Intracellular delivery of monoclonal antibodies

ACE2 Receptor-Targeted Inhaled Nanoemulsions Inhibit SARS-CoV-2 and Attenuate Inflammatory Responses

Three kinds of coronaviruses are highly pathogenic to humans, and two of them mainly infect humans through Angiotensin-converting enzyme 2 （ACE2）receptors. Therefore, specifically blocking ACE2 binding at the interface with the receptor-binding domain is promising to achieve both preventive and therapeutic effects of coronaviruses. Alternatively, drug-targeted delivery based on ACE2 receptors can further improve the efficacy and safety of inhalation drugs. Here, these two approaches are innovatively combined by designing a nanoemulsion (NE) drug delivery system (termed NE-AYQ) for inhalation that targets binding to ACE2 receptors. This inhalation-delivered remdesivir nanoemulsion (termed RDSV-NE-AYQ) effectively inhibits the infection of target cells by both wild-type and mutant viruses. The RDSV-NE-AYQ strongly inhibits Severe acute respiratory syndrome coronavirus 2 at two dimensions: they not only block the binding of the virus to host cells at the cell surface but also restrict virus replication intracellularly. Furthermore, in the mouse model of acute lung injury, the inhaled drug delivery system loaded with anti-inflammatory drugs (TPCA-1-NE-AYQ) can significantly alleviate the lung tissue injury of mice. This smart combination provides a new choice for dealing with possible emergencies in the future and for the rapid development of inhaled drugs for the treatment of respiratory diseases.

Post-genomic platform for development of oligonucleotide vaccines against RNA viruses: diamond cuts diamond

The coronavirus pandemic has starkly demonstrated the need to create highly effective vaccines against various viral diseases. The emerging new platforms for vaccine creation (adenovirus vectors and mRNA vaccines) have shown their worth in the fight against the prevention of coronavirus infection. However, adenovirus vectors and mRNA vaccines have a serious disadvantage: as a rule, only the S protein of the coronavirus is presented as an antigen. This tactic for preventing infection allows the ever-mutating virus to escape quickly from the immunity protection provided by such vaccines. Today, viral genomic databases are well-developed, which makes it possible to create new vaccines on a fundamentally new post-genomic platform. In addition, the technology for the synthesis of nucleic acids is currently experiencing an upsurge in demand in various fields of molecular biology. The accumulated experience suggests that the unique genomic sequences of viruses can act as antigens that trigger powerful humoral and cellular immunity. To achieve this effect, the following conditions must be created: the structure of the nucleic acid must be single-stranded, have a permanent 3D nanostructure, and have a unique sequence absent in the vaccinated organism. Oligonucleotide vaccines are able to resist the rapidly changing genomic sequences of RNA viruses by using conserved regions of their genomes to generate a long-term immune response, acting according to the adage that a diamond cuts a diamond. In addition, oligonucleotide vaccines will not contribute to antibody-dependent enhanced infection, since the nucleic acid of the coronavirus is inside the viral particle. It is obvious that new epidemics and pandemics caused by RNA viruses will continue to arise periodically in the human population. The creation of new, safe, and effective platforms for the production of vaccines that can flexibly change and adapt to new subtypes of viruses is very urgent and at this moment should be considered as a strategically necessary task.

An effective cell-penetrating antibody delivery platform

Despite their well-recognized success in the clinic, antibodies generally do not penetrate cellular membranes to target intracellular molecules, many of which underlie incurable diseases. Here we show that covalently conjugating phosphorothioated DNA oligonucleotides to antibodies enabled their efficient cellular internalization. Antibody cell penetration was partially mediated by membrane potential alteration. Moreover, without an antigen to bind, intracellular levels of the modified antibodies underwent cellular clearance, which involved efflux and lysosomal degradation, enabling detection of intended intracellular molecules as tested in fibroblasts, tumor cells, and T cells. This target-dependent cellular retention of modified antibodies extended to in vivo studies. Both local and systemic administrations of low doses of modified antibodies effectively inhibited intracellular targets, such as transcription factors Myc, interferon regulatory factor 4, and tyrosine-protein kinase SRC, and expression of their downstream genes in tumors, resulting in tumor cell apoptosis and tumor growth inhibition. This simple modification enables the use of antibodies to detect and modulate intracellular molecules in both cultured living cells and in whole animals, forming the foundation for a new paradigm for antibody-based research, diagnostics, and therapeutics.

