A Phase 2 study of L-asparaginase encapsulated in erythrocytes in elderly patients with Philadelphia chromosome negative acute lymphoblastic leukemia: The GRASPALL/GRAALL-SA2-2008 study

Recent advances with erythrocytes as therapeutics carriers

Erythrocytes have gained popularity as a natural option for in vivo drug delivery due to their advantages, which include lengthy circulation times, biocompatibility, and biodegradability. Consequently, the drug's pharmacokinetics and pharmacodynamics in red blood cells can be considerably up the dosage. Here, we provide an overview of the erythrocyte membrane's structure and discuss the characteristics of erythrocytes that influence their suitability as carrier systems. We also cover current developments in the erythrocyte-based nanocarrier, which could be used for both active and passive targeting of disease tissues, particularly those of the reticuloendothelial system (RES) and cancer tissues. We also go over the most recent discoveries about the in vivo and in vitro uses of erythrocytes for medicinal and diagnostic purposes. Moreover, the clinical relevance of erythrocytes is discussed in order to improve comprehension and enable the potential use of erythrocyte carriers in the management of various disorders.

Inotuzumab Ozogamicin and Low-Intensity Chemotherapy in Older Patients With Newly Diagnosed CD22+ Philadelphia Chromosome-Negative B-Cell Precursor Acute Lymphoblastic Leukemia

PURPOSE

The use of inotuzumab ozogamicin (InO), a conjugated anti-CD22 monoclonal antibody, is becoming a promising frontline treatment for older patients with ALL.

PATIENTS AND METHODS

EWALL-INO is an open-label prospective multicenter phase II trial (ClinicalTrials.gov identifier: NCT03249870). Patients age 55 years and older with newly diagnosed CD22+ Philadelphia chromosome-negative (Ph-) B-cell precursor (BCP) ALL were eligible. After a prephase, a first induction consisting of vincristine, dexamethasone, and three injections of InO (0.8 mg/m2 day 1, 0.5 mg/m2 day 8/day 15) was followed by a second induction combining cyclophosphamide, dexamethasone, and two injections of InO (0.5 mg/m2 day 1/day 8). Responders received up to six cycles of chemotherapy consolidation and 18-month chemotherapy maintenance. Allotransplant was allowed after three consolidations. The primary end point was 1-year overall survival (OS).

RESULTS

Between December 2017 and March 2022, 131 patients (median age 68 years) were included. Three patients died during induction 1 (n = 130), two from multiple organ failure and one from hemorrhage, and none during induction 2 (n = 120). After induction 2, 90% of the patients achieved complete remission (CR) or CR with incomplete platelet recovery (CRp) and 80% had measurable residual disease (MRD2) <10-4. Among responders (n = 119), 47 relapsed and 14 died in CR/CRp. One-year OS, relapse-free survival (RFS), and cumulative incidence of relapse (CIR) rates were 73.2%, 66%, and 25%, respectively. High-risk cytogenetics and lower CD22 expression (<70%) were associated with worse OS, while both high-risk cytogenetics and MRD2 ≥10-4 were associated with lower RFS and higher CIR. The 10 allotransplanted patients had very favorable outcomes (90% 2-year OS/RFS and no relapse). Only one nonfatal sinusoidal obstructive syndrome was documented during the study.

CONCLUSION

Our results support InO's use in first-line regimens for older patients with CD22+ Ph- BCP-ALL.

Unlocking the power of nanomedicine: Cell membrane-derived biomimetic cancer nanovaccines for cancer treatment

Over the past decades, nanomedicine researchers have dedicated their efforts to developing nanoscale platforms capable of more precisely delivering drug payloads to attack tumors. Cancer nanovaccines are exhibiting a distinctive capability in inducing tumor-specific antitumor responses. Nevertheless, there remain numerous challenges that must be addressed for cancer nanovaccines to evoke sufficient therapeutic effects. Cell membrane-derived nanovaccines are an emerging class of cancer vaccines that comprise a synthetic nanoscale core camouflaged by naturally derived cell membranes. The specific cell membrane has a biomimetic nanoformulation with several distinctive abilities, such as immune evasion, enhanced biocompatibility, and tumor targeting, typically associated with a source cell. Here, we discuss the advancements of cell membrane-derived nanovaccines and how these vaccines are used for cancer therapeutics. Translational endeavors are currently in progress, and additional research is also necessary to effectively address crucial areas of demand, thereby facilitating the future successful translation of these emerging vaccine platforms.

Artificial cells for in vivo biomedical applications through red blood cell biomimicry

Recent research in artificial cell production holds promise for the development of delivery agents with therapeutic effects akin to real cells. To succeed in these applications, these systems need to survive the circulatory conditions. In this review we present strategies that, inspired by the endurance of red blood cells, have enhanced the viability of large, cell-like vehicles for in vivo therapeutic use, particularly focusing on giant unilamellar vesicles. Insights from red blood cells can guide modifications that could transform these platforms into advanced drug delivery vehicles, showcasing biomimicry's potential in shaping the future of therapeutic applications.

