Therapeutic efficacy of anti-ErbB2 immunoliposomes targeted by a phage antibody selected for cellular endocytosis

Unleashing the Potential: Designing Antibody-Targeted Lipid Nanoparticles for Industrial Applications with CMC Considerations and Clinical Outlook

Antibody-targeted lipid nanoparticles (Ab-LNPs) are rapidly gaining traction as multifaceted platforms in precision medicine, adept at delivering a diverse array of therapeutic agents, including nucleic acids and small molecules. This review provides an incisive overview of the latest developments in the field of Ab-LNP technology, with a special emphasis on pivotal design aspects such as antibody engineering, bioconjugation strategies, and advanced formulation techniques. Furthermore, it addresses critical chemistry, manufacturing, and controls (CMC) considerations and thoroughly examines the in vivo dynamics of Ab-LNPs, underscoring their promising potential for clinical application. By seamlessly blending scientific advancements with practical industrial perspectives, this review casts a spotlight on the burgeoning role of Ab-LNPs as an innovative and potent tool in the realm of targeted drug delivery.

Novel Oxygen-Dependent Degradable Immunotoxin Regulated by the Ubiquitin-Proteasome System Reduces Nonspecific Cytotoxicity

The use of bacterial toxins as antitumor agents has received considerable attention. Immunotoxins based on antigen recognition of single-chain antibodies have been widely explored for cancer therapy. Despite their impressive killing effect on tumor cells, immunotoxins still display unspecific toxicity with undesired side effects. High levels of hypoxia-inducible factor 1α (HIF-1α) are well-known indicators of hypoxia in cancer cells. In this study, different linkers were employed to fuse the immunotoxin DAB389-4D5 scFv (DS) with the oxygen-dependent degradation domain (ODDD) of HIF-1α, a domain selectively facilitating the accumulation of HIF-1α under hypoxia, to construct the oxygen-dependent degradable immunotoxin DS-ODDD (DSO). The engineered fusion protein DSO-2 containing a linker (G₄S)₃ possesses the best killing effect on cancer cells under hypoxia and displayed considerably reduced nonspecific toxicity to normal cells under normoxic conditions. Flow cytometry, immunofluorescence, and immunoblot analyses demonstrated that DSO-2 was degraded via the ubiquitin-proteasome pathway regulated by the oxygen-sensitive mechanism. Western blot analysis indicated that the degradation of DSO-2 significantly decreased the activation of apoptosis-related molecules in normal cells. The engineered immunotoxin with oxygen-sensing properties developed herein is a potential therapeutic agent for cancer treatment.

The ROS-generating photosensitizer-free NaYF4:Yb,Tm@SiO2upconverting nanoparticles for photodynamic therapy application

In this work we adapt rare-earth-ion-doped NaYF₄nanoparticles coated with a silicon oxide shell (NaYF₄:20%Yb,0.2%Tm@SiO₂) for biological and medical applications (for example, imaging of cancer cells and therapy at the nano level). The wide upconversion emission range under 980 nm excitation allows one to use the nanoparticles for cancer cell (4T1) photodynamic therapy (PDT) without a photosensitizer. The reactive oxygen species (ROS) are generated by Tm/Yb ion upconversion emission (blue and UV light). Thein vitroPDT was tested on 4T1 cells incubated with NaYF₄:20%Yb,0.2%Tm@SiO₂nanoparticles and irradiated with NIR light. After 24 h, cell viability decreased to below 10%, demonstrating very good treatment efficiency. High modification susceptibility of the SiO₂shell allows for attachment of biological molecules (specific antibodies). In this work we attached the anti-human IgG antibody to silane-PEG-NHS-modified NaYF₄:20%Yb,0.2%Tm@SiO₂nanoparticles and a specifically marked membrane model by bio-conjugation. Thus, it was possible to perform a selective search (a high-quality optical method with a very low-level organic background) and eventually damage the targeted cancer cells. The study focuses on therapeutic properties of NaYF₄:20%Yb,0.2%Tm@SiO₂nanoparticles and demonstrates, upon biological functionalization, their potential for targeted therapy.

Challenges towards Targeted Drug Delivery in Cancer Nanomedicines

Despite cancer nanomedicine celebrates already thirty years since its introduction, together with the achievements and progress in cancer treatment area, it still undergoes serious disadvantages that must be addressed. Since the first observation that macromolecules tend to accumulate in tumor tissue due to fenestrated endothelial of vasculature, considered as the “royal gate” in drug delivery field, more than dozens of nanoformulations have been approved and introduced into the practice for cancer treatment. Lipid, polymeric, and hybrid nanocarriers are biocompatible nano-drug delivery systems (NDDs) having suitable physicochemical properties and modulate payload release in response to specific chemical or physical stimuli. Biopharmaceutical properties of NDDs and their efficacy in animal models and humans can significantly affect their impact and perspective in nanomedicine. One of the future directions could be focusing on personalized cancer treatment, considering the heterogeneity and complexity of each patient tumor tissue and the designing of multifunctional targeted NDDs combining synthetic nanomaterials and biological components, like cellular membranes, circulating proteins, RNAi/DNAi, which enforce the efficacy of NDDs and boost their therapeutic effect.

A Triptolide Loaded HER2-Targeted Nano-Drug Delivery System Significantly Suppressed the Proliferation of HER2-Positive and BRAF Mutant Colon Cancer

Background

Colon cancer (CRC) was a malignant tumor and there were about 25% of patients with tumor metastasis at diagnosis stage. Chemotherapeutic agents for metastatic CRC patients were with great side effects and the clinical treatment results of advanced CRC were still not satisfactory. Human epidermal growth factor receptor 2 (HER2) is overexpressed in some CRC patients and is an effective target for CRC patient treatment. Anti-HER2 therapy had a beneficial role in the treatment of HER2-positive metastatic CRC with fewer side effects. CRC patients with BRAF mutations were resistant to HER2 antibodies treatment. Therefore, there was an urgent need to develop new therapeutic agents.

