Recent advances in prodrug-based nanoparticle therapeutics.

Extensive research into prodrug modification of active pharmaceutical ingredients and nanoparticle drug delivery systems has led to unprecedented levels of control over the pharmacological properties of drugs and resulted in the approval of many prodrug or nanoparticle-based therapies. In recent years, the combination of these two strategies into prodrug-based nanoparticle drug delivery systems (PNDDS) has been explored as a way to further advance nanomedicine and identify novel therapies for difficult-to-treat indications. Many of the PNDDS currently in the clinical development pipeline are expected to enter the market in the coming years, making the rapidly evolving field of PNDDS highly relevant to pharmaceutical scientists. This review paper is intended to introduce PNDDS to the novice reader while also updating those working in the field with a comprehensive summary of recent efforts. To that end, first, an overview of FDA-approved prodrugs is provided to familiarize the reader with their advantages over traditional small molecule drugs and to describe the chemistries that can be used to create them. Because this article is part of a themed issue on nanoparticles, only a brief introduction to nanoparticle-based drug delivery systems is provided summarizing their successful application and unfulfilled opportunities. Finally, the review's centerpiece is a detailed discussion of rationally designed PNDDS formulations in development that successfully leverage the strengths of prodrug and nanoparticle approaches to yield highly effective therapeutic options for the treatment of many diseases.

Development and Preclinical Evaluation of New Inhaled Lipoglycopeptides for the Treatment of Persistent Pulmonary Methicillin-Resistant Staphylococcus aureus Infections.

Chronic pulmonary methicillin-resistant Staphylococcus aureus (MRSA) disease in cystic fibrosis (CF) has a high probability of recurrence following treatment with standard-of-care antibiotics and represents an area of unmet need associated with reduced life expectancy. We developed a lipoglycopeptide therapy customized for pulmonary delivery that not only demonstrates potent activity against planktonic MRSA, but also against protected colonies of MRSA in biofilms and within cells, the latter of which have been linked to clinical antibiotic failure. A library of next-generation potent lipoglycopeptides was synthesized with an emphasis on attaining superior pharmacokinetics (PK) and pharmacodynamics to similar compounds of their class. Our strategy focused on hydrophobic modification of vancomycin, where ester and amide functionality were included with carbonyl configuration and alkyl length as key variables. Candidates representative of each carbonyl attachment chemistry demonstrated potent activity in vitro, with several compounds being 30 to 60 times more potent than vancomycin. Selected compounds were advanced into in vivo nose-only inhalation PK evaluations in rats, where RV94, a potent lipoglycopeptide that utilizes an inverted amide linker to attach a 10-carbon chain to vancomycin, demonstrated the most favorable lung residence time after inhalation. Further in vitro evaluation of RV94 showed superior activity to vancomycin against an expanded panel of Gram-positive organisms, cellular accumulation and efficacy against intracellular MRSA, and MRSA biofilm killing. Moreover, in vivo efficacy of inhaled nebulized RV94 in a 48 h acute model of pulmonary MRSA (USA300) infection in neutropenic rats demonstrated statistically significant antibacterial activity that was superior to inhaled vancomycin.

Antifungal Efficacy of an Intravenous Formulation Containing Monomeric Amphotericin B, 5-Fluorocytosine, and Saline for Sodium Supplementation.

PURPOSE: Amphotericin B (AmB) and 5-fluorocytosine (5-FC) exhibit additive to synergistic activity against systemic mycoses. Incompatibility of prescribed formulations precludes concomitant IV administration, a route with distinct advantages. Previously, we used PEG-DSPE micelles to produce a reformulation of Fungizone (AmB-SD), AmB solubilized by sodium deoxycholate, called mAmB-90. Herein, we describe a second reformulation that facilitates co-delivery of mAmB-90 and 5-FC, and evaluate the effect of PEG-DSPE micelles on the combination's activity against Candida albicans. METHODS: We assessed the effect of 5-FC addition on the stability, in vitro toxicity, and antifungal efficacy of mAmB-90. The aggregation state and particle size of mAmB-90 combined with 5-FC (FmAmB-90) was evaluated over 48 h. Hemolytic activity was measured in vitro. Antifungal activity was determined in vitro against C. albicans. The efficacy of monotherapy and combination treatment was evaluated in a neutropenic mouse model of disseminated candidiasis. RESULTS: The aggregation state, particle size, and hemolytic activity of mAmB-90 were unaffected by 5-FC. While antifungal activity was similar in vitro, mAmB-90 alone and combined with 5-FC was more potent than AmB-SD in vivo. CONCLUSIONS: Short-term stability and in vivo efficacy of our formulation suggest potential to simultaneously deliver AmB and 5-FC for potent antifungal efficacy.