Drug-loaded erythrocytes: Modern approaches for advanced drug delivery for clinical use

Scientific organizations worldwide are striving to create drug delivery systems that provide a high local concentration of a drug in pathological tissue without side effects on healthy organs in the body. Important physiological properties of red blood cells (RBCs), such as frequent renewal ability, good oxygen carrying ability, unique shape and membrane flexibility, allow them to be used as natural carriers of drugs in the body. Erythrocyte carriers derived from autologous blood are even more promising drug delivery systems due to their immunogenic compatibility, safety, natural uniqueness, simple preparation, biodegradability and convenience of use in clinical practice. This review is focused on the achievements in the clinical application of targeted drug delivery systems based on osmotic methods of loading RBCs, with an emphasis on advancements in their industrial production. This article describes the basic methods used for encapsulating drugs into erythrocytes, key strategic approaches to the clinical use of drug-loaded erythrocytes obtained by hypotonic hemolysis. Moreover, clinical trials of erythrocyte carriers for the targeted delivery are discussed. This article explores the recent advancements and engineering approaches employed in the encapsulation of erythrocytes through hypotonic hemolysis methods, as well as the most promising inventions in this field. There is currently a shortage of reviews focused on the automation of drug loading into RBCs; therefore, our work fills this gap. Finally, further prospects for the development of engineering and technological solutions for the automatic production of drug-loaded RBCs were studied. Automated devices have the potential to provide the widespread production of RBC-encapsulated therapeutic drugs and optimize the process of targeted drug delivery in the body. Furthermore, they can expedite the widespread introduction of this innovative treatment method into clinical practice, thereby significantly expanding the effectiveness of treatment in both surgery and all areas of medicine.

Advances in Drug Delivery Systems Based on Red Blood Cells and Their Membrane-Derived Nanoparticles

Red blood cells (RBCs) and RBC membrane-derived nanoparticles have been historically developed as bioinspired drug delivery systems to combat the issues of premature clearance, toxicity, and immunogenicity of synthetic nanocarriers. RBC-based delivery systems possess characteristics including biocompatibility, biodegradability, and long circulation time, which make them suited for systemic administration. Therefore, they have been employed in designing optimal drug formulations in various preclinical models and clinical trials to treat a wide range of diseases. In this review, we provide an overview of the biology, synthesis, and characterization of drug delivery systems based on RBCs and their membrane including whole RBCs, RBC membrane-camouflaged nanoparticles, RBC-derived extracellular vesicles, and RBC hitchhiking. We also highlight conventional and latest engineering strategies, along with various therapeutic modalities, for enhanced precision and effectiveness of drug delivery. Additionally, we focus on the current state of RBC-based therapeutic applications and their clinical translation as drug carriers, as well as discussing opportunities and challenges associated with these systems.

Approach to the Treatment of Philadelphia Chromosome-Negative B-cell ALL in Older Adults: Is Age Becoming just a Number?

PURPOSE OF REVIEW

Despite progress in the treatment of pediatric B-cell acute lymphoblastic leukemia (ALL) and PH + ALL, fewer advancements have been for older adults with PH-negative B-cell ALL. Treatment of this population is mired by higher incidence of poor risk biologic features, increased incidence of medical comorbidities, and higher rates of treatment-related mortality (TRM). Here, we review the difficulties in managing elderly patients with PH-negative ALL.

RECENT FINDINGS

The development of novel agents has brought additional tools to the armamentarium of drugs and has changed the landscape of treatment. More recent clinical trials and future clinical trials focus on blinatumomab, inotuzomab ozogamicin (IO), and/or chimeric antigen receptor T-cell (CAR-T) either alone or integrated with dose-reduced chemotherapy regimens. The introduction of novel agents/therapies and incorporation into our current treatment paradigms may finally offer an avenue to improve the dismal outcomes seen in this population.

Design of erythrocyte-derived carriers for bioimaging applications

Erythrocytes are physiological entities that have been exploited in both preclinical and clinical trials for the delivery of exogenous agents. Over the years, diverse erythrocyte-derived carriers (ECs) have been developed with related patents granted for industrial and commercial purposes. However, most ECs have only been exploited for drug delivery. Serious discussions regarding their applications in imaging are scarce. This article reviews the role of ECs in enhancing imaging efficiency and subsequently delineates strategies for engineering and optimising their preclinical and clinical performance. With a snapshot of the latest developments and use of ECs in imaging, directions to streamline the clinical translation of related technologies can be attained for future research.

Targeting amino acid metabolism in cancer

Metabolic rewiring is a characteristic hallmark of cancer cells. This phenomenon sustains uncontrolled proliferation and resistance to apoptosis by increasing nutrients and energy supply. However, reprogramming comes together with vulnerabilities that can be used against tumor and can be applied in targeted therapy. In the last years, the genetic background of tumors has been identified thoroughly and new therapies targeting those mutations tested. Nevertheless, we propose that targeting the phenotype of cancer cells could be another way of treatment aiming to avoid drug resistance and non-responsiveness of cancer patients. Amino acid metabolism is part of the altered processes in cancer cells. Amino acids are building blocks and also sensors of signaling pathways regulating main biological processes. In this comprehensive review, we described four amino acids (asparagine, arginine, methionine, and cysteine) which have been actively investigated as potential targets for anti-tumor therapy. Asparagine depletion is successfully used for decades in the treatment of acute lymphoblastic leukemia and there is a strong implication to apply it to other types of tumors. Arginine auxotrophic tumors are great candidates for arginine-starvation therapy. Higher requirement for essential amino acids such as methionine and cysteine point out promising targetable weaknesses of cancer cells.

