Extracellular vesicle surface display enhances the therapeutic efficacy and safety profile of cancer immunotherapy.

Immunotherapy has emerged as a mainstay in cancer therapy, yet its efficacy is constrained by the risk of immune-related adverse events. In this study, we present a nanoparticle-based delivery system that enhances the therapeutic efficacy of immunomodulatory ligands while concurrently limiting systemic toxicity. We demonstrate that extracellular vesicles (EVs), lipid bilayer enclosed particles released by cells, can be efficiently engineered via inverse electron demand Diels-Alder (iEDDA)-mediated conjugation to display multiple immunomodulatory ligands on their surface. Display of immunomodulatory ligands on the EV surface conferred substantial enhancements in signaling efficacy, particularly for tumor necrosis factor receptor superfamily (TNFRSF) agonists, where the EV surface display served as an alternative FcγR-independent approach to induce ligand multimerization and efficient receptor crosslinking. EVs displaying a complementary combination of immunotherapeutic ligands were able to shift the tumor immune milieu toward an anti-tumorigenic phenotype and significantly suppress tumor burden and increase survival in multiple models of metastatic cancer to a greater extent than an equivalent dose of free ligands. In summary, we present an EV-based delivery platform for cancer immunotherapeutic ligands that facilitates superior anti-tumor responses at significantly lower doses with fewer side effects than is possible with conventional delivery approaches.

Red blood cell extracellular vesicles deliver therapeutic siRNAs to skeletal muscles for treatment of cancer cachexia.

Cancer cachexia is a multifactorial syndrome characterized by a significant loss of skeletal muscle, which negatively affects the quality of life. Inhibition of myostatin (Mstn), a negative regulator of skeletal muscle growth and differentiation, has been proven to preserve muscle mass in muscle atrophy diseases, including cachexia. However, myostatin inhibitors have repeatedly failed clinical trials because of modest therapeutic effects and side effects due to the poor efficiency and toxicity of existing delivery methods. Here, we describe a novel method for delivering Mstn siRNA to skeletal muscles using red blood cell-derived extracellular vesicles (RBCEVs) in a cancer cachectic mouse model. Our data show that RBCEVs are taken up by myofibers via intramuscular administration. Repeated intramuscular administrations with RBCEVs allowed the delivery of siRNAs, thereby inhibiting Mstn, increasing muscle growth, and preventing cachexia in cancer-bearing mice. We observed the same therapeutic effects when delivering siRNAs against malonyl-CoA decarboxylase, an enzyme driving dysfunctional fatty acid metabolism in skeletal muscles during cancer cachexia. We demonstrate that intramuscular siRNA delivery by RBCEVs is safe and non-inflammatory. Hence, this method is useful to reduce the therapeutic dose of siRNAs, to avoid toxicity and off-target effects caused by systemic administration of naked siRNAs at high doses.

Endocytosis of red blood cell extracellular vesicles by macrophages leads to cytoplasmic heme release and prevents foam cell formation in atherosclerosis.

Extracellular vesicles (EVs) can be produced from red blood cells (RBCs) on a large scale and used to deliver therapeutic payloads efficiently. However, not much is known about the native biological properties of RBCEVs. Here, we demonstrate that RBCEVs are primarily taken up by macrophages and monocytes. This uptake is an active process, mediated mainly by endocytosis. Incubation of CD14+ monocytes with RBCEVs induces their differentiation into macrophages with an Mheme-like phenotype, characterized by upregulation of heme oxygenase-1 (HO-1) and the ATP-binding cassette transporter ABCG1. Moreover, macrophages that take up RBCEVs exhibit a reduction in surface CD86 and decreased secretion of TNF-α under inflammatory stimulation. The upregulation of HO-1 is attributed to heme derived from haemoglobin in RBCEVs. Heme is released from internalized RBCEVs in late endosomes and lysosomes via the heme transporter, HRG1. Consequently, RBCEVs exhibit the ability to attenuate foam cell formation from oxidized low-density lipoproteins (oxLDL)-treated macrophages in vitro and reduce atherosclerotic lesions in ApoE knockout mice on a high-fat diet. In summary, our study reveals the uptake mechanism of RBCEVs and their delivery of heme to macrophages, suggesting the potential application of RBCEVs in the treatment of atherosclerosis.