Targeted Intracellular Delivery of Antibodies: The State of the Art

A dominant area of antibody research is the extension of the use of this mighty experimental and therapeutic tool for the specific detection of molecules for diagnostics, visualization, and activity blocking. Despite the ability to raise antibodies against different proteins, numerous applications of antibodies in basic research fields, clinical practice, and biotechnology are restricted to permeabilized cells or extracellular antigens, such as membrane or secreted proteins. With the exception of small groups of autoantibodies, natural antibodies to intracellular targets cannot be used within living cells. This excludes the scope of a major class of intracellular targets, including some infamous cancer-associated molecules. Some of these targets are still not druggable via small molecules because of large flat contact areas and the absence of deep hydrophobic pockets in which small molecules can insert and perturb their activity. Thus, the development of technologies for the targeted intracellular delivery of antibodies, their fragments, or antibody-like molecules is extremely important. Various strategies for intracellular targeting of antibodies via protein-transduction domains or their mimics, liposomes, polymer vesicles, and viral envelopes, are reviewed in this article. The pitfalls, challenges, and perspectives of these technologies are discussed.

NLS-Cholic Acid Conjugation to IL-5Rα-Specific Antibody Improves Cellular Accumulation and In Vivo Tumor-Targeting Properties in a Bladder Cancer Model

Receptor-mediated internalization followed by trafficking and degradation of antibody-conjugates (ACs) via the endosomal-lysosomal pathway is the major mechanism for delivering molecular payloads inside target tumor cells. Although a mainstay for delivering payloads with clinically approved ACs in cancer treatment and imaging, tumor cells are often able to decrease intracellular payload concentrations and thereby reduce the effectiveness of the desired application. Thus, increasing payload intracellular accumulation has become a focus of attention for designing next-generation ACs. We developed a composite compound (ChAcNLS) that enables ACs to escape endosome entrapment and route to the nucleus resulting in the increased intracellular accumulation as an interleukin-5 receptor α-subunit (IL-5Rα)-targeted agent for muscle invasive bladder cancer (MIBC). We constructed ⁶⁴Cu-A14-ChAcNLS, ⁶⁴Cu-A14-NLS, and ⁶⁴Cu-A14 and evaluated their performance by employing mechanistic studies for endosome escape coupled to nuclear routing and determining whether this delivery system results in improved ⁶⁴Cu cellular accumulation. ACs consisting of ∼20 ChAcNLS or NLS moieties per ⁶⁴Cu-A14 were prepared in good yield, high monomer content, and maintaining high affinity for IL-5Rα. Confocal microscopy analysis demonstrated ChAcNLS mediated efficient endosome escape and nuclear localization. ⁶⁴Cu-A14-ChAcNLS increased ⁶⁴Cu cellular accumulation in HT-1376 and HT-B9 cells relative to ⁶⁴Cu-A14 and ⁶⁴Cu-A14-NLS. In addition, we tested ⁶⁴Cu-A14-ChAcNLS in vivo to evaluate its tissue distribution properties and, ultimately, tumor uptake and targeting. A model of human IL-5Rα MIBC was developed by implanting NOD/SCID mice with subcutaneous HT-1376 or HT-B9MIBC tumors, which grow containing high and low IL-5Rα-positive tumor cell densities, respectively. ACs were intravenously injected, and daily blood sampling, biodistribution at 48 and 96 h, and positron emission tomography (PET) at 24 and 48 h were performed. Region of interest (ROI) analysis was also performed on reconstructed PET images. Pharmacokinetic analysis and biodistribution studies showed that ⁶⁴Cu-A14-ChAcNLS had faster clearance rates from the blood and healthy organs relative to ⁶⁴Cu-A14. However, ⁶⁴Cu-A14-ChAcNLS maintained comparable tumor accumulation relative to ⁶⁴Cu-A14. This resulted in ⁶⁴Cu-A14-ChAcNLS having superior tumor/normal tissue ratios at both 48 and 96 h biodistribution time points. Visualization of AC distribution by PET and ROI analysis confirmed that ⁶⁴Cu-A14-ChAcNLS had improved targeting of MIBC tumor relative to ⁶⁴Cu-A14. In addition, ⁶⁴Cu-A14 modified with only NLS had poor tumor targeting. This was a result of poor tumor uptake due to extremely rapid clearance. Thus, the overall findings in this model of human IL-5Rα-positive MIBC describe an endosome escape-nuclear localization cholic-acid-linked peptide that substantially enhances AC cellular accumulation and tumor targeting.