Methods

HER2 targeted nanoparticles (TPLNP) drug delivery system loading triptolide (TPL) were prepared and identified. The effects of TPLNP and free TPL on cell viability, targeting and cell cycle progression on HT29 (BRAF mutation) with HER2 overexpression, were evaluated by Cell Counting Kit-8 (CCK8), Fluorescence Activating Cell Sorter (FACS) and immunofluorescence methods, respectively. The anti-tumor efficacies of TPLNP were evaluated in subcutaneous xenograft model of colon cancer and the survival rate, tumor volume, liver and kidney indexes of tumor-bearing mice were measured.

Results

TPLNP was small in nanosize (73.4±5.2nm) with narrow size distribution (PDI=0.15±0.02) and favorable zeta potential (pH=9.6, zeta potential: −57.3±6.69mV; pH=7.0, zeta potential: −28.7±5.1mV; pH=5.6, zeta potential: −21.1±4.73mV). Comparing with free TPL treatment group, TPLNP developed stranger colon cancer-killing efficiency in a dose- and time-dependent manner detected with CCK8 method; achieved good in vitro colon cancer targeting detected with flow cytometry and immunofluorescence experiments; enhanced more HT29-HER2 apoptosis and induced more cell cycle arrested in G1-S phase detected with FACS in vitro. As for in vivo antitumor response, TPLNP remarkably inhibited the growth of colon cancer in the colon cancer xenograft model, significantly improved the survival rate and did not exhibit significant liver and kidney toxicity in contrast with free TPL in vivo.

Conclusion

TPLNP was effectively against colon cancer with HER2 overexpression and BRAF mutation in pre-clinical models. In summary, the TPLNP appeared to be a promising treatment option for CRC in clinical application based on improved efficacy and the favorable safety profile.

Surface Plasmon Resonance as a Characterization Tool for Lipid Nanoparticles Used in Drug Delivery

The development of drug carriers based in lipid nanoparticles (LNPs) aims toward the synthesis of non-toxic multifunctional nanovehicles that can bypass the immune system and allow specific site targeting, controlled release and complete degradation of the carrier components. Among label free techniques, Surface Plasmon Resonance (SPR) biosensing is a versatile tool to study LNPs in the field of nanotherapeutics research. SPR, widely used for the analysis of molecular interactions, is based on the immobilization of one of the interacting partners to the sensor surface, which can be easily achieved in the case of LNPs by hydrophobic attachment onto commercial lipid- capture sensor chips. In the last years SPR technology has emerged as an interesting strategy for studying molecular aspects of drug delivery that determines the efficacy of the nanotherapeutical such as LNPs' interactions with biological targets, with serum proteins and with tumor extracelullar matrix. Moreover, SPR has contributed to the obtention and characterization of LNPs, gathering information about the interplay between components of the formulations, their response to organic molecules and, more recently, the quantification and molecular characterization of exosomes. By the combination of available sensor platforms, assay quickness and straight forward platform adaptation for new carrier systems, SPR is becoming a high throughput technique for LNPs' characterization and analysis.

Conventional Nanosized Drug Delivery Systems for Cancer Applications

Clinical responses and tolerability of conventional nanocarriers (NCs) are sometimes different from those expected in anticancer therapy. Thus, new smart drug delivery systems (DDSs) with stimuli-responsive properties and novel materials have been developed. Several clinical trials demonstrated that these DDSs have better clinical therapeutic efficacy in the treatment of many cancers than free drugs. Composition of DDSs and their surface properties increase the specific targeting of therapeutics versus cancer cells, without affecting healthy tissues, and thus limiting their toxicity versus unspecific tissues. Herein, an extensive revision of literature on NCs used as DDSs for cancer applications has been performed using the available bibliographic databases.

Immunoliposomes bearing lymphocyte activation gene 3 fusion protein and P5 peptide: A novel vaccine for breast cancer

LAG3-Ig as an immune adjuvant has elicited potent anti-tumor immune responses in several preclinical and clinical studies, but the full potential immunostimulatory of LAG3-Ig has yet to be achieved. We hypothesized that by anchoring LAG3-Ig to the surface of liposomes, the adjuvant activity of LAG3-Ig could be improved. We also investigated the immunotherapy by co-delivery of liposome-coupled LAG3-Ig and P5 tumor antigen in mice model of TUBO breast cancer. We prepared and characterized novel PEGylated liposomes bearing surface conjugated LAG3-Ig and P5. Consistent with our hypothesis, liposomes-conjugated LAG3-Ig via multivalent binding to MHC class II molecules exerted immunostimulatory of LAG3-Ig and markedly induced maturation of dendritic cells more efficiently than free LAG3-Ig. LAG3-Ig-P5-immunoliposomes effectively elicited protective anti-tumor responses more than locally injected soluble LAG3-Ig + P5. The higher percentage of CD4⁺ and CD8⁺ T cells in the spleen and more rapid and pronounced infiltration of these effector cells into the site of the tumor were seen following immunoliposome therapy. Finally, anti-tumor immunity induced by LAG3-Ig-P5-immunoliposomes translated into the more tumor regression and prolonged survival of treated mice, compared to soluble immunotherapy. Taken together, our findings suggest that LAG3-Ig-P5-immunoliposomes can be considered as a valuable candidate for developing a liposome-based therapeutic cancer vaccine in treating HER2/ neu⁺ breast cancer patients.

Liposomes targeted to MHC-restricted antigen improve drug delivery and antimelanoma response

Purpose

Melanoma is the most aggressive form of skin cancer. Chemotherapy at a late stage fails due to low accumulation in tumors, indicating the need for targeted therapy.

Materials and methods

To increase drug uptake by tumor cells, we have targeted doxorubicin-containing liposomes using a T-cell receptor (TCR)-like antibody (scFv G8 and Hyb3) directed against melanoma antigen A1 (MAGE-A1) presented by human leukocyte antigen A1 (M1/A1). With the use of flow cytometry and confocal microscopy, we have tested our formulation in vitro. In vivo pharmacokinetics was done in tumor-free nu/nu mice, while biodistribution and efficacy study was done in nu/nu mice xenograft.

