Liposome-encapsulated prednisolone phosphate inhibits growth of established tumors in mice

CRISPR-Cas9 genome and long non-coding RNAs as a novel diagnostic index for prostate cancer therapy via liposomal-coated compounds

CRISPR/Cas9 is a recently discovered genomic editing technique that altered scientist's sight in studying genes function. Cas9 is controlled via guide (g) RNAs, which match the DNA targeted in cleavage to modify the respective gene. The development in prostate cancer (PC) modeling directed not only to novel resources for recognizing the signaling pathways overriding prostate cell carcinoma, but it has also created a vast reservoir for complementary tools to examine therapies counteracting this type of cancer. Various cultured somatic rat models for prostate cancer have been developed that nearly mimic human prostate cancer. Nano-medicine can passively target cancer cells via increasing bioavailability and conjugation via specific legend, contributing to reduced systemic side-effects and increased efficacy. This article highlights liposomal loaded Nano-medicine as a potential treatment for prostate cancer and clarifies the CRISPR/Cas9 variation accompanied with prostate cancer. PC is induced experimentally in western rat model via ethinyl estradiol for 4 weeks and SC. dose of 3, 2'- dimethyl-4-aminobiphenyl estradiol (DAE) (50mg/kg) followed by treatment via targeted liposomal-coated compounds such as liposomal dexamethasone (DXM), liposomal doxorubicin (DOX) and liposomal Turmeric (TUR) (3mg/kg IP) for four weeks in a comparative study to their non-targeted analogue dexamethasone, doxorubicin and Turmeric. 3, 2'- dimethyl-4-aminobiphenylestradiol elicit prostate cancer in western rats within 5 months. Simultaneous supplementations with these liposomal compounds influence on prostate cancer; tumor markers were investigated via prostate-specific antigen (PSA), Nitric oxide (NOX) and CRISPR/Cas9 gene editing. Several long non-coding RNAs were reported to be deregulated in prostate cell carcinoma, including MALAT1. On the other hand, gene expression of apoptotic biomarkers focal adhesion kinase (AKT-1), phosphatidylinistol kinase (PI3K) and glycogen synthase kinase-3 (GSK-3) was also investigated and further confirming these results via histopathological examination. Liposomal loaded dexamethasone; doxorubicin and Turmeric can be considered as promising therapeutic agents for prostate cancer via modulating CRISPR/Cas9 gene editing and long non coding gene MALAT1.

A phase I first-in-man study to investigate the pharmacokinetics and safety of liposomal dexamethasone in patients with progressive multiple myeloma

Despite the introduction of multiple new drugs and combination therapies, conventional dexamethasone remains a cornerstone in the treatment of multiple myeloma (MM). Its application is, however, limited by frequent adverse effects of which the increased infection rate may have the strongest clinical impact. The efficacy-safety ratio of dexamethasone in MM may be increased by encapsulation in long-circulating PEG-liposomes, thereby both enhancing drug delivery to MM lesions and reducing systemic corticosteroid exposure. We evaluated the preliminary safety and feasibility of a single intravenous (i.v.) infusion of pegylated liposomal dexamethasone phosphate (Dex-PL) in heavily pretreated relapsing or progressive symptomatic MM patients within a phase I open-label non-comparative interventional trial at two dose levels. In the 7 patients that were enrolled (prior to having to close the study prematurely due to slow recruitment), Dex-PL was found to be well tolerated and, as compared to conventional dexamethasone, no new or unexpected adverse events were detected. Pharmacokinetic analysis showed high and persisting concentrations of dexamethasone in the circulation for over a week after i.v. administration, likely caused by the long-circulation half-life of the liposomes that retain dexamethasone as the inactive phosphate prodrug form, something which could significantly limit systemic exposure to the active parent drug. Thus, despite the limitations of this small first-in-man trial, Dex-PL seems safe and well tolerated without severe side effects. Follow-up studies are needed to confirm this in a larger patient cohort and to evaluate if i.v. Dex-PL can provide a safer and more efficacious dexamethasone treatment option for MM.

Skin drug delivery using lipid vesicles: A starting guideline for their development

Lipid vesicles can provide a cost-effective enhancement of skin drug absorption when vesicle production process is optimised. It is an important challenge to design the ideal vesicle, since their properties and features are related, as changes in one affect the others. Here, we review the main components, preparation and characterization methods commonly used, and the key properties that lead to highly efficient vesicles for transdermal drug delivery purposes. We stand by size, deformability degree and drug loading, as the most important vesicle features that determine the further transdermal drug absorption. The interest in this technology is increasing, as demonstrated by the exponential growth of publications on the topic. Although long-term preservation and scalability issues have limited the commercialization of lipid vesicle products, freeze-drying and modern escalation methods overcome these difficulties, thus predicting a higher use of these technologies in the market and clinical practice.

Radiation-assisted strategies provide new perspectives to improve the nanoparticle delivery to tumor

Nanoparticles (NPs), with advantages in tumor targeting, have been extensively developed for anticancer treatment. However, the delivery efficacy of NPs tends to be heterogeneous in clinical research. Surprisingly, a traditional cancer treatment, radiotherapy (radiation), has been observed with the potential to improve the delivery of NPs by influencing the features of the tumor microenvironment, which provides new perspectives to overcome the barriers in the NPs delivery. Since the effect of radiation can also be enhanced by versatile NPs, these findings of radiation-assisted NPs delivery suggest innovative strategies combining radiotherapy with nanotherapeutics. This review summarizes the research on the delivery and therapeutic efficacy of NPs that are improved by radiation, focusing on relative mechanisms and existing challenges and opportunities.

Macrophage phenotype-switching in cancer

Tumour-associated macrophages (TAMs) have been found to be of great importance in tumorigenesis and in promoting malignant progression, including tumour angiogenesis and metastasis. Moreover, the TAM phenotype is more likely to be an M2 type. Transforming TAMs by M2-polarization into the tumour-suppressive M1-phenotype is an important approach for tumour therapy. In this review, we analysed the effects of the tumour microenvironment on macrophage phenotype-switching, including hypoxia and cytokines, and the mechanisms of drugs targeting TAMs. Furthermore, we analysed the effects of exosomes on macrophage polarization, phenotype switching of macrophages, and the mechanisms of lipid mediators targeting TAMs.

