Selective intracellular delivery of dexamethasone into activated endothelial cells using an E-selectin-directed immunoconjugate

The medicinal chemistry evolution of antibody-drug conjugates

Antibody-drug conjugates (ADCs) comprise 3 components of wildly differing sizes: antibody (150 000 Da), linker (typically <500 Da) and payload (typically <500 Da). While the drug-linker makes up only a small percent of the ADC it has a disproportionately massive impact on all aspects of the ADC. Replacing maleimide with bromoacetamide (BrAc) affords stable attachment of the linker to the antibody cysteine, supports total flexibility for linker design and affords a more homogenous ADC. Optimisation of the protease cleavable dipeptide reduces aggregation, facilitates moderation of the physicochemical properties of the ADC and enables long-term stability to facilitate subcutaneous self-administration. Payloads are designed specifically to afford the optimal ADC. Structural information and SAR guide design to improve both potency and selectivity to the small molecule target improving the therapeutic index of resulting ADCs. Minimising the solvent exposed hydrophobic surface area improves the drug-like properties of the ADC, the realisation that the attachment heteroatom can be more than just the site for linker attachment as it can also drive potency and selectivity of the payload and the adoption of a prodrug strategy at project initiation are key areas that medicinal chemistry drives. For an optimal ADC the symbiotic relationship of the three structurally disparate components requires they all function in unison and medicinal chemistry has a huge role to ensure this happens.

Minimising the payload solvent exposed hydrophobic surface area optimises the antibody-drug conjugate properties

Glucocorticoid receptor modulators (GRMs) are an established and successful compound class for the treatment of multiple diseases. In addition, they are an area of high interest as payloads for antibody-drug conjugate s(ADCs) in both immunology and oncology. Solving the crystal structure of compound 2, the GRM payload from ABBV-3373 and ABBV-154, in the ligand binding domain of the glucocorticoid receptor (GR) revealed key information to facilitate optimal ADC payload design. All four critical H-bonds between the oxygen functional groups on the hexadecahydro-1H-cyclopenta[a]phenanthrene ring system of the small molecule and protein were shown to be made (carbonyl at C3 to Gln570 and Arg611 and Asn564, carbonyl at C20 to Thr739, hydroxyl at C21 to Asn 564 and Thr739). In addition, an extra H-bond between the linker attachment site on compound 2, the aniline in the biaryl region, was observed. Confirmation of the stereochemistry of the acetal in compound 2 as (R) was established. Finally, the importance of minimising the exposed hydrophobic surface area of a payload to reduce the negative impact on the properties of resulting ADCs, like aggregation, was rationalised by comparison of (R)-acetal compound 2 and (S)-acetal compound 3.

The Evolving Landscape of Antibody-Drug Conjugates: In Depth Analysis of Recent Research Progress

Antibody-drug conjugates (ADCs) are targeted immunoconjugate constructs that integrate the potency of cytotoxic drugs with the selectivity of monoclonal antibodies, minimizing damage to healthy cells and reducing systemic toxicity. Their design allows for higher doses of the cytotoxic drug to be administered, potentially increasing efficacy. They are currently among the most promising drug classes in oncology, with efforts to expand their application for nononcological indications and in combination therapies. Here we provide a detailed overview of the recent advances in ADC research and consider future directions and challenges in promoting this promising platform to widespread therapeutic use. We examine data from the CAS Content Collection, the largest human-curated collection of published scientific information, and analyze the publication landscape of recent research to reveal the exploration trends in published documents and to provide insights into the scientific advances in the area. We also discuss the evolution of the key concepts in the field, the major technologies, and their development pipelines with company research focuses, disease targets, development stages, and publication and investment trends. A comprehensive concept map has been created based on the documents in the CAS Content Collection. We hope that this report can serve as a useful resource for understanding the current state of knowledge in the field of ADCs and the remaining challenges to fulfill their potential.

Antibody drug conjugates beyond cytotoxic payloads

For many years, antibody drug conjugates (ADC) have teased with the promise of targeted payload delivery to diseased cells, embracing the targeting of the antibody to which a cytotoxic payload is conjugated. During the past decade this promise has started to be realised with the approval of more than a dozen ADCs for the treatment of various cancers. Of these ADCs, brentuximab vedotin really laid the foundations of a template for a successful ADC with lysosomal payload release from a cleavable dipeptide linker, measured DAR by conjugation to the Cys-Cys interchain bonds of the antibody and a cytotoxic payload. Using this ADC design model oncology has now expanded their repertoire of payloads to include non-cytotoxic compounds. These new payload classes have their origins in prior medicinal chemistry programmes aiming to design selective oral small molecule drugs. While this may not have been achieved, the resulting compounds provide excellent starting points for ADC programmes with some compounds amenable to immediate linker attachment while for others extensive SAR and structural information offer invaluable design insights. Many of these new oncology payload classes are of interest to other therapeutic areas facilitating rapid access to drug-linkers for exploration as non-oncology ADCs. Other therapeutic areas have also pursued unique payload classes with glucocorticoid receptor modulators (GRM) being the most clinically advanced in immunology. Here, ADC payloads come full circle, as oncology is now investigating GRM payloads for the treatment of cancer. This chapter aims to cover all these new ADC approaches while describing the medicinal chemistry origins of the new non-cytotoxic payloads.

Self-Immolative Carbamate Linkers for CD19-Budesonide Antibody-Drug Conjugates

Antibody-drug conjugates consist of potent small-molecule payloads linked to a targeting antibody. Payloads must possess a viable functional group by which a linker for conjugation can be attached. Linker-attachment options remain limited for the connection to payloads via hydroxyl groups. A releasing group based on 2-aminopyridine was developed to enable stable attachment of para-aminobenzyl carbamate (PABC) linkers to the C21-hydroxyl group of budesonide, a glucocorticoid receptor agonist. Payload release involves a cascade of two self-immolative events that are initiated by the protease-mediated cleavage of the dipeptide-PABC bond. Budesonide release rates were determined for a series of payload-linker intermediates in buffered solution at pH 7.4 and 5.4, leading to the identification of 2-aminopyridine as the preferred releasing group. Addition of a poly(ethylene glycol) group improved linker hydrophilicity, thereby providing CD19-budesonide ADCs with suitable properties. ADC23 demonstrated targeted delivery of budesonide to CD19-expressing cells and inhibited B-cell activation in mice.