Results

We demonstrated two to five times higher binding and internalization of these immunoliposomes by M1⁺/A1⁺ melanoma cells in vitro in comparison with nontargeted liposomes. Cytotoxicity assay showed significant tumor cell kill at 10 µM doxorubicin (DXR) for targeted vs nontargeted liposomes. In vivo pharmacokinetics of nontargeted and targeted liposomes were similar, while accumulation of targeted liposomes was 2- to 2.5-fold and 6.6-fold enhanced when compared with nontargeted liposomes and free drug, respectively. Notably, we showed a superior antitumor activity of MAGE-A1-targeted DXR liposomes toward M1⁺/A1⁺ expressing tumors in mice compared with the treatment of M1⁻/A1⁺ tumors. Our results indicate that targeted liposomes showed better cytotoxicity in vitro and pharmacokinetics in vivo.

Conclusion

Liposomes decorated with TCR-mimicking scFv antibodies effectively and selectively target antigen-positive melanoma. We showed that DXR-loaded liposomes coupled to anti-M1/-A1 scFv inflict a significant antitumor response. Targeting tumor cells specifically promotes internalization of drug-containing nanoparticles and may improve drug delivery and ultimately antitumor efficacy. Our data argue that targeting MAGE in A1 context, by nanosized carriers decorated with TCR-like antibodies mimicking scFv, can be used as a theragnostic platform for drug delivery, immunotherapy, and potentially imaging, and diagnosis of melanoma.

Surface Engineering of Nanoparticles for Targeted Delivery to Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-associated deaths worldwide. There is a lack of efficient therapy for HCC; the only available first-line systemic drug, sorafenib, can merely improve the average survival by two months. Among the efforts to develop an efficient therapy for HCC, nanomedicine has drawn the most attention, owing to its unique features such as high drug-loading capacity, intrinsic anticancer activities, integrated diagnostic and therapeutic functionalities, and easy surface engineering with targeting ligands. Despite its tremendous advantages, no nanomedicine can be effective unless it successfully targets the tumor site, which is a challenging task. In this review, the features of HCC are described, and the physiological hurdles that prevent nanoparticles from targeting HCC are discussed. Then, the surface physicochemical factors of nanoparticles that can influence targeting efficiency are discussed. Finally, a thorough description of the physiological barriers that nanomedicine must conquer before uptake by HCC cells if possible is provided, as well as the surface engineering approaches to nanomedicine to achieve targeted delivery to HCC cells. The physiological hurdles and corresponding solutions summarized in this review provide a general guide for the rational design of HCC targeting nanomedicine systems.

Multifunctional Transmembrane Protein Ligands for Cell-Specific Targeting of Plasma Membrane-Derived Vesicles

Liposomes and nanoparticles that bind selectively to cell-surface receptors can target specific populations of cells. However, chemical conjugation of ligands to these particles is difficult to control, frequently limiting ligand uniformity and complexity. In contrast, the surfaces of living cells are decorated with highly uniform populations of sophisticated transmembrane proteins. Toward harnessing cellular capabilities, here it is demonstrated that plasma membrane vesicles (PMVs) derived from donor cells can display engineered transmembrane protein ligands that precisely target cells on the basis of receptor expression. These multifunctional targeting proteins incorporate (i) a protein ligand, (ii) an intrinsically disordered protein spacer to make the ligand sterically accessible, and (iii) a fluorescent protein domain that enables quantification of the ligand density on the PMV surface. PMVs that display targeting proteins with affinity for the epidermal growth factor receptor (EGFR) bind at increasing concentrations to breast cancer cells that express increasing levels of EGFR. Further, as an example of the generality of this approach, PMVs expressing a single-domain antibody against green fluorescence protein (eGFP) bind to cells expressing eGFP-tagged receptors with a selectivity of ≈50:1. The results demonstrate the versatility of PMVs as cell targeting systems, suggesting diverse applications from drug delivery to tissue engineering.

Relationship between Targeting Efficacy of Liposomes and the Dosage of Targeting Antibody Using Surface Plasmon Resonance

Surface plasmon resonance (SPR) was used in this research to investigate the targeting efficacy (i.e., the binding affinity) of antibody-modified liposomes. The results indicated that liposomes modified by targeting antibodies exhibited an increase in apparent binding affinity, a result attributed to the avidity effect. More specifically, the targeting effect improved as the surface density of the targeting antibody increased, an increase primarily attributed to the decrease of the dissociation rate. However, this trend stopped when the surface density reached a threshold of approximately 1.5 × 10(8) antibody/mm(2). This surface density was found to be quite consistent regardless of the liposome size and the type of targeting antibody. In addition, a traditional cell binding experiment was conducted to confirm the saturation point obtained from SPR.

Simultaneous targeting of VEGF-receptors 2 and 3 with immunoliposomes enhances therapeutic efficacy

BACKGROUND

Tumor progression depends on angiogenesis. Vascular endothelial growth factor (VEGF) receptors (VEGFRs) are the main signal transducers that stimulate endothelial cell migration and vessel sprouting. At present, only VEGFR2 is targeted in the clinical practice.

PURPOSE

To develop new, anti-angiogenic nanoparticles (immunoliposomes, ILs), that redirect cytotoxic compounds to tumor-associated vascular cells.

METHODS

Pegylated liposomal doxorubicin (PLD) was targeted against VEGFR2- and VEGFR3-expressing cells by inserting anti-VEGFR2 and/or anti-VEGFR3 antibody fragments into the lipid bilayer membrane of PLD. These constructs were tested in vitro, and in vivo in the Rip1Tag2 mouse model of human cancer.

RESULTS

The combination treatment with anti-VEGFR2-ILs-dox and anti-VEGFR3-ILs-dox was superior to targeting only VEGFR2 cells and provides a highly efficient approach of depleting tumor-associated vasculature. This leads to tumor starvation and pronounced reduction of tumor burden.

CONCLUSION

Nanoparticles against VEGFR2 and -3 expressing tumor-associated endothelial cells represent a promising and novel anti-cancer strategy.