Two Types of Liposomal Formulations Improve the Therapeutic Ratio of Prednisolone Phosphate in a Zebrafish Model for Inflammation

Glucocorticoids (GCs) are effective anti-inflammatory drugs, but their clinical use is limited by their side effects. Using liposomes to target GCs to inflammatory sites is a promising approach to improve their therapeutic ratio. We used zebrafish embryos to visualize the biodistribution of liposomes and to determine the anti-inflammatory and adverse effects of the GC prednisolone phosphate (PLP) encapsulated in these liposomes. Our results showed that PEGylated liposomes remained in circulation for long periods of time, whereas a novel type of liposomes (which we named AmbiMACs) selectively targeted macrophages. Upon laser wounding of the tail, both types of liposomes were shown to accumulate near the wounding site. Encapsulation of PLP in the PEGylated liposomes and AmbiMACs increased its potency to inhibit the inflammatory response. However, encapsulation of PLP in either type of liposome reduced its inhibitory effect on tissue regeneration, and encapsulation in PEGylated liposomes attenuated the activation of glucocorticoid-responsive gene expression throughout the body. Thus, by exploiting the unique possibilities of the zebrafish animal model to study the biodistribution as well as the anti-inflammatory and adverse effects of liposomal formulations of PLP, we showed that PEGylated liposomes and AmbiMACs increase the therapeutic ratio of this GC drug.

Remodeling tumor microenvironment by liposomal codelivery of DMXAA and simvastatin inhibits malignant melanoma progression

Anti-angiogenic therapies for melanoma have not yet been translated into meaningful clinical benefit for patients, due to the development of drug-induced resistance in cancer cells, mainly caused by hypoxia-inducible factor 1α (HIF-1α) overexpression and enhanced oxidative stress mediated by tumor-associated macrophages (TAMs). Our previous study demonstrated synergistic antitumor actions of simvastatin (SIM) and 5,6-dimethylxanthenone-4-acetic acid (DMXAA) on an in vitro melanoma model via suppression of the aggressive phenotype of melanoma cells and inhibition of TAMs-mediated angiogenesis. Therefore, we took the advantage of long circulating liposomes (LCL) superior tumor targeting capacity to efficiently deliver SIM and DMXAA to B16.F10 melanoma in vivo, with the final aim of improving the outcome of the anti-angiogenic therapy. Thus, we assessed the effects of this novel combined tumor-targeted treatment on s.c. B16.F10 murine melanoma growth and on the production of critical markers involved in tumor development and progression. Our results showed that the combined liposomal therapy almost totally inhibited (> 90%) the growth of melanoma tumors, due to the enhancement of anti-angiogenic effects of LCL-DMXAA by LCL-SIM and simultaneous induction of a pro-apoptotic state of tumor cells in the tumor microenvironment (TME). These effects were accompanied by the partial re-education of TAMs towards an M1 phenotype and augmented by combined therapy-induced suppression of major invasion and metastasis promoters (HIF-1α, pAP-1 c-Jun, and MMPs). Thus, this novel therapy holds the potential to remodel the TME, by suppressing its most important malignant biological capabilities.

Repurpose but also (nano)-reformulate! The potential role of nanomedicine in the battle against SARS-CoV2

The coronavirus disease-19 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) has taken the world by surprise. To date, a worldwide approved treatment remains lacking and hence in the context of rapid viral spread and the growing need for rapid action, drug repurposing has emerged as one of the frontline strategies in the battle against SARS-CoV2. Repurposed drugs currently being evaluated against COVID-19 either tackle the replication and spread of SARS-CoV2 or they aim at controlling hyper-inflammation and the rampaged immune response in severe disease. In both cases, the target for such drugs resides in the lungs, at least during the period where treatment could still provide substantial clinical benefit to the patient. Yet, most of these drugs are administered systemically, questioning the percentage of administered drug that actually reaches the lung and as a consequence, the distribution of the remainder of the dose to off target sites. Inhalation therapy should allow higher concentrations of the drug in the lungs and lower concentrations systemically, hence providing a stronger, more localized action, with reduced adverse effects. Therefore, the nano-reformulation of the repurposed drugs for inhalation is a promising approach for targeted drug delivery to lungs. In this review, we critically analyze, what nanomedicine could and ought to do in the battle against SARS-CoV2. We start by a brief description of SARS-CoV2 structure and pathogenicity and move on to discuss the current limitations of repurposed antiviral and immune-modulating drugs that are being clinically investigated against COVID-19. This account focuses on how nanomedicine could address limitations of current therapeutics, enhancing the efficacy, specificity and safety of such drugs. With the appearance of new variants of SARS-CoV2 and the potential implication on the efficacy of vaccines and diagnostics, the presence of an effective therapeutic solution is inevitable and could be potentially achieved via nano-reformulation. The presence of an inhaled nano-platform capable of delivering antiviral or immunomodulatory drugs should be available as part of the repertoire in the fight against current and future outbreaks.

Targeted Nanotherapeutics for Respiratory Diseases: Cancer, Fibrosis, and Coronavirus

Systemic delivery of therapeutics for treatment of lung diseases has several limitations including poor organ distribution of delivered payload with relatively low accumulation of active substances in the lungs and severe adverse side effects. In contrast, nanocarrier based therapeutics provide a broad range of opportunities due to their ability to encapsulate substances with different aqueous solubility, transport distinct types of cargo, target therapeutics specifically to the deceased organ, cell, or cellular organelle limiting adverse side effects and increasing the efficacy of therapy. Moreover, many nanotherapeutics can be delivered by inhalation locally to the lungs avoiding systemic circulation. In addition, nanoscale based delivery systems can be multifunctional, simultaneously carrying out several tasks including diagnostics, treatment and suppression of cellular resistance to the treatment. Nanoscale delivery systems improve the clinical efficacy of conventional therapeutics allowing new approaches for the treatment of respiratory diseases which are difficult to treat or possess intrinsic or acquired resistance to treatment. The present review summarizes recent advances in the development of nanocarrier based therapeutics for local and targeted delivery of drugs, nucleic acids and imaging agents for diagnostics and treatment of various diseases such as cancer, cystic fibrosis, and coronavirus.