Current Use of Asparaginase in Acute Lymphoblastic Leukemia/Lymphoblastic Lymphoma

Pediatric Acute Lymphoblastic Leukemia (ALL) cure rates have improved exponentially over the past five decades with now over 90% of children achieving long-term survival. A direct contributor to this remarkable feat is the development and expanded understanding of combination chemotherapy. Asparaginase is the most recent addition to the ALL chemotherapy backbone and has now become a hallmark of therapy. It is generally accepted that the therapeutic effects of asparaginase is due to depletion of the essential amino acid asparagine, thus occupying a unique space within the therapeutic landscape of ALL. Pharmacokinetic and pharmacodynamic profiling have allowed a detailed and accessible insight into the biochemical effects of asparaginase resulting in regular clinical use of therapeutic drug monitoring (TDM). Asparaginase's derivation from bacteria, and in some cases conjugation with a polyethylene glycol (PEG) moiety, have contributed to a unique toxicity profile with hypersensitivity reactions being the most salient. Hypersensitivity, along with several other toxicities, has limited the use of asparaginase in some populations of ALL patients. Both TDM and toxicities have contributed to the variety of approaches to the incorporation of asparaginase into the treatment of ALL. Regardless of the approach to asparagine depletion, it has continually demonstrated to be among the most important components of ALL therapy. Despite regular use over the past 50 years, and its incorporation into the standard of care treatment for ALL, there remains much yet to be discovered and ample room for improvement within the utilization of asparaginase therapy.

Morphological Characteristics, Hemoglobin Content, and Membrane Mechanical Properties of Red Blood Cell Delivery Systems

Red blood cell (RBC)-based systems are under extensive development as platforms for the delivery of various biomedical agents. While the importance of the membrane biochemical characteristics in relation to circulation kinetics of RBC delivery systems has been recognized, the membrane mechanical properties of such carriers have not been extensively studied. Using optical methods in conjunction with image analysis and mechanical modeling, we have quantified the morphological and membrane mechanical characteristics of RBC-derived microparticles containing the near-infrared cargo indocyanine green (ICG). We find that these particles have a significantly lower surface area, volume, and deformability as compared to normal RBCs. The residual hemoglobin has a spatially distorted distribution in the particles. The membrane bending modulus of the particles is about twofold higher as compared to normal RBCs and exhibits greater resistance to flow. The induced increase in the viscous characteristics of the membrane is dominant over the elastic and entropic effects of ICG. Our results suggest that changes to the membrane mechanical properties are a result of impaired membrane-cytoskeleton attachment in these particles. We provide a mechanistic explanation to suggest that the compromised membrane-cytoskeleton attachment and altered membrane compositional and structural asymmetry induce curvature changes to the membrane, resulting in mechanical remodeling of the membrane. These findings highlight the importance of membrane mechanical properties as an important criterion in the design and engineering of future generations of RBC-based delivery systems to achieve prolonged circulation.

Brain-Targeted Codelivery of Bcl-2/Bcl-xl and Mcl-1 Inhibitors by Biomimetic Nanoparticles for Orthotopic Glioblastoma Therapy

Glioblastoma (GBM) is among the most treatment-resistant solid tumors and often recurrs after resection. One of the mechanisms through which GBM escapes various treatment modalities is the overexpression of anti-apoptotic Bcl-2 family proteins (e.g., Bcl-2, Bcl-xl, and Mcl-1) in tumor cells. Small-molecule inhibitors such as ABT-263 (ABT), which can promote mitochondrial-mediated cell apoptosis by selectively inhibiting the function of Bcl-2 and Bcl-xl, have been proven to be promising anticancer agents in clinical trials. However, the therapeutic prospects of ABT for GBM treatment are hampered by its limited blood-brain barrier (BBB) penetration, dose-dependent thrombocytopenia, and the drug resistance driven by Mcl-1, which is overexpressed in GBM cells and further upregulated upon treatment with ABT. Herein, we reported that the Mcl-1-specific inhibitor A-1210477 (A12) can act synergistically with ABT to induce potent cell apoptosis in U87 MG cells, drug-resistant U251 cells, and patient-derived GBM cancer stem cells. We further designed a biomimetic nanomedicine, based on the apolipoprotein E (ApoE) peptide-decorated red blood cell membrane and pH-sensitive dextran nanoparticles, for the brain-targeted delivery of ABT and A12. The synergistic anti-GBM effect was retained after encapsulation in the nanomedicine. Additionally, the obtained nanomedicine possessed good biocompatibility, exhibited efficient BBB penetration, and could effectively suppress tumor growth and prolong the survival time of mice bearing orthotopic GBM xenografts without inducing detectable adverse effects.