An evolved Mxe GyrA intein for enhanced production of fusion proteins

Expressing antibodies as fusions to the non-self-cleaving Mxe GyrA intein enables site-specific, carboxy-terminal chemical modification of the antibodies by expressed protein ligation (EPL). Bacterial antibody-intein fusion protein expression platforms typically yield insoluble inclusion bodies that require refolding to obtain active antibody-intein fusion proteins. Previously, we demonstrated that it was possible to employ yeast surface display to express properly folded single-chain antibody (scFv)-intein fusions, therefore permitting the direct small-scale chemical functionalization of scFvs. Here, directed evolution of the Mxe GyrA intein was performed to improve both the display and secretion levels of scFv-intein fusion proteins from yeast. The engineered intein was shown to increase the yeast display levels of eight different scFvs by up to 3-fold. Additionally, scFv- and green fluorescent protein (GFP)-intein fusion proteins can be secreted from yeast, and while fusion of the scFvs to the wild-type intein resulted in low expression levels, the engineered intein increased scFv-intein production levels by up to 30-fold. The secreted scFv- and GFP-intein fusion proteins retained their respective binding and fluorescent activities, and upon intein release, EPL resulted in carboxy-terminal azide functionalization of the target proteins. The azide-functionalized scFvs and GFP were subsequently employed in a copper-free, strain-promoted click reaction to site-specifically immobilize the proteins on surfaces, and it was demonstrated that the functionalized, immobilized scFvs retained their antigen binding specificity. Taken together, the evolved yeast intein platform provides a robust alternative to bacterial intein expression systems.

D-Amino acid peptide residualizing agents bearing N-hydroxysuccinimido- and maleimido-functional groups and their application for trastuzumab radioiodination

INTRODUCTION

Proteins that undergo receptor-mediated endocytosis are subject to lysosomal degradation, requiring radioiodination methods that minimize loss of radioactivity from tumor cells after this process occurs. To accomplish this, we developed the residualizing radioiodination agent N(ϵ)-(3-[(*)I]iodobenzoyl)-Lys(5)-N(α)-maleimido-Gly(1)-D-GEEEK (Mal-D-GEEEK-[(*)I]IB), which enhanced tumor uptake but also increased kidney activity and necessitates generation of sulfhydryl moieties on the protein. The purpose of the current study was to synthesize and evaluate a new D-amino acid based agent that might avoid these potential problems.

METHODS

N(α)-(3-iodobenzoyl)-(5-succinimidyloxycarbonyl)-D-EEEG (NHS-IB-D-EEEG), which contains 3 D-glutamates to provide negative charge and a N-hydroxysuccinimide function to permit conjugation to unmodified proteins, and the corresponding tin precursor were produced by solid phase peptide synthesis and subsequent conjugation with appropriate reagents. Radioiodination of the anti-HER2 antibody trastuzumab using NHS-IB-D-EEEG and Mal-D-GEEEK-IB was compared. Paired-label internalization assays on BT474 breast carcinoma cells and biodistribution studies in athymic mice bearing BT474M1 xenografts were performed to evaluate the two radioiodinated D-peptide trastuzumab conjugates.

RESULTS

NHS-[(131)I]IB-D-EEEG was produced in 53.8%±13.4% and conjugated to trastuzumab in 39.5%±7.6% yield. Paired-label internalization assays with trastuzumab-NHS-[(131)I]IB-D-EEEG and trastuzumab-Mal-D-GEEEK-[(125)I]IB demonstrated similar intracellular trapping for both conjugates at 1h ((131)I, 84.4%±6.1%; (125)I, 88.6%±5.2%) through 24h ((131)I, 60.7%±6.8%; (125)I, 64.9%±6.9%). In the biodistribution experiment, tumor uptake peaked at 48 h (trastuzumab-NHS-[(131)I]IB-D-EEEG, 29.8%±3.6%ID/g; trastuzumab-Mal-D-GEEEK-[(125)I]IB, 45.3%±5.3%ID/g) and was significantly higher for (125)I at all time points. In general, normal tissue levels were lower for trastuzumab-NHS-[(131)I]IB-D-EEEG, with the differences being greatest in kidneys ((131)I, 2.2%±0.4%ID/g; (125)I, 16.9%±2.8%ID/g at 144 h).

CONCLUSION

NHS-[(131)I]IB-D-EEEG warrants further evaluation as a residualizing radioiodination agent for labeling internalizing antibodies/fragments, particularly for applications where excessive renal accumulation could be problematic.

New Horizons in Therapeutic Antibody Discovery

Antibody drugs have become an increasingly significant component of the therapeutic landscape. Their success has been driven by some of their unique properties, in particular their very high specificity and selectivity, in contrast to the off-target liabilities of small molecules (SMs). Antibodies can bring additional functionality to the table with their ability to interact with the immune system, and this can be further manipulated with advances in antibody engineering. This review summarizes what antibody therapeutics have achieved to date and what opportunities and challenges lie ahead. The target landscape for large molecules (LMs) versus SMs and some of the challenges for antibody drug development are discussed. Effective penetration of membrane barriers and intracellular targeting is one challenge, particularly across the highly resistant blood-brain barrier. The expanding pipeline of antibody-drug conjugates offers the potential to combine SM and LM modalities in a variety of creative ways, and antibodies also offer exciting potential to build bi- and multispecific molecules. The ability to pursue more challenging targets can also be further exploited but highlights the need for earlier screening in functional cell-based assays. I discuss how this might be addressed given the practical constraints imposed by high-throughput screening sample type and process differences in antibody primary screening.

Stealth anti-CD4 conjugated immunoliposomes with dual antiretroviral drugs--modern Trojan horses to combat HIV

Highly active antiretroviral therapy (HAART) is the currently employed therapeutic intervention against AIDS where a drug combination is used to reduce the viral load. The present work envisages the development of a stealth anti-CD4 conjugated immunoliposomes containing two anti-retroviral drugs (nevirapine and saquinavir) that can selectively home into HIV infected cells through the CD4 receptor. The nanocarrier was characterized using transmission electron microscopy, FTIR, differential scanning calorimetry, particle size and zeta potential. The cell uptake was also evaluated qualitatively using confocal microscopy and quantitatively by flow cytometry. The drug to lipid composition was optimized for maximum encapsulation of the two drugs. Both drugs were found to localize in different regions of the liposome. The release of the reverse transcriptase inhibitor was dominant during the early phases of the release while in the later phases, the protease inhibitor is the major constituent released. The drugs delivered via anti-CD4 conjugated immunoliposomes inhibited viral proliferation at a significantly lower concentration as compared to free drugs. In vitro studies of nevirapine to saquinavir combination at a ratio of 6.2:5 and a concentration as low as 5 ng/mL efficiently blocked viral proliferation suggesting that co-delivery of anti-retroviral drugs holds a greater promise for efficient management of HIV-1 infection.