Self-assembled protein nanocarrier for intracellular delivery of antibody

Despite the great potential of antibodies as intracellular therapeutics, there is a significant, unmet challenge in delivering sufficient amounts of folded antibodies inside cells. We describe an all-protein self-assembled nanocarrier capable of delivering functional antibodies to the cytosol. By combining an α-helical peptide that self-assembles into a hexameric coiled-coil bundle and an Fc-binding Protein A fragment, we generated the Hex nanocarrier that is efficiently internalized by cells without cytotoxicity. Localization of multiple Fc-binding domains on the hexameric core allowed the Hex nanocarrier to tightly bind antibody with sub-nanomolar affinity regardless of pH and the antibody's originating species. The size of the Hex nanocarrier ranges from 25 to 35nm depending on the antibody loading ratio. We demonstrated the capacity of the Hex nanocarrier to deliver functional antibodies to the cytosol by employing anti-β-tubulin or anti-nuclear pore complex antibody as cargo. The design of the Hex nanocarrier is modular, which enables functionalization beyond Fc-binding. We exploited this feature to improve the cytosolic delivery efficiency of the Hex nanocarrier by addition of an endosomolytic motif to the core. The modified Hex nanocarrier exhibited similar antibody-binding behavior, but delivered more antibodies to their cytosolic targets at a faster rate. This work demonstrates an efficient intracellular antibody delivery platform with significant advantages over existing approaches as it does not require modification of the antibody, is biodegradable, and has an antibody to carrier mass ratio of 13, which is greater than other reported antibody carriers.

Nanoparticles for the delivery of therapeutic antibodies: Dogma or promising strategy?

INTRODUCTION

Over the past two decades, therapeutic antibodies have demonstrated promising results in the treatment of a wide array of diseases. However, the application of antibody-based therapy implies multiple administrations and a high cost of antibody production, resulting in costly therapy. Another disadvantage inherent to antibody-based therapy is the limited stability of antibodies and the low level of tissue penetration. The use of nanoparticles as delivery systems for antibodies allows for a reduction in antibody dosing and may represent a suitable alternative to increase antibody stability Areas covered: We discuss different nanocarriers intended for the delivery of antibodies as well as the corresponding encapsulation methods. Recent developments in antibody nanoencapsulation, particularly the possible toxicity issues that may arise from entrapment of antibodies into nanocarriers, are also assessed. In addition, this review will discuss the alterations in antibody structure and bioactivity that occur with nanoencapsulation. Expert opinion: Nanocarriers can protect antibodies from degradation, ensuring superior bioavailability. Encapsulation of therapeutic antibodies may offer some advantages, including potential targeting, reduced immunogenicity and controlled release. Furthermore, antibody nanoencapsulation may aid in the incorporation of the antibodies into the cells, if intracellular components (e.g. intracellular enzymes, oncogenic proteins, transcription factors) are to be targeted.