Targeted miR-21 loaded liposomes for acute myocardial infarction

Acute and persistent myocardial ischemia is the main cause of acute myocardial infarction (AMI) and heart failure. MicroRNA-21(miR-21) contributes to the pathophysiological consequences of acute myocardial infarction by targeting downstream crucial regulators. Thus, miR-21 mimics are a promising strategy for the treatment of AMI. However, their poor stability and insufficient cellular uptake are the major challenges. Herein, we encapsulated miR-21 mimics into liposomes modified with the cardiac troponin T (cTnT) antibody for targeted delivery of miR-21(cT-21-LIPs) to the ischemic myocardium. The cT-21-LIPs exhibited enhanced targeting efficiency to hypoxia primary cardiomyocytes in vitro and improved accumulation in the ischemic heart of AMI rats after injection via the tail vein due to the specifical target to overexpressed troponin. The cT-21-LIPs could significantly improve the cardiac function and decrease the infarct size after AMI, while maintaining the viability of cardiomyocytes. This design provides a novel strategy for delivering small nucleotide drugs specifically to the infarcted heart, which may find great potential in clinics.

Assessments of in vitro and in vivo antineoplastic potentials of β-sitosterol-loaded PEGylated niosomes against hepatocellular carcinoma

β-sitosterol (BS), a phytosterol, exhibits ameliorative effects on hepatocellular carcinoma (HCC) due to its antioxidant activities. However, its poor aqueous solubility and negotiated bioavailability and short elimination half-life is a huge limitation for its therapeutic applications. To overcome these two shortcomings, BS-loaded niosomes were made to via, film hydration method and process parameters were optimized using a three-factor Box-Behnken design. The optimized formulation (BSF) was further surface-modified with polyethylene glycol (PEG). The resulting niosomes (BSMF) have spherical shapes, particle sizes, 219.6 ± 1.98 nm with polydispersity index (PDI) and zeta potential of 0.078 ± 0.04 and -19.54 ± 0.19 mV, respectively. The drug loading, entrapment efficiency, and drug release at 24 h of the BSMF were found to be 16.72 ± 0.09%, 78.04 ± 0.92%, and 75.10 ± 3.06%, respectively. Moreover, BSMF showed significantly greater cytotoxic potentials on Hep G2 cells with an enhanced cellular uptake relative to pure BS and BSF. The BSMF also displayed potentially improved curative property of HCC in albino wistar rat. Thus, the BSMF could be one of the promising therapeutic modalities for HCC treatment in terms of targeting potential resulting in enhanced therapeutic efficacy.

Complete Tumor Regression by Liposomal Bortezomib in a Humanized Mouse Model of Multiple Myeloma

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Liposomal simvastatin sensitizes C26 murine colon carcinoma to the antitumor effects of liposomal 5-fluorouracil in vivo

5-Fluorouracil-based therapy remains the main approach in colorectal cancer, even though there are still some drawbacks, such as chemoresistance. In this study we combined 5-fluorouracil encapsulated in long-circulating liposomes with simvastatin, also encapsulated in long-circulating liposomes, that was previously proved to exert antitumor actions on the same tumor model. The production of angiogenic/inflammatory proteins was assessed by protein array and the production of markers for tumor aggressiveness (Bcl-2, Bax, and nuclear factor [NF]-κB) were determined by western blot analysis. Intratumor oxidative stress was evaluated through measurement of malondialdehyde level by HPLC, and through spectrophotometric analysis of catalytic activity of catalase and of total antioxidant capacity. Immunohistochemical analysis of tumors for CD31 expression was assessed. Intratumor activity of MMP-2 by gelatin zymography was also carried out. Our results revealed that combined therapies based on liposomal formulations exerted enhanced antitumor activities compared with combined treatment with free drugs. Sequential treatment with liposomal simvastatin and liposomal 5-fluorouracil showed the strongest antitumor activity in C26 colon carcinoma in vivo, mainly through inhibition of tumor angiogenesis. Important markers for cancer progression (Bcl-2, Bax, NF-κB, and intratumor antioxidants) showed that liposomal simvastatin might sensitize C26 cells to liposomal 5-fluorouracil treatment in both regimens tested. The outcome of simultaneous treatment with liposomal formulations was superior to sequential treatment with both liposomal types as the invasive capacity of C26 tumors was strongly increased after the latest treatment. The antitumor efficacy of combined therapy in C26 colon carcinoma might be linked to the restorative effects on proteins balance involved in tumor angiogenesis.

Nanovesicles of sorbitan isostearate: a novel sustained-release non-ionic surfactant

Sorbitan isostearate (Span 120) is a novel non-ionic surfactant for development of vesicular systems. The present work aimed to develop, characterise and evaluate Span 120 based niosomes for enhanced drug delivery. Span 120 niosomes were prepared by using the thin-film hydration method and naproxen sodium was used as a model drug. Fourier transform infrared spectroscopy analysis was also done for preformulation studies. Niosomes prepared with Span 120 and cholesterol (2:1) were spherical, as shown by transmission electron microscopy, with a mean size of 173 ± 2·96 nm, a polydispersity index of 0·28 ± 0·02, a zeta potential of −50 ± 1·2 mV and an entrapment efficiency of 91·92%. The in vitro release study showed a sustained release (21·9%) of naproxen sodium in 12 h. The release kinetics was uniform and followed the Korsmeyer–Peppas model, with n > 0·5. Accordingly, niosomes with a molar ratio of 2:1 was selected for in vivo anti-inflammatory activity. A carrageenan-induced paw oedema test was performed, which showed an enhanced inhibitory effect of loaded niosomes with Span 120 compared to the standard drug. In conclusion, the use of Span 120 is a promising approach to formulating niosomes with an improved and sustained effect.

Co-delivery of curcumin and doxorubicin in PEGylated liposomes favored the antineoplastic C26 murine colon carcinoma microenvironment

Our recent studies have demonstrated that the antitumor efficacy of doxorubicin (DOX), administered in long-circulating liposomes (LCL), could be considerably improved after its co-encapsulation with curcumin (CURC). Thus, the question addressed within this article is whether LCL-CURC-DOX can be exploited more efficiently than liposomal DOX for future colorectal cancer therapy. Therefore, we investigated the physicochemical and biological properties of LCL-CURC-DOX and the mechanisms of its antitumor activity in C26 murine colon carcinoma in vivo. Our results proved that the developed nanoformulation based on the co-encapsulation of CURC and DOX met the requirements of a modern drug delivery system for future cancer therapy, demonstrating enhanced antitumor activity on C26 colon carcinoma in vivo. The antitumor efficacy of LCL-CURC-DOX relied on suppressive effects on main protumor processes such as angiogenesis, inflammation, oxidative stress, invasion and resistance to apoptosis, and on the dysregulation of Th1/Th2 cell axis which favored the antineoplastic phenotype of cells in tumor microenvironment (TME). The development of multitargeted strategies aiming at stimulating antitumor effects within the tumor milieu and counteracting the escape mechanisms of cancer cells would be beneficial in the management of colon cancer in the future.

