Preparation and biodistribution of [18F]FP2OP as myocardial perfusion imaging agent for positron emission tomography.
Myocardial extractions of pyridaben, a mitochondrial complex I (MC-I) inhibitor, is well correlated with blood flow. Based on the synthesis and characterization of pyridaben analogue 2-tert-butyl-5-[2-(2-[(18)F]fluroethoxy)ethoxy]benzyloxy]-4-chloro-2H-pyridazin-3-one ([(18)F]FP2OP), this study assessed its potential to be developed as myocardial perfusion imaging (MPI) agent.


METHODS
The tosylate labeling precursor 2-(2-(4-(tert-butyl-5-chloro-6-oxo-1,6-dihydro-pyridazin-4-yloxymethyl)benzyloxy)ethoxy)ethyl ester (OTs-P2OP) and the nonradioactive 2-tert-butyl-5-[2-(2-[(19)F]fluroethoxy)ethoxy]benzyloxy]-4-chloro-2H-pyridazin-3-one ([(19)F]FP2OP) were synthesized and characterized by IR, (1)H NMR, (13)C NMR and MS analysis. By substituting tosyl of precursor OTs-P2OP with (18)F, the radiolabeled complex [(18)F]FP2OP was prepared and further evaluated for its in vitro physicochemical properties, in vivo biodistribution, the metabolic stability in mice, ex vivo autoradiography and cardiac PET/CT imaging.


RESULTS
Starting with [(18)F]F(-) Kryptofix 2.2.2./K(2)CO(3) solution, the total reaction time for [(18)F]FP2OP was about 100 min, with final high-performance liquid chromatography purification included. Typical decay-corrected radiochemical yield stayed at 41+/-5.3%, the radiochemical purity, 98% or more. Biodistribution in mice showed that the heart uptake of [(18)F]FP2OP was 41.90+/-4.52%ID/g at 2 min post-injection time, when the ratio of heart/liver, heart/lung and heart/blood reached 6.83, 9.49 and 35.74, respectively. Lipophilic molecule was further produced by metabolized [(18)F]FP2OP in blood and urine at 30 min. Ex vivo autoradiography demonstrates that [(18)F]FP2OP may have high affinity with MC-I and that can be blocked by [(19)F]FP2OP or rotenone (a known MC-I inhibitor). Cardiac PET images were obtained in a Chinese mini-swine at 5, 15, 30 and 60 min post-injection time with high quality.


CONCLUSIONS
[(18)F]FP2OP was synthesized with high radiochemical yield. The promising biological properties of [(18)F]FP2OP suggest high potential as MPI agent for positron emission tomography in the future.
Mou
Tiantian
T
Key Laboratory of Radiopharmaceuticals, Ministry of Education, College of Chemistry, Beijing Normal University, 19 Xinjiekou Outer St, Beijing 100875, China.
Jing
Huihui
H
Yang
Wenjiang
W
Fang
Wei
W
Peng
Cheng
C
Guo
Feng
F
Zhang
Xianzhong
X
Pang
Yan
Y
Ma
Yunchuan
Y
D000818:Animals; D005461:Fluorine / Q000737:chemistry; D051379:Mice; D009206:Myocardium / Q000378:metabolism*; D055420:Perfusion Imaging / Q000379:methods*; D049268:Positron-Emission Tomography / Q000379:methods*; D011724:Pyridazines / Q000138:chemical synthesis / Q000737:chemistry; D019275:Radiopharmaceuticals / Q000138:chemical synthesis / Q000737:chemistry*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013552:Swine
D011724:Pyridazines; D019275:Radiopharmaceuticals; D005461:Fluorine; C428725:pyridaben