Intracellular targeting with engineered proteins

If the isolation, production, and clinical use of insulin marked the inception of the age of biologics as therapeutics, the convergence of molecular biology and combinatorial engineering techniques marked its coming of age. The first wave of recombinant protein-based drugs in the 1980s demonstrated emphatically that proteins could be engineered, formulated, and employed for clinical advantage. Yet despite the successes of protein-based drugs such as antibodies, enzymes, and cytokines, the druggable target space for biologics is currently restricted to targets outside the cell. Insofar as estimates place the number of proteins either secreted or with extracellular domains in the range of 8000 to 9000, this represents only one-third of the proteome and circumscribes the pathways that can be targeted for therapeutic intervention. Clearly, a major objective for this field to reach maturity is to access, interrogate, and modulate the majority of proteins found inside the cell. However, owing to the large size, complex architecture, and general cellular impermeability of existing protein-based drugs, this poses a daunting challenge. In recent years, though, advances on the two related fronts of protein engineering and drug delivery are beginning to bring this goal within reach. First, prompted by the restrictions that limit the applicability of antibodies, intense efforts have been applied to identifying and engineering smaller alternative protein scaffolds for the modulation of intracellular targets. In parallel, innovative solutions for delivering proteins to the intracellular space while maintaining their stability and functional activity have begun to yield successes. This review provides an overview of bioactive intrabodies and alternative protein scaffolds amenable to engineering for intracellular targeting and also outlines advances in protein engineering and formulation for delivery of functional proteins to the interior of the cell to achieve therapeutic action.

ChAcNLS, a Novel Modification to Antibody-Conjugates Permitting Target Cell-Specific Endosomal Escape, Localization to the Nucleus, and Enhanced Total Intracellular Accumulation

The design of antibody-conjugates (ACs) for delivering molecules for targeted applications in humans has sufficiently progressed to demonstrate clinical efficacy in certain malignancies and reduced systemic toxicity that occurs with standard nontargeted therapies. One area that can advance clinical success for ACs will be to increase their intracellular accumulation. However, entrapment and degradation in the endosomal-lysosomal pathway, on which ACs are reliant for the depositing of their molecular payload inside target cells, leads to reduced intracellular accumulation. Innovative approaches that can manipulate this pathway may provide a strategy for increasing accumulation. We hypothesized that escape from entrapment inside the endosomal-lysosomal pathway and redirected trafficking to the nucleus could be an effective approach to increase intracellular AC accumulation in target cells. Cholic acid (ChAc) was coupled to the peptide CGYGPKKKRKVGG containing the nuclear localization sequence (NLS) from SV-40 large T-antigen, which is termed ChAcNLS. ChAcNLS was conjugated to the mAb 7G3 (7G3-ChAcNLS), which has nanomolar affinity for the cell-surface leukemic antigen interleukin-3 receptor-α (IL-3Rα). Our aim was to determine whether 7G3-ChAcNLS increased intracellular accumulation while retaining nanomolar affinity and IL-3Rα-positive cell selectivity. Competition ELISA and cell treatment assays were performed. Cell fractionation, confocal microscopy, flow cytometry, and Western blot techniques were used to determine the level of antibody accumulation inside cells and in corresponding nuclei. In addition, the radioisotope copper-64 ((64)Cu) was also utilized as a surrogate molecular cargo to evaluate nuclear and intracellular accumulation by radioactivity counting. 7G3-ChAcNLS effectively escaped endosome entrapment and degradation resulting in a unique intracellular distribution pattern. mAb modification with ChAcNLS maintained 7G3 nM affinity and produced high selectivity for IL-3Rα-positive cells. In contrast, 7G3 ACs with the ability to either escape endosome entrapment or traffic to the nucleus was not superior to 7G3-ChAcNLS for increasing intracellular accumulation. Transportation of (64)Cu when complexed to 7G3-ChAcNLS also resulted in increased nuclear and intracellular radioactivity accumulation. Thus, ChAcNLS is a novel mAb functionalizing technology that demonstrates its ability to increase AC intracellular accumulation in target cells through escaping endosome entrapment coupled to nuclear trafficking.

Investigation of the stability and cellular uptake of self-associated monoclonal antibody (MAb) nanoparticles by non-small lung cancer cells

