8pyDTZ is a pyridyl diphenylterazine (DTZ) analog and an ATP-independent pyridyl substrate of LumiLuc luciferase, exhibiting spectrally shifted emission and improved water solubility, suitable for in vivo luminescence imaging.

8pyDTZ, with a solubility of 1711 μM, significantly increases water solubility by 13-fold over DTZ (131 μM). This compound not only shows a capability for red-shifted chemiluminescence and bioluminescence emission compared to DTZ but also produces the most red-shifted emission, allowing for improved tissue penetration. In evaluations using human embryonic kidney 293T cells expressing luciferase (HEK 293T cells), the LumiLuc-8pyDTZ combination yields approximately 3-5 times more bioluminescence than the teLuc-8pyDTZ pair. Additionally, when comparing far-red emission intensities with a 600-700 nm bandpass filter, LumiLuc-8pyDTZ consistently achieves 1.6-3.9 times higher photon flux than teLuc-DTZ across substrate concentrations ranging from 6.25 to 100 μM, without affecting ATP levels in LumiLuc-expressing cells treated with 8pyDTZ.

The LumiLuc-8pyDTZ pair was evaluated alongside various standard reporters within a tumor xenograft mouse model, exhibiting high sensitivity and eliminating the need for organic cosolvents for in vivo administration. Additionally, LumiScarlet-8pyDTZ demonstrated equivalence to Akaluc-AkaLumine, the most luminous ATP-dependent luciferase-luciferin pair, in detecting cells within deep mouse tissues.