Plasma Stability and Plasma Metabolite Concentration-Time Profiles of Oligo(Lactic Acid)8-Paclitaxel Prodrug Loaded Polymeric Micelles.

Paclitaxel (PTX) is a frequently prescribed chemotherapy drug used to treat a wide variety of solid tumors. Oligo(lactic acid)8-PTX prodrug (o(LA)8-PTX) loaded poly(ethylene glycol)-b-poly(lactic acid) (PEG-b-PLA) micelles have higher loading, slower release and higher antitumor efficacy in murine tumor models over PTX-loaded PEG-b-PLA micelles. The goal of this work is to study plasma stability of o(LA)8-PTX-loaded PEG-b-PLA micelles and its pharmacokinetics after IV injection in rats. In rat plasma, o(LA)8-PTX prodrug is metabolized into o(LA)1-PTX and PTX. In human plasma, o(LA)8-PTX is metabolized more slowly into o(LA)2-PTX, o(LA)1-PTX, and PTX. After IV injection of 10 mg/kg PTX-equiv of o(LA)8-PTX prodrug loaded PEG-b-PLA micelles in Sprague-Dawley rats, metabolite abundance in plasma follows the order: o(LA)1-PTX > o(LA)2-PTX > o(LA)4-PTX > o(LA)6-PTX. Bile metabolite profiles of the o(LA)8-PTX prodrug is similar to plasma metabolite profiles. In comparison to equivalent doses of Abraxane®, plasma PTX exposure is two orders of magnitude higher for Abraxane® than PTX from o(LA)8-PTX prodrug loaded PEG-b-PLA micelles, and plasma o(LA)1-PTX exposure is fivefold higher than PTX from Abraxane®, demonstrating heightened plasma metabolite exposure for enhanced antitumor efficacy.

Production of paclitaxel-loaded PEG-b-PLA micelles using PEG for drug loading and freeze-drying.

A new approach named PEG-assist is introduced for the production of drug-loaded polymeric micelles. The method is based on the use of PEG as the non-selective solvent for PEG-b-PLA in the fabrication procedure. Both hydration temperature and PEG molecular weight are shown to have a significant effect on the encapsulation efficiency of PTX in PEG4kDa-b-PLA2kDa micelles. The optimal procedure for fabrication includes the use of PEG1kDa as the solvent at 60 °C, cooling the mixture to 40 °C, hydration at 40 °C, freezing at -80 °C and freeze-drying at -35 °C, 15 Pa. No significant difference (p > 0.05) in PTX encapsulation, average particle size and polydispersity index is observed between the samples before freeze-drying and after reconstitution of the freeze-dried cake. The prepared PTX formulations are stable at room temperature for at least 8 h. Scaling the batch size to 25× leads to no significant change (p > 0.05) in PTX encapsulation, average particle size and polydispersity index. PEG-assist method is applicable to other drugs such as 17-AAG, and copolymers of varied molecular weights. The use of no organic solvent, simplicity, cost-effectiveness, and efficiency makes PEG-assist a very promising approach for large scale production of drug-loaded polymeric micelles.

Oligo(Lactic Acid)8-Docetaxel Prodrug-Loaded PEG-b-PLA Micelles for Prostate Cancer.

Docetaxel (DTX) is among the most frequently prescribed chemotherapy drugs and has recently been shown to extend survival in advanced prostate cancer patients. However, the poor water solubility of DTX prevents full exploitation of this potent anticancer drug. The current marketed formulation, Taxotere®, contains a toxic co-solvent that induces adverse reactions following intravenous injection. Nano-sized polymeric micelles have been proposed to create safer, water-soluble carriers for DTX, but many have failed to reach the clinic due to poor carrier stability in vivo. In this study, we aimed to improve micelle stability by synthesizing an ester prodrug of DTX, oligo(lactic acid)8-docetaxel (o(LA)8-DTX), for augmented compatibility with the core of poly(ethylene glycol)-b-poly(lactic acid) (PEG-b-PLA) micelles. Due to the enhancement of drug-carrier compatibility, we were able to load 50% (w/w) prodrug within the micelle, solubilize 20 mg/mL o(LA)8-DTX (~12 mg/mL DTX-equivalent) in aqueous media, and delay payload release. While the micelle core prohibited premature degradation, o(LA)8-DTX was rapidly converted to parent drug DTX through intramolecular backbiting (t1/2 = 6.3 h) or esterase-mediated degradation (t1/2 = 2.5 h) following release. Most importantly, o(LA)8-DTX micelles proved to be as efficacious but less toxic than Taxotere® in a preclinical mouse model of prostate cancer.

Acyl and oligo(lactic acid) prodrugs for PEG-b-PLA and PEG-b-PCL nano-assemblies for injection.