Asparaginase encapsulated in erythrocytes as second-line treatment in hypersensitive patients with acute lymphoblastic leukaemia

Asparaginase is essential in treating acute lymphoblastic leukaemia (ALL). Asparaginase-related hypersensitivity causes treatment discontinuation, which is associated with decreased event-free survival. To continue asparaginase treatment after hypersensitivity, a formulation of asparaginase encapsulated in erythrocytes (eryaspase) was developed. In NOR-GRASPALL 2016 (NCT03267030) the safety and efficacy of eryaspase was evaluated in 55 patients (aged 1-45 years; median: 6.1 years) with non-high-risk ALL and hypersensitivity to asparaginase conjugated with polyethylene glycol (PEG-asparaginase). Eryaspase (150 u/kg) was scheduled to complete the intended course of asparaginase (1-7 doses) in two Nordic/Baltic treatment protocols. Forty-nine (96.1%) patients had asparaginase enzyme activity (AEA) ≥100 iu/l 14 ± 2 days after the first eryaspase infusion [median AEA 511 iu/l; interquartile range (IQR), 291-780], whereas six of nine (66.7%) patients had AEA ≥100 iu/l 14 ± 2 days after the fourth infusion (median AEA 932 iu/l; IQR, 496-163). The mean terminal half-life of eryaspase following the first infusion was 15.3 ± 15.5 days. Few asparaginase-related adverse events were reported; five patients (9.1%) developed clinical allergy associated with enzyme inactivation. Replacement therapy was successfully completed in 50 patients (90.9%). Eryaspase was well tolerated, and most patients had AEA levels above the therapeutic target after the first infusion. The half-life of eryaspase confirmed that a 2-week schedule is appropriate.

Novel Insights on the Use of L-Asparaginase as an Efficient and Safe Anti-Cancer Therapy

Simple Summary

L-asparaginase (L-ASNase) therapy is key for achieving the very high cure rate of pediatric acute lymphoblastic leukemia (ALL), yet its use is mostly confined to this indication. One main reason preventing the expansion of today’s FDA-approved L-ASNases to solid cancers is their high toxicity and side effects, which become especially challenging in adult patients. The design of optimized L-ASNase molecules provides opportunities to overcome these unwanted toxicities. An additional challenge to broader application of L-ASNases is how cells can counter the pharmacological effect of this drug and the identification of L-ASNases resistance mechanisms. In this review, we discuss recent insights into L-ASNase adverse effects, resistance mechanisms, and how novel L-ASNase variants and drug combinations can expand its clinical applicability, with a focus on both hematological and solid tumors.

Abstract

L-Asparaginase (L-ASNase) is an enzyme that hydrolyses the amino acid asparagine into aspartic acid and ammonia. Systemic administration of bacterial L-ASNase is successfully used to lower the bioavailability of this non-essential amino acid and to eradicate rapidly proliferating cancer cells with a high demand for exogenous asparagine. Currently, it is a cornerstone drug in the treatment of the most common pediatric cancer, acute lymphoblastic leukemia (ALL). Since these lymphoblasts lack the expression of asparagine synthetase (ASNS), these cells depend on the uptake of extracellular asparagine for survival. Interestingly, recent reports have illustrated that L-ASNase may also have clinical potential for the treatment of other aggressive subtypes of hematological or solid cancers. However, immunogenic and other severe adverse side effects limit optimal clinical use and often lead to treatment discontinuation. The design of optimized and novel L-ASNase formulations provides opportunities to overcome these limitations. In addition, identification of multiple L-ASNase resistance mechanisms, including ASNS promoter reactivation and desensitization, has fueled research into promising novel drug combinations to overcome chemoresistance. In this review, we discuss recent insights into L-ASNase adverse effects, resistance both in hematological and solid tumors, and how novel L-ASNase variants and drug combinations can expand its clinical applicability.

L-asparaginase mediated therapy in L-asparagine auxotrophic cancers: A review

Microbial L-asparaginase is the most effective first-line therapeutic used in the treatment protocols of paediatric and adult leukemia. Leukemic cell's auxotrophy for L-asparagine is exploited as a therapeutic strategy to mediate cell death through metabolic blockade of L-asparagine using L-asparaginase. Escherichia coli and Erwinia chrysanthemi serve as the major enzyme deriving sources accepted in clinical practise and the enzyme has bestowed improvements in patient outcomes over the last 40 years. However, an array of side effects generated by the native enzymes due to glutamine co-catalysis and short serum stays augmenting frequent dosages, intended a therapeutic switch towards the development of biobetter alternatives for the enzyme including the formulations resulting in sustained local depletion of L-asparagine. In addition, the treatment with L-asparaginase in few cancer types has proven to elicit drug-induced cytoprotective autophagy mechanisms and therefore warrants concern. Although the off-target glutamine hydrolysis has been viewed in contributing the drug-induced secondary responses in cells deficient with asparagine synthetase machinery, the beneficial role of glutaminase-asparaginase in proliferative regulation of asparagine prototrophic cells has been looked forward. The current review provides an overview on the enzyme's clinical applications in leukemia and possible therapeutic implications in other solid tumours, recent advancements in drug formulations, and discusses the aspects of two-sided roles of glutaminase-asparaginases and drug-induced cytoprotective autophagy mechanisms.