Liposomal dexamethasone inhibits tumor growth in an advanced human-mouse hybrid model of multiple myeloma

Glucocorticoids are the cornerstone in the clinic for treatment of hematological malignancies, including multiple myeloma. Nevertheless, poor pharmacokinetic properties of glucocorticoids require high and frequent dosing with the off-target adverse effects defining the maximum dose. Recently, nanomedicine formulations of glucocorticoids have been developed that improve the pharmacokinetic profile, limit adverse effects and improve solid tumor accumulation. Multiple myeloma is a hematological malignancy characterized by uncontrolled growth of plasma cells. These tumors initiate increased angiogenesis and microvessel density in the bone marrow, which might be exploited using nanomedicines, such as liposomes. Nano-sized particles can accumulate as a result of the increased vascular leakiness at the bone marrow tumor lesions. Pre-clinical screening of novel anti-myeloma therapeutics in vivo requires a suitable animal model that represents key features of the disease. In this study, we show that fluorescently labeled long circulating liposomes were found in plasma up to 24 h after injection in an advanced human-mouse hybrid model of multiple myeloma. Besides the organs involved in clearance, liposomes were also found to accumulate in tumor bearing human-bone scaffolds. The therapeutic efficacy of liposomal dexamethasone phosphate was evaluated in this model showing strong tumor growth inhibition while free drug being ineffective at an equivalent dose (4 mg/kg) regimen. The liposomal formulation slightly reduced total body weight of myeloma-bearing mice during the course of treatment, which appeared reversible when treatment was stopped. Liposomal dexamethasone could be further developed as monotherapy or could fit in with existing therapy regimens to improve therapeutic outcomes for multiple myeloma.

Glucocorticoids promote the development of azoxymethane and dextran sulfate sodium-induced colorectal carcinoma in mice

BACKGROUND

Stress has been suggested as a promoter of tumor growth and development. Glucocorticoids (GCs) are the main stress hormones and widely prescribed as drugs. However, the effect of GCs on the development and progression of colorectal carcinoma (CRC) is unclear.

METHODS

We evaluated the effect of corticosterone (CORT) on azoxymethane and dextran sulfate sodium (AOM/DSS)-induced carcinogenesis in the colorectum of C57BL/6 strain mice. Plasma level of CORT was detected by radioimmunoassay. The expression of proliferation markers (Ki-67 and PCNA), nuclear factor (NF)-κB p65 and phosphoto-p65 (P-p65), as well as cyclooxygenase (COX)-2 were determined by immunohistochemistry. Inflammation in colorectum was evaluated by histopathology.

RESULTS

CORT feeding in drinking water of mice not only significantly elevated plasma CORT concentration, but also significantly increased the incidence and neoplasms burden (number and size of neoplasms) in colorectum. CORT also significant enhanced the expression of cell proliferation marker (Ki-67 and PCNA), NF-κB p65 and P-p65 as well as COX-2 in colorectal neoplasm of AOM/DSS-treated mice.

CONCLUSION

In this study, we have found for the first time that CORT at stress level potentially promotes the growth and development of AOM/DSS-induced colorectal adenoma and carcinoma in mice. Up-regulation of NF-κB and COX-2 may be involved in the promoting effect of CORT.

The availability of drug by liposomal drug delivery : Individual kinetics and tissue distribution of encapsulated and released drug in mice after administration of PEGylated liposomal prednisolone phosphate

Lately, the usefulness of liposomal drug delivery systems has been debated. To better understand the underlying pharmacokinetics of the targeted drug delivery by liposomes, individual encapsulated and non-encapsulated drug concentrations in blood, tumor, liver, spleen and kidneys were quantified after i.v. administration of liposomal prednisolone phosphate in mice. Kinetic analysis shows that the tumor influx of encapsulated drug is not dominant compared to the uptake by the other tissues. Further, from a quantitative point of view, the availability of non-encapsulated drug in the tumor tissue after liposomal delivery is not pronounced as compared to the other tissues studied. However, drug release in the tumor seems more extended than in the other tissues and the non-encapsulated drug concentration decreases more slowly in the tumor than in the liver and spleen. The spleen shows a high affinity for the uptake of encapsulated drug as well as the release of drug from the liposomes. Subsequently, released drug in the spleen, and possibly also in other tissues, is probably quickly redistributed towards the blood and other tissues. This also impairs the drug delivery effect of the liposomes. In contrast to the released drug in the central circulation, liver and spleen, the released drug concentration in the tumor remains at a fairly constant level likely due to the extended release kinetics from the liposomes. These extended release characteristics in the tumor most probably contribute to the beneficial effect. Nevertheless, it should be noted that larger released drug concentrations are formed in healthy tissues.

Nanomedicines for the treatment of hematological malignancies

Hematological malignancies (HM) are a collection of malignant transformations originating from cells in the primary or secondary lymphoid organs. Leukemia, lymphoma, and multiple myeloma comprise the three major types of HM. Current treatment consists of bone marrow transplantation, radiotherapy, immunotherapy and chemotherapy. Although, many chemotherapeutic drugs are clinically available for the treatment of HM, the use of these agents is limited due to dose-related toxicity and lack of specificity to tumor tissue. Moreover, the poor pharmacokinetic profile of most of the chemotherapeutics requires high dosage and frequent administration to maintain therapeutic levels at the target site, both increasing adverse effects. This underlines an urgent need for a suitable drug delivery system to improve efficacy, safety, and pharmacokinetic properties of conventional therapeutics. Nanomedicines have proven to enhance these properties for anticancer therapeutics. The most extensively studied nanomedicine systems are lipid-based nanoparticles and polymeric nanoparticles. Typically, nanomedicines are small sub-micron sized particles in the size range of 20-200 nm. The biocompatible and biodegradable nature of nanomedicines makes them attractive vehicles to improve drug delivery. Their small size allows them to extravasate and accumulate at malignant sites passively by means of the enhanced permeability and retention (EPR) effect, resulting from rapid angiogenesis and inflammation. Moreover, the specificity to the target tissue can be further enhanced by surface modification of nanoparticles. This review describes currently available therapies as well as limitations and potential advantages of nanomedicine formulations for treatment of various types of HM. Additionally, recent investigational and approved nanomedicine formulations and their limited applications in HM are discussed.

