CELT-426 is a potent, partially selective fluorescent antagonist of the human D2 dopamine receptor, exhibiting Ki values of 89.3 nM, 194.8 nM, and 263.6 nM for D2, D3, and D4 dopamine receptors, respectively, in radioligand binding assays. This compound serves as an effective fluorescent probe for dopamine receptors, facilitating its application in a range of techniques including fluorescence binding assays, live cell imaging, flow cytometry, and fluorescence polarization assays. It provides an alternative to GPCR radiolabeling ligands. CELT-426 possesses excitation and emission maxima (λ) of 560 nm and 571 nm, respectively, making it suitable for use as an acceptor dye in Time-Resolved Fluorescence Resonance Energy Transfer (TR-FRET) assays in conjunction with the CoraFluor1 TR-FRET donor.