An Overview of the Development and Preclinical Evaluation of Antibody-Drug Conjugates for Non-Oncological Applications

Typically, antibody-drug conjugates (ADCs) are made up of a humanized antibody and a small-molecule medication connected by a chemical linker. ADCs' ability to deliver cytotoxic agents to the specific site with reduced side effects showed promising results in oncology. To date, fourteen ADCs have been approved by the US Food and Drug Administration, and approximately 297 ADCs are in pre-clinical/clinical stages in the oncology area. Inspired by these outcomes, a few scientists explored the potential of antibody-drug conjugates in non-oncological conditions such as arthritis, myasthenia gravis, immunological disorders, and kidney failure. However, there are limited data available on the non-oncological applications of antibody-drug conjugates. This current review focuses on the non-oncological applications of antibody-drug conjugates, their developmental studies, testing procedures, in vitro evaluations, and pre-clinical testing. Additionally, a summary of the restrictions, difficulties, and prospects for ADCs in non-oncological applications is provided.

Synthesis and Characterization of Nanoparticle-Based Dexamethasone-Polypeptide Conjugates as Potential Intravitreal Delivery Systems

The use of dexamethasone for eye disease treatment is limited by its low solubility, bioavailability, and rapid elimination when applied topically. The covalent conjugation of dexamethasone with polymeric carriers is a promising strategy to overcome existing drawbacks. In this work, amphiphilic polypeptides capable of self-assembly into nanoparticles were proposed as potential delivery systems for intravitreal delivery. The nanoparticles were prepared and characterized using poly(L-glutamic acid-co-D-phenylalanine) and poly(L-lysine-co-D/L-phenylalanine) as well as poly(L-lysine-co-D/L-phenylalanine) covered with heparin. The critical association concentration for the polypeptides obtained was in the 4.2-9.4 μg/mL range. The hydrodynamic size of the formed nanoparticles was between 90 and 210 nm, and they had an index of polydispersity between 0.08 and 0.27 and an absolute zeta-potential value between 20 and 45 mV. The ability of nanoparticles to migrate in the vitreous humor was examined using intact porcine vitreous. Conjugation of DEX with polypeptides was performed by additional succinylation of DEX and activation of carboxyl groups introduced to react with primary amines in polypeptides. The structures of all intermediate and final compounds were verified by ¹H NMR spectroscopy. The amount of conjugated DEX can be varied from 6 to 220 µg/mg of polymer. The hydrodynamic diameter of the nanoparticle-based conjugates was increased to 200-370 nm, depending on the polymer sample and drug loading. The release of DEX from the conjugates due to hydrolysis of the ester bond between DEX and the succinyl moiety was studied both in a buffer medium and a vitreous/buffer mixture (50/50, v/v). As expected, the release in the vitreous medium was faster. However, the release rate could be controlled in the range of 96-192 h by varying the polymer composition. In addition, several mathematical models were used to assess the release profiles and figure out how DEX is released.

Discovery of ABBV-3373, an Anti-TNF Glucocorticoid Receptor Modulator Immunology Antibody Drug Conjugate

Using a convergent synthetic route to enable multiple points of diversity, a series of glucocorticoid receptor modulators (GRM) were profiled for potency, selectivity, and drug-like properties in vitro. Despite covering a large range of diversity, profiling the nonconjugated small molecule was suboptimal and they were conjugated to a mouse antitumor necrosis factor (TNF) antibody using the MP-Ala-Ala linker. Screening of the resulting antibody drug conjugates (ADCs) provided a better assessment of efficacy and physical properties, reinforcing the need to conduct structure-activity relationship studies on the complete ADC. DAR4 ADCs were screened in an acute mouse contact hypersensitivity model measuring biomarkers to ensure a sufficient therapeutic window. In a chronic mouse arthritis model, mouse anti-TNF GRM ADCs were efficacious after a single dose of 10 mg/kg i.p. for over 30 days. Data on the unconjugated payloads and mouse surrogate anti-TNF ADCs identified payload 17 which was conjugated to a human anti-TNF antibody and advanced to the clinic as ABBV-3373.

Reactive Oxygen Species Scavenging Nanomedicine for the Treatment of Ischemic Heart Disease

Ischemic heart disease (IHD) is the leading cause of disability and mortality worldwide. Reactive oxygen species (ROS) have been shown to play key roles in the progression of diabetes, hypertension, and hypercholesterolemia, which are independent risk factors that lead to atherosclerosis and the development of IHD. Engineered biomaterial-based nanomedicines are under extensive investigation and exploration, serving as smart and multifunctional nanocarriers for synergistic therapeutic effect. Capitalizing on cell/molecule-targeting drug delivery, nanomedicines present enhanced specificity and safety with favorable pharmacokinetics and pharmacodynamics. Herein, the roles of ROS in both IHD and its risk factors are discussed, highlighting cardiovascular medications that have antioxidant properties, and summarizing the advantages, properties, and recent achievements of nanomedicines that have ROS scavenging capacity for the treatment of diabetes, hypertension, hypercholesterolemia, atherosclerosis, ischemia/reperfusion, and myocardial infarction. Finally, the current challenges of nanomedicines for ROS-scavenging treatment of IHD and possible future directions are discussed from a clinical perspective.

Current innovative engineered antibodies

Antibody engineering has developed very intensively since the invention of the hybridoma technology in 1975, and it now can generate therapeutic agents with high specificity and reduced adverse effects. Indeed, antibodies have become one of the most innovative therapeutic agents in recent years, with some landing in the top 10 bestselling pharmaceutical drugs. New antibodies are being approved every year, in different formats and for treating various illnesses, including cancer, autoimmune inflammatory diseases, metabolic diseases and infectious diseases. In this review, I summarize current progress in innovative engineered antibodies. Overall, this progress has led to the approval by regulatory authorities of more than 100 antibody-based molecules, with many others at various stages of clinical development, indicating the high growth potential of the field.

A homogeneous high-DAR antibody-drug conjugate platform combining THIOMAB antibodies and XTEN polypeptides

The antibody-drug conjugate (ADC) is a well-validated modality for the cell-specific delivery of small molecules with impact expanding rapidly beyond their originally-intended purpose of treating cancer. However, antibody-mediated delivery (AMD)...

Antibody-Drug Conjugates: Functional Principles and Applications in Oncology and Beyond

In the era of precision medicine, antibody-based therapeutics are rapidly enriched with emerging advances and new proof-of-concept formats. In this context, antibody-drug conjugates (ADCs) have evolved to merge the high selectivity and specificity of monoclonal antibodies (mAbs) with the cytotoxic potency of attached payloads. So far, ten ADCs have been approved by FDA for oncological indications and many others are currently being tested in clinical and preclinical level. This paper summarizes the essential components of ADCs, from their functional principles and structure up to their limitations and resistance mechanisms, focusing on all latest bioengineering breakthroughs such as bispecific mAbs, dual-drug platforms as well as novel linkers and conjugation chemistries. In continuation of our recent review on anticancer implication of ADC's technology, further insights regarding their potential usage outside of the oncological spectrum are also presented. Better understanding of immunoconjugates could maximize their efficacy and optimize their safety, extending their use in everyday clinical practice.

