Liposomal drug formulations in the treatment of rheumatoid arthritis

Liposomes have been extensively investigated as drug delivery systems in the treatment of rheumatoid arthritis (RA). Low bioavailability, high clearance rates and limited selectivity of several important drugs used for RA treatment require high and frequent dosing to achieve sufficient therapeutic efficacy. However, high doses also increase the risk for systemic side effects. The use of liposomes as drug carriers may increase the therapeutic index of these antirheumatic drugs. Liposomal physicochemical properties can be changed to optimize penetration through biological barriers and retention at the site of administration, and to prevent premature degradation and toxicity to nontarget tissues. Optimal liposomal properties depend on the administration route: large-sized liposomes show good retention upon local injection, small-sized liposomes are better suited to achieve passive targeting. PEGylation reduces the uptake of the liposomes by liver and spleen, and increases the circulation time, resulting in increased localization at the inflamed site due to the enhanced permeability and retention (EPR) effect. Additionally liposomal surfaces can be modified to achieve selective delivery of the encapsulated drug to specific target cells in RA. This review gives an overview of liposomal drug formulations studied in a preclinical setting as well as in clinical practice. It covers the use of liposomes for existing antirheumatic drugs as well as for new possible treatment strategies for RA. Both local administration of liposomal depot formulations and intravenous administration of passively and actively targeted liposomes are reviewed.     

The use of single chain Fv as targeting agents for immunoliposomes: an update on immunoliposomal drugs for cancer treatment

Importance of the field: Targeted liposomal drugs represent the next evolution of liposomal drug delivery in cancer treatment. In various preclinical cancer models, antibody-targeted PEGylated liposomal drugs have demonstrated superior therapeutic effects over their non-targeted counterparts. Single chain Fv (scFv) has gained popularity in recent years as the targeting agent of choice over traditional targeting agents such as monoclonal antibodies (mAb) and antibody fragments (e.g., Fab′).

Areas covered in this review: This review is focused mainly on advances in scFv-targeted liposomal drug delivery for the treatment of cancers, based on a survey of the recent literature, and on experiments done in a murine model of human B-lymphoma, using anti-CD19 targeted liposomes targeted with whole mAb, Fab′ fragments and scFv fragments.

What the reader will gain: This review examines the recent advances in PEGylated immunoliposomal drug delivery, focusing on scFv fragments as targeting agents, in comparison with Fab′ and mAb.

Take home message: For clinical development, scFv are potentially preferred targeting agents for PEGylated liposomes over mAb and Fab′, owing to factors such as decreased immunogenicity, and pharmacokinetics/biodistribution profiles that are similar to non-targeted PEGylated (Stealth^®) liposomes.     

In vitro optimization of liposomal nanocarriers prepared from breast tumor cell specific phage fusion protein

Fusion proteins created by phage display peptides with tumor cell specificity and the pVIII major coat protein of filamentous phages have been explored recently as a simple and cost-effective means for preparing tumor-targeted liposomes that improve the cytotoxicity of anticancer drugs in vitro. The next step in the development of this approach is the optimization of the liposome composition for the maximum targeting activity and subsequent testing in vivo. This study aimed to investigate the impact of preparation protocols, lipid composition and phage protein content on the targeting efficiency of phage protein-modified liposomes. Analysis of size, zeta potential and morphology was used to investigate the effect of preparation protocols on the stability and homogeneity of the phage liposomes. A previously developed coculture targeting assay and a factorial design approach were used to determine the role of lipid composition of the liposomal membrane on the target cell specificity of the phage liposomes. Western blot combined with proteinase K treatment detected the orientation of targeted phage protein in liposomal membrane. Phage protein, DPPG and PEG_2k-PE showed positive effects on target specificity of phage liposomes. The results served to identify optimal formulation that offer an improved liposomal affinity for target tumor cells over the non-optimized formulation.     

High-affinity targeting of biotin-labeled liposomes to streptavidin-conjugated ligands