Analytical methods for investigating in vivo fate of nanoliposomes: A review

Nanoliposomes are considered to be the most successful nanoparticle drug delivery system, but their fate in vivo has not been fully understood due to lack of reliable bioanalytical methods, which seriously limits the development of liposomal drugs. Hence, an overview of currently used bioanalytical methods is imperative to lay the groundwork for the need of developing a bioanalytical method for liposome measurements in vivo. Currently, major analytical methods for nanoliposomes measurement in vivo include fluorescence labeling, radiolabeling, magnetic resonance imaging (MRI), mass spectrometry and computed tomography. In this review, these bioanalytical methods are summarized, and the advantages and disadvantages of each are discussed. We provide insights into the applicability and limitations of these analytical methods in the application of nanoliposomes measurement in vivo, and highlight the recent development of instrumental analysis techniques. The review is devoted to providing a comprehensive overview of the investigation of nanoliposomes design and associated fate in vivo, promoting the development of bioanalytical techniques for nanoliposomes measurement, and understanding the pharmacokinetic behavior, effectiveness and potential toxicity of nanoliposomes in vivo.

Nano-engineering of biomedical prednisolone liposomes: evaluation of the cytotoxic effect on human colon carcinoma cell lines

Objectives

Liposomes have attracted the attention of researchers due to their potential to act as drug delivery systems for cancer treatment. The present investigation aimed to develop liposomes loaded with prednisolone base and the evaluation of the antiproliferative effect on human colon carcinoma cell lines.

Methods

Liposomes were elaborated by following a reproducible thin film hydration technique. The physicochemical characterization of liposomes included photon correlation spectroscopy, microscopy analysis, Fourier transform infrared spectroscopy, rheological behaviour and electrophoresis. On the basis of these data and drug loading values, the best formulation was selected. Stability and drug release properties were also tested.

Key findings

Resulting liposomes exhibited optimal physicochemical and stability properties, an excellent haemocompatibility and direct antiproliferative effect on human colon carcinoma T-84 cell lines.

Conclusions

This study shows direct antitumour effect of prednisolone liposomal formulation, which opens the door for liposomal glucocorticoids as novel antitumour agents.

Liposome encapsulated luteolin showed enhanced antitumor efficacy to colorectal carcinoma

Luteolin is a falconoid compound that is present in various types of plants and possesses remarkable potential as a chemopreventive agent. However, the poor aqueous solubility of luteolin limits its clinical application. In the present study, an approach towards chemoprevention was explored using liposomes to deliver luteolin, and the antitumor efficacy was investigated in colorectal carcinoma. The present findings demonstrated that luteolin was efficiently encapsulated into liposomes with an encapsulation efficiency as high as 90%. The particle size of the liposomal luteolin (Lipo-Lut) and ζ-potential were optimized. In vitro studies demonstrated that, Lipo-Lut had a significant inhibitory effect on the growth on the CT26 colorectal carcinoma cell line compared with free luteolin (Free-Lut). The in vivo study indicated that Lipo-Lut could achieve superior antitumor effects against CT26 tumor compared with luteolin alone. The present results suggested that liposome delivery of luteolin improved solubility, bioavailability and may have potential applications in chemoprevention in clinical settings.

Up-regulation of Rho-associated kinase 1/2 by glucocorticoids promotes migration, invasion and metastasis of melanoma

Although glucocorticoids (GCs) regulate proliferation, differentiation and apoptosis of tumor cells, their influence on metastasis of tumor cells is poorly understood. Melanoma is a type of skin cancers with high metastasis. We investigated the effect of GCs on metastasis of melanoma cells and its mechanism. We found that GCs significantly promoted the adhesion, migration, invasion of melanoma cells in vitro and lung metastasis in experimental melanoma metastasis mice. Dexamethasone (Dex), a synthetic GC, did not change the RhoA, RhoB and RhoC signalings, but significantly increased the expression and activity of Rho-associated kinase 1/2 (ROCK1/2). The effect of Dex was to increase ROCK1/2 stability mediated by glucocorticoid receptor. Inhibiting ROCK1/2 activity with Y-27632, a ROCK1/2 inhibitor abrogated the pro-migration and pro-metastasis effects of GCs in vitro and in vivo, indicating that ROCK1/2 mediated the pro-metastasis effects of GCs. Activation of PI3K/AKT also contributed to the pro-migration and pro-invasion effects of Dex partially through up-regulating ROCK1/2 expression. Additionally, Dex also down-regulated the expression of tissue inhibitors of matrix metalloproteinase-2. Taken together, our findings provide new data to understand the possible promoting roles and mechanisms of GCs in melanoma metastasis.

Novel Drug Delivery Systems Tailored for Improved Administration of Glucocorticoids

Glucocorticoids (GC) are one of the most popular and versatile classes of drugs available to treat chronic inflammation and cancer, but side effects and resistance constrain their use. To overcome these hurdles, which are often related to the uniform tissue distribution of free GC and their short half-life in biological fluids, new delivery vehicles have been developed including PEGylated liposomes, polymeric micelles, polymer-drug conjugates, inorganic scaffolds, and hybrid nanoparticles. While each of these nanoformulations has individual drawbacks, they are often superior to free GC in many aspects including therapeutic efficacy when tested in cell culture or animal models. Successful application of nanomedicines has been demonstrated in various models of neuroinflammatory diseases, cancer, rheumatoid arthritis, and several other disorders. Moreover, investigations using human cells and first clinical trials raise the hope that the new delivery vehicles may have the potential to make GC therapies more tolerable, specific and efficient in the future.

Exploiting the cancer niche: Tumor-associated macrophages and hypoxia as promising synergistic targets for nano-based therapy

The tumor microenvironment has been widely exploited as an active participant in tumor progression. Extensive reports have defined the dual role of tumor-associated macrophages (TAMs) in tumor development. The protumoral effect exerted by the M2 phenotype has been correlated with a negative outcome in most solid tumors. The high infiltration of immune cells in the hypoxic cores of advanced solid tumors leads to a chain reaction of stimuli that enhances the expression of protumoral genes, thrives tumor malignancy, and leads to the emergence of drug resistance. Many studies have shown therapeutic targeting systems, solely to TAMs or tumor hypoxia, however, novel therapeutics that target both features are still warranted. In the present review, we discuss the role of hypoxia in tumor development and the clinical outcome of hypoxia-targeted therapeutics, such as hypoxia-inducible factor (HIF-1) inhibitors and hypoxia-activated prodrugs. Furthermore, we review the state-of-the-art of macrophage-based cancer therapy. We thoroughly discuss the development of novel therapeutics that simultaneously target TAMs and tumor hypoxia. Nano-based systems have been highlighted as interesting strategies for dual modality treatments, with somewhat improved tissue extravasation. Such approach could be seen as a promising strategy to overcome drug resistance and enhance the efficacy of chemotherapy in advanced solid and metastatic tumors, especially when exploiting cell-based nanotherapies. Finally, we provide an in-depth opinion on the importance of exploiting the tumor microenvironment in cancer therapy, and how this could be translated to clinical practice.

