Seung Rim Hwang

Nano-enabled delivery systems across the blood–brain barrier

The development of drugs to treat disorders of the central nervous system (CNS) faces difficulties in achieving penetration of a drug through the blood–brain barrier (BBB) and allowing the drug to reach its intended target in the brain. There have been strategies to improve drug delivery to the brain through endogenous transport pathways such as passive diffusion, endocytosis, and active transport. Among various strategies, nano-enabled delivery systems offer a promising solution to improve the uptake and targeted delivery of drugs into the brain. Various nanocarriers including liposomes, bolaamphiphiles and nanoparticles can be used as a means to encapsulate drugs, either alone or in combination with targeting ligands. Moreover, most of materials used in nanocarrier fabrication are both biodegradable and biocompatible, thereby increasing the clinical utility of them. Here, we review the possibility to employ nano-enabled materials for delivery of drug across the BBB and the recent advances in nanotechnologies for therapy of the CNS diseases.

Advances in oral macromolecular drug delivery

Introduction: Various macromolecules including polypeptides, proteins, genes and polysaccharides have been drawing attention for their therapeutic potential. The passage through intestinal epithelium is the major barrier for the oral delivery of macromolecules, by either paracellular or transcellular pathways. However, most macromolecules are poorly absorbed in oral route due to their high molecular weight and low stability in the gastrointestinal (GI) tract. Nonetheless, advancing in oral macromolecular drug delivery will be significant in expanding the clinical use of therapeutic macromolecules. Areas covered: Technologies using chemical conjugation, absorption enhancers and nano-/micro-particulate systems have been developed to improve oral bioavailability of macromolecules, and some of them are in the process of clinical trials. In this review, they are discussed in the context of their progression states, hurdles and modes of action. Expert opinion: According to the better understanding of receptor or transporter structure and transport mechanisms in the GI tract, the progress ineffective oral delivery systems for therapeutic macromolecules is anticipated over the next decades. In addition, the advent of numerous particulate systems will also speed up the development of novel drug delivery technologies. This offers an optimistic perspective on the potential clinical usage of oral macromolecular drugs.

Preliminary safety evaluation of a taurocholate-conjugated low-molecular-weight heparin derivative (LHT7): a potent angiogenesis inhibitor

In our previous studies, taurocholic acid (TA)‐conjugated low‐molecular‐weight heparin derivative (LHT7) has been proven to be a potent anti‐angiogenic agent by demonstrated successful blockage capability of vascular endothelial growth factors (VEGF). Preliminary safety evaluations were conducted based on its mechanism of action and chemical behavior. For this purpose, acute toxicity study, and hematological and serological evaluations were carried out. Additionally, in order to evaluate mechanism‐related side effects, both blood pressure and the occurrence of proteinuria were measured using a treatment regime of multiple high doses of LHT7 in a biodistribution study. LD50 values for LHT7 in female and male mice were 56.9 and 64.7 mg kg–1 doses, respectively. There were no vital fluctuations in the serological and hematological parameters, except for the elevated levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) at 100 and 200 mg kg–1 doses of LHT7, representing vital changes in the liver function. Moreover, the results of mechanism‐related studies showed that blood pressure at 50 mg kg–1 did not change but showed elevated levels of protein in urine. In the biodistribution study, a slight accumulation of LHT7 in the kidney and the liver were observed at the 50 mg kg–1 repeated dose owing to the presence of bile acid. No fatal damage was observed in this study; most observations were related to the chemical composition or the mechanism of action of the material. Copyright

Safety studies on intravenous infusion of a potent angiogenesis inhibitor: taurocholate-conjugated low molecular weight heparin derivative LHT7 in preclinical models

Abstract Context: As a class of angiogenesis inhibitors, heparin conjugates have shown significant effectiveness in several studies. Objectives: The purpose of our current study is to evaluate the effectiveness and safety of infusing the conjugate of low molecular weight heparin and taurocholate (LHT7), which has been developed as a potent angiogenesis inhibitor. Methods: To evaluate its safety, the method of intravenous infusion was compared with its i.v. bolus administration. Intravenous infusion was administered at a rate of 400 μl/min/kg of body weight for 30 min. Pharmacokinetic (PK) analysis, organ accumulation, and plasma concentration profiles of LHT7 were measured. The anticancer effect of LHT7 was evaluated in murine and human xenograft models, and preclinical studies were performed in SD rats and beagle dogs. Results: The results of the PK studies showed reduced organ accumulation in mice and the AUC(0–96 h) (area under the curve) was increased up to 1485 ± 125 h × μg/ml. The efficacy, at dose 1 mg/kg/2 d was higher for i.v. infusion than for i.v. bolus administration in both murine and human cancer models. The preclinical studies showed the safety dose of LHT7 is less than 20 mg/kg in SD rats and in the next safety analysis in beagle dogs showed that there were no organ-specific adverse effects in higher doses, such as, 12 mg/kg. LHT7 showed sustained effects with minimized adverse events when administered through i.v. infusion. Conclusions: LHT7 (i.v. infusion) could be safely used for further clinical development as a multi-targeting anti-angiogenic agent.

