EAPB0203 and EAPB0503, and imiquimod at high concentrations, inhibit polymerization of tubulin <i>in vitro</i>.

<p>Purified tubulin polymerization was quantitated by turbidimetry measurement at 350 nm with or without (blank) various concentrations of EAPB0203, EAPB0503, imiquimod, and colchicine as positive control, or warfarin (1,600 μM) as negative control. Various parameters representative of the polymerization process were calculated: A_max (maximum absorbance plateau value), t_1/10 (abscissa value of the A_max/10 absorbance), p (slope of the plot log(A(t)/A_max) versus log(t) during the elongation process, i.e. from 1 min to the time of 80% A_max), and k_obs (pseudo-first order rate constant of elongation, determined by plotting ln(1 –A(t)/ A_max) as a function of time). The ratio to blank values are reported here. The red line embodies the ratio of 1, meaning identity to blank. Mean ± SD, n = 1 to 6. (<b>A)</b> EAPB0203, EAPB0503, imiquimod and colchicine at 0.1 to 10 μM concentrations. (<b>B)</b> Imiquimod at 160 to 1,600 μM concentrations. Mean ± SD, n = 1 or 2.