Robust delivery of RIG-I agonists using extracellular vesicles for anti-cancer immunotherapy.

The RIG-I pathway can be activated by RNA containing 5' triphosphate, leading to type I interferon release and immune activation. Hence, RIG-I agonists have been used to induce immune responses against cancer as potential immunotherapy. However, delivery of 5' triphosphorylated RNA molecules as RIG-I agonists to tumour cells in vivo is challenging due to the susceptibility of these molecules to degradation. In this study, we demonstrate the use of extracellular vesicles (EVs) from red blood cells (RBCs), which are highly amenable for RNA loading and taken up robustly by cancer cells, for RIG-I agonist delivery. We evaluate the anti-cancer activity of two novel RIG-I agonists, the immunomodulatory RNA (immRNA) with a unique secondary structure for efficient RIG-I activation, and a 5' triphosphorylated antisense oligonucleotide with dual function of RIG-I activation and miR-125b inhibition (3p-125b-ASO). We find that RBCEV-delivered immRNA and 3p-125b-ASO trigger the RIG-I pathway, and induce cell death in both mouse and human breast cancer cells. Furthermore, we observe a significant suppression of tumour growth coupled with increased immune cell infiltration mediated by the activation of RIG-I cascade after multiple intratumoral injections of RBCEVs loaded with immRNA or 3p-125b-ASO. Targeted delivery of immRNA using RBCEVs with EGFR-binding nanobody administrated via intrapulmonary delivery facilitates the accumulation of RBCEVs in metastatic cancer cells, leading to potent tumour-specific CD8+ T cells immune response. This contributes to prominent suppression of breast cancer metastasis in the lung. Hence, this study provides a new strategy for efficient RIG-I agonist delivery using RBCEVs for immunotherapy against cancer and cancer metastasis.

Extracellular vesicles and lipoproteins - Smart messengers of blood cells in the circulation.

Blood cell-derived extracellular vesicles (BCEVs) and lipoproteins are the major circulating nanoparticles in blood that play an important role in intercellular communication. They have attracted significant interest for clinical applications, given their endogenous characteristics which make them stable, biocompatible, well tolerated, and capable of permeating biological barriers efficiently. In this review, we describe the basic characteristics of BCEVs and lipoproteins and summarize their implications in both physiological and pathological processes. We also outline well accepted workflows for the isolation and characterization of these circulating nanoparticles. Importantly, we highlight the latest progress and challenges associated with the use of circulating nanoparticles as diagnostic biomarkers and therapeutic interventions in multiple diseases. We spotlight novel engineering approaches and designs to facilitate the development of these nanoparticles by enhancing their stability, targeting capability, and delivery efficiency. Therefore, the present work provides a comprehensive overview of composition, biogenesis, functions, and clinical translation of circulating nanoparticles from the bench to the bedside.

CD33-targeting extracellular vesicles deliver antisense oligonucleotides against FLT3-ITD and miR-125b for specific treatment of acute myeloid leukaemia.

INTRODUCTION: Acute Myeloid Leukaemia (AML) is the most common blood cancer in adults. Although 2 out of 3 AML patients go into total remission after chemotherapies and targeted therapies, the disease recurs in 60%-65% of younger adult patients within 3 years after diagnosis with a dramatically decreased survival rate. Therapeutic oligonucleotides are promising treatments under development for AML as they can be designed to silence oncogenes with high specificity and flexibility. However, there are not many well validated approaches for safely and efficiently delivering oligonucleotide drugs. This issue could be resolved by utilizing a new generation of delivery vehicles such as extracellular vesicles (EVs). METHODS: In this study, we harness red blood cell-derived EVs (RBCEVs) and engineer them via exogenous drug loading and surface functionalization to develop an efficient drug delivery system for AML. Particularly, EVs are designed to target CD33, a common surface marker with elevated expression in AML cells via the conjugation of a CD33-binding monoclonal antibody onto the EV surface. RESULTS: The conjugation of RBCEVs with the CD33-binding antibody significantly increases the uptake of RBCEVs by CD33-positive AML cells, but not by CD33-negative cells. We also load CD33-targeting RBCEVs with antisense oligonucleotides (ASOs) targeting FLT3-ITD or miR-125b, 2 common oncogenes in AML, and demonstrate that the engineered EVs improve leukaemia suppression in in vitro and in vivo models of AML. CONCLUSION: Targeted RBCEVs represent an innovative, efficient, and versatile delivery platform for therapeutic ASOs and can expedite the clinical translation of oligonucleotide drugs for AML treatments by overcoming current obstacles in oligonucleotide delivery.