Statins anticancer targeted delivery systems: re-purposing an old molecule

OBJECTIVES

Exploring the use of statins as anticancer agents and exploiting different drug delivery systems in targeting these molecules to cancerous sites. Literature review was performed to investigate the use of statins in cancer treatment in one hand, and the different pharmaceutical approaches to deliver and target these drugs to their site of action.

KEY FINDINGS

Statins were used for decades as antihypercholestrolemic drugs but recently have been proven potential for broad anticancer activities. The incorporation of statins in nanoparticulate drug delivery systems not only augmented the cytotoxicity of statins but also overcame the resistance of cancerous cells against the traditional chemotherapeutic agents. Statins-loaded nanoparticles could be easily tampered to target the cancerous cells and consequently minimal drug amount could be utilized.

SUMMARY

This review reconnoitered the different endeavors to incorporate statins in various nanoparticles and summarized the successful effects in targeting cancerous cells and reducing their proliferation without the side effects of commonly used chemotherapeutic agents.

Radiation effects on the tumor microenvironment: Implications for nanomedicine delivery

The tumor microenvironment has an important influence on cancer biological and clinical behavior and radiation treatment (RT) response. However, RT also influences the tumor microenvironment in a complex and dynamic manner that can either reinforce or inhibit this response and the likelihood of long-term disease control in patients. It is increasingly evident that the interplay between RT and the tumor microenvironment can be exploited to enhance the accumulation and intra-tumoral distribution of nanoparticles, mediated by changes to the vasculature and stroma with secondary effects on hypoxia, interstitial fluid pressure (IFP), solid tissue pressure (STP), and the recruitment and activation of bone marrow-derived myeloid cells (BMDCs). The use of RT to modulate nanoparticle drug delivery offers an exciting opportunity to improve antitumor efficacy. This review explores the interplay between RT and the tumor microenvironment, and the integrated effects on nanoparticle drug delivery and efficacy.

First in vivo MRI study on theranostic dendrimersomes

Amphiphilic Janus-dendrimers are able to self-assemble into nanosized vesicles named dendrimersomes. We recently synthesized the 3,5-C₁₂-EG-(OH)₄ dendrimer that generates dendrimersomes with very promising safety and stability profiles, that can be loaded with different contrast agents for in vivo imaging. In this contribution, nanovesicles were loaded with both the Magnetic Resonance Imaging (MRI) reporter GdDOTAGA(C₁₈)₂ and the glucocorticoid drug Prednisolone Phosphate (PLP), in order to test their effective potential as theranostic nanocarriers on murine melanoma tumour models. The incorporation of GdDOTAGA(C₁₈)₂ into the membrane resulted in dendrimersomes with a high longitudinal relaxivity (r₁=39.1mM^-1s^-1, at 310K and 40MHz) so that, after intravenous administration, T₁-weighted MRI showed a consistent contrast enhancement in the tumour area. Furthermore, the nanovesicles encapsulated PLP with good efficiency and displayed anti-tumour activity both in vitro and in vivo, thus enabling their practical use for biomedical theranostic applications.

Loss of 11βHSD1 enhances glycolysis, facilitates intrahepatic metastasis, and indicates poor prognosis in hepatocellular carcinoma

11Beta-hydroxysteroid dehydrogenase type 1 (11βHSD1), converting glucocorticoids from hormonally inactive cortisone to active cortisol, plays an essential role in glucose homeostasis. Accumulating evidence suggests that enhanced glycolytic activity is closely associated with postoperative recurrence and prognosis of hepatocellular carcinoma (HCC). Whether 11βHSD1 contributes to HCC metastasis and recurrence remains unclear. Here we found that expression of 11βHSD1 in human HCC (310 pairs) was frequently decreased compared to the adjacent non-neoplastic liver tissues (ANT), which correlated well with the intrahepatic-metastatic index, serum glycemia, and other malignant clinicopathological characteristics of HCC and predicted poor prognosis. Knockdown of 11βHSD1 in BEL-7402 cells drastically reduced the pH of culture medium and induced cell death. Meanwhile, overexpression of 11βHSD1 in SMMC-7721 HCC cells resulted in repression of cell migration, invasion, angiogenesis, and proliferation in vitro. When transferred into BALB/c nude mice, 11βHSD1 overexpression resulted in decreased intrahepatic metastasis, angiogenesis, and tumor size. F-18-2-fluoro-2-deoxyglucose accumulation assay measured by positron emission tomography elucidated that 11βHSD1 reduced glucose uptake and glycolysis in SMMC-7721 cells in vitro, and intrahepatic metastasis foci and subcutaneous tumor growth in vivo. We showed that 11βHSD1 repressed cell metastasis, angiogenesis and proliferation of HCC by causing disruption of glycolysis via the HIF-1α and c-MYC pathways. In conclusion, 11βHSD1 inhibits the intrahepatic metastasis of HCC via restriction of tumor glycolysis activity and may serve as a prognostic biomarker for patients.

Differential uptake of nanoparticles by human M1 and M2 polarized macrophages: protein corona as a critical determinant

AIM

To investigate the interaction behavior of M1- and M2-type macrophages with nanoparticles of different sizes with/without the presence of serum.

MATERIALS & METHODS

THP-1 human monocytes were differentiated into M1 and M2 macrophages, and the uptake of silica nanoparticle (50-1000 nm) was studied using flow cytometry and different microscopies.

RESULTS

Without serum, higher uptake of all-sized nanoparticles was observed by M1 compared with M2. With serum, uptake of nanoparticles (200-1000 nm) was dramatically increased by M2. Furthermore, serum proteins adsorbed (corona) by nanoparticles were found to be the ligands for receptors expressed by M2, as revealed by SDS-PAGE and gene profiling analyses.

CONCLUSION

The observed differential uptake by M1 and M2 macrophages will help understand the fate of nanoparticles in vivo.