L-Lysine α-Oxidase: Enzyme with Anticancer Properties

L-lysine α-oxidase (LO), one of L-amino acid oxidases, deaminates L-lysine with the yield of H2O2, ammonia, and α-keto-ε-aminocaproate. Multiple in vitro and in vivo studies have reported cytotoxic, antitumor, antimetastatic, and antitumor activity of LO. Unlike asparaginase, LO has a dual mechanism of action: depletion of L-lysine and formation of H2O2, both targeting tumor growth. Prominent results were obtained on murine and human tumor models, including human colon cancer xenografts HCT 116, LS174T, and T47D with maximum T/C 12, 37, and 36%, respectively. The data obtained from human cancer xenografts in immunodeficient mice confirm the potential of LO as an agent for colon cancer treatment. In this review, we discuss recently discovered molecular mechanisms of biological action and the potential of LO as anticancer enzyme.

Clinical progress and advanced research of red blood cells based drug delivery system

Red blood cells (RBCs) are biocompatible carriers that can be employed to deliver different bioactive substances. In the past few decades, many strategies have been developed to encapsulate or attach drugs to RBCs. Osmotic-based encapsulation methods have been industrialized recently, and some encapsulated RBC formulations have reached the clinical stage for treating tumors and neurological diseases. Inspired by the intrinsic properties of intact RBCs, some advanced delivery strategies have also been proposed. These delivery systems combine RBCs with other novel systems to further exploit and expand the application of RBCs. This review summarizes the clinical progress of drugs encapsulated into intact RBCs, focusing on the loading and clinical trials. It also introduces the latest advanced research based on developing prospects and limitations of intact RBCs drug delivery system (DDS), hoping to provide a reference for related research fields and further application potential of intact RBCs based drug delivery system.

Bioactive nanotherapeutic trends to combat triple negative breast cancer

The management of aggressive breast cancer, particularly, triple negative breast cancer (TNBC) remains a formidable challenge, despite treatment advancement. Although newer therapies such as atezolizumab, olaparib, and sacituzumab can tackle the breast cancer prognosis and/or progression, but achieved limited survival benefit(s). The current research efforts are aimed to develop and implement strategies for improved bioavailability, targetability, reduce systemic toxicity, and enhance therapeutic outcome of FDA-approved treatment regimen. This review presents various nanoparticle technology mediated delivery of chemotherapeutic agent(s) for breast cancer treatment. This article also documents novel strategies to employ cellular and cell membrane cloaked (biomimetic) nanoparticles for effective clinical translation. These technologies offer a safe and active targeting nanomedicine for effective management of breast cancer, especially TNBC.

Construction and evaluation of red blood cells-based drug delivery system for chemo-photothermal therapy

In this study, a novel tumor-targeting drug delivery system (DDS) based on red blood cells (RBCs) were fabricated for combinational chemo-phototherapy against cancer. Cyclic peptide (cRGD) and indocyanine green (ICG) were applied to the surface of RBCs to increase the targeting and photothermal effect, respectively. Doxorubicin (DOX) as a model drug was loaded into RBCs by the hypotonic dialysis method. A series of tests have been carried out to evaluate the RBCs-based DDS and these tasks include physicochemical properties, cellular uptake, targeting ability, and combination therapeutic efficiency. As a result, the DOX was successfully loaded into RBCs and the drug loading amount was 0.84 ± 0.09 mg/mL. There was no significant change of particle size after surface modification of RBCs. The RBCs-based DDS could target to the surface of cancer cells, which delivery DOX to the lesions efficiently and accurately. Meanwhile, due to the combined treatment effect, the RBCs-based DDS can effectively inhibit tumor growth. The RBCs-based DDS constructed in this research may have promising applications in cancer therapy due to their highly synergistic efficient therapy and to investigate its possibility for tumor therapy.

Lipid membrane-based therapeutics and diagnostics

Success rates in drug discovery are extremely low, and the imbalance between new drugs entering clinical research and their approval is steadily widening. Among the causes of the failure of new therapeutic agents are the lack of safety and insufficient efficacy. On the other hand, timely disease diagnosis may enable an early management of the disease, generally leading to better and less costly outcomes. Several strategies have been explored to overcome the barriers for drug development and facilitate diagnosis. Using lipid membranes as platforms for drug delivery or as biosensors are promising strategies, due to their biocompatibility and unique physicochemical properties. We examine some of the lipid membrane-based strategies for drug delivery and diagnostics, including their advantages and shortcomings. Regarding synthetic lipid membrane-based strategies for drug delivery, liposomes are the archetypic example of a successful approach, already with a long period of well-succeeded clinical application. The use of lipid membrane-based structures from biological sources as drug carriers, currently under clinical evaluation, is also discussed. These biomimetic strategies can enhance the in vivo lifetime of drug and delivery system by avoiding fast clearance, consequently increasing their therapeutic window. The strategies under development using lipid membranes for diagnostic purposes are also reviewed.