The development of immunoconjugates for targeted cancer therapy

Immunoconjugates are specific, highly effective, minimally toxic anticancer therapies that are beginning to show promise in the clinic. Immunoconjugates consist of three separate components: an antibody that binds to a cancer cell antigen with high specificity, an effector molecule that has a high capacity to kill the cancer cell, and a linker that will ensure the effector does not separate from the antibody during transit and will reliably release the effector to the cancer cell or tumour stroma. The high affinity antibody-antigen interaction allows specific and selective delivery of a range of effectors, including pharmacologic agents, radioisotopes, and toxins, to cancer cells. Some anticancer molecules are not well tolerated when administered systemically owing to unacceptable toxicity to the host. However, this limitation can be overcome through the linking of such cytotoxins to specific antibodies, which mask the toxic effects of the drug until it reaches its target. Conversely, many unconjugated antibodies are highly specific for a cancer target, but have low therapeutic potential and can be repurposed as delivery vehicles for highly potent effectors. In this Review, we summarize the successes and shortcomings of immunoconjugates, and discuss the future potential for the development of these therapies.

Anticancer drug-loaded multifunctional nanoparticles to enhance the chemotherapeutic efficacy in lung cancer metastasis

Background

Inhalation of chemotherapeutic drugs directly into the lungs augments the drug exposure to lung cancers. The inhalation of free drugs however results in over exposure and causes severe adverse effect to normal cells. In the present study, epidermal growth factor (EGF)-modified gelatin nanoparticles (EGNP) was developed to administer doxorubicin (DOX) to lung cancers.

Results

The EGNP released DOX in a sustained manner and effectively internalized in EGFR overexpressing A549 and H226 lung cancer cells via a receptor-mediated endocytosis. In vitro cytotoxicity assay showed that EGNP effectively inhibited the growth of A549 and H226 cells in a dose-dependent manner. In vivo biocompatibility study showed that both GNP and EGNP did not activate the inflammatory response and had a low propensity to cause immune response. Additionally, EGNP maintained a high therapeutic concentration in lungs throughout up to 24 h comparing to that of free drug and GNP, implying the effect of ligand-targeted tumor delivery. Mice treated with EGNP remarkably suppressed the tumor growth (~90% tumor inhibition) with 100% mice survival rate. Furthermore, inhalation of EGNP resulted in elevated levels of cleaved caspase-3 (apoptotic marker), while MMP-9 level significantly reduced comparing to that of control group.

Conclusions

Overall, results suggest that EGF surface-modified nanocarriers could be delivered to lungs via inhalation and controlled delivery of drugs in the lungs will greatly improve the therapeutic options in lung cancer therapy. This ligand-targeted nanoparticulate system could be promising for the lung cancer treatment.

Topical delivery of Avastin to the posterior segment of the eye in vivo using annexin A5-associated liposomes

Effective delivery to the retina is presently one of the most challenging areas in drug development in ophthalmology, due to anatomical barriers preventing entry of therapeutic substances. Intraocular injection is presently the only route of administration for large protein therapeutics, including the anti-Vascular Endothelial Growth Factors Lucentis (ranibizumab) and Avastin (bevacizumab). Anti-VEGFs have revolutionised the management of age-related macular degeneration and have increasing indications for use as sight-saving therapies in diabetes and retinal vascular disease. Considerable resources have been allocated to develop non-invasive ocular drug delivery systems. It has been suggested that the anionic phospholipid binding protein annexin A5, may have a role in drug delivery. In the present study we demonstrate, using a combination of in vitro and in vivo assays, that the presence of annexin A5 can significantly enhance uptake and transcytosis of liposomal drug carrier systems across corneal epithelial barriers. This system is employed to deliver physiologically significant concentrations of Avastin to the posterior of the rat eye (127 ng/g) and rabbit retina (18 ng/g) after topical application. Our observations provide evidence to suggest annexin A5 mediated endocytosis can enhance the delivery of associated lipidic drug delivery vehicles across biological barriers, which may have therapeutic implications.

Application of pharmacokinetic and pharmacodynamic analysis to the development of liposomal formulations for oncology

Liposomal formulations of anticancer agents have been developed to prolong drug circulating lifetime, enhance anti-tumor efficacy by increasing tumor drug deposition, and reduce drug toxicity by avoiding critical normal tissues. Despite the clinical approval of numerous liposome-based chemotherapeutics, challenges remain in the development and clinical deployment of micro- and nano-particulate formulations, as well as combining these novel agents with conventional drugs and standard-of-care therapies. Factors requiring optimization include control of drug biodistribution, release rates of the encapsulated drug, and uptake by target cells. Quantitative mathematical modeling of formulation performance can provide an important tool for understanding drug transport, uptake, and disposition processes, as well as their role in therapeutic outcomes. This review identifies several relevant pharmacokinetic/pharmacodynamic models that incorporate key physical, biochemical, and physiological processes involved in delivery of oncology drugs by liposomal formulations. They capture observed data, lend insight into factors determining overall antitumor response, and in some cases, predict conditions for optimizing chemotherapy combinations that include nanoparticulate drug carriers.

Monitoring subcellular biotransformation of N-L-leucyldoxorubicin by micellar electrokinetic capillary chromatography coupled to laser-induced fluorescence detection

Development of prodrugs is a promising alternative to address cytotoxicity and nonspecificity of common anticancer agents. N-L-leucyldoxorubicin (LeuDox) is a prodrug that is biotransformed to the anticancer drug doxorubicin (Dox) in the extracellular space; however, its biotransformation may also occur intracellularly in endocytic organelles. Such organelle-specific biotransformation is yet to be determined. In this study, magnetically enriched endocytic organelle fractions from human uterine sarcoma cells were treated with LeuDox. Micellar electrokinetic chromatography with laser-induced fluorescence detection (MEKC-LIF) was used to determine that 10% of LeuDox was biotransformed to Dox, accounting for ~43% of the biotransformation occurring in the post-nuclear fraction. This finding suggests that endocytic organelles also participate in the intracellular biotransformation of LeuDox to Dox.

