Eribulin, a synthetic analogue of a chemotherapeutically active compound derived from the sea sponge Halichondria okadai, acts as an inhibitor of microtubule dynamics. It is registered as palliative chemotherapy in advanced breast cancer after anthracyclines and taxanes. Studies with eribulin treatment have shown similar efficacy compared to anthracyclines and taxanes, but less toxicity. Those studies showed that often the dose of eribulin had to be reduced during treatment due to toxicity without compromising the efficacy of the treatment.