Shifting the Gears of Metabolic Plasticity to Drive Cell State Transitions in Cancer

Cancer metabolism is a hallmark of cancer. Metabolic plasticity defines the ability of cancer cells to reprogram a plethora of metabolic pathways to meet unique energetic needs during the various steps of disease progression. Cell state transitions are phenotypic adaptations which confer distinct advantages that help cancer cells overcome progression hurdles, that include tumor initiation, expansive growth, resistance to therapy, metastasis, colonization, and relapse. It is increasingly appreciated that cancer cells need to appropriately reprogram their cellular metabolism in a timely manner to support the changes associated with new phenotypic cell states. We discuss metabolic alterations that may be adopted by cancer cells in relation to the maintenance of cancer stemness, activation of the epithelial-mesenchymal transition program for facilitating metastasis, and the acquisition of drug resistance. While such metabolic plasticity is harnessed by cancer cells for survival, their dependence and addiction towards certain metabolic pathways also present therapeutic opportunities that may be exploited.

Novel engineering: Biomimicking erythrocyte as a revolutionary platform for drugs and vaccines delivery

Over the years, extensive studies on erythrocytes, also known as red blood cells (RBCs), as a mechanism for drug delivery, have been explored mainly because the cell itself is the most abundant and has astonishing properties such as a long life span of 100-120 days, low immunogenicity, good biocompatibility, and flexibility. There are various types of RBC-based systems for drug delivery, including those that are genetically engineered, non-genetically engineered RBCs, as well as employing erythrocyte as nanocarriers for drug loading. Although promising, these systems are still in an early development stage. In this review, we aimed to highlight the development of biomimicking RBC-based drug and vaccine delivery systems, as well as the loading methods with illustrative examples. Drug-erythrocyte associations will also be discussed and highlighted in this review. We have highlighted the possibility of exploiting erythrocytes for the sustained delivery of drugs and vaccines, encapsulation of these biological agents within the erythrocyte or coupling to the surface of carrier erythrocytes, and provided insights on genetically- and non-genetically engineered erythrocytes-based strategies. Erythrocytes have been known as effective cellular carriers for therapeutic moieties for several years. Herein, we outline various loading methods that can be used to reap the benefits of these natural carriers. It has been shown that drugs and vaccines can be delivered via erythrocytes but it is important to select appropriate methods for increasing the drug encapsulated or conjugated on the surface of the erythrocyte membrane. The outlined examples will guide the selection of the most effective method as well as the impact of using erythrocytes as delivery systems for drugs and vaccines.

Erythrocytes and Nanoparticles: New Therapeutic Systems

Nano-delivery systems represent one of the most studied fields, thanks to the associated improvement in the treatment of human diseases. The functionality of nanostructures is a crucial point, which the effectiveness of nanodrugs depends on. A hybrid approach strategy using synthetic nanoparticles (NPs) and erythrocytes offers an optimal blend of natural and synthetic materials. This, in turn, allows medical practitioners to exploit the combined advantages of erythrocytes and NPs. Erythrocyte-based drug delivery systems have been investigated for their biocompatibility, as well as the long circulation time allowed by specific surface receptors that inhibit immune clearance. In this review, we will discuss several methods—whole erythrocytes as drug carriers, red blood cell membrane-camouflaged nanoparticles and nano-erythrosomes (NERs)—while paying attention to their application and specific preparation methods. The ability to target cells makes erythrocytes excellent drug delivery systems. They can carry a wide range of therapeutic molecules while also acting as bioreactors; thus, they have many applications in therapy and in the diagnosis of many diseases.

Ongoing Developments and Clinical Progress in Drug-Loaded Red Blood Cell Technologies

Engineered red blood cells (RBCs) appear to be a promising method for therapeutic drug and protein delivery. With a number of agents in clinical trials (e.g., dexamethasone 21-phosphate in ataxia telangiectasia, asparaginase in pancreatic cancer/acute lymphoblastic leukemia, thymidine phosphorylase in mitochondrial neurogastrointestinal encephalomyopathy, RTX-134 in phenylketonuria, etc.), this leading article summarizes the ongoing efforts in developing these agents, focuses on the clinical progress, and provides a brief background into engineered RBCs and the different ways in which they can be exploited for therapeutic/diagnostic purposes. References to available data on safety, efficacy, and tolerability are reported. Due to the continuous progress in this field, the information is updated as of January 2020 from databases, websites, and press releases of the involved companies and information that is in the public domain.

Preclinical developments of enzyme-loaded red blood cells

INTRODUCTION

Therapeutic enzymes are currently used in the treatment of several diseases. In most cases, the benefits are limited due to poor in vivo stability, immunogenicity, and drug-induced inactivating antibodies. A partial solution to the problem is obtained by masking the therapeutic protein by chemical modifications. Unfortunately, this is not a satisfactory solution because frequent adverse events, including anaphylaxis, can arise.