Antibody conjugated PLGA nanoparticles for targeted delivery of paclitaxel palmitate: efficacy and biofate in a lung cancer mouse model

Aberrant signaling of the epidermal growth factor receptor (EGFR) is common to a variety of human cancers and is also found to be over-expressed in most cases of non-small cell lung cancer. For the development of a molecularly targeted therapy, cetuximab-conjugated nanoparticles (immunonanoparticles, INPs) are designed and loaded with the lipophilic paclitaxel palmitate (pcpl) prodrug. Oleyl cysteineamide (OCA) is synthesized whereby its amphiphilic nature enables interfacial anchoring and thiol surface functionalization of PLGA NPs, facilitating bioconjugation to cetuximab by thioether bonds. It is demonstrated that the in vitro targeting efficiency and improved cellular internalization and cytotoxicity of this targeted delivery system in lung cancer cells over-expressing EGFR. A quantitative measure of the high binding affinity of INPs to EGFR is demonstrated using surface plasmon resonance. In vivo tolerability and enhanced efficacy of cetuximab pcpl INPs in a metastatic lung cancer model are reported. Its therapeutic efficacy in A549-luc-C8 lung tumors is shown using non-invasive bioluminescent imaging. Intravenous administration of cetuximab pcpl INPs to mice results in significantly higher inhibition of tumor growth and increased survival rates as compared to the non-targeted drug solution, drug-loaded nanoparticles or blank INPs. Pharmacokinetics and organ biodistribution of the prodrug and parent drug are evaluated by LC-MS/MS in lung tumor bearing mice. No enhanced total accumulation of nanoparticles or INPs is found at the tumor tissue. However, persistent pcpl levels with sustained conversion and release of paclitaxel are observed for the encapsulated prodrug possibly suggesting the formation of a drug reservoir. The overall results indicate the potential of this promising targeted platform for the improved treatment of lung cancer and other EGFR positive tumors.

Ligand-targeted liposome design: challenges and fundamental considerations

Nanomedicine, particularly liposomal drug delivery, has expanded considerably over the past few decades, and several liposomal drugs are already providing improved clinical outcomes. Liposomes have now progressed beyond simple, inert drug carriers and can be designed to be highly responsive in vivo, with active targeting, increased stealth, and controlled drug-release properties. Ligand-targeted liposomes (LTLs) have the potential to revolutionize the treatment of cancer. However, these highly engineered liposomes generate new problems, such as accelerated clearance from circulation, compromised targeting owing to non-specific serum protein binding, and hindered tumor penetration. This article highlights recent challenges facing LTL strategies and describes the advanced design elements used to circumvent them.

Impact of tumor HER2/ERBB2 expression level on HER2-targeted liposomal doxorubicin-mediated drug delivery: multiple low-affinity interactions lead to a threshold effect

Numerous targeted nanotherapeutics have been described for potential treatment of solid tumors. Although attention has focused on antigen selection and molecular design of these systems, there has been comparatively little study of how cellular heterogeneity influences interaction of targeted nanoparticles with tumor cells. Antigens, such as HER2/ERBB2, are heterogeneously expressed across different indications, across patients, and within individual tumors. Furthermore, antigen expression in nontarget tissues necessitates optimization of the therapeutic window. Understanding the performance of a given nanoparticle under different regimens of antigen expression has the ability to inform patient selection and clinical development decisions. In this work, HER2-targeted liposomal doxorubicin was used as a model-targeted nanoparticle to quantitatively investigate the effect of HER2 expression levels on delivery of doxorubicin to the nucleus. We find quantitatively greater nuclear doxorubicin delivery with increasing HER2 expression, exhibiting a threshold effect at approximately 2 × 10(5) HER2 receptors/cell. Kinetic modeling indicated that the threshold effect arises from multiple low-affinity interactions between the targeted liposome and HER2. These results support previous data showing little or no uptake into human cardiomyocytes, which express levels of HER2 below the threshold. Finally, these results suggest that HER2-targeted liposomal doxorubicin may effectively target tumors that fall below traditional definitions of HER2-positive tumors, thereby expanding the potential population of patients that might benefit from this agent.

Sub-100 nm biodegradable nanoparticles: in vitro release features and toxicity testing in 2D and 3D cell cultures

A big challenge in tumor targeting by nanoparticles (NPs), taking advantage of the enhanced permeability and retention effect, is the fabrication of small size devices for enhanced tumor penetration, which is considered fundamental to improve chemotherapy efficacy. The purposes of this study are (i) to engineer the formulation of doxorubicin-loaded poly(D,L-lactic-co-glycolic acid) (PLGA)-block-poly(ethylene glycol) (PEG) NPs to obtain <100 nm devices and (ii) to translate standard 2D cytotoxicity studies to 3D collagen systems in which an initial step gradient of the NPs is present. Doxorubicin release can be prolonged for days to weeks depending on the NP formulation and the pH of the release medium. Sub-100 nm NPs are effectively internalized by HeLa cells in 2D and are less cytotoxic than free doxorubicin. In 3D, <100 nm NPs are significantly more toxic than larger ones towards HeLa cells, and the cell death rate is affected by the contributions of drug release and device transport through collagen. Thus, the reduction of NP size is a fundamental feature from both a technological and a biological point of view and must be properly engineered to optimize the tumor response to the NPs.

Application of poly(ethylene glycol)-distearoylphosphatidylethanolamine (PEG-DSPE) block copolymers and their derivatives as nanomaterials in drug delivery

Poly(ethylene glycol)–distearoylphosphatidylethanolamine (PEG-DSPE) block copolymers are biocompatible and amphiphilic polymers that can be widely utilized in the preparation of liposomes, polymeric nanoparticles, polymer hybrid nanoparticles, solid lipid nanoparticles, lipid–polymer hybrid nanoparticles, and microemulsions. Particularly, the terminal groups of PEG can be activated and linked to various targeting ligands, which can prolong the circulation time, improve the drug bioavailability, reduce undesirable side effects, and especially target specific cells, tissues, and even the intracellular localization in organelles. This review herein aims to describe recent developments in drug carriers exploiting PEG-DSPE block copolymers and their derivatives, and the incorporation of different ligands to the end groups of PEG-DSPE to target delivery, focusing on their modification approaches, advantages, applications, and the probable associated drawbacks.

