DUPA(OtBu)-OH is a DUPA precursor. DUPA is used as the targeting moiety to actively deliver Docetaxel (DTX) for treatment of Prostate-Specific Membrane Antigen (PSMA) expressing prostate cancer. In Vitro: DUPA(OtBu)-OH (DUPA precursor 17) is a 2-[3-(1,3-dicarboxypropyl)ureido]pentanedioic acid (DUPA) reagent^[1]. The targeting ligand DUPA enhances the transport capability and selectivity of Paclitaxel (PTX) to tumor cells via prostate-specific membrane antigen (PSMA) mediated endocytosis. Besides, DUPA is conjugated with PTX via a disulfide bond, which facilitates the rapid and differential drug release in tumor cells^[2]. In Vivo: DUPA-targeted Docetaxel (DTX) conjugate with longer spacer has no toxicity in major organs of treated mice^[3].