AREA COVERED

Among the delivery systems, we focused on red blood cells for the delivery of therapeutic enzymes. Erythrocytes possess a long circulation time, a reduced immunogenicity, there is no need of chemical modifications and the encapsulated enzyme remains active because it is protected by the cell membrane. Here we discuss some representative applications of the preclinical developments of the field. Some of these are currently in clinic, others are approaching the clinic and others are illustrative of the development process. The selected examples are not always the most recent, but they are the most useful for a comparative approach.

EXPERT OPINION

The results discussed confirm the central role that red blood cells can play in the treatment of several conditions and suggest the benefit in using a natural cellular carrier in terms of pharmacokinetic, biodistribution, safety, and efficacy.

Biological Cells as Therapeutic Delivery Vehicles

One of the significant challenges remaining in the field of drug delivery is insufficient targeting of diseased tissues or cells. While efforts to perform targeted drug delivery by engineered nanoparticles have shown some success, there are underlying targeting, toxicity, and immunogenicity challenges. By contrast, live cells usually have innate targeting mechanisms, and can be used as drug-delivery vehicles to increase the efficiency with which a drug accumulates to act on the intended tissue. In some cases, when no native cell types exhibit the desired therapeutic phenotype, preferred outcomes can be achieved by genetically modifying and reprogramming cells with gene circuits. This review highlights recent advances in the use of cells to deliver therapeutics. Specifically, we discuss how red blood cells (RBCs), platelets, neutrophils, mesenchymal stem cells (MSCs), and bacteria have been utilized to advance drug delivery.

Targeted Cellular Micropharmacies: Cells Engineered for Localized Drug Delivery

The recent emergence of engineered cellular therapies, such as Chimeric antigen receptor (CAR) CAR T and T cell receptor (TCR) engineered T cells, has shown great promise in the treatment of various cancers. These agents aggregate and expand exponentially at the tumor site, resulting in potent immune activation and tumor clearance. Moreover, the ability to elaborate these cells with therapeutic agents, such as antibodies, enzymes, and immunostimulatory molecules, presents an unprecedented opportunity to specifically modulate the tumor microenvironment through cell-mediated drug delivery. This unique pharmacology, combined with significant advances in synthetic biology and cell engineering, has established a new paradigm for cells as vectors for drug delivery. Targeted cellular micropharmacies (TCMs) are a revolutionary new class of living drugs, which we envision will play an important role in cancer medicine and beyond. Here, we review important advances and considerations underway in developing this promising advancement in biological therapeutics.

Application of advances in endocytosis and membrane trafficking to drug delivery

Multidisciplinary research efforts in the field of drug delivery have led to the development of a variety of drug delivery systems (DDS) designed for site-specific delivery of diagnostic and therapeutic agents. Since efficient uptake of drug carriers into target cells is central to effective drug delivery, a comprehensive understanding of the biological pathways for cellular internalization of DDS can facilitate the development of DDS capable of precise tissue targeting and enhanced therapeutic outcomes. Diverse methods have been applied to study the internalization mechanisms responsible for endocytotic uptake of extracellular materials, which are also the principal pathways exploited by many DDS. Chemical inhibitors remain the most commonly used method to explore endocytotic internalization mechanisms, although genetic methods are increasingly accessible and may constitute more specific approaches. This review highlights the molecular basis of internalization pathways most relevant to internalization of DDS, and the principal methods used to study each route. This review also showcases examples of DDS that are internalized by each route, and reviews the general effects of biophysical properties of DDS on the internalization efficiency. Finally, options for intracellular trafficking and targeting of internalized DDS are briefly reviewed, representing an additional opportunity for multi-level targeting to achieve further specificity and therapeutic efficacy.

Erythrocytes as Carriers of Therapeutic Enzymes

Therapeutic enzymes are administered for the treatment of a wide variety of diseases. They exert their effects through binding with a high affinity and specificity to disease-causing substrates to catalyze their conversion to a non-noxious product, to induce an advantageous physiological change. However, the metabolic and clinical efficacies of parenterally or intramuscularly administered therapeutic enzymes are very often limited by short circulatory half-lives and hypersensitive and immunogenic reactions. Over the past five decades, the erythrocyte carrier has been extensively studied as a strategy for overcoming these limitations and increasing therapeutic efficacy. This review examines the rationale for the different therapeutic strategies that have been applied to erythrocyte-mediated enzyme therapy. These strategies include their application as circulating bioreactors, targeting the monocyte-macrophage system, the coupling of enzymes to the surface of the erythrocyte and the engineering of CD34+ hematopoietic precursor cells for the expression of therapeutic enzymes. An overview of the diverse biomedical applications for which they have been investigated is also provided, including the detoxification of exogenous chemicals, thrombolytic therapy, enzyme replacement therapy for metabolic diseases and antitumor therapy.