The inability to deliver MAbs to intracellular targets still remains a limitation to their application in cancer therapy and diagnosis. Selective targeting of MAbs to oncoproteins in cancer cells while avoiding their accumulation in normal cells may reduce some of the well-documented adverse effects accompanying antibody therapy. One of the remarkable characteristics of malignant cells is the alteration in the biological properties of the cellular plasma membrane. Taking advantage of this alteration, we hope to selectively deliver self-associated MAb nanoparticles to cancer cells while reducing their accumulation in normal cells. We hypothesized that self-associated MAb nanoparticles can be preferentially taken up by non-small lung cancer cells in comparison to normal cells due to the absence or dysfunction of tight junctions (TJ) in confluent cancer cells and increased permeability of the cancer cell membrane. Self-associated bevacizumab nanoparticles were prepared and characterized for particle size and biochemical stability. Fluorescence microscopy, TEM, and flow cytometry revealed that these bevacizumab nanoparticles were internalized by A549 cells three times more than MRC-5 cells. Macropinocytosis and energy-dependent pathways were elucidated to be involved in their uptake by A549 cells. Further, uptake was by nonspecific interaction with cell membrane. Results obtained from this study suggest that self-associated MAb nanoparticles can be selectively delivered to cancer cells.

Comparative study on the interaction of cell-penetrating polycationic polymers with lipid membranes

Cell-penetrating peptides are arginine- and lysine-rich cationic peptides that can readily enter cells not only by themselves but also carrying other macromolecular cargos. In fact, we have reported that polycationic polymer such as poly-l-lysine (PLL) and poly-l-arginine (PLA) translocate through negatively charged phospholipid liposome membranes. In this work, we made a comparative study of the interaction of PLL or PLA with lipid membranes consisting of negatively charged phospholipids to understand the role of basic amino acid residue (i.e. arginine and lysine) in the membrane-penetrating activity of polypeptides. PLA and PLL translocated into giant unilamellar vesicle composed of soybean phospholipids. ζ-potential and turbidity measurements demonstrated the electrostatic binding of PLL and PLA to large unilamellar vesicle (LUV). Fluorescence studies using membrane probes revealed that the binding of PLA and PLL to LUV affects the hydration and packing of the membrane interface region, in which the membrane insertion of PLA appeared to be greater than PLL. Differential scanning calorimetry showed that the enthalpy of the gel to liquid-crystalline phase transition for dipalmitoyl phosphatidylglycerol vesicle was greatly reduced by binding of PLL and PLA, in which the reduction is much larger in PLA than in PLL. Circular dichroism measurements in 2,2,2-trifluoroethanol/water mixture or in the presence of LUV indicated that the propensity of PLA to form α-helical structure is greater than PLL. Consistently, attenuated total reflection-Fourier transform infrared spectroscopy revealed that there is greater α-helical structure in PLA bound to LUV compared to PLL, which has much less ordered structure. Furthermore, isothermal titration calorimetry measurements demonstrated that the contribution of enthalpy to the energetics of binding to LUV is two-fold larger in PLA than in PLL. These results suggest that the stronger interaction of arginine residue with negatively charged phospholipid membranes compared to lysine residue appears to facilitate the conformational change in cationic polypeptide and its insertion into lipid membrane interior.

Targeting antibodies to the cytoplasm

A growing number of research consortia are now focused on generating antibodies and recombinant antibody fragments that target the human proteome. A particularly valuable application for these binding molecules would be their use inside a living cell, e.g., for imaging or functional intervention. Animal-derived antibodies must be brought into the cell through the membrane, whereas the availability of the antibody genes from phage display systems allows intracellular expression. Here, the various technologies to target intracellular proteins with antibodies are reviewed.

Cell Penetrating Peptides: Intracellular Pathways and Pharmaceutical Perspectives

Cell penetrating peptides, generally categorized as amphipathic or cationic depending on their sequence, are increasingly drawing attention as a non-invasive delivery technology for macromolecules. Delivery of a diverse set of cargo in terms of size and nature ranging from small molecules to particulate cargo has been attempted using different types of cell penetrating peptides (CPPs) in vitro and in vivo. However, the internalization mechanism of CPPs is an unresolved issue to date, with dramatic changes in view regarding the involvement of endocytosis as a pathway of internalization. A key reason for the lack of consensus on the mechanism can be attributed to the methodology in deciphering the internalization mechanism. In this review, we highlight some of the methodology concerns, focus more on the internalization pathway and also provide a novel perspective about the intracellular processing of CPPs, which is a crucial aspect to consider when selecting a cell penetrating peptide as a drug delivery system. In addition, recent applications of cell penetrating peptides for the delivery of small molecules, peptides, proteins, oligonucleotides, nanoparticles and liposomes have been reviewed.

