Targeting tubulin in rapidly dividing tumor cells is a sound strategy for cancer therapy.Despite recent advances in this field,identification of both potent and selective antimitotic molecules affecting tubulin/microtubule structure and dynamics is a convoluted multi-stage procedure.We have devised a "one-pot" phenotypic in vivo assay for the rapid evaluation of tubulin inhibitors using the sea urchin embryo model.The proposed procedure involves i) fertilized egg test for mitotic alteration/arrest and ii) behavioral assessment of a free-swimming blastulae.Changes of the embryo swimming pattern,i.e.rapid embryo spinning instead of forward movement,indicate the tubulin destabilizing activity caused by a test article.The assay is highly reproducible yielding rapid information on antiproliferative,antimitotic,cytotoxic,and tubulin destabilizing activities of the molecules along with their solubility and permeability potential.Using the method we identified several novel diverse tubulin destabilizing compounds with effective concentrations in nanomolar range.Measured potencies of tubulin destabilizers correlated well with the values in both purified tubulin polymerization and cell-based assays.A combination of the sea urchin embryo assay with the tests on cultured human tumor cells allowed for the rapid identification and SAR study of promising and specific tubulin inhibitors from different chemical classes.