Targeting drug delivery in the vascular system: Focus on endothelium

The bloodstream is the main transporting pathway for drug delivery systems (DDS) from the site of administration to the intended site of action. In many cases, components of the vascular system represent therapeutic targets. Endothelial cells, which line the luminal surface of the vasculature, play a tripartite role of the key target, barrier, or victim of nanomedicines in the bloodstream. Circulating DDS may accumulate in the vascular areas of interest and in off-target areas via mechanisms bypassing specific molecular recognition, but using ligands of specific vascular determinant molecules enables a degree of precision, efficacy, and specificity of delivery unattainable by non-affinity DDS. Three decades of research efforts have focused on specific vascular targeting, which have yielded a multitude of DDS, many of which are currently undergoing a translational phase of development for biomedical applications, including interventions in the cardiovascular, pulmonary, and central nervous systems, regulation of endothelial functions, host defense, and permeation of vascular barriers. We discuss the design of endothelial-targeted nanocarriers, factors underlying their interactions with cells and tissues, and describe examples of their investigational use in models of acute vascular inflammation with an eye on translational challenges.

Antibody Conjugates-Recent Advances and Future Innovations

Monoclonal antibodies have evolved from research tools to powerful therapeutics in the past 30 years. Clinical success rates of antibodies have exceeded expectations, resulting in heavy investment in biologics discovery and development in addition to traditional small molecules across the industry. However, protein therapeutics cannot drug targets intracellularly and are limited to soluble and cell-surface antigens. Tremendous strides have been made in antibody discovery, protein engineering, formulation, and delivery devices. These advances continue to push the boundaries of biologics to enable antibody conjugates to take advantage of the target specificity and long half-life from an antibody, while delivering highly potent small molecule drugs. While the "magic bullet" concept produced the first wave of antibody conjugates, these entities were met with limited clinical success. This review summarizes the advances and challenges in the field to date with emphasis on antibody conjugation, linker-payload chemistry, novel payload classes, absorption, distribution, metabolism, and excretion (ADME), and product developability. We discuss lessons learned in the development of oncology antibody conjugates and look towards future innovations enabling other therapeutic indications.

Pushing the Envelope: Advancement of ADCs Outside of Oncology

The majority of ADCs in preclinical and clinical development are for oncology indications where cytotoxic payloads are targeted to antigen-expressing cancer cells. However, the modulation of pathogenic cellular activity via ADC-mediated delivery of bioactive small molecules is also an attractive concept for non-oncology indications leading to an expanded application of the technology. Here we summarize those ADCs that have been described so far for non-oncology applications and which cover a variety of payload mechanisms beyond cell killing, from early in vitro proof-of-concept experiments to clinical trials. As our understanding of ADC technology continues to grow, it is anticipated that the development of ADCs as therapeutics for disease areas outside of oncology will also increase.

Carnosic Acid, Tangeretin, and Ginkgolide-B Anti-neoplastic Cytotoxicity in Dual Combination with Dexamethasone-[anti-EGFR] in Pulmonary Adenocarcinoma (A549)

Background:

Traditional chemotherapeutics of low-molecular weight diffuse passively across intact membrane structures of normal healthy cells found in tissues and organ systems in a non-specific unrestricted manner which largely accounts for the induction of most sequelae which restrict dosage, administration frequency, and duration of therapeutic intervention. Molecular strategies that offer enhanced levels of potency, greater efficacy and broader margins-of-safety include the discovery of alternative candidate therapeutics and development of methodologies capable of mediating properties of selective “targeted” delivery.

Materials and Methods:

The covalent immunopharmaceutical, dexamethasone-(C21-phosphoramidate)-[anti- EGFR] was synthesized utilizing organic chemistry reactions that comprised a multi-stage synthesis regimen. Multiple forms of analysis were implemented to vadliate the successful synthesis (UV spectrophotometric absorbance), purity and molar-incorporation-index (UV spectrophotometric absorbance, chemical-based protein determination), absence of fragmentation/polymerization (SDS-PAGE/chemiluminescent autoradiography), retained selective binding-avidity of IgG-immunoglobulin (cell-ELISA); and selectively “targeted” antineoplastic cytotoxicity (biochemistry-based cell vitality/viability assay).

Results:

The botanicals carnosic acid, ginkgolide-B and tangeretin, each individually exerted maximum antineoplastic cytotoxicity levels of 58.1%, 5.3%, and 41.1% respectively against pulmonary adenocarcinoma (A549) populations. Dexamethasone-(C21-phosphoramidate)-[anti-EGFR] formulated at corticosteroid/ glucocorticoid equivalent concentrations produced anti-neoplastic cytotoxicity at levels of 7.7% (10-9 M), 26.9% (10-8 M), 64.9% (10-7 M), 69.9% (10-6 M) and 73.0% (10-5 M). Ccarnosic acid, ginkgolide-B and tangeretin in simultaneous dual-combination with dexamethasone-(C21-phosphoramidate)-[anti-EGFR] exerted maximum anti-neoplastic cytotoxicity levels of 70.5%, 58.6%, and 69.7% respectively.

Discussion:

Carnosic acid, ginkgolide-B and tangeretin botanicals exerted anti-neoplastic cytotoxicity against pulmonary adenocarcinoma (A549) which additively contributed to the anti-neoplastic cytotoxic potency of the covalent immunopharmaceutical, dexamethasone-(C21-phosphoramidate)-[anti-EGFR]. Carnosic acid and tangeretin were most potent in this regard both individually and in dual-combination with dexamethasone-(C21- phosphoramidate)-[anti-EGFR]. Advantages and attributes of carnosic acid and tangeretin as potential monotherapeutics are a wider margin-of-safety of conventional chemotherapeutics which would readily complement the selective “targeted” delivery properties of dexamethasone-(C21-phosphoramidate)-[anti-EGFR] and possibly other covalent immunopharmaceuticals in addition to providing opportunities for the discovery of combination therapies that provide heightened levels of anti-neoplastic efficacy.

