Recent Developments in Drug Delivery to Prolong Allograft Survival in Lung Transplant Patients

Mitigation of Tacrolimus-Associated Nephrotoxicity by PLGA Nanoparticulate Delivery Following Multiple Dosing to Mice while Maintaining its Immunosuppressive Activity

The aim of this study was to assess the ability of PLGA nanoparticles (NPs) to reduce the tacrolimus (TAC)-associated nephrotoxicity following multiple dose administration. The mean diameter of prepared NPs was in the range of 227 to 263 nm with an 8.32% drug loading (w/w). Moreover, in vitro release profile of TAC-loaded NPs showed a sustained release of the drug with only less than 30% release within 12 days. Flow cytometry as well as fluorescence microscopy results confirmed the uptake of FITC-labelled PLGA NPs by dendritic cells. The ex vivo study showed that TAC-loaded NPs caused a significant suppression of the proliferation of CD4⁺ and CD8⁺ cells, which was comparable to the control formulation (Prograf). In vivo immunosuppressive activity as well as the kidney function were assessed following drug administration to mice. The animals received TAC subcutaneously at a daily dose of 1 mg/kg for 30 days delivered as the control formulation (Prograf) or TAC-loaded NPs. The results revealed significantly lower drug-associated toxicity with an activity comparable to Prograf for TAC-loaded PLGA NPs. These findings show a potential for PLGA NPs in reducing the nephrotoxicity of TAC while preserving the immunosuppressive activity.

Reduced variability in tacrolimus pharmacokinetics following intramuscular injection compared to oral administration in cynomolgus monkeys: Investigating optimal dosing regimens

Tacrolimus is one of the most commonly used immunosuppressive agents in animal models of transplantation. However, in these models, oral administration is often problematic due to the lowered compliance associated with highly invasive surgery and due to malabsorption in the intestinal tract. Therefore, we carried out a study to determine the pharmacokinetics of tacrolimus after intramuscular (IM) injection and to determine the optimal IM dosing regimens in primate models. Six male cynomolgus monkeys (Macaca fascicularis) were used in the study. Doses of 0.1 mg/kg and 5 mg were administered via IM injection and oral administration, respectively, once to determine single-dose pharmacokinetics and once daily for 5 days to determine multiple-dose pharmacokinetics. According to pharmacokinetic model estimates, the inter- and intra-individual variabilities in bioavailability following IM injection were remarkably reduced compared with those following oral administration. Monte Carlo simulations revealed that C_peak, C_trough and AUC would also have less variability following IM injection compared with oral administration. In this study, we found that the pharmacokinetic characteristics of tacrolimus were more constant following IM injection compared with oral administration. These results suggest that IM injection can be an alternative route of administration fin non-human primate model studies.

The analysis of pneumatic atomization of Newtonian and non-Newtonian fluids for different medical nebulizers

OBJECTIVE

The article contains results of the experimental studies on atomization process of inhaled drugs and aqueous solutions of glycerol with aqueous solutions of glycerol polyacrylamide (Rokrysol WF1) in pneumatic nebulizers. In experiments, the different concentration of aqueous solutions of glycerol polyacrylamide have been tested. In addition, the effect of nebulizer design on atomization process has been determined. The one of the main elements of medical pneumatic nebulizer is nebulizer cup.

SIGNIFICANCE

The experiment with this scope is new and is very important from the point of view of aerosol therapy.

METHODS

The results have been obtained by the use of the digital microphotography technique. In order to determine a physicochemical properties of tested liquids, a rheological measurements and measurements of the surface tension were carried out.

RESULTS

The differences between characteristics of aerosol for the liquids have been observed. The analysis of the droplets size distributions shows that the different diameters of droplets for Newtonian and non-Newtonian fluids have been formed during atomization in pneumatic nebulizers equipped with different nebulizer cups. The effect of the mouthpiece location on the droplets diameters has been shown.

CONCLUSIONS

Precise design of nebulizer and nebulizer cups, and also physicochemical properties of atomized liquids are of high importance in order to the effectiveness of drug delivery to patient's respiratory tracts.

Nanotechnological Approaches to Immunosuppression and Tolerance Induction

PURPOSE OF REVIEW

Several preclinical studies have engineered nanoparticles for immune regulation, and have shown promising results in the fields of autoimmunity and cancer. In solid organ transplantation, the use of nanoparticle-based immune regulation has only just begun to emerge but holds significant promise for the improvement of our current standard of care immunosuppressive regimens. In this review, we will shed light on the current status of nanoparticle-engineered immunotherapeutics, and the potential application of these technologies to the field of organ transplantation. Further we discuss different strategies for delivery and potential cellular targeting moieties that could be utilized to obviate the need for high dose systemic immunosuppressive regimens.

RECENT FINDINGS

Recent studies have shown the potential of immunosuppressive laden nanoparticles to increase bioavailability, drug release, and specifically target immune cell compartments as methods to provide recipient immunosuppressive sparing strategies.

