Surfen and oxalyl surfen are well tolerated by Tg [HuC::hTau^P301L; DsRed] embryos. a Chemical structure of Surfen (1,3-bis(4-amino-2-methylquinolin-6-yl) urea), oxalyl surfen (N1,N2- bis(4-amino-2-methylquinolin-6-yl)oxalamide) and hemisurfen (1-(4-amino-2-methylquinolin-6- yl)urea). b Phenotypic analysis of 72 hpf wild-type (WT) and Tg [HuC::hTau^P301L; DsRed] (hTau^P301L) embryos incubated for 2 days in E3 medium containing 1% DMSO (hTau^P301L + 1% DMSO), 80 mM LiCl (hTau^P301L + LiCl), 3 μM surfen (hTau^P301L + surfen), 2 μM oxalyl surfen (hTau^P301L + oxalyl surfen) or 3 μM hemisurfen (hTau^P301L + hemisurfen), showed that embryonic development is not impaired by the treatments. Magnification × 40. c Survival rate of 72 hpf wild-type (WT) and Tg [HuC::hTau^P301L; DsRed] (hTau^P301L) embryos incubated for 2 days in E3 medium containing 1% DMSO (hTau^P301L + 1% DMSO), 80 mM LiCl (hTau^P301L + LiCl), 3 μM surfen (hTau^P301L + surfen), 2 μM oxalyl surfen (hTau^P301L + oxalyl surfen), or 3 μM hemisurfen (hTau^P301L + hemisurfen), demonstrated that embryonic mortality was not significantly increased by treatments (n = 250, P > 0.05, Student’s t test)