E-beam crosslinked nanogels conjugated with monoclonal antibodies in targeting strategies

Poly(N-vinyl pyrrolidone)-based-nanogels (NGs), produced by e-beam irradiation, are conjugated with monoclonal antibodies (mAb) for active targeting purposes. The uptake of immuno-functionalized nanogels is tested in an endothelial cell line, ECV304, using confocal and epifluorescence microscopy. Intracellular localization studies reveal a faster uptake of the immuno-nanogel conjugate with respect to the ‘bare’ nanogel. The specific internalization pathway of these immuno-nanogels is clarified by selective endocytosis inhibition experiments, flow cytometry and confocal microscopy. Active targeting ability is also verified by conjugating a monoclonal antibody which recognizes the αvβ3 integrin on activated endothelial cells. Epifluorescence images of the ‘wound healing assay’ on ECV304 cells provide evidence of nanogels localization only in the target cells. Therefore, the immuno-nanogels produced have the potential to recognize specific cell types in heterogeneous systems, which makes them promising candidates for targeted drug delivery applications.

Dexamethasone-(C21-phosphoramide)-[anti-EGFR]: molecular design, synthetic organic chemistry reactions, and antineoplastic cytotoxic potency against pulmonary adenocarcinoma (A549)

PURPOSE

Corticosteroids are effective in the management of a variety of disease states, such as several forms of neoplasia (leukemia and lymphoma), autoimmune conditions, and severe inflammatory responses. Molecular strategies that selectively "target" delivery of corticosteroids minimize or prevents large amounts of the pharmaceutical moiety from passively diffusing into normal healthy cell populations residing within tissues and organ systems.

MATERIALS AND METHODS

The covalent immunopharmaceutical, dexamethasone-(C21-phosphoramide)-[anti-EGFR] was synthesized by reacting dexamethasone-21-monophosphate with a carbodiimide reagent to form a dexamethasone phosphate carbodiimide ester that was subsequently reacted with imidazole to create an amine-reactive dexamethasone-(C21-phosphorylimidazolide) intermediate. Monoclonal anti-EGFR immunoglobulin was combined with the amine-reactive dexamethasone-(C21-phosphorylimidazolide) intermediate, resulting in the synthesis of the covalent immunopharmaceutical, dexamethasone-(C21-phosphoramide)-[anti-EGFR]. Following spectrophotometric analysis and validation of retained epidermal growth factor receptor type 1 (EGFR)-binding avidity by cell-ELISA, the selective anti-neoplasic cytotoxic potency of dexamethasone-(C21-phosphoramide)-[anti-EGFR] was established by MTT-based vitality stain methodology using adherent monolayer populations of human pulmonary adenocarcinoma (A549) known to overexpress the tropic membrane receptors EGFR and insulin-like growth factor receptor type 1.

RESULTS

The dexamethasone:IgG molar-incorporation-index for dexamethasone-(C21-phosphoramide)-[anti-EGFR] was 6.95:1 following exhaustive serial microfiltration. Cytotoxicity analysis: covalent bonding of dexamethasone to monoclonal anti-EGFR immunoglobulin did not significantly modify the ex vivo antineoplastic cytotoxicity of dexamethasone against pulmonary adenocarcinoma at and between the standardized dexamethasone equivalent concentrations of 10(-9) M and 10(-5) M. Rapid increases in antineoplastic cytotoxicity were observed at and between the dexamethasone equivalent concentrations of 10(-9) M and 10(-7) M where cancer cell death increased from 7.7% to a maximum of 64.9% (92.3%-35.1% residual survival), respectively, which closely paralleled values for "free" noncovalently bound dexamethasone.

DISCUSSION

Organic chemistry reaction regimens were optimized to develop a multiphase synthesis regimen for dexamethasone-(C21-phosphoramide)-[anti-EGFR]. Attributes of dexamethasone-(C21-phosphoramide)-[anti-EGFR] include a high dexamethasone molar incorporation-index, lack of extraneous chemical group introduction, retained EGFR-binding avidity ("targeted" delivery properties), and potential to enhance long-term pharmaceutical moiety effectiveness.

Targeted endothelial nanomedicine for common acute pathological conditions

Endothelium, a thin monolayer of specialized cells lining the lumen of blood vessels is the key regulatory interface between blood and tissues. Endothelial abnormalities are implicated in many diseases, including common acute conditions with high morbidity and mortality lacking therapy, in part because drugs and drug carriers have no natural endothelial affinity. Precise endothelial drug delivery may improve management of these conditions. Using ligands of molecules exposed to the bloodstream on the endothelial surface enables design of diverse targeted endothelial nanomedicine agents. Target molecules and binding epitopes must be accessible to drug carriers, carriers must be free of harmful effects, and targeting should provide desirable sub-cellular addressing of the drug cargo. The roster of current candidate target molecules for endothelial nanomedicine includes peptidases and other enzymes, cell adhesion molecules and integrins, localized in different domains of the endothelial plasmalemma and differentially distributed throughout the vasculature. Endowing carriers with an affinity to specific endothelial epitopes enables an unprecedented level of precision of control of drug delivery: binding to selected endothelial cell phenotypes, cellular addressing and duration of therapeutic effects. Features of nanocarrier design such as choice of epitope and ligand control delivery and effect of targeted endothelial nanomedicine agents. Pathological factors modulate endothelial targeting and uptake of nanocarriers. Selection of optimal binding sites and design features of nanocarriers are key controllable factors that can be iteratively engineered based on their performance from in vitro to pre-clinical in vivo experimental models. Targeted endothelial nanomedicine agents provide antioxidant, anti-inflammatory and other therapeutic effects unattainable by non-targeted counterparts in animal models of common acute severe human disease conditions. The results of animal studies provide the basis for the challenging translation endothelial nanomedicine into the clinical domain.

Cell-Mediated Dexamethasone Release from Semi-IPNs Stimulates Osteogenic Differentiation of Encapsulated Mesenchymal Stem Cells

Scaffold-based delivery of bioactive molecules capable of directing stem cell differentiation is critical to the development of point-of-care cell therapy for orthopedic repair. Dexamethasone-conjugated hyaluronic acid (HA-DXM) was synthesized and combined with hydrolytically degradable, photo-cross-linkable PEG-bis(2-acryloyloxy propanoate) (PEG-bis-AP) to form semi-IPNs. Dexamethasone (DX) release was limited in physiological buffer and substantially increased in the presence of encapsulated human mesenchymal stem cells (hMSCs) or exogenous hyaluronidase, confirming that release occurred primarily by a cell-mediated enzymatic mechanism. hMSCs encapsulated in PEG-bis-AP/HA-DXM semi-IPNs increased osteoblast-specific gene expression, alkaline phosphatase activity, and matrix mineralization, attaining levels that were not significantly different from positive controls consisting of hMSCs in PEG-bis-AP/native HA cultured with DX supplementation in the culture medium. These studies demonstrate that PEG-bis-AP/HA-DXM semi-IPNs can provide cell-mediated release of bioactive free DX that induces hMSC osteogenic differentiation. This approach offers an efficient system for local delivery of osteogenic molecules empowering point of care applications.

