Synthesis, radiolabeling and initial in vivo evaluation of [11C]KSM-01 for imaging PPAR-[alpha] receptors

Peroxisome proliferator-activated receptor alpha (PPAR-[alpha]) is a ligand-activated nuclear receptor transcription factor that regulates the fatty acid [beta]-oxidation. An in vitro assay identified the p-methoxy phenyl ureido thiobutyric acid derivative KSM-01 (IC50 = 0.28 +/- 0.09 nM) having a higher affinity to activate PPAR-[alpha] than the PPAR-[alpha] agonist GW7647 (IC50 = 0.46 +/- 0.19 nM). In this study, we report the synthesis and initial in vivo evaluation of [11C]KSM-01. The radiosynthesis was carried out by first alkylating the corresponding p-phenol precursor with [11C]MeI in DMF using NaOH, followed by deprotection of the t-butyl ester group by TFA, yielding [11C]KSM-01. SUV analysis of dynamic micro PET/CT imaging data showed that [11C]KSM-01 accumulation was similar to 2.0-fold greater in cardiac-specific PPAR-[alpha] overexpressing transgenic mice compared to wild-type littermates. The post-PET biodistribution studies were consistent with these results and demonstrated 2.5-fold greater radiotracer uptake in the heart of transgenic mice compared to the wild-type littermates. These results demonstrate the potential utility of PPAR-[alpha] agonists as PET radiopharmaceuticals.