Synthesis Andin Vivocharacterization Of A Promising 11-Carbon Labeled Receptor Interacting Protein 1 (Rip1) Kinase Radioligand

1042 Objectives: Receptor interacting protein 1 (RIP1) kinase is a crucial upstream regulator of necroptosis, and the association of RIP1 kinase with a variety of pathologies, such as ischemic injury, inflammatory diseases, and neurodegenerative diseases(PD, MS and ALS), has been investigated. Inhibitors of RIP1 kinase have the potential to provide new therapeutic opportunities to neurodegenerative diseases with significant unmet medical needs. A new 7-oxo-2,4,5,7-tetrahydro-6H-pyrazolo[3,4-c]pyridine derivative was reported as a novel receptor interacting protein 1 (RIP1) kinase inhibitors. This compound significantly suppressed necroptotic cell death both in mouse and human cells. To investigate the RIP1 kinase regulate functions for the brain disorders, we radiosynthesized [11C]TZ7774 and performed initial in vivo in rodent to determine if [11C]TZ7774 could be a suitable PET radiotracer for imaging RIP1 kinase in the brain. Methods: The radiosynthesis of [11C]TZ7774 was accomplished by N-[11C]methylation of its amide precursor TZ7799 with [11C]CH3I under basic condition (NaOH) in DMF, heated at ~80 oC for 5 min. The radiolabeled product was purified on semi-preparative reversed phase HPLC column combined with solid phase extraction (SPE). The biodistribution study of [11C]TZ7774 was performed using male Sprague Dawley (SD) rats. Animals were euthanized at 5, 30, 60 min post i.v. injection of [11C]TZ7774. Tissues of interests were collected, weighed, and counted on an automated Beckman Gamma counter. The uptake of radioactivity was calculated as percentage injected dose per gram (%I.D./g).\n Results: The radiosynthesis of [11C]TZ7774 was successfully achieved with good radiochemical yield (30-40%), high chemical and radiochemical purity (\u003e 99%), and high specific activity (\u003e 700 Ci/mmol, decay corrected to EOB). The biodistribution study indicated that the initial brain uptake was high with %ID/gram values of 0.53 at 5 min and then washed out quickly with %ID/gram values of 0.14 at 30 min, and 0.07 at 60 min.\n Conclusions: Our preliminary biodistribution results suggested that [11C]TZ7774 has good brain uptake. Together, [11C]TZ7774 has great potential to be a PET tracer for imaging RIPK1 in vivo. Further in vitro autoradiography studies and microPET studies of [11C]TZ7774 in animal model of diseases to assess the RIP1 expression response to the progression of disease are ongoing. Research support: NIH/NS075527, NS103988.\nReferences: ADDIN EN.REFLIST J. Med. Chem., 2018, 61, 2384-2409; Cell Rep., 2015, 10, 1836-1849; Neural Regener. Res. 2015, 10,1120-1124; Science, 2016, 353, 603-608.