A dual-delivery system of pH-responsive chitosan-functionalized mesoporous silica nanoparticles bearing BMP-2 and dexamethasone for enhanced bone regeneration

Bone morphogenetic protein-2 (BMP-2) is considered one of the most effective and extensively used growth factors to induce osteoblast differentiation and accelerate bone regeneration. Dexamethasone (Dex) with suitable dosage can enhance BMP-2-induced osteoblast differentiation. To strengthen this synergistic osteoinductive effect, a pH-responsive chitosan-functionalized mesoporous silica nanoparticle (chi-MSN) ensemble was fabricated for dual-delivery of BMP-2 and Dex. The MSNs are prepared by a CTAB-templated sol-gel method, and further coated by chitosan via the crosslinking of glycidoxypropyltrimethoxysilane (GPTMS). The small Dex is encapsulated in the mesopores and the large BMP-2 is incorporated into the chitosan coating. These chi-MSNs can quickly release BMP-2 in a bioactive form and can then be efficiently endocytosed and further realize a controlled release of Dex with the decreased pH value into/in cells. With the synergistic action of BMP-2 and Dex outside and inside the cell, this dual hybrid delivery system can significantly stimulate osteoblast differentiation and bone regeneration in vitro and in vivo. Together, this dual-delivery strategy for osteogenic protein delivery may enhance clinical outcomes by retaining the bioactivity and optimizing the release mode of the drug/protein.

Icam-1 targeted nanogels loaded with dexamethasone alleviate pulmonary inflammation

Lysozyme dextran nanogels (NG) have great potential in vitro as a drug delivery platform, combining simple chemistry with rapid uptake and cargo release in target cells with “stealth” properties and low toxicity. In this work, we study for the first time the potential of targeted NG as a drug delivery platform in vivo to alleviate acute pulmonary inflammation in animal model of LPS-induced lung injury. NG are targeted to the endothelium via conjugation with an antibody (Ab) directed to Intercellular Adhesion Molecule-1(ICAM-NG), whereas IgG conjugated NG (IgG-NG) are used for control formulations. The amount of Ab conjugated to the NG and distribution in the body after intravenous (IV) injection have been quantitatively analyzed using a tracer isotope-labeled [¹²⁵I]IgG. As a proof of concept, Ab-NG are loaded with dexamethasone, an anti-inflammatory therapeutic, and the drug uptake and release kinetics are measured by HPLC. In vivo studies in mice showed that: i) ICAM-NG accumulates in mouse lungs (∼120% ID/g vs ∼15% ID/g of IgG-NG); and, ii) DEX encapsulated in ICAM-NG, but not in IgG-NG practically blocks LPS-induced overexpression of pro-inflammatory cell adhesion molecules including ICAM-1 in the pulmonary inflammation.

Relationship between Leukopenia and Intercellular Adhesion Molecules in Graves' Disease

OBJECTIVE

Changes in soluble intercellular adhesion molecule-1 (sICAM-1) and E-selectin levels as well as leukocyte count were examined in this study to explore the relationship between leukopenia and ICAMs in Graves' disease (GD).

METHODS

Fasting blood samples were obtained from 37 GD patients with normal leukocytes and 32 GD patients with leukopenia. Enzyme-linked immunosorbent assay (ELISA) was performed to determine serum sICAM-1 and E-selectin levels for comparison. The same analyses were repeated for the GD patients with leukopenia after glucocorticoid treatment (15 mg/day to 30 mg/day prednisone).

RESULTS

The ELISA results showed that E-selectin levels were higher in GD patients with leukopenia than those with normal leukocytes (p < 0.05), but these levels decreased after glucocorticoid (prednisone) treatment (p < 0.05). No significant change in sICAM-1 levels was observed (p = 0.12). Correlation analysis showed that leukocyte count and E-selectin were negatively correlated (r = -0.778; p < 0.05).

CONCLUSION

E-selectin may have an important function in GD with leukopenia, and glucocorticoids (prednisone) could decrease E-selectin level, which may be a new therapy target for GD with leukopenia.

Vascular targeting of nanocarriers: perplexing aspects of the seemingly straightforward paradigm

Targeted nanomedicine holds promise to find clinical use in many medical areas. Endothelial cells that line the luminal surface of blood vessels represent a key target for treatment of inflammation, ischemia, thrombosis, stroke, and other neurological, cardiovascular, pulmonary, and oncological conditions. In other cases, the endothelium is a barrier for tissue penetration or a victim of adverse effects. Several endothelial surface markers including peptidases (e.g., ACE, APP, and APN) and adhesion molecules (e.g., ICAM-1 and PECAM) have been identified as key targets. Binding of nanocarriers to these molecules enables drug targeting and subsequent penetration into or across the endothelium, offering therapeutic effects that are unattainable by their nontargeted counterparts. We analyze diverse aspects of endothelial nanomedicine including (i) circulation and targeting of carriers with diverse geometries, (ii) multivalent interactions of carrier with endothelium, (iii) anchoring to multiple determinants, (iv) accessibility of binding sites and cellular response to their engagement, (v) role of cell phenotype and microenvironment in targeting, (vi) optimization of targeting by lowering carrier avidity, (vii) endocytosis of multivalent carriers via molecules not implicated in internalization of their ligands, and (viii) modulation of cellular uptake and trafficking by selection of specific epitopes on the target determinant, carrier geometry, and hydrodynamic factors. Refinement of these aspects and improving our understanding of vascular biology and pathology is likely to enable the clinical translation of vascular endothelial targeting of nanocarriers.

Polyglycerolsulfate functionalized gold nanorods as optoacoustic signal nanoamplifiers for in vivo bioimaging of rheumatoid arthritis

We have synthesized a targeted imaging agent for rheumatoid arthritis based on polysulfated gold nanorods. The CTAB layer on gold nanorods was first replaced with PEG-thiol and then with dendritic polyglycerolsulfate at elevated temperature, which resulted in significantly reduced cytotoxicity compared to polyanionic gold nanorods functionalized by non-covalent approaches. In addition to classical characterization methods, we have established a facile UV-VIS based BaCl₂ agglomeration assay to confirm a quantitative removal of unbound ligand. With the help of a competitive surface plasmon resonance-based L-selectin binding assay and a leukocyte adhesion-based flow cell assay, we have demonstrated the high inflammation targeting potential of the synthesized gold nanorods in vitro. In combination with the surface plasmon resonance band of AuNRs at 780 nm, these findings permitted the imaging of inflammation in an in vivo mouse model for rheumatoid arthritis with high contrast using multispectral optoacoustic tomography. The study offers a robust method for otherwise difficult to obtain covalently functionalized polyanionic gold nanorods, which are suitable for biological applications as well as a low-cost, actively targeted, and high contrast imaging agent for the diagnosis of rheumatoid arthritis. This paves the way for further research in other inflammation associated pathologies, in particular, when photothermal therapy can be applied.