Pharmacokinetics and Renal Toxicity of Monomeric Amphotericin B in Rats after a Multiple Dose Regimen.

BACKGROUND: Delivery of monomeric Amphotericin B (AmB), i.e. deaggregated AmB, has been a major tactic in the reduction of renal toxicity at a membrane level, taking advantage of the selectivity of monomeric AmB for binding ergosterol over cholesterol. OBJECTIVE: The aim of this study was to characterize the pharmacokinetic (PK) and renal toxicity of monomeric AmB in rats following a multiple dose regimen. METHOD: AmB existed primarily in a monomeric state in poly(ethylene glycol)-block-poly(N-hexyl stearate L-aspartamide) (PEG-b-PHSA) micelles (mAmB) at 2:1 ratio (mol:mol), whereas AmB as its standard formulation, Fungizone®, was highly self-aggregated based on absorption spectroscopy. RESULTS: After single intravenous injection, mAmB significantly (p < 0.001) increased the area under the plasma drug concentration-time curve (AUC) and reduced the volume of distribution (Vd) and total systemic clearance (CL) relative to Fungizone®. After daily intravenous injections at dose of 1.0 mg/kg for 7 days, PK parameters of mAmB and Fungizone® were similar to day 1. The treatment of Fungizone® also significantly (p < 0.05) increased levels of urinary enzymes, N-acetyl-ß-D-glucosaminidase (NAG) and kidney injury molecule-1 (KIM-1) by 3.1- and 3.0 fold, respectively, whereas levels of NAG and KIM-1 were unchanged for mAmB, consistent with hematoxylin and eosin (H&E) staining of excised kidneys. CONCLUSION: In summary, mAmB has less renal toxicity than AmB as Fungizone® in rats after a multiple dose regimen, validating the aggregation state hypothesis of AmB in vivo.

Pharmacokinetics, antitumor and cardioprotective effects of liposome-encapsulated phenylaminoethyl selenide in human prostate cancer rodent models.

PURPOSE: Cardiotoxicity associated with the use of doxorubicin (DOX), and other chemotherapeutics, limits their clinical potential. This study determined the pharmacokinetics and antitumor and cardioprotective activity of free and liposome encapsulated phenyl-2-aminoethyl-selenide (PAESe). METHODS: The pharmacokinetics of free PAESe and PAESe encapsulated in liposomes (SSL-PAESe) were determined in rats using liquid chromatography tandem mass-spectrometry. The antitumor and cardioprotective effects were determined in a mouse xenograft model of human prostate (PC-3) cancer and cardiomyocytes (H9C2). RESULTS: The encapsulation of PAESe in liposomes increased the circulation half-life and area under the drug concentration time profile, and decreased total systemic clearance significantly compared to free PAESe. Free- and SSL-PAESe improved survival, decreased weight-loss and prevented cardiac hypertrophy significantly in tumor bearing and healthy mice following treatment with DOX at 5 and 12.5 mg/kg. In vitro studies revealed PAESe treatment altered formation of reactive oxygen species (ROS), cardiac hypertrophy and gene expression, i.e., atrial natriuretic peptide and myosin heavy chain complex beta, in H9C2 cells. CONCLUSIONS: Treatment with free and SSL-PAESe exhibited antitumor activity in a prostate xenograft model and mitigated DOX-mediated cardiotoxicity.

The antioxidant phenylaminoethyl selenide reduces doxorubicin-induced cardiotoxicity in a xenograft model of human prostate cancer.

