Potent anticancer drug used to treat a variety of cancers in clinic.[1] Previously, liquid-oil filled NPs have been created to provide DX. Nevertheless, in spite of theJohn A. McNeill Distinguished Prof. R. J. Mumper, Corresponding Author, Center for Nanotechnology in Drug Delivery, Division of Molecular Pharmaceutics, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA, UNC Lineberger Extensive Cancer Center, University of North Carolina at Chapel Hill, NC, USA, CB# 7355, 100G Beard Hall, University of North Carolina at Chapel Hill, [email protected] et al.Pagedesirable formulation properties (e.g., monodisperse particle size, apparent drug entrapment efficiency, etc.), DX was found to become very speedily released in mouse plasma in-vitro. To overcome the poor retention of DX within the oil-filled NPs in easy aqueous phase and in biologically relevant medium, DX was modified by attaching fatty acid chains with diverse chain lengths for the 2′-position of DX via an ester bond.[4] The 3 DX-lipid conjugates synthesized in the prior research enhanced the drug solubility in oil phase by 10-fold. Consequently, the DX-lipid conjugates had been nicely retained in the NPs even in 100 plasma. The retention of DX conjugates within the long-circulating NPs resulted in substantially decreased elimination and high and prolonged systemic drug HCV Protease Inhibitor Compound exposure. Nevertheless, in-vitro cytotoxicity studies revealed that these DX conjugates were significantly significantly less potent than the unmodified DX.[4] Related results have already been reported by other groups.[5] It has been extended recognized that the 2′-OH is important for the microtubule binding and cytotoxic effect of DX.[6] Hence, the biological activity of these ester prodrugs mostly is dependent upon the liberation of active DX. The compromised cytotoxicity suggests inefficient release of DX in cell culture. The in-vitro hydrolysis and in-vivo pharmacokinetics also revealed sub-optimal hydrolysis kinetics of those conjugates.[4] Ali et al. synthesized a series of lipid paclitaxel (PX) prodrugs with or devoid of a bromine atom in the 2-position on the fatty acid chain.[7] In general, the prodrugs lacking bromine had been 50- to 250-fold less active than their bromoacyl counterparts indicating that the electron-withdrawing group facilitated the cleavage of active PX. The bromoacylated PX showed higher anticancer efficacy against OVCAR-3 tumor in-vivo.[7,8] Their findings suggest that this rationale and facile modification has the possible to favorably change the BRaf Source physicochemical and biological properties in the DX conjugates. The objective of those present research was to further tune the prodrug hydrolysis kinetics even though retaining the higher drug entrapment and retention in the oil-filled NPs. With optimized activation kinetics, the new prodrug containing NPs have been expected to attain sustained release of active drug, low systemic toxicity, and enhanced antitumor efficacy in-vivo.NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author Manuscript 2. Results2.1. Synthesis and characterization of 2-Br-C16-DX DX was modified towards the more lipophilic prodrug, 2-Br-C16-DX, by a one-step esterification reaction with a 2-bromohexadecanoyl chain attached to the 2′-position of DX (Figure 1). The 2′-OH would be the most reactive hydroxyl group among the many hydroxyl groups in DX molecule, followed by 7-OH and 10-OH.[5] The presence of bromine on the acyl chain produced the carboxylic acid additional reactive than its counterpart.