Surface-engineered extracellular vesicles for targeted delivery of therapeutic RNAs and peptides for cancer therapy.

The advent of novel therapeutics in recent years has urged the need for a safe, non-immunogenic drug delivery vector capable of delivering therapeutic payloads specifically to diseased cells, thereby increasing therapeutic efficacy and reducing side effects. Extracellular vesicles (EVs) have garnered attention in recent years as a potentially ideal vector for drug delivery, taking into account their intrinsic ability to transfer bioactive cargo to recipient cells and their biocompatible nature. However, natural EVs are limited in their therapeutic potential and many challenges need to be overcome before engineered EVs satisfy the levels of efficiency, stability, safety and biocompatibility required for therapeutic use. Here, we demonstrate that an enzyme-mediated surface functionalization method in combination with streptavidin-mediated conjugation results in efficient surface functionalization of EVs. Surface functionalization using the above methods permits the stable and biocompatible conjugation of peptides, single domain antibodies and monoclonal antibodies at high copy number on the EV surface. Functionalized EVs demonstrated increased accumulation in target cells expressing common cancer associated markers such as CXCR4, EGFR and EpCAM both in vitro and in vivo. The functionality of this approach was further highlighted by the ability of targeting EVs to specifically deliver therapeutic antisense oligonucleotides to a metastatic breast tumor model, resulting in increased knockdown of a targeted oncogenic microRNA and improved metastasis suppression. The method was also used to equip EVs with a bifunctional peptide that targets EVs to leukemia cells and induces apoptosis, leading to leukemia suppression. Moreover, we conducted extensive testing to verify the biocompatibility, and safety of engineered EVs for therapeutic use, suggesting that surface modified EVs can be used for repeated dose treatment with no detectable adverse effects. This modular, biocompatible method of EV engineering offers a promising avenue for the targeted delivery of a range of therapeutics while addressing some of the safety concerns associated with EV-based drug delivery.

Covalent conjugation of extracellular vesicles with peptides and nanobodies for targeted therapeutic delivery.

Natural extracellular vesicles (EVs) are ideal drug carriers due to their remarkable biocompatibility. Their delivery specificity can be achieved by the conjugation of targeting ligands. However, existing methods to engineer target-specific EVs are tedious or inefficient, having to compromise between harsh chemical treatments and transient interactions. Here, we describe a novel method for the covalent conjugation of EVs with high copy numbers of targeting moieties using protein ligases. Conjugation of EVs with either an epidermal growth factor receptor (EGFR)-targeting peptide or anti-EGFR nanobody facilitates their accumulation in EGFR-positive cancer cells, both in vitro and in vivo. Systemic delivery of paclitaxel by EGFR-targeting EVs at a low dose significantly increases drug efficacy in a xenografted mouse model of EGFR-positive lung cancer. The method is also applicable to the conjugation of EVs with peptides and nanobodies targeting other receptors, such as HER2 and SIRP alpha, and the conjugated EVs can deliver RNA in addition to small molecules, supporting the versatile application of EVs in cancer therapies. This simple, yet efficient and versatile method for the stable surface modification of EVs bypasses the need for genetic and chemical modifications, thus facilitating safe and specific delivery of therapeutic payloads to target cells.

microRNA exchange via extracellular vesicles in cancer.

Cells utilize different means of inter-cellular communication to function properly. Here, we review the crosstalk between cancer cells and their surrounding environment through microRNA (miRNA)-containing extracellular vesicles (EVs). The current findings suggest that the export of miRNAs and uptake of miRNA-containing EVs might be an active process. As post-transcriptional regulators of gene expression, cancer-derived miRNAs that are taken up by normal cells can change the translational profile of the recipient cell towards a transformed proteome. Stromal cells can also deliver miRNAs via EVs to cancer cells to support tumour growth and cancer progression. Therefore, gaining a better understanding of EV-mediated inter-cellular communication in the tumour microenvironment might lead to the development of novel diagnostic and therapeutic strategies.