Anthracyclines are potent anticancer agents, but cardiotoxicity mediated by free radical generation limits their clinical use. This study evaluated the anticancer activity of phenyl-2-aminoethyl selenide (PAESe) and its potential to reduce doxorubicin (DOX)-induced cardiotoxicity. Growth inhibitory effects of PAESe with DOX, and vincristine, clinically used anticancer agents, and tert-butylhydroperoxide (TBHP), a known oxidant, on the growth of human prostate carcinoma (PC-3) cells was determined. PAESe (≤1µm) did not alter the growth of PC-3 cells, however, concomitant use of PAESe decreased the oxidative-mediated cytotoxicity of TBHP, but had limited effect on vincristine or DOX activity. Further, PAESe decreased the formation of intracellular reactive oxygen species from TBHP and DOX. The effect of PAESe on the activity of DOX was determined using a tumor (PC-3) xenograft model in mice. PAESe did not alter DOX antitumor activity and showed evidence of direct antitumor activity relative to controls. DOX treatment decreased mice body weight significantly, whereas concomitant administration of PAESe and DOX was similar to controls. Most importantly, PAESe decreased DOX-mediated infiltration of neutrophil and macrophages into the myocardium. These data suggest PAESe had in vivo antitumor activity and in combination with DOX decreased early signs of cardiotoxicity while preserving its antitumor activity.

Interpenetrating polymer network (IPN) scaffolds of sodium hyaluronate and sodium alginate for chondrocyte culture.

In this study, porous sodium hyaluronic acid/sodium alginate (HA/SA) scaffold based on interpenetrating polymeric network (IPN) technique has been fabricated, where HA and SA were cross-linked with poly(ethylene glycol) diglycidyl ether (PEGDG) and calcium chloride, respectively. The mean pore size and the swelling ratio of fabricated scaffolds decreased, and the compressive strength increased as the content of SA increased in HA/SA IPN scaffold. Rabbit chondrocytes were seeded within the HA/SA IPN scaffolds, and then their proliferation as well as chondrogenic differentiation was examined. DNA contents observed from the chondrocytes cultured in the IPN scaffolds increased with time over 21 days, which demonstrated that the rabbit chondrocytes continued to proliferate in HA/SA scaffolds. Results of the 1,9-dimethylmethylene blue (DMMB) and p-dimethylaminobenzaldehyde (DMBA) assays showed that glycosaminoglycan (s-GAG) and collagen contents increased over culture period, indicating the chondrogenic differentiation in the scaffold. Reverse transcription-polymerase chain reaction (RT-PCR) results showed the expression of type II collagen, the main chondrogenic differentiation marker. The bands indicating mRNA expression of type II collagen increased with the culture period. These results demonstrated that the porous HA/SA IPN scaffolds were successfully prepared and could serve as an effective delivery system of the three-dimensional culture of chondrocytes.

Novel porous matrix of hyaluronic acid for the three-dimensional culture of chondrocytes.

A novel three-dimensional (3D) scaffold of chemically unmodified hyaluronic acid (HA) with minimum cross-linkage was developed for the culture of chondrocytes, thereby to promote cartilage repair. The porous structure of the scaffold was observed by scanning electron microscopy (SEM), and the pore size was controlled by fabrication conditions including swelling time and composition of the HA matrix. Rabbit primary chondrocytes and human chondrocytic cell lines (C-20/A4) were cultured in the HA matrix to investigate whether they can be applied to construct the cartilage tissue in vitro. The chondrocytes retained chondrocytic spherical morphology in this HA matrix. Moreover, results from the MTT assay showed good cellular viability within the HA matrix; optical density increased for up to 28 days, demonstrating that the cells continued to proliferate inside the HA matrix. Phenotypic analysis (RT-PCR, Alcian blue staining and quantification of s-GAG) showed that chondrocytes, when three-dimensionally cultured within the HA matrix, expressed transcripts encoding collagen type II and aggrecan, and produced sulfated glycosaminoglycans (s-GAG), indicating chondrogenic differentiation. The new HA matrix therefore appears as a potentially promising scaffold for the three-dimensional culture of chondrocytes for cartilage tissue engineering.