3D tissue engineered supramolecular hydrogels for controlled chondrogenesis of human mesenchymal stem cells

Despite a wide investigation of hydrogels as an artificial extracellular matrix, there are few scaffold systems for the facile spatiotemporal control of mesenchymal stem cells (MSCs). Here, we report 3D tissue engineered supramolecular hydrogels prepared with highly water-soluble monofunctionalized cucurbit[6]uril-hyaluronic acid (CB[6]-HA), diaminohexane conjugated HA (DAH-HA), and drug conjugated CB[6] (drug-CB[6]) for the controlled chondrogenesis of human mesenchymal stem cells (hMSCs). The mechanical property of supramolecular HA hydrogels was modulated by changing the cross-linking density for the spatial control of hMSCs. In addition, the differentiation of hMSCs was temporally controlled by changing the release profiles of transforming growth factor-β3 (TGF-β3) and/or dexamethasone (Dexa) from the hydrolyzable Dexa-CB[6]. The effective chondrogenic differentiation of hMSCs encapsulated in the monoCB[6]/DAH-HA hydrogel with TGF-β3 and Dexa-CB[6] was confirmed by biochemical glycosaminoglycan content analysis, real-time quantitative PCR, histological, and immunohistochemical analyses. Taken together, we could confirm the feasibility of cytocompatible monoCB[6]/DAH-HA hydrogels as a platform scaffold with controlled drug delivery for cartilage regeneration and other various tissue engineering applications.

Delivery of Polymeric Nanoparticles to Target Vascular Diseases

Current advances in nanotechnology have paved the way for the early detection, prevention and treatment of various diseases such as vascular disorders and cancer. These advances have provided novel approaches or modalities of incorporating or adsorbing therapeutic, biosensor and targeting agents into/on nanoparticles. With significant progress, nanomedicine for vascular therapy has shown significant advantages over traditional medicine because of its ability to selectively target the disease site and reduce adverse side effects. Targeted delivery of nanoparticles to vascular endothelial cells or the vascular wall provides an effective and more efficient way for early detection and/or treatment of vascular diseases such as atherosclerosis, thrombosis and Cerebrovascular Amyloid Angiopathy (CAA). Clinical applications of biocompatible and biodegradable polymers in areas such as vascular graft, implantable drug delivery, stent devices and tissue engineering scaffolds have advanced the candidature of polymers as potential nano-carriers for vascular-targeted delivery of diagnostic agents and drugs. This review focuses on the basic aspects of the vasculature and its associated diseases and relates them to polymeric nanoparticle-based strategies for targeting therapeutic agents to diseased vascular site.

Effective siRNA delivery to inflamed primary vascular endothelial cells by anti-E-selectin and anti-VCAM-1 PEGylated SAINT-based lipoplexes

The endothelium represents an attractive therapeutic target due to its pivotal role in many diseases including chronic inflammation and cancer. Small interfering RNAs (siRNAs) specifically interfere with the expression of target genes and are considered an important new class of therapeutics. However, due to their size and charge, siRNAs do not spontaneously enter unperturbed endothelial cells (EC). To overcome this problem, we developed novel lipoplexes for siRNA delivery that are based on the cationic amphiphilic lipid SAINT-C18. Antibodies recognizing disease induced cell adhesion molecules were employed to create cell specificity resulting in so-called antibody-SAINTargs. To improve particle stability, antibody-SAINTargs were further optimized for EC-specific siRNA-mediated gene silencing by addition of polyethylene glycol (PEG). Although PEGylated antibody-SAINTargs maintained specificity, they lost their siRNA delivery capacity. Coupling of antibodies to the distal end of PEG (so-called antibody-SAINTPEGargs), resulted in anti-E-selectin- and anti-vascular cell adhesion molecule (VCAM)-1-SAINTPEGarg that preserved their antigen recognition and their capability to specifically deliver siRNA into inflammation-activated primary endothelial cells. The enhanced uptake of siRNA by antibody-SAINTPEGargs was followed by improved silencing of the target gene VE-cadherin, demonstrating that antibody-SAINTPEGargs were capable of functionally delivering siRNA into primary endothelial cells originating from different vascular beds. In conclusion, the newly developed, physicochemically stable, and EC-specific siRNA carrying antibody-SAINTPEGargs selectively down-regulate target genes in primary endothelial cells that are generally difficult to transfect.

Targeted Drug Delivery to Endothelial Adhesion Molecules

Endothelial cells represent important targets for therapeutic and diagnostic interventions in many cardiovascular, pulmonary, neurological, inflammatory, and metabolic diseases. Targeted delivery of drugs (especially potent and labile biotherapeutics that require specific subcellular addressing) and imaging probes to endothelium holds promise to improve management of these maladies. In order to achieve this goal, drug cargoes or their carriers including liposomes and polymeric nanoparticles are chemically conjugated or fused using recombinant techniques with affinity ligands of endothelial surface molecules. Cell adhesion molecules, constitutively expressed on the endothelial surface and exposed on the surface of pathologically altered endothelium—selectins, VCAM-1, PECAM-1, and ICAM-1—represent good determinants for such a delivery. In particular, PECAM-1 and ICAM-1 meet criteria of accessibility, safety, and relevance to the (patho)physiological context of treatment of inflammation, ischemia, and thrombosis and offer a unique combination of targeting options including surface anchoring as well as intra- and transcellular targeting, modulated by parameters of the design of drug delivery system and local biological factors including flow and endothelial phenotype. This review includes analysis of these factors and examples of targeting selected classes of therapeutics showing promising results in animal studies, supporting translational potential of these interventions.