Cell-specific delivery of drug-loaded liposomal carrier systems can be achieved through the use of liposomes with covalently attached proteins. For such targeting strategies to be successful a number of potential difficulties, related to the preparation of the liposomes as well as optimization of properties that maximize in vivo access and binding to a defined target cell population, must be overcome. The studies summarized here have attempted to identify specific factors that will promote binding of targeted liposomes to defined target surfaces. Liposomes containing biotinylated phospha-tidylethanolamine were used to demonstrate that the avidity of a targeted liposome for streptavidin-coated ELISA plates and cells is influenced by liposome lipid composition, the amount of targeting molecule present per liposome, the nature of the targeting ligand, and the target surface. Specifically, it is demonstrated that the three most important factors (in order of importance) controlling the apparent affinity of targeted liposomes are (1) target ligand concentration in the liposomal membrane; (2) the presence of a spacer grout between the biotin and the phospholipid headgroup; and (3) the addition of cholesterol. Other less important factors that influence target liposome binding include whether the target ligand is attached to a saturated phospholipid compared to an unsaturated lipid and whether the bulk phospholipid species in the liposome is unsaturated versus saturated. These studies suggest that targeted liposomes exhibiting a broad range of binding avidities, as estimated by the concentration of liposomes required to achieve saturation of a target surface, can be prepared by selective design of the liposomal carrier. Advantages of the biotinylated liposome for targeting include the relative ease of preparation the possibility of preparation of large-scale batches suitable for clinical development), the ease of incorporation of the targeting ligand, and, importantly, the ability to alter the apparent affinity of the liposome for the target cell through choice of the biotin-labeled lipid and targeting molecule concentration. The potential for developing a two-step targeting strategy based on the use of biotinylated liposomes is discussed.     

纳米脂质体药物在类风湿性关节炎治疗中的研究进展

类风湿性关节炎（RA）是一种病因未明的自身免疫性疾病,典型病理改变为慢性滑膜炎,严重影响患者生活质量。目前的治疗药物能够缓解症状,延缓病程,但均存在明显的不良反应。以脂质体为代表的纳米药物递送系统在临床上已显现出了明显的优势,其能够通过被动或主动靶向从而提高药物的治疗效应及减少不良反应。在本文中,我们回顾了脂质体药物递送系统在RA治疗中的作用,阐述了其在临床前研究和临床试验的进展,并讨论了可能阻碍其临床转化的因素。     

Liposomes in the treatment of infectious diseases

Phospholipids and other polar lipids can form liposomes and similar colloidal particles that can be used as drug carrier systems. The potential of liposomal delivery systems to increase the therapeutic index (efficacy to safety ratio) of clinically important drugs has been realised with the recent approval of liposomal oncologic and antifungal drugs. The application of liposomes to the treatment of infectious diseases initially focused on intracellular pathogens, based on the natural targeting of liposomes to phagocytic cells and on the antifungal drug amphotericin B, based on its unique affinity for lipids. Recent studies with small, low-clearance liposomes have shown that more specialised formulations may provide benefits over simpler ‘first generation’ liposomes for the treatment of infectious diseases, including prolonged residence in plasma, increased tissue exposure and targeting to sites of infection. These improved biopharmaceutical properties have been associated with both curative and prophylactic activity against a range of non-intracellular pathogens, including Staphylococcus and Klebsiella. These and other highly engineered liposome formulations may provide effective delivery systems for specific antibacterial, antifungal and antiviral indications in the future. Adequate patent protection will be crucial in fully exploiting these advanced liposome technologies and in maintaining market share for liposomal products. This review discusses some of the patent issues related to liposomes and their use in the treatment of infectious diseases.     

High-affinity targeting of biotin-labeled liposomes to streptavidin-conjugated ligands

Abstract

Cell-specific delivery of drug-loaded liposomal carrier systems can be achieved through the use of liposomes with covalently attached proteins. For such targeting strategies to be successful a number of potential difficulties, related to the preparation of the liposomes as well as optimization of properties that maximize in vivo access and binding to a defined target cell population, must be overcome. The studies summarized here have attempted to identify specific factors that will promote binding of targeted liposomes to defined target surfaces. Liposomes containing biotinylated phospha-tidylethanolamine were used to demonstrate that the avidity of a targeted liposome for streptavidin-coated ELISA plates and cells is influenced by liposome lipid composition, the amount of targeting molecule present per liposome, the nature of the targeting ligand, and the target surface. Specifically, it is demonstrated that the three most important factors (in order of importance) controlling the apparent affinity of targeted liposomes are (1) target ligand concentration in the liposomal membrane; (2) the presence of a spacer grout between the biotin and the phospholipid headgroup; and (3) the addition of cholesterol. Other less important factors that influence target liposome binding include whether the target ligand is attached to a saturated phospholipid compared to an unsaturated lipid and whether the bulk phospholipid species in the liposome is unsaturated versus saturated. These studies suggest that targeted liposomes exhibiting a broad range of binding avidities, as estimated by the concentration of liposomes required to achieve saturation of a target surface, can be prepared by selective design of the liposomal carrier. Advantages of the biotinylated liposome for targeting include the relative ease of preparation the possibility of preparation of large-scale batches suitable for clinical development), the ease of incorporation of the targeting ligand, and, importantly, the ability to alter the apparent affinity of the liposome for the target cell through choice of the biotin-labeled lipid and targeting molecule concentration. The potential for developing a two-step targeting strategy based on the use of biotinylated liposomes is discussed.     

