HMN-214 is an oral prodrug of HMN-176, a stilbene derivative that interferes with the subcellular spatial location of polo-like kinase-1 (PLK-1), a serine/threonine kinase that regulates critical mitotic events. HMN-214 was synthesized as an oral prodrug because of the poor oral absorption of HMN-176 itself. In the in vivo analysis of the schedule-dependency of HMN-214, the repeated administration for over 5 days elicited potent antitumor activity, as expected from the exposure-dependency of the cytotoxicity of HMN-176 and from the cytometric studies. The antitumor activity of HMN-214 against human tumor xenografts was equal or superior to that of clinically available agents, including cis-platinum, adriamycin, vincristine, and UFT without severe toxicity such as neurotoxicity. A phase I pharmacokinetic study indicated that there was no accumulation of HMN-176, the metabolite of HMN-214, with repeated dosing. Phase I trials in Japan and the US was done several years ago and no further development has been reported, therefore it is assumed that HMN-214 investigation to be discontinued.