Strategies for improving the intratumoral distribution of liposomal drugs in cancer therapy

INTRODUCTION

A major limitation of current liposomal cancer therapies is the inability of liposome therapeutics to penetrate throughout the entire tumor mass. This inhomogeneous distribution of liposome therapeutics within the tumor has been linked to treatment failure and drug resistance. Both liposome particle transport properties and tumor microenvironment characteristics contribute to this challenge in cancer therapy. This limitation is relevant to both intravenously and intratumorally administered liposome therapeutics.

AREAS COVERED

Strategies to improve the intratumoral distribution of liposome therapeutics are described. Combination therapies of intravenous liposome therapeutics with pharmacologic agents modulating abnormal tumor vasculature, interstitial fluid pressure, extracellular matrix components, and tumor associated macrophages are discussed. Combination therapies using external stimuli (hyperthermia, radiofrequency ablation, magnetic field, radiation, and ultrasound) with intravenous liposome therapeutics are discussed. Intratumoral convection-enhanced delivery (CED) of liposomal therapeutics is reviewed.

EXPERT OPINION

Optimization of the combination therapies and drug delivery protocols are necessary. Further research should be conducted in appropriate cancer types with consideration of physiochemical features of liposomes and their timing sequence. More investigation of the role of tumor associated macrophages in intratumoral distribution is warranted. Intratumoral infusion of liposomes using CED is a promising approach to improve their distribution within the tumor mass.

Liposomal delivery of dexamethasone attenuates prostate cancer bone metastatic tumor growth in vivo

BACKGROUND

The inflammatory tumor microenvironment, and more specifically the tumor-associated macrophages, plays an essential role in the development and progression of prostate cancer towards metastatic bone disease. Tumors are often characterized by a leaky vasculature, which - combined with the prolonged circulation kinetics of liposomes - leads to efficient tumor localization of these drug carriers, via the so-called enhanced permeability and retention (EPR) -effect. In this study, we evaluated the utility of targeted, liposomal drug delivery of the glucocorticoid dexamethasone in a model of prostate cancer bone metastases.

METHODS

Tumor-bearing Balb-c nu/nu mice were treated intravenously with 0.2-1.0-5.0 mg/kg/week free- and liposomal DEX for 3-4 weeks and tumor growth was monitored by bioluminescent imaging.

RESULTS

Intravenously administered liposomes localize efficiently to bone metastases in vivo and treatment of established bone metastases with (liposomal) dexamethasone resulted in a significant inhibition of tumor growth up to 26 days after initiation of treatment. Furthermore, 1.0 mg/kg liposomal dexamethasone significantly outperformed 1.0 mg/kg free dexamethasone, and was found to be well-tolerated at clinically-relevant dosages that display potent anti-tumor efficacy.

CONCLUSIONS

Liposomal delivery of the glucocorticoid dexamethasone inhibits the growth of malignant bone lesions. We believe that liposomal encapsulation of dexamethasone offers a promising new treatment option for advanced, metastatic prostate cancer which supports further clinical evaluation.

Inhibition of 11β-Hydroxysteroid Dehydrogenase Type II Suppresses Lung Carcinogenesis by Blocking Tumor COX-2 Expression as Well as the ERK and mTOR Signaling Pathways

Lung cancer is by far the leading cause of cancer death. Early diagnosis and prevention remain the best approach to reduce the overall morbidity and mortality. Experimental and clinical evidence have shown that cyclooxygenase-2 (COX-2) derived prostaglandin E₂ (PGE2) contributes to lung tumorigenesis. COX-2 inhibitors suppress the development and progression of lung cancer. However, increased cardiovascular risks of COX-2 inhibitors limit their use in chemoprevention of lung cancers. Glucocorticoids are endogenous and potent COX-2 inhibitors, and their local actions are down-regulated by 11β–hydroxysteroid dehydrogenase type II (11ßHSD2)-mediated metabolism. We found that 11βHSD2 expression was increased in human lung cancers and experimental lung tumors. Inhibition of 11βHSD2 activity enhanced glucocorticoid-mediated COX-2 inhibition in human lung carcinoma cells. Furthermore, 11βHSD2 inhibition suppressed lung tumor growth and invasion in association with increased tissue active glucocorticoid levels, decreased COX-2 expression, inhibition of ERK and mTOR signaling pathways, increased tumor endoplasmic reticulum stress as well as increased lifespan. Therefore, 11βHSD2 inhibition represents a novel approach for lung cancer chemoprevention and therapy by increasing tumor glucocorticoid activity, which in turn selectively blocks local COX-2 activity and/or inhibits the ERK and mTOR signaling pathways.

Preparation and in vitro characterization of chitosan nanobubbles as theranostic agents

Theranostic delivery systems are nanostructures that combine the modality of therapy and diagnostic imaging. Polymeric micro- and nanobubbles, spherical vesicles containing a gas core, have been proposed as new theranostic carriers for MRI-guided therapy. In this study, chitosan nanobubbles were purposely tuned for the co-delivery of prednisolone phosphate and a Gd(III) complex, as therapeutic and MRI diagnostic agent, respectively. Perfluoropentane was used for filling up the internal core of the formulation. These theranostic nanobubbles showed diameters of about 500nm and a positive surface charge that allows the interaction with the negatively charged Gd-DOTP complex. Pluronic F68 was added to the nanobubble aqueous suspension as stabilizer agent. The encapsulation efficiency was good for both the active compounds, and a prolonged drug release profile was observed in vitro. The effect of ultrasound stimulation on prednisolone phosphate release was evaluated at 37°C. A marked increase on drug release kinetics with no burst effect was obtained after the exposure of the system to ultrasound. Furthermore, the relaxivity of the MRI probe changed upon incorporation in the nanobubble shell, thereby offering interesting opportunity in dual MRI-US experiments. The ultrasound characterization showed a good in vitro echogenicity of the theranostic nanobubbles. In summary, chitosan drug-loaded nanobubbles with Gd(III) complex bound to their shell might be considered a new platform for imaging and drug delivery with the potential of improving anti-cancer treatments.