Landscape phage fusion protein-mediated targeting of nanomedicines enhances their prostate tumor cell association and cytotoxic efficiency

Tumor-specific cytotoxicity of drugs can be enhanced by targeting them to tumor receptors using tumor-specific ligands. Phage display offers a high-throughput approach to screen for the targeting ligands. We have successfully isolated phage fusion peptides selective and specific for PC3 prostate cancer cells. Also, we have demonstrated a novel approach of targeting liposomes through tumor-specific phage fusion coat proteins, exploiting the intrinsic properties of the phage coat protein as an integral membrane protein. Here we describe the production of Rhodamine-labeled liposomes as well as doxorubicin-loaded long-circulating liposomes targeted to PC3 prostate tumor cells via PC-specific phage peptides, as an extension of our previous studies. Targeting of labeled liposomes was demonstrated using fluorescence microscopy as well as flow cytometry. Targeting of doxorubicin-loaded liposomes enhanced their cytotoxic effect against PC3 cells in vitro, indicating a possible therapeutic advantage. The simplicity of the approach for generating targeted liposomes coupled with the ability to rapidly obtain tumor-specific phage fusion proteins via phage display may contribute to a combinatorial system for the production of targeted liposomal therapeutics for advanced stages of prostate tumor.From the Clinical EditorThis paper demonstrates targeting cytotoxic agents to tumor receptors using tumor-specific ligands. The authors describe the production of Rhodamine-labeled liposomes as well as doxorubicin loaded long circulating liposomes targeted to PC3 prostate tumor cells via PC-specific phage peptides. This approach may be especially relevant for advanced prostate tumors.     

New generation of liposomal drugs for cancer

This review is focused on liposomes as a delivery system for anticancer agents and more specifically on the advantages of using liposomes as drug nanocarrier in cancer chemotherapy. The main advantages of liposomal drugs over the non-encapsulated drugs include: (1) improved pharmacokinetics and drug release, (2) enhanced intracellular penetration, (3) tumor targeting and preventing adverse side effects and (4) ability to include several active ingredients in one complex liposomal drug delivery system (DDS). The review also includes our recent data on advanced liposomal anticancer drug delivery systems. As a conclusion we propose a novel liposomal DDS which includes inhibitors of pump resistance combined in one liposomal drug delivery system with an inhibitor of antiapoptotic cellular defense, an apoptosis inducer (a traditional anticancer drug) and a targeting moiety. The proposed drug delivery system utilizes a novel three tier approach, simultaneously targeting three molecular targets: (1) extracellular receptors or antigen expressed on the surface of plasma membrane of cancer cells in order to direct the whole system specifically to the tumor, preventing adverse side effects on healthy tissues; (2) drug efflux pumps in order to inhibit them and enhance drug retention by cancer cells, increasing intracellular drug accumulation and thereby limiting the need for prescribed high drug doses that cause adverse drug side effects; and (3) intracellular controlling mechanisms of apoptosis in order to suppress cellular antiapoptotic defense.     

Targeting properties of peptide-modified radiolabeled liposomal nanoparticles

Radiolabeled PEGylated liposomal nanoparticles (NPs) open new possibilities for a variety of applications including diagnosis, drug delivery, targeted therapy, and monitoring treatment effects. Here we describe the characterization of liposomal NPs (liposomes and micelles) derivatized with the somatostatin analogue tyrosine-3-octreotide as a proof of concept for tumor targeting. NPs were radiolabeled with indium-111, and targeting properties were evaluated in vitro on rat pancreatic tumor cells (AR42J), demonstrating specific binding and IC(50) values in the low nanomolar range. Biodistribution studies were performed in Lewis rats and compared to single-photon emission computed tomography images. Moderate tumor uptake was found in xenografted nude mice (<2.5% ID/g tissue) as compared to control. Micelles and liposomes revealed comparable pharmacokinetics and targeting properties. This study provides insight into tumor-targeting characteristics of peptide-derivatized liposomal NPs and can serve as a basis for further improvement of these constructs. FROM THE CLINICAL EDITOR: The authors investigated tumor-targeting characteristics of peptide-derivatized liposomal NPs. Similar radiolabeled PEGylated liposomal NPs open new possibilities for a variety of applications including diagnosis, drug delivery, targeted therapy, and treatment monitoring.     

