Time lapse photography of HeLa EB1-GFP cells was taken every 15 seconds for ten minutes to observe the addition of the GFP-tagged EB1 microtubule associated protein to the plus ends of the microtubules. At five minutes, treatments were added and photography continued. Treatments consisted of 1×, 10× or 30× the IC50 for leiodermatolide, 30× IC50 vincristine or DMSO. Treatment with leiodermatolide immediately caused cessation of GFP-EB-1 comets similar to, but faster than, that observed for the depolymerizing agent vincristine.