Immunoglobulin free light chains are biomarkers of poor prognosis in basal-like breast cancer and are potential targets in tumor-associated inflammation

Inflammation is an important component of various cancers and its inflammatory cells and mediators have been shown to have prognostic potential. Tumor-infiltrating mast cells can promote tumor growth and angiogenesis, but the mechanism of mast cell activation is unclear. In earlier studies, we demonstrated that immunoglobulin free light chains (FLC) can trigger mast cells in an antigen-specific manner. Increased expression of FLC was observed within stroma of various human cancers including those of breast, colon, lung, pancreas, kidney and skin, and FLC expression co-localized with areas of mast cell infiltration. In a large cohort of breast cancer patients, FLC expression was shown associated with basal-like cancers with an aggressive phenotype. Moreover, lambda FLC was found expressed in areas of inflammatory infiltration and its expression was significantly associated with poor clinical outcome. Functional importance of FLCs was shown in a murine B16F10 melanoma model, where inhibition of FLC-mediated mast cell activation strongly reduced tumor growth. Collectively, this study identifies FLCs as a ligand in the pro-tumorigenic activation of mast cells. Blocking this pathway may open new avenues for the inhibition of tumor growth, while immunohistochemical staining of FLC may be helpful in the diagnosis and prognosis of cancer.

Plasma, blood and liver tissue sample preparation methods for the separate quantification of liposomal-encapsulated prednisolone phosphate and non-encapsulated prednisolone

Besides the development of sample preparation methods for the determination of separate liposomal-encapsulated prednisolone phosphate and non-encapsulated prednisolone concentrations in murine plasma and blood, this article also presents the first description of an accurate sample preparation method for the determination of such separate concentrations in the murine liver. The quantitative differentiation is based on the immediate hydrolysis of prednisolone phosphate (PP) into prednisolone (P) after its release from the liposomes in vivo: PP represents the encapsulated drug, while P represents the non-encapsulated drug. The use of 10 ml methanol/g tissue during homogenization of liver tissue ensures complete liposome rupture, prevention of the dephosphorylation of PP released during homogenization, sufficient clean supernatants, excellent extraction of P and sufficient extraction of PP and excellent accuracies and precision complying with the internal guidelines for pre-clinical studies (80-120% and maximal 20%, respectively). Similarly, the matching sample preparation methods for plasma and blood involve protein precipitation with four equivalents of methanol also ensuring accuracies and precision complying with the internal guidelines for pre-clinical studies. Application of these sample preparation methods is going to generate the first pharmacokinetic (PK) profile of a liposomal preparation, in which the encapsulated and non-encapsulated drug concentrations in a tissue are measured separately. Such separated concentration profiles can gain important insights into the PKs of liposomal PP and probably also with regard to liposomal formulations in general, like the quantification of the in vivo drug release from the liposomes.

A novel approach to overcome multidrug resistance: utilization of P-gp mediated efflux of paclitaxel to attack neighboring vascular endothelial cells in tumors

We tried to overcome the paclitaxel (PTX) resistance of cancer cells due to P-glycoprotein (P-gp) overexpression in the in vivo anti-tumor chemotherapy by utilizing polyethylene glycol-modified liposomal paclitaxel (PL-PTX). First of all, established were PTX-resistant Colon-26 cancer cells (C26/PTX) overexpressing P-gp, which provided IC50 value of PTX solution about 30 times larger than that obtained for control C26 (C26/control) in the in vitro MTT assay. Western blot analysis confirmed P-gp expression in C26/PTX 10 times higher than that in C26/control, indicating that the resistance acquisition of C26/PTX to PTX would be ascribed to the enhanced efflux of PTX by P-gp overexpressed in C26/PTX. However, the in vivo anti-tumor effect of PL-PTX in C26/PTX-bearing mice was similar to that in C26/control-bearing mice. Double immunohistochemical staining of vascular endothelial cells and apoptotic cells within tumor tissues demonstrated that the apoptotic cell death was preferentially observed in vascular endothelial cells in C26/PTX tumors after intravenous administration of PL-PTX, while that was in tumor cells in C26/control tumors. These results suggest that the in vivo anti-tumor effect of PL-PTX in C26/PTX-bearing mice would be ascribed to the cytotoxic action of PTX pumped out of tumor cells by overexpressed P-gp to vascular endothelial cells in tumor tissues.

Liposomal corticosteroids for the treatment of inflammatory disorders and cancer

Glucocorticoids (GC) are known for their potent immunosuppressive and anti-inflammatory properties. As a consequence, they have been extensively used for the treatment of many different diseases. Prolonged and/or high-dose GC therapy, however, generally comes with severe side effects, resulting not only from their very diverse mechanism(s) of action, but also from their relatively poor biodistribution. Drug delivery systems, and in particular liposomes, have been extensively used to enhance the biodistribution and the target site accumulation of GC, and to thereby improve the balance between their efficacy and their toxicity. Many different types of liposomes have been employed, and both local and systemic treatments have been evaluated. We here summarize the progress made in the use of liposomal GC formulations for the treatment of asthma, rheumatoid arthritis, multiple sclerosis and cancer, and we show that the targeted delivery of GC to pathological sites holds significant clinical potential.

In vitro confirmation of the quantitative differentiation of liposomal encapsulated and non-encapsulated prednisolone (phosphate) tissue concentrations by murine phosphatases

The quantitative differentiation of liposomal encapsulated and non-encapsulated drug tissue concentrations is desirable, since the efficacy and toxicity are only related to the level of non-encapsulated drug. However, such separate concentration profiles in tissues have still not been reported due to lacking analytical methodology. The encapsulation of prodrugs like prednisolone phosphate (PP) in liposomes offers new, analytical opportunities. Instantaneous dephosphorylation of PP into prednisolone (P) by phosphatases after its release from the liposome in vivo makes it possible to differentiate between the encapsulated and the non-encapsulated drug for such preparations of liposomal PP: PP represents the encapsulated drug, while P represents the non-encapsulated drug. In the here described study, the instantaneous dephosphorylation of PP by murine liver and kidney phosphatases has been verified by incubation of PP in liver and kidney homogenates followed by estimation of the dephosphorylation rate constants k and the dephosphorylation time of the expected maximal in vivo non-encapsulated drug concentrations. In vitro PP has been rapidly converted into P in the presence of homogenate from the excretory organs. The calculated values for k have shown that the liver contains more active sites per gram of tissue than the kidneys. However, the dephosphorylation of PP by these active sites is slower compared with the kidneys. Compared with other pharmacokinetic processes of P, the estimated dephosphorylation times of the expected maximal in vivo non-encapsulated drug concentrations in the liver and the kidneys are considered to be instantaneous. This enables the separate determination of the encapsulated and non-encapsulated drug concentrations in the excretory organs after administration of liposomal PP in mice generating the first pharmacokinetic profile of a liposomal preparation, in which the in vivo encapsulated and free drug tissues concentrations are measured separately. This can also gain important insights into the pharmacokinetics of liposomal formulations in general.