonodynamic therapies. To develop a new imaging probe to estimate the ALA-induced PpIX accumulation, (11)C-labeled ALA analog (4), an ALA-dehydratase inhibitor, was radiosynthesized via (11)C-methylation of a Schiff-base-activated precursor in the presence of tetrabutylammonium fluoride, followed by the hydrolysis of ester and imine groups. The cellular uptake of 4 linearly increased with time and was inhibited by ALA and other transporter competitors. Monitoring analog 4 with positron emission tomography might be useful to estimate the ALA-induced PpIX accumulation in tumors.
Keywords: 5-Aminolevulinic acid (ALA); Photodynamic therapy (PDT); Positron emission tomography (PET); Radiosynthesis; Sonodynamic therapy (SDT).
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