Novel possibilities of development and therapeutical application of liposomes

Properties and possibilities of application of liposomal drug delivery systems are summarized in this review. Technological and biopharmeceutical criteria that have to be taken into consideration in the course of development of biocompatible liposomes are discussed. The manner and possibilities of active and passive targeting are shown according to the literary data and special liposome-based drug delivery systems responsible for pathologic or arteficial stimuli are introduced.     

Development of ligand-targeted liposomes for cancer therapy

The continued evolution of targeted liposomal therapeutics has resulted in new agents with remarkable antitumour efficacy and relatively mild toxicity profiles. A careful selection of the ligand is necessary to reduce immunogenicity, retain extended circulation lifetimes, target tumour-specific cell surface epitopes, and induce internalisation and subsequent release of the therapeutic substance from the liposome. Methods for assembling targeted liposomes, including a novel micellar insertion technology, for incorporation of targeting molecules that efficiently transforms a non-targeted liposomal therapeutic to a targeted one, greatly assist the translation of targeted liposome technology into the clinic. Targeting strategies with liposomes directed at solid tumours and vascular targets are discussed. The authors believe the development of ligand-targeted liposomes is now in the advanced stage and offers unique and important advantages among other targeted therapies. Anti-HER2 immunoliposomal doxorubicin is awaiting Phase I clinical trials, the results of which should provide new insights into the promise of ligand-targeted liposomal therapies.     

Development of ligand-targeted liposomes for cancer therapy

The continued evolution of targeted liposomal therapeutics has resulted in new agents with remarkable antitumour efficacy and relatively mild toxicity profiles. A careful selection of the ligand is necessary to reduce immunogenicity, retain extended circulation lifetimes, target tumour-specific cell surface epitopes, and induce internalisation and subsequent release of the therapeutic substance from the liposome. Methods for assembling targeted liposomes, including a novel micellar insertion technology, for incorporation of targeting molecules that efficiently transforms a non-targeted liposomal therapeutic to a targeted one, greatly assist the translation of targeted liposome technology into the clinic. Targeting strategies with liposomes directed at solid tumours and vascular targets are discussed. The authors believe the development of ligand-targeted liposomes is now in the advanced stage and offers unique and important advantages among other targeted therapies. Anti-HER2 immunoliposomal doxorubicin is awaiting Phase I clinical trials, the results of which should provide new insights into the promise of ligand-targeted liposomal therapies.     

Organic nanocarriers for cancer drug delivery

A major focus in translational cancer research is the study of nanocarriers as novel delivery systems for chemotherapeutics. Organic vesicular nanocarriers, such as liposomes and micelles, have the advantage of low toxicity and the versatility to carry diverse drugs and conjugate to targeting agents. This offers the potential for combining treatment and diagnosis (theranostics). Successful incorporation into these nanoformulations has been demonstrated for classical chemotherapeutic drugs that are mostly hydrophobic, small interfering RNA, biological therapeutics and specific nanoparticles, such as superparamagnetic nanoparticles. Liposomes and micelles appear to take advantage of the enhanced permeability and retention (EPR) effect in solid tumours to increase accumulation at the target site (passive targeting). This translates to the clinic, where liposomal drug formulations are reported to exhibit higher efficacy and less side effects. Multidrug formulations and combinations with other treatments, for example, radiation or radiofrequency ablation, to trigger drug release from the nanocarrier at the target site, are mostly at the pre-clinical stage. More complex formulations that incorporate treatment agents together with targeting (active targeting) and imaging molecules have also been investigated in in vivo models with encouraging results.     

Tumor cell targeting of liposome-entrapped drugs with phospholipid-anchored folic acid-PEG conjugates

Targeting of liposomes with phospholipid-anchored folate conjugates is an attractive approach to deliver chemotherapeutic agents to folate receptor (FR) expressing tumors. The use of polyethylene glycol (PEG)-coated liposomes with folate attached to the outer end of a small fraction of phospholipid-anchored PEG molecules appears to be the most appropriate way to combine long-circulating properties critical for liposome deposition in tumors and binding of liposomes to FR on tumor cells. Although a number of important formulation parameters remain to be optimized, there are indications, at least in one ascitic tumor model, that folate targeting shifts intra-tumor distribution of liposomes to the cellular compartment. In vitro, folate targeting enhances the cytotoxicity of liposomal drugs against FR-expressing tumor cells. In vivo, the therapeutic data are still fragmentary and appear to be formulation- and tumor model-dependent. Further studies are required to determine whether folate targeting can confer a clear advantage in efficacy and/or toxicity to liposomal drugs.     

