A Novel Anti-HIV Dextrin–Zidovudine Conjugate Improving the Pharmacokinetics of Zidovudine in Rats

The aim of this study was to investigate a newly synthesized dextrin–zidovudine (AZT) conjugate designed as a sustained release prodrug of AZT for parenteral administration. AZT was first reacted with succinic anhydride to form a succinoylated AZT which was subsequently coupled with dextrin to yield the dextrin–AZT conjugate. The structure of the conjugate was characterized by FT-IR and 1H-NMR spectroscopy. The drug content of the conjugate was 18.9 wt.%. The release in vitro of free AZT and succinoylated AZT was investigated in buffer solutions at pH 5.5 and 7.4 and in human plasma. AZT and succinoylated AZT release from the conjugate was 1.4% (pH 5.5), 41.7% (pH 7.4) and 78.4% in human plasma after 24 h. Release was complete in human plasma after 48 h. A pharmacokinetic study in rats following intravenous administration of the conjugate showed prolonged plasma levels of AZT compared to free AZT. The use of the conjugate extended the plasma half-life of AZT from 1.3 to 19.3 h and the mean residence time from 0.4 to 23.6 h. Furthermore, the conjugate provided a significant greater area under the plasma concentration-time curve and reduced the systemic clearance of AZT. This study suggested the potential of this novel dextrin–AZT conjugate as a new intravenous preparation of AZT

Engineered human Tmpk fused with truncated cell-surface markers: versatile cell-fate control safety cassettes

Cell-fate control gene therapy (CFCGT)-based strategies can augment existing gene therapy and cell transplantation approaches by providing a safety element in the event of deleterious outcomes. Previously, we described a novel enzyme/prodrug combination for CFCGT. Here, we present results employing novel lentiviral constructs harboring sequences for truncated surface molecules (CD19 or low-affinity nerve growth factor receptor) directly fused to that CFCGT cDNA (TmpkF105Y). This confers an enforced one-to-one correlation between cell marking and eradication functions. In-vitro analysis demonstrated the full functionality of the fusion product. Next, low-dose 3'-azido-3'-deoxythymidine (AZT) administration to non-obese diabetic/severe combined immunodeficiency (NOD/SCID) mice injected with transduced clonal K562 cells suppressed tumor growth; furthermore, one integrated vector on average was sufficient to mediate cytotoxicity. Further, in a murine xenogeneic leukemia-lymphoma model we also demonstrated in-vivo control over transduced Raji cells. Finally, in a proof-of-principle study to examine the utility of this cassette in combination with a therapeutic cDNA, we integrated this novel CFCGT fusion construct into a lentivector designed for treatment of Fabry disease. Transduction with this vector restored enzyme activity in Fabry cells and retained AZT sensitivity. In addition, human Fabry patient CD34(+) cells showed high transduction efficiencies and retained normal colony-generating capacity when compared with the non-transduced controls. These collective results demonstrated that this novel and broadly applicable fusion system may enhance general safety in gene- and cell-based therapies.Fil: Scaife, Matthew. University of Toronto; CanadáFil: Pacienza, Natalia Alejandra. University Health Network. Ontario Cancer Institute; Canadá. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Au, B. C. Y.. University Health Network. Ontario Cancer Institute; CanadáFil: Wang, J. C. M.. University Health Network. Ontario Cancer Institute; CanadáFil: Devine, S.. University of Toronto; CanadáFil: Scheid, E.. Mc Master University; CanadáFil: Lee, C. J.. University Health Network. Ontario Cancer Institute; CanadáFil: Lopez Perez, O.. University Health Network. Ontario Cancer Institute; CanadáFil: Neschadim, A.. University of Toronto; CanadáFil: Fowler, D. H.. National Institutes of Health; Estados UnidosFil: Foley, R.. Mc Master University; CanadáFil: Medin, J. A.. University of Toronto; Canadá. University Health Network. Ontario Cancer Institute; Canad

Dextrin–Colistin Conjugates as a Model Bioresponsive Treatment for Multidrug Resistant Bacterial Infections

Polymer therapeutics offer potential benefits in the treatment of multidrug resistant (MDR) infections; affording targeted delivery of biologically active agents to the site of inflammation, potential decreases in systemic toxicity, and the retention of antimicrobial activity at the target site. As a prototype model, these studies developed and characterized a library of dextrin–colistin conjugates (dextrin molecular weight: 7500–48 000 g/mol) as a means of targeting the delivery of colistin. Optimum colistin release kinetics (following dextrin degradation by physiological concentrations of amylase (100 IU/L)) were observed in conjugates containing low molecular weight (∼7500 g/mol) dextrin with ∼1 mol % succinoylation (∼80% drug release within 48 h, compared to ∼33% from sodium colistin methanesulfonate (CMS, Colomycin)). These conjugates exhibited comparable antimicrobial activity to CMS in conventional MIC assays against a range of Gram-negative pathogens, but with significantly reduced in vitro toxicity toward kidney (IC50 = CMS, 15.4 μg/mL; dextrin–colistin, 63.9 μg/mL) and macrophage (IC50 = CMS, 111.3 μg/mL; dextrin–colistin, 303.9 μg/mL) cells. In vivo dose-escalation studies in rats demonstrated improved pharmacokinetics of the conjugates, with prolonged plasma levels of colistin (t1/2 135–1271 min vs 53 min) and decreased toxicity, compared to colistin sulfate. These studies highlight the potential utility of “nanoantibiotic” polymer therapeutics to aid the safe, effective, and targeted delivery of colistin in the management of MDR infections