A novel 7-((4-(3-((2-[ 18 F]fluoropyridin-3-yl)oxy)propyl)-1 H -1,2,3-triazol-1-yl)methyl)-1 H -benzo[ d ]imidazole derivative of the angiotensin II type-1 receptor (AT 1 R) blocker candesartan, [ 18 F]fluoropyridine–candesartan, was synthesized via the copper-catalyzed azide–alkyne cycloaddition click reaction between 2-[ 18 F]fluoro-3-(pent-4-yn-1-yloxy)pyridine ([ 18 F]FPyKYNE) and the tetrazole-protected azido-candesartan derivative, followed by acid deprotection. This three-step, two-pot, and two-step purification synthesis was done within 2 h. The use of tris[(1-hydroxypropyl-1 H -1,2,3-triazol-4-yl)methyl]amine (THPTA) as a Cu(I) stabilizing agent increased the overall radiochemical yield by 4-fold (10 ± 2%, n = 13) compared to the reaction without THPTA (2.4 ± 0.2%, n = 3; decay-corrected from 18 F produced at the end-of-beam). Complete separation of [ 18 F]FPyKYNE from its nitro precursor and [ 18 F]fluoropyridine–candesartan from the deprotected azido-candesartan allowed for high molar activities (>380 GBq/μmol) of the tracer. The use of 0.1% trifluoroacetic acid in water for reformulation and the addition of sodium ascorbate to the final formulation (1.6 ± 0.2 GBq/mL, n = 3) prevented tracer radiolysis with >97% radiochemical purity for a period of up to 10 h after the end-of-synthesis. A significant reduction in the uptake (86 ± 3%, n = 8) of the tracer was observed ex vivo in rats (at 20 min postinjection) in the AT 1 R-rich kidney cortex following pretreatment with saturating doses of the AT 1 R antagonist candesartan or losartan. This specific binding to AT 1 R was confirmed in vitro in the rat renal cortex (autoradiography) by a reduction of 26 ± 5% ( n = 12) with losartan coincubation (10 μM). These favorable binding properties support further studies to assess the potential of [ 18 F]fluoropyridine–candesartan as a tracer for the positron emission tomography imaging of renal AT 1 R.

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