The investigational product (IP) Oratecan is comprised of the approved drug irinotecan with HM30181 methanesulfonate monohydrate (HM30181), a novel p-glycoprotein (P-gp) pump inhibitor. Oratecan is intended for the treatment of irinotecan-responsive cancers. The antitumor activity of Oratecan is due to the action of irinotecan. Combining HM30181 with irinotecan allows intestinal absorption and systemic exposure of irinotecan and its active metabolite, SN38, at therapeutic levels after oral administration.