Nuclisome--targeting the tumor cell nucleus

The Nuclisome concept builds on a novel two-step targeting strategy with the aim to deliver short-range Auger-electron-emitting radionuclides to nuclear DNA of tumor cells. The concept is based on the use of Nuclisome-particles, i.e., tumor-targeted PEG-stabilized liposomes loaded with a unique DNA-intercalating compound that enables specific and effective delivery of radionuclides to DNA. The specific and potent two-step targeting leads to eradication of tumor cells while toxicity to normal organs is reduced to a minimum. Results of in vitro and in vivo studies point towards the Nuclisome concept as a promising strategy for the treatment of small tumor masses and, in particular, for the elimination of spread single cells and micrometastases.

Selection and characterization of cell binding and internalizing phage antibodies

Many therapeutic targets are cell surface receptors, which can be challenging antigens for antibody generation. For many therapeutic applications, one needs antibodies that not only bind the cell surface receptor but also are internalized into the cell. This allows use of the antibody to deliver various payloads into the cell to achieve a therapeutic effect. Phage antibody technology has proven a powerful tool for the generation and optimization of human antibodies to any antigen. While applied to the generation of antibodies to purified proteins, it is possible to directly select cell binding and internalizing antibodies on cells. Potential advantages of this approach include: cell surface receptors are in native conformation on intact cells while this might not be so for recombinant proteins; antibodies can be selected for both cell binding and internalization properties; the antibodies can be used to identify their tumor associated antigens; and such antibodies can be used for human treatment directly since they are human in sequence. This review will discuss the factors that impact the successful selection of cell binding and internalizing antibodies. These factors include the cell types used for selection, the impact of different phage antibody library formats, and the specific selection protocols used.

PREPARATION OF GELATIN NANOPARTICLES WITH EGFR SELECTION ABILITY VIA BIOTINYLATED-EGF CONJUGATION FOR LUNG CANCER TARGETING

Lung cancer is the most malignant cancer today, and specific drug delivery has been developed for superior outcome. In this study, gelatin nanoparticles (GPs) were firstly employed as native carriers. Second, NeutrAvidinFITC was then grafted on the particle surface (GP-Av); finally much more amount of biotinylated EGF were able to be conjugated with NeutrAvidinFITC forming ligand- binding nanoparticles (GP-Av-bEGF) to enhance the targeting efficiency. These nanoparticles were applied as EGFR-seeking agents to detect lung cancer cells.

Results of particle characterization show that the modification process had no influence on size (230 nm). Round and smooth nanoparticles were observed by AFM. The surface property of nanoparticles was characterized by surface plasmon resonance (SPR) and flowcytometry analysis as well as by examining the interaction of the modified EGF on particle surface with the ability to recognize EGFR.

The binding ability of GPs with or without EGF modification is different. SPR assay showed that EGF-conjugated particles (GP-Av-bEGF) have stronger and faster bonding signal than the unmodified one (GP-Av). Free EGF competition results from SPR and A549 cell (lung adenocarcinoma cells) culture also confirmed the EGF receptormediated endocytosis mechanism for nanoparticles with EGF-modified binding. The in vitro targeting ability was confirmed by the uptake rate of different cells via flow cytometry assay. GP-Av-bEGF resulted in higher entrance efficiency on A549 than on normal lung cells (HFL1) and U2-OS (osteosarcoma cells) due to A549 possessing more amounts of EGFR. The targeting ability of GP-Av-bEGF nanoparticles with specific EGFR tracing ability was proved, which holds promise for further anticancer drug applications.

HER2-targeted liposomal doxorubicin displays enhanced anti-tumorigenic effects without associated cardiotoxicity

Anthracycline-based regimens are a mainstay of early breast cancer therapy, however their use is limited by cardiac toxicity. The potential for cardiotoxicity is a major consideration in the design and development of combinatorial therapies incorporating anthracyclines and agents that target the HER2-mediated signaling pathway, such as trastuzumab. In this regard, HER2-targeted liposomal doxorubicin was developed to provide clinical benefit by both reducing the cardiotoxicity observed with anthracyclines and enhancing the therapeutic potential of HER2-based therapies that are currently available for HER2-overexpressing cancers. While documenting the enhanced therapeutic potential of HER2-targeted liposomal doxorubicin can be done with existing models, there has been no validated human cardiac cell-based assay system to rigorously assess the cardiotoxicity of anthracyclines. To understand if HER2-targeting of liposomal doxorubicin is possible with a favorable cardiac safety profile, we applied a human stem cell-derived cardiomyocyte platform to evaluate the doxorubicin exposure of human cardiac cells to HER2-targeted liposomal doxorubicin. To the best of our knowledge, this is the first known application of a stem cell-derived system for evaluating preclinical cardiotoxicity of an investigational agent. We demonstrate that HER2-targeted liposomal doxorubicin has little or no uptake into human cardiomyocytes, does not inhibit HER2-mediated signaling, results in little or no evidence of cardiomyocyte cell death or dysfunction, and retains the low penetration into heart tissue of liposomal doxorubicin. Taken together, this data ultimately led to the clinical decision to advance this drug to Phase I clinical testing, which is now ongoing as a single agent in HER2-expressing cancers.

Discovery of internalizing antibodies to tumor antigens from phage libraries

Phage antibody technology can be used to generate human antibodies to essentially any antigen. Many therapeutic target antigens are cell surface receptors, which can be challenging targets for antibody generation. In addition, for many therapeutic applications, one needs antibodies that not only bind the cell surface receptor but also are internalized into the cell upon binding. This allows use of the antibody to deliver a range of payloads into the cell to achieve a therapeutic effect. In this chapter, we describe how human phage antibody libraries can be selected directly on tumor cell lines to generate antibodies that bind cell surface receptors and which upon binding are rapidly internalized into the cell. Specific protocols show how to (1) directly select cell binding and internalizing antibodies from human phage antibody libraries, (2) screen the phage antibodies in a high-throughput flow cytometry assay for binding to the tumor cell line used for selection, (3) identify the antigen bound by the phage antibody using immunoprecipitation and mass spectrometry, and (4) direct cell binding and internalizing selections to a specific tumor antigen by sequential selection on a tumor cell line followed by selection on yeast displaying the target tumor antigen on the yeast surface.