Preclinical safety evaluation of low molecular weight heparin-deoxycholate conjugates as an oral anticoagulant.

The preclinical safety of a newly developed oral anticoagulant, the low molecular weight heparin–deoxycholate conjugate (OH09208), was evaluated by a comprehensive evaluating program in compliance with standard guidelines. The single dose oral toxicity study in rats receiving 2000 and 5000 mg kg−1 of OH09208 did not reveal any mortality, unusual body weight changes or necropsy findings. The results of the 4‐week oral toxicity study with a 4‐week recovery program in rats receiving OH09208 in doses of 100, 300 and 1000 mg kg−1 day−1 did not reveal any mortality, or indicate any unusual clinical signs, or show any toxicokinetic relationships to the administration of OH09208. Although the increase in liver enzymes in one male dog treated with 300 mg kg−1 day−1 and one female dog treated with 1000 mg kg−1 day−1 could not be excluded from the effect of the test substance, no other toxicologically significant changes were observed in the 4‐week oral toxicity study with a 4‐week recovery in beagle dogs. Thus, while the no‐observed‐adverse‐effect level value from the 4‐week study in both male and female rats was 1000 mg kg−1 day−1, those from the 4‐week study in male and female beagle dogs were 300 and 1000 mg kg−1 day−1, respectively. Furthermore, OH09208 did not induce anaphylactic reactions in guinea pigs, micronucleated bone marrow cells in male ICR mice, chromosomal aberration in Chinese hamster lung cell lines, bacterial reverse mutation, and any abnormalities in hERG current assay, mouse central nervous system and dog cardiovascular studies. Overall, there were no unexpected toxicities in this preclinical study that might have precluded the safe administration of OH09208 to humans. Copyright

Preparation and in vivo evaluation of an orally available enteric-microencapsulated parathyroid hormone (1-34)-deoxycholic acid nanocomplex.

The N-terminal 34-amino-acid peptide fragment of human parathyroid hormone PTH (1-34), is used clinically to treat osteoporosis; however, it is currently administered by a once-daily subcutaneous injection, resulting in poor patient compliance. We have developed enteric microcapsules containing an ionic nanocomplex between PTH (1-34) and lysine-linked deoxycholic acid (LysDOCA) for the oral delivery of PTH (1-34). We measured the particle size of the PTH/LysDOCA complex and assessed its biological activity by determining the cAMP content in MC3T3-E1 cells. We also assessed its permeability across a Caco-2 cell monolayer and the bioavailability of the intrajejunally administered PTH/LysDOCA complex compared with PTH (1-34) in rats. In addition, the antiosteoporotic activity of the PTH/LysDOCA complex, encapsulated in an enteric carrier by coaxial ultrasonic atomization, was evaluated after it was orally administered to ovariectomized (OVX) rats. The formation of an ionic complex between PTH (1-34) and LysDOCA produced nanoparticles of diameter 33.0±3.36 nm, and the bioactivity of the complex was comparable with that of PTH (1-34). The Caco-2 cell permeability and AUClast value of the PTH/LysDOCA (1:10) nanocomplex increased by 2.87- and 16.3-fold, respectively, compared with PTH (1-34) alone. Furthermore, the OVX rats treated with oral PTH/LysDOCA-loaded enteric microcapsules showed an increase in bone mineral density (159%), bone volume fraction (175%), and trabecular number (174%) compared with those in the OVX control group. Therefore, the PTH/LysDOCA nanocomplex oral delivery system is a promising treatment modality for osteoporosis because it improves osteogenesis and trabecular connectivity.

Self-assembled nanocomplex of PEGylated protamine and heparin–suramin conjugate for accumulation at the tumor site

Heparin-like sulfated polysaccharides are potential drug candidates owing to their ability to interact with angiogenic factors and inhibit angiogenesis, tumor growth, and metastasis. This study aimed to improve the delivery of heparin-like anticancer polysaccharides for accumulation at the tumor site. We designed a nanocarrier system using protamine attached to polyethylene glycol (PEG) and evaluated the stability, tumor targeting, and tumor growth inhibition of the nanocarrier loaded with heparin derivatives. When mixed with various polyanionic heparin derivatives, the polycationic PEG-protamine formed stable self-assembled nanocomplexes via ionic interactions, with flexible PEG chains located on the outside. Among the complexes, a nanocomplex loaded with a low-molecular-weight heparin-suramin conjugate (LHsura) had the most suitable average size (101.9nm) for the enhanced permeability and retention effect and allowed accumulation of LHsura at the tumor site for up to 48h. In a tumor-bearing mouse model, the PEG-protamine and LHsura nanocomplex (10mg/kg/3days, intravenously), which could be extravasated through the tumor vasculature, significantly inhibited tumor growth, more than LHsura alone did. Overall, the self-assembled nanocomplexation of PEG-protamine and LHsura helped control the release and extravasation of LHsura, which resulted in an antitumor effect on the target tumor cells.