Multi-ligand poly(L-lactic-co-glycolic acid) nanoparticles inhibit activation of endothelial cells

Endothelial cell (EC) activation and inflammation is a key step in the initiation and progression of many cardiovascular diseases. Targeted delivery of therapeutic reagents to inflamed EC using nanoparticles is challenging as nanoparticles do not arrest on EC efficiently under high shear stress. In this study, we developed a novel polymeric platelet-mimicking nanoparticle for strong particle adhesion onto ECs and enhanced particle internalization by ECs. This nanoparticle was encapsulated with dexamethasone as the anti-inflammatory drug, and conjugated with polyethylene glycol, glycoprotein 1b, and trans-activating transcriptional peptide. The multi-ligand nanoparticle showed significantly greater adhesion on P-selectin, von Willebrand Factor, than the unmodified particles, and activated EC in vitro under both static and flow conditions. Treatment of injured rat carotid arteries with these multi-ligand nanoparticles suppressed neointimal stenosis more than unconjugated nanoparticles did. These results indicate that this novel multi-ligand nanoparticle is efficient to target inflamed EC and inhibit inflammation and subsequent stenosis.

E-selectin as a target for drug delivery and molecular imaging

E-selectin, also known as CD62E, is a cell adhesion molecule expressed on endothelial cells activated by cytokines. Like other selectins, it plays an important part in inflammation and in the adhesion of metastatic cancer cells to the endothelium. E-selectin recognizes and binds to sialylated carbohydrates present on the surface proteins of certain leukocytes. E-selectin has been chosen as a target for several therapeutic and medical imaging applications, based on its expression in the vicinity of inflammation, infection or cancer. These systems for drug delivery and molecular imaging include immunoconjugates, liposomes, nanoparticles, and microparticles prepared from a wide range of starting materials including lipids, synthetic polymers, polypeptides and organo-metallic structures. After a brief introduction presenting the selectin family and their implication in physiology and pathology, this review focuses on the formulation of these new delivery systems targeting E-selectin at a molecular level.

Recent developments in carbohydrate-decorated targeted drug/gene delivery

Targeted delivery of a drug or gene to its site of action has clear therapeutic advantages by maximizing its therapeutic efficiency and minimizing its systemic toxicity. Generally, targeted drug or gene delivery is performed by loading a macromolecular carrier with an appropriate drug or gene, and by targeting the drug/gene carrier to specific cell or tissue with the help of specific targeting ligand. The emergence of glycobiology, glycotechnology, and glycomics and their continual adaptation by pharmaceutical scientists have opened exciting avenue of medicinal applications of carbohydrates. Among them, the biocompatibility and specific receptor recognition ability confer the ability of carbohydrates as potential targeting ligands for targeted drug and gene delivery applications. This review summarizes recent progress of carbohydrate-decorated targeted drug/gene delivery applications.

Inhibition of proinflammatory genes in anti-GBM glomerulonephritis by targeted dexamethasone-loaded AbEsel liposomes

E-selectin-directed targeted drug delivery was analyzed in anti-glomerular basement membrane glomerulonephritis. Liposomes conjugated with anti-E-selectin antibodies (AbEsel liposomes) were internalized by activated endothelial cells in vitro through E-selectin-mediated endocytosis. At the onset of glomerulonephritis in mice, E-selectin was expressed on glomerular endothelial cells, which resulted in homing of AbEsel liposomes to glomeruli after intravenous administration. Accumulation of AbEsel liposomes in the kidney was 3.6 times higher than nontargeted IgG liposomes, whereas the accumulation of both liposomes in the clearance organs liver and spleen and in heart and lungs was comparable. In glomeruli, the AbEsel liposomes colocalized with the endothelial cell marker CD31. Quantitative RT-PCR analysis of laser-microdissected arterioles, glomeruli, and postcapillary venules demonstrated that targeted delivery of dexamethasone by AbEsel liposomes reduced glomerular endothelial expression of P-selectin, E-selectin, and vascular cell adhesion molecule-1 by 60–70%. The expression of these genes was not modulated in endothelial cells in nontargeted renal microvasculatures. Decrease of glomerular endothelial activation at disease onset was followed by reduced albuminuria at day 7. This study demonstrates the potential of vascular bed-specific drug delivery aimed at disease-induced epitopes on the microvascular endothelial cells as a therapeutic strategy for glomerulonephritis.

Delivery of Anti-Platelet-Endothelial Cell Adhesion Molecule Single-Chain Variable Fragment-Urokinase Fusion Protein to the Cerebral Vasculature Lyses Arterial Clots and Attenuates Postischemic Brain Edema

Efficacy and safety of current means to prevent cerebrovascular thrombosis in patients at high risk of stroke are suboptimal. In theory, anchoring fibrinolytic plasminogen activators to the luminal surface of the cerebral endothelium might arrest formation of occlusive clots in this setting. We tested this approach using the recombinant construct antiplatelet-endothelial cell adhesion molecule (PECAM) single-chain variable fragment (scFv)-urokinase-type plasminogen activator (uPA), fusing low-molecular-weight single-chain urokinase-type plasminogen activator with a scFv of an antibody directed to the stably expressed endothelial surface determinant PECAM-1, implicated in inflammation and thrombosis. Studies in mice showed that scFv-uPA, but not unconjugated uPA 1) accumulates in the brain after intravascular injection, 2) lyses clots lodged in the cerebral arterial vasculature without hemorrhagic complications, 3) provides rapid and stable cerebral reperfusion, and 4) alleviates post-thrombotic brain edema. Effective and safe thromboprophylaxis in the cerebral arterial circulation by anti-PECAM scFv-uPA represents a prototype of a new paradigm to prevent recurrent cerebrovascular thrombosis.

Factors modulating the delivery and effect of enzymatic cargo conjugated with antibodies targeted to the pulmonary endothelium

Vascular drug targeting may improve therapies, yet a thorough understanding of the factors that regulate effects of drugs directed to the endothelium is needed to translate this approach into the clinical domain. To define factors modulating the efficacy and effects of endothelial targeting, we used a model enzyme (glucose oxidase, GOX) coupled with monoclonal antibodies (anti-TM(34) or anti-TM(201)) to distinct epitopes of thrombomodulin, a surface determinant enriched in the pulmonary endothelium. GOX delivery results in conversion of glucose and oxygen into H(2)O(2) leading to lung damage, a clear physiologic endpoint. Results of in vivo studies in mice showed that the efficiency of cargo delivery and its effect are influenced by a number of factors including: 1) The level of pulmonary uptake of the targeting antibody (anti-TM(201) was more efficient than anti-TM(34)); 2) The amount of an active drug delivered to the target; 3) The amount of target antigen on the endothelium (animals with suppressed TM levels showed less targeting); and, 4) The substrate availability for the enzyme cargo in the target tissue (hyperoxia augmented GOX-induced injury). Therefore, both activities of the conjugates and biological factors control targeting and effects of enzymatic cargo. Understanding the nature of such "modulating biological factors" will hopefully allow optimization and ultimately applications of drug targeting for "individualized" pharmacotherapy.