Combined flow cytometry and confocal laser scanning microscopy for evaluation of BR96 antibody cancer cell targeting and internalization

BACKGROUND

Monoclonal antibodies (mAb) are important tools in the management of tumor disease, and the discovery of antibodies with both specific cancer cell targeting and capacity to enter the cells by internalization are critical to improve the therapeutic efficacy.

METHOD

Antibody cancer cell targeting and internalization properties of fluoroscein-conjugated mAb made against Lewis Y (BR96) were evaluated quantitatively and qualitatively by means of flow cytometry (FCM) and confocal laser scanning microscopy (CLSM), respectively, on cells from a rat tumor cell line (BN7005-H1D2).

RESULTS

The study demonstrated a specific binding of BR96 to LewisY (LeY) located in the cell membrane and as BR96/LeY immunocomplexes (BR96/LeY) internalized into the cytoplasm. BR96/LeY was internalized into about 15% of the cells, usually distributed throughout the cytoplasm, but also located close to the nuclei. Cytotoxic effects by BR96 were indicated, and CLSM visualized subpopulations containing cells with bound or internalized BR96/LeY that possessed morphologically pyknotic nuclei and disrupted DNA.

CONCLUSION

The spatial-temporal pattern by BR96 cell targeting and internalization processes of BR96/LeY into the cancer cells expressing LeY was demonstrated by FCM and CLSM. Used together, the FCM and CLSM techniques provide a valuable tool for preclinical analyses of antibody targeting and their capacities as carriers of cytotoxic conjugates for the use in cancer therapy.

Cell cycle inhibition by an anti-cyclin D1 antibodychemically modified for intracellular delivery

Antibodies, especially monoclonal antibodies, are highly specific for their target antigens and have found extensive clinical application in the treatment of infectious diseases and neoplasia. However, they have a major shortcoming which, if overcome, would greatly expand their utility: an inability to penetrate the outer membrane of cells and act on intracellular targets. We demonstrated previously that this deficiency could be overcome by covalent linkage of an oligoarginine sequence to the conserved carbohydrate moiety present in the CH2 region of immunoglobulins. Immune specificity was maintained but no attempt was made to test for biological activity related to specificity. Here, we report that a polyarginated monoclonal anti-cyclin D1 enters cells and inhibits cell cycle progression. We demonstrate this with NIH 3T3 cells and with two tumor cell lines, HT29 and SW480. As many tumors overexpress cyclin D1, an intracellular anti-cyclin D1, properly targeted, has the potential to be a novel broad range inhibitor of tumor cell multiplication. Moreover, success with intracellular anti-cyclin D1 suggests that polyarginated antibodies, in general, could be a new, widely applicable experimental tool to investigate and influence intracellular processes, whether native to cells or introduced into cells by outside entities such as viruses.

Monoclonal antibody mediated intracellular targeting of tallysomycin S10b

The potency of tallysomycin S(10b) (TLM S(10b)) an analogue bleomycin was enhanced by up to 875-fold when it was conjugated to the internalizing antibody BR96. Attachment to the antibody is achieved via a Cathepsin B cleavable linker. The enhancement in potency is believed to be a result of cellular uptake of the conjugate upon antigen binding followed by rapid release of the drug inside the lysosome. This method provides a novel approach for increasing the potency and therapeutic index of nominally moderately-active cytotoxic agents.

Intracellular Delivery of Functional Proteins via Decoration with Transporter Peptides

Despite numerous attractive intracellular targets, protein therapeutics have been principally confined to the extracellular space due to the lack of a straightforward way to deliver functional polypeptides to the cell interior. Peptide sequences facilitating intracellular protein delivery have been identified; however, current strategies to apply them require problematic steps, such as generation of new in-frame fusion proteins, covalent chemical conjugation, and denaturation. We have developed a new approach to protein transfer into cells and tissues that relies on single-step decoration by cysteine-flanked, arginine-rich transporter peptides. This approach facilitated cell and tissue delivery of a variety of functional proteins, including antibodies and enzymes. Decoration with transporter peptides thus provides an attractive general means of intracellular delivery of functional proteins in vitro and in tissue.