Recombinant antibodies and in vitro selection technologies

Over the past decade, the accumulation of detailed knowledge of antibody structure and function has enabled antibody phage display to emerge as a powerful in vitro alternative to hybridoma methods for creating antibodies. Many antibodies produced using phage display technology have unique properties that are not obtainable using traditional hybridoma technologies. In phage display, selections are performed under controlled, in vitro conditions that are tailored to suit demands of the antigen and the sequence encoding the antibody is immediately available. These features obviate many of the limitations of hybridoma methodology, and because the entire process relies on scalable molecular biology techniques, phage display is also suitable for high-throughput applications. Thus, antibody phage display technology is well suited for genome-scale biotechnology and therapeutic applications. This review describes the antibody phage display technology and highlights examples of antibodies with unique properties that cannot easily be obtained by other technologies.

Building and characterizing antibody-targeted lipidic nanotherapeutics

Immunoliposomes provide a complementary, and in many instances advantageous, drug delivery strategy to antibody-drug conjugates. Their high carrying capacity of 20,000-150,000 drug molecules/liposome, allows for the use of a significantly broader range of moderate-to-high potency small molecule drugs when compared to the comparably few subnanomolar potency maytansinoid- and auristatin-based immunoconjugates. The multivalent display of 5-100 antibody fragments/liposome results in an avidity effect that can make use of even moderate affinity antibodies, as well as a cross-linking of cell surface receptors to induce the internalization required for intracellular drug release and subsequent activity. The underlying liposomal drug must be effectively engineered for long circulating pharmacokinetics and stable in vivo drug retention in order to allow for the drug to be efficiently delivered to the target tissue and take advantage of the site-specific bioavailability provided for by the targeting arm. In this chapter, we describe the rationale for engineering stable immunoliposome-based therapeutics, methods required for preparation of immunoliposomes, as well as for their physicochemical and in vivo characterization.

In vitro evaluation and biodistribution of HER2-targeted liposomes loaded with an (125)I-labelled DNA-intercalator

BACKGROUND

Increasing attention is currently focussed on the issue of finding strategies for the delivery of Auger-electron-emitting radionuclides into tumor cell nuclei.

PURPOSE

In this study, we investigated tumor-cell uptake and cell-killing ability in vitro as well as in vivo biodistribution of an (125)I-labelled anthracycline derivative administered by means of HER2-targeted liposomes.

METHODS

Anthracycline derivative Comp1 was radiolabelled with Auger-emitting (125)I and encapsulated in liposomes (DSPC:Chol:DSPE-PEG) using pH-gradient loading. Single-chain fragment F5 was anchored to the liposomes as targeting device for HER2. Uptake and specificity of (125)I-Comp1 delivered via targeting and non-targeting liposomes were analysed in cultured HER2-overexpressing cells. Cell-killing efficacy was evaluated in SKOV3 cells and biodistribution for up to 48 h was studied after intraperitoneal injection in tumor-bearing female BALB/c nu/nu mice.

RESULTS

(125)I-Comp1 was specifically taken up by the cultured cells when administered by means of HER2-targeted liposomes and a clear dose-effect correlation in survival of cells was seen with increasing specific activity. The biodistribution studies revealed that (125)I-Comp1 accumulated in tumors when distributed using HER2-targeted liposomes and that this effect was absent when using non-targeting liposomes.

CONCLUSION

The HER2-targeted liposomes possess the properties needed to bring about tumor-specific delivery and therapeutic effect of (125)I-Comp1.

State of the art in tumor antigen and biomarker discovery

Our knowledge of tumor immunology has resulted in multiple approaches for the treatment of cancer. However, a gap between research of new tumors markers and development of immunotherapy has been established and very few markers exist that can be used for treatment. The challenge is now to discover new targets for active and passive immunotherapy. This review aims at describing recent advances in biomarkers and tumor antigen discovery in terms of antigen nature and localization, and is highlighting the most recent approaches used for their discovery including “omics” technology.

Novel human single chain antibody fragments that are rapidly internalizing effectively target epithelioid and sarcomatoid mesotheliomas

Human antibodies targeting all subtypes of mesothelioma could be useful to image and treat this deadly disease. Here we report tumor targeting of a novel internalizing human single chain antibody fragment (scFv) labeled with (⁹⁹m)Tc ((⁹⁹m)Tc-M40) in murine models of mesothelioma of both epithelioid (M28) and sarcomatoid (VAMT-1) origins. (⁹⁹m)Tc-M40 was taken up rapidly and specifically by both subtype tumor cells in vitro, with 68% to 92% internalized within 1 hour. The specificity of binding was evidenced by blocking (up to 95%) with 10-fold excess of unlabeled M40. In animal studies, tumors of both subtypes were clearly visualized by SPECT/CT as early as 1 hour postinjection of (⁹⁹m)Tc-M40. Tumor uptake measured as percent of injected dose per gram tissue (%ID/g) at 3 hours was 4.38 and 5.84 for M28 and VAMT-1 tumors, respectively, significantly greater than all organs or tissues studied (liver, 2.62%ID/g; other organs or tissues <1.7%ID/g), except the kidneys (130.7%ID/g), giving tumor-to-blood ratios of 5:1 and 7:1 and tumor-to-muscle ratios of 45:1 and 60:1, for M28 and VAMT-1, respectively. The target-mediated uptake was confirmed by a nearly 70% reduction in tumor activity following administration of 10-fold excess of unlabeled scFv. Taken together, these results indicate that M40 can rapidly and specifically target epithelioid and sarcomatoid tumor cells, demonstrating the potential of this agent as a versatile targeting ligand for imaging and therapy of all subtypes of mesothelioma.