Fig. 1: Synthesis of cell impermeable staurosporine analog (CIMSS) and the effects of the parental drug and the analog on cell proliferation and viability.

a Scheme illustrating the synthetic route to the sodium salt of CIMSS: the secondary amine of staurosporine was derivatized via amidation of succinic anhydride and the resulting carboxylate (compound 5) was condensed with aminomethyl-triazol-propane-sulfonate (compound 4, which was obtained in four steps from NBoc-propargylamine and azidopropanol) to afford CIMSSNa in modest yield as a white powder. b HaCat cells (~50% confluence) were cultured in media containing increasing concentrations of staurosporine or CIMSS (0.1–100 μM) or the equivalent concentration of DMSO (0.1, 0.5, or 1%) and cell proliferation and viability (optical densitometry units, odu) quantified after 24 and 72 h. c Confluent HaCat cells were cultured in media containing 10 μM CIMSS, 10 μM staurosporine or 0.1% DMSO (control) and viability assessed after 24, 72 and 120 h. Note that staurosporine was completely cytotoxic after 72 and 120 h of exposure and thus no bar is visible. d Primary vaginal epithelial cells (~50% confluent) were cultured in media containing 0.5% DMSO, 10 or 50 μM CIMSS or 1 or 10 μM staurosporine for 120 h and cell proliferation and viability monitored. Results are presented as mean ± SEM odu as a percentage of the DMSO control (n = 2 independent experiments each conducted in duplicate for c and 1 experiment conducted in duplicate for d). Results in b–d were compared by ANOVA, *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001).