SUMMARY

Nanoparticle centered immunosuppressive strategies hold the potential to usher in a new era in transplant recipient management and could hold the key to minimizing off-target effects of immunosuppressants, along with prolonging transplant survival.

Reformulating cyclosporine A (CsA): More than just a life cycle management strategy

Cyclosporine A (CsA) is a well-known immunosuppressive agent that gained considerable importance in transplant medicine in the late 1970s due to its selective and reversible inhibition of T-lymphocytes. While CsA has been widely used to prevent graft rejection in patients undergoing organ transplant it was also used to treat several systemic and local autoimmune disorders. Currently, the neuro- and cardio-protective effects of CsA (CiCloMulsion®; NeuroSTAT®) are being tested in phase II and III trials respectively and NeuroSTAT® received orphan drug status from US FDA and Europe in 2010. The reformulation strategies focused on developing Cremophor® EL free formulations and address variable bioavailability and toxicity issues of CsA. This review is an attempt to highlight the progress made so far and the room available for further improvements to realize the maximum benefits of CsA.

Solid self-nanoemulsifying drug delivery system (SNEDDS) for enhanced oral bioavailability of poorly water-soluble tacrolimus: physicochemical characterisation and pharmacokinetics

To develop a novel self-nanoemulsifying drug delivery system (solid SNEDDS) with better oral bioavailability of tacrolimus, the solid SNEDDS was obtained by spray-drying the solutions containing the liquid SNEDDS and colloidal silica. Its reconstitution properties were determined and correlated to solid state characterisation of the powder. Moreover, the dissolution and pharmacokinetics in rats was done in comparison to the commercial product. Among the liquid SNEDDS formulations tested, the liquid SNEDDS comprised of Capryol PGMC, Transcutol HP and Labrasol (10:15:75, v/v/v) presented the highest dissolution rate. In the solid SNEDDS, this liquid SNEDDS was absorbed in the pores and attached onto the surface of the colloidal silica. Drug was present in the amorphous state in it. The solid SNEDDS with 5% w/v tacrolimus produced the nanoemulsions and improved the oral bioavailability of tacrolimus in rats. Therefore, this solid SNEDDS would be a potential candidate for enhancing the oral bioavailability of tacrolimus.

Development of novel fast-dissolving tacrolimus solid dispersion-loaded prolonged release tablet

The goal of this research was to develop a novel prolonged release tablet bioequivalent to the commercial sustained release capsule. A number of tacrolimus-loaded fast-dissolving solid dispersions containing various amounts of DOSS were prepared using the spray drying technique. Their solubility, dissolution and pharmacokinetics in rats were studied. DOSS increased drug solubility and dissolution in the solid dispersions. Compared with the drug powder, the solubility, dissolution and bioavailability of tacrolimus with the fast-dissolving solid dispersion containing tacrolimus/HP-β-CD/DOSS in the weight ratio of 5:40:4 were boosted by approximately 700-, 30- and 2-fold, respectively. Several tablet formulations were accomplished with this solid dispersion in combination with various ratios of HPMC/ethylcellulose. The release behaviour and pharmacokinetic studies in beagle dogs were assessed compared with the commercial prolonged release capsule. A decrease in HPMC/ethylcellulose ratios reduced the dissolution of tacrolimus from the tablets. Particularly, the tacrolimus-loaded prolonged release tablet consisting of fast-dissolving tacrolimus solid dispersion, HPMC, ethylcellulose and talc at the weight ratio of 20:66:112:2 exhibited a dissolution profile similar to that produced by the commercial prolonged release capsule. Furthermore, there were no significant differences in the AUC, Cmax, Tmax and MRT values between them in beagle dogs. Consequently, this tacrolimus-loaded prolonged release tablet might be bioequivalent to the tacrolimus-loaded commercial capsule.

Characterization and pharmacokinetic analysis of tacrolimus dispersion for nebulization in a lung transplanted rodent model

Lung transplantation animal models have been well established and enabled the investigation of a variety of new pharmacotherapeutic strategies for prevention of lung allograft rejection. Direct administration of immunosuppressive agents to the lung is a commonly investigated approach; however, can prove challenging due to the poor solubility of the drug molecule, the tortuous pathways of the lung periphery, and the limited number of excipients approved for inhalation. In this study, we aimed to evaluate a solubility enhancing formulation of tacrolimus for localized therapy in a lung transplanted rat model and determine the extent of drug absorption into systemic circulation. Characterization of the nebulized tacrolimus dispersion for nebulization showed a fine particle fraction (FPF) of 46.1% and a mass median aerodynamic diameter (MMAD) of 4.06 microm. After single dose administration to transplanted and non-transplanted rats, a mean peak transplanted lung concentration of 399.8+/-29.2 ng/g and mean peak blood concentration of 4.88+/-1.6 ng/mL were achieved. It is theorized that enhanced lung retention of tacrolimus is due to lipophilic associations with bronchial tissue and phospholipid surfactants in lung fluid. These findings indicate that tacrolimus dispersion for nebulization can achieve highly localized therapy for lung transplant recipients.