Nanocarriers for cancer-targeted drug delivery

Nanoparticles as drug delivery system have received much attention in recent years, especially for cancer treatment. In addition to improving the pharmacokinetics of the loaded poorly soluble hydrophobic drugs by solubilizing them in the hydrophobic compartments, nanoparticles allowed cancer specific drug delivery by inherent passive targeting phenomena and adopted active targeting strategies. For this reason, nanoparticles-drug formulations are capable of enhancing the safety, pharmacokinetic profiles and bioavailability of the administered drugs leading to improved therapeutic efficacy compared to conventional therapy. The focus of this review is to provide an overview of various nanoparticle formulations in both research and clinical applications with a focus on various chemotherapeutic drug delivery systems for the treatment of cancer. The use of various nanoparticles, including liposomes, polymeric nanoparticles, dendrimers, magnetic and other inorganic nanoparticles for targeted drug delivery in cancer is detailed.     

Antibody-modified liposomes for cancer chemotherapy

Background: Liposomes, phospholipids, nanosized bubbles with a bilayered membrane structure, have drawn a lot of interest as pharmaceutical carriers for drugs and genes. In particular, liposomes are widely used for drug delivery into tumors. Objective: In many cases, to enhance the efficacy of the liposomal drugs, drug-loaded liposomes are targeted to the tumors by means of different specific ligands, such as monoclonal antibodies. Thus, this review analyzes the application of antibody-targeted liposomes loaded with various chemotherapeutic agents and various liposomal products under development at experimental and preclinical level. Methods: The papers published on the subject of cancer-targeted liposomes mainly over the last 10 - 15 years are discussed. Conclusion: Antibody-targeted liposomes loaded with anticancer drugs demonstrate high potential for clinical applications.     

Liposomal drug delivery systems: an update review

The discovery of liposome or lipid vesicle emerged from self forming enclosed lipid bi-layer upon hydration; liposome drug delivery systems have played a significant role in formulation of potent drug to improve therapeutics. Recently the liposome formulations are targeted to reduce toxicity and increase accumulation at the target site. There are several new methods of liposome preparation based on lipid drug interaction and liposome disposition mechanism including the inhibition of rapid clearance of liposome by controlling particle size, charge and surface hydration. Most clinical applications of liposomal drug delivery are targeting to tissue with or without expression of target recognition molecules on lipid membrane. The liposomes are characterized with respect to physical, chemical and biological parameters. The sizing of liposome is also critical parameter which helps characterize the liposome which is usually performed by sequential extrusion at relatively low pressure through polycarbonate membrane (PCM). This mode of drug delivery lends more safety and efficacy to administration of several classes of drugs like antiviral, antifungal, antimicrobial, vaccines, anti-tubercular drugs and gene therapeutics. Present applications of the liposomes are in the immunology, dermatology, vaccine adjuvant, eye disorders, brain targeting, infective disease and in tumour therapy. The new developments in this field are the specific binding properties of a drug-carrying liposome to a target cell such as a tumor cell and specific molecules in the body (antibodies, proteins, peptides etc.); stealth liposomes which are especially being used as carriers for hydrophilic (water soluble) anticancer drugs like doxorubicin, mitoxantrone; and bisphosphonate-liposome mediated depletion of macrophages. This review would be a help to the researchers working in the area of liposomal drug delivery.     

Targeting Anticancer Drugs to Tumor Vasculature Using Cationic Liposomes

Liposomal drug delivery systems improve the therapeutic index of chemotherapeutic agents, and the use of cationic liposomes to deliver anticancer drugs to solid tumors has recently been recognized as a promising therapeutic strategy to improve the effectiveness of conventional chemotherapeutics. This review summarizes the selective targeting of cationic liposomes to tumor vasculature, the merits of incorporating the polymer polyethylene-glycol (PEG), and the impact of the molar percent of the cationic lipid included in cationic liposomes on liposomal targeting efficacy. In addition, the discussion herein includes the therapeutic benefit of a dual targeting approach, using PEG-coated cationic liposomes in vascular targeting (of tumor endothelial cells), and tumor targeting (of tumor cells) of anticancer drugs. Cationic liposomes have shown considerable promise in preclinical xenograft models and are poised for clinical development.     

Liposomes for intravenous drug targeting: design and applications

Drug targeting with liposomes has been studied for over 25 years and has demonstrated its value in clinical practice. This mini review offers an overview of the design and application of liposomes for i.v. drug targeting. Two approaches are outlined: passive and active targeting. The former approach is based on liposomes with prolonged circulation and selective target localization properties, while in the latter approach specific targeting ligands are coupled to the liposome surface in order to achieve enhanced interaction with target cell membranes.