Poly(ethylene glycol)-block-poly(D,L-lactic acid) (PEG-b-PLA) and poly(ethylene glycol)-block-poly(ε-caprolactone) (PEG-b-PCL) form nano-assemblies, including micelles and nanoparticles, that increase the water solubility of anticancer drugs for injection. PEG-b-PLA and PEG-b-PCL are less toxic than commonly used organic solvents or solubilizers for injection, such as Cremophor EL® in Taxol®. Formulating paclitaxel in PEG-b-PLA micelles, as Genexol-PM®, permits dose escalation over Taxol®, enhancing antitumor efficacy in breast, lung and ovarian cancers. To expand the repertoire of anticancer drugs for injection, acyl and oligo(lactic acid) ester prodrugs have been synthesized for PEG-b-PLA and PEG-b-PCL nano-assemblies, compatibility, and novel nanomedicines for injection. Notably, acyl and oligo(lactic acid) taxane prodrugs delivered by PEG-b-PLA and PEG-b-PCL nano-assemblies display heightened plasma exposure, reduction in biodistribution into major organs and enhanced tumor exposure in murine tumor models, versus parent anticancer drugs in conventional formulations. As a result, acyl and oligo(lactic acid) ester prodrugs are less toxic and induce durable antitumor responses. In summary, acyl and oligo(lactic acid) ester prodrugs widen the range of anticancer drugs that can be tested safely and effectively by using PEG-b-PLA and PEG-b-PCL nano-assemblies, and they display superior anticancer efficacy over parent anticancer drugs, which are often approved products. Oligo(lactic acid) ester taxane prodrugs are in pre-clinical development as novel drug combinations and immunotherapy combinations for cancer therapy.

Probing the subcutaneous absorption of a PEGylated FUD peptide nanomedicine via in vivo fluorescence imaging.

The Functional Upstream Domain (FUD) peptide is a potent inhibitor of fibronectin assembly and a therapeutic candidate for disorders linked with hyperdeposition of fibronectin-modulated ECM proteins. Most recently, experiments involving subcutaneous (s.c.) administration of a PEGylated FUD (PEG-FUD) of 27.5 kDa molecular weight yielded a significant reduction of fibronectin and collagen deposition in a murine model of renal fibrosis. The benefits of FUD PEGylation need to be studied to unlock the full potential of the PEG-FUD platform. This work studies the impact of PEGylating the FUD peptide with differently sized PEG on its absorption from the site of injection following s.c. delivery using non-invasive in vivo fluorescence imaging. The FUD and mFUD (control) peptides and their 10 kDa, 20 kDa, and 40 kDa PEG conjugates were labeled with the sulfo-Cy5 fluorophore. Isothermal titration calorimetry (ITC) and confocal fluorescence microscopy experiments verified FUD and PEG-FUD fibronectin binding activity preservation following sulfo-Cy5 labeling. Fluorescence in vivo imaging experiments revealed a linear relationship between the absorption apparent half-life (t1/2) and the MW of FUD, mFUD, and their PEG conjugates. Detected drug signal in the kidney and bladder regions of mice suggests that smaller peptides of both the FUD and mFUD series enter the kidney earlier and in higher amounts than their larger PEG conjugates. This work highlights an important delayed dose absorption enhancement that MW modification via PEGylation can contribute to a drug when combined with the subcutaneous route of delivery.

Oligo(Lactic Acid)8-Rapamycin Prodrug-Loaded Poly(Ethylene Glycol)-block-Poly(Lactic Acid) Micelles for Injection.

PURPOSE: To prepare an oligo(lactic acid)8-rapamycin prodrug (o(LA)8-RAP)-loaded poly(ethylene glycol)-block-poly(lactic acid) (PEG-b-PLA) micelle for injection and characterize its compatibility and performance versus a RAP-loaded PEG-b-PLA micelle for injection in vitro and in vivo. METHODS: Monodisperse o(LA)8 was coupled on RAP at the C-40 via DCC/DMAP chemistry, and conversion of o(LA)8-RAP prodrug into RAP was characterized in vitro. Physicochemical properties of o(LA)8-RAP- and RAP-loaded PEG-b-PLA micelles and their antitumor efficacies in a syngeneic 4 T1 breast tumor model were compared. RESULTS: Synthesis of o(LA)8-RAP prodrug was confirmed by 1H NMR and mass spectroscopy. The o(LA)8-RAP prodrug underwent conversion in PBS and rat plasma by backbiting and esterase-mediated cleavage, respectively. O(LA)8-RAP-loaded PEG-b-PLA micelles increased water solubility of RAP equivalent to 3.3 mg/ml with no signs of precipitation. Further, o(LA)8-RAP was released more slowly than RAP from PEG-b-PLA micelles. With added physical stability, o(LA)8-RAP-loaded PEG-b-PLA micelles significantly inhibited tumor growth relative to RAP-loaded PEG-b-PLA micelles in 4 T1 breast tumor-bearing mice without signs of acute toxicity. CONCLUSIONS: An o(LA)8-RAP-loaded PEG-b-PLA micelle for injection is more stable than a RAP-loaded PEG-b-PLA micelle for injection, and o(LA)8-RAP converts into RAP rapidly in rat plasma (t1/2 = 1 h), resulting in antitumor efficacy in a syngeneic 4 T1 breast tumor model.