Targeting of angiogenic endothelial cells at sites of inflammation by dexamethasone phosphate-containing RGD peptide liposomes inhibits experimental arthritis

OBJECTIVE

To investigate whether RGD peptide-exposing long circulating polyethylene glycol (PEG) liposomes (RGD-PEG-L) targeted to alphavbeta3 integrins expressed on angiogenic vascular endothelial cells (VECs) are able to bind VECs at sites of inflammation and whether such liposomes containing dexamethasone phosphate (DEXP) can be used as carriers to interfere with the development of experimental arthritis.

METHODS

Binding and internalization of RGD-PEG-L were studied by fluorescence-activated cell sorting and confocal microscopy using fluorescently labeled liposomes. Radiolabeled liposomes were used to test in vivo pharmacokinetics and inflammation site targeting in lipopolysaccharide (LPS)-induced inflammation and adjuvant-induced arthritis (AIA) in rats. In vivo inflammation targeting was visualized by intravital microscopy using fluorescently labeled RGD-PEG-L. Therapeutic efficacy of DEXP-encapsulating RGD-PEG-L compared with nontargeted liposomes was evaluated in rats with AIA.

RESULTS

RGD-PEG-L bound to and were taken up by proliferating human VECs in vitro. In vivo, increased targeting of radiolabeled RGD-PEG-L to areas of LPS-induced inflammation in rats was observed. Specific association with the blood vessel wall at the site of inflammation was confirmed by intravital microscopy. One single intravenous injection of DEXP encapsulated in RGD-PEG-L resulted in a strong and long-lasting antiarthritic effect in rat AIA.

CONCLUSION

RGD-targeted PEG liposomes represent an endothelial cell-specific drug delivery system that targets VECs at sites of inflammation. Use of these liposomes to deliver DEXP to VECs at arthritis-affected sites proved efficacious in rat adjuvant arthritis. These data indicate that VECs have an essential role in the inflammation process and suggest the possibility of using VEC targeting for therapeutic intervention in inflammatory processes such as arthritis.

Endothelial targeting of high-affinity multivalent polymer nanocarriers directed to intercellular adhesion molecule 1

Targeting of diagnostic and therapeutic agents to endothelial cells (ECs) provides an avenue to improve treatment of many maladies. For example, intercellular adhesion molecule 1 (ICAM-1), a constitutive endothelial cell adhesion molecule up-regulated in many diseases, is a good determinant for endothelial targeting of therapeutic enzymes and polymer nanocarriers (PNCs) conjugated with anti-ICAM (anti-ICAM/PNCs). However, intrinsic and extrinsic factors that control targeting of anti-ICAM/PNCs to ECs (e.g., anti-ICAM affinity and PNC valency and flow) have not been defined. In this study we tested in vitro and in vivo parameters of targeting to ECs of anti-ICAM/PNCs consisting of either prototype polystyrene or biodegradable poly(lactic-coglycolic) acid polymers (approximately 200 nm diameter spheres carrying approximately 200 anti-ICAM molecules). Anti-ICAM/PNCs, but not control IgG/PNCs 1) rapidly (t1/2 approximately 5 min) and specifically bound to tumor necrosis factor-activated ECs in a dose-dependent manner (Bmax approximately 350 PNC/cell) at both static and physiological shear stress conditions and 2) bound to ECs and accumulated in the pulmonary vasculature after i.v. injection in mice. Anti-ICAM/PNCs displayed markedly higher EC affinity versus naked anti-ICAM (Kd approximately 80 pM versus approximately 8 nM) in cell culture and, probably because of this factor, higher value (185.3 +/- 24.2 versus 50.5 +/- 1.5% injected dose/g) and selectivity (lung/blood ratio 81.0 +/- 10.9 versus 2.1 +/- 0.02, in part due to faster blood clearance) of pulmonary targeting. These results 1) show that reformatting monomolecular anti-ICAM into high-affinity multivalent PNCs boosts their vascular immuno-targeting, which withstands physiological hydrodynamics and 2) support potential anti-ICAM/PNCs utility for medical applications.

Lysosomal enzyme delivery by ICAM-1-targeted nanocarriers bypassing glycosylation- and clathrin-dependent endocytosis

Enzyme replacement therapy, a state-of-the-art treatment for many lysosomal storage disorders, relies on carbohydrate-mediated binding of recombinant enzymes to receptors that mediate lysosomal delivery via clathrin-dependent endocytosis. Suboptimal glycosylation of recombinant enzymes and deficiency of clathrin-mediated endocytosis in some lysosomal enzyme-deficient cells limit delivery and efficacy of enzyme replacement therapy for lysosomal disorders. We explored a novel delivery strategy utilizing nanocarriers targeted to a glycosylation- and clathrin-independent receptor, intercellular adhesion molecule (ICAM)-1, a glycoprotein expressed on diverse cell types, up-regulated and functionally involved in inflammation, a hallmark of many lysosomal disorders. We targeted recombinant human acid sphingomyelinase (ASM), deficient in types A and B Niemann-Pick disease, to ICAM-1 by loading this enzyme to nanocarriers coated with anti-ICAM. Anti-ICAM/ASM nanocarriers, but not control ASM or ASM nanocarriers, bound to ICAM-1-positive cells (activated endothelial cells and Niemann-Pick disease patient fibroblasts) via ICAM-1, in a glycosylation-independent manner. Anti-ICAM/ASM nanocarriers entered cells via CAM-mediated endocytosis, bypassing the clathrin-dependent pathway, and trafficked to lysosomes, where delivered ASM displayed stable activity and alleviated lysosomal lipid accumulation. Therefore, lysosomal enzyme targeting using nanocarriers targeted to ICAM-1 bypasses defunct pathways and may improve the efficacy of enzyme replacement therapy for lysosomal disorders, such as Niemann-Pick disease.

Biomedical aspects of targeted delivery of drugs to pulmonary endothelium

Drug targeting to selected subcellular compartments of the pulmonary endothelium may optimise treatment of many diseases. This paper describes endothelial determinants that are potentially useful for such targeting, including endothelial ectopeptidases, cell adhesion molecules and novel candidates identified by high-throughput methods, as well as the means to achieve optimal subcellular targeting of drugs in the endothelium that have been explored in cell culture and animal studies. Criteria for determining the applicability for targeting include accessibility, specificity, safety and subcellular precision. The effects of endothelial delivery of therapeutic agents, including the effects mediated by the intervention in the function of the target determinants, must be characterised in the context of given pathological conditions.