Adipocyte-Based Cell Therapy in Oncology: The Role of Cancer-Associated Adipocytes and Their Reinterpretation as Delivery Platforms

Cancer-associated adipocytes have functional roles in tumor development through secreted adipocyte-derived factors and exosomes and also through metabolic symbiosis, where the malignant cells take up the lactate, fatty acids and glutamine produced by the neighboring adipocytes. Recent research has demonstrated the value of adipocytes as cell-based delivery platforms for drugs (or prodrugs), nucleic acids or loaded nanoparticles for cancer therapy. This strategy takes advantage of the biocompatibility of the delivery system, its ability to locate the tumor site and also the predisposition of cancer cells to come in functional contact with the adipocytes from the tumor microenvironment for metabolic sustenance. Also, their exosomal content can be used in the context of cancer stem cell reprogramming or as a delivery vehicle for different cargos, like non-coding nucleic acids. Moreover, the process of adipocytes isolation, processing and charging is quite straightforward, with minimal economical expenses. The present review comprehensively presents the role of adipocytes in cancer (in the context of obese and non-obese individuals), the main methods for isolation and characterization and also the current therapeutic applications of these cells as delivery platforms in the oncology sector.

Erythrocytes as Carriers: From Drug Delivery to Biosensors

Drug delivery using natural biological carriers, especially erythrocytes, is a rapidly developing field. Such erythrocytes can act as carriers that prolong the drug's action due to its gradual release from the carrier; as bioreactors with encapsulated enzymes performing the necessary reactions, while remaining inaccessible to the immune system and plasma proteases; or as a tool for targeted drug delivery to target organs, primarily to cells of the reticuloendothelial system, liver and spleen. To date, erythrocytes have been studied as carriers for a wide range of drugs, such as enzymes, antibiotics, anti-inflammatory, antiviral drugs, etc., and for diagnostic purposes (e.g. magnetic resonance imaging). The review focuses only on drugs loaded inside erythrocytes, defines the main lines of research for erythrocytes with bioactive substances, as well as the advantages and limitations of their application. Particular attention is paid to in vivo studies, opening-up the potential for the clinical use of drugs encapsulated into erythrocytes.

Indicator dye based screening of glutaminase free L-asparaginase producer and kinetic evaluation of enzyme production process

Several soil isolates from 1 g of soil sample were isolated and screened for the production of L-asparaginase. Primary screening was performed using rapid plate assay; dye indicator studies were conducted, and phenol red with 0.005% concentration was found to be optimum. The secondary screening was carried out using the Nesslerization method. The bacteria screened for L-asparaginase production with no glutaminase activity was identified as Bacillus subtilis. Crude L-asparaginase enzyme was partially purified 1.57 folds of purity and 110 U/mg of specific activity. The glutaminase-free L-asparaginase activity was also confirmed using LC-MS analysis. The presence of mass peaks at 147.0 in the reaction mixture suggested an absence of glutaminase activity. An optimized medium obtained comprised of Dextrose 1.5 g/L, K₂HPO₄ 1.2 g/L, L-asparagine 15 g/L, and Tryptone 5 g/L. The highest L-asparaginase activity was observed at 6.0 pH and 30 °C. Kinetic parameters associated with biomass and L-asparaginase production were also studied. The computed values were µ_m 0.104 h^-1, X_m 6g/L P₀ 1.7U/mL P_m 8.2 U/mL Y_X/S 4 g-cell/g-glucose µP_m 0.35 h^-1 q_p 5.46 U/g/h Y_P/x 13.6667 U/g-cell. The novel bacterial isolates showed promise as a potential glutaminase-free L-asparaginase producer, which can prove to be of industrial applications.

Multiple Severe Toxicities of L-Asparaginase and Their Innovative Management during Induction Therapy of Acute Lymphoblastic Leukemia in an Adult Patient

L-asparaginase is a key chemotherapeutic agent in acute lymphoblastic leukemia (ALL). It is also known for multiple and severe specific toxicities, without consensual management. We report the case of a 51-year-old man treated with L-asparaginase for recently diagnosed T-cell ALL. During the treatment, he developed a coma due to multifactorial diffuse cerebral edema, by hepatic encephalopathy, cerebral venous thrombosis, and hyperammonemia, all linked to toxicity of L-asparaginase. Specific and innovative treatments were employed to manage these toxicities: supplementation with L-carnitine, thiamine, and pyridoxine for hepatic toxicity, perfusion of sodium benzoate to decrease ammonemia, and extrahepatic albumin-based dialysis sessions, along with anticoagulation. The patient improved within two weeks and is currently alive 13 months later, in first complete remission, without sequelae, on an alleviated chemotherapy regimen.

Differentiation of Baboon (Papio anubis) Induced-Pluripotent Stem Cells into Enucleated Red Blood Cells

As cell culture methods and stem cell biology have progressed, the in vitro production of cultured RBCs (cRBCs) has emerged as a viable option to produce cells for transfusion or to carry therapeutic cargoes. RBCs produced in culture can be quality-tested either by xeno-transfusion of human cells into immuno-deficient animals, or by transfusion of autologous cells in immuno-competent models. Although murine xeno-transfusion methods have improved, they must be complemented by studies in immuno-competent models. Non-human primates (NHPs) are important pre-clinical, large animal models due to their high biological and developmental similarities with humans, including their comparable hematopoietic and immune systems. Among NHPs, baboons are particularly attractive to validate cRBCs because of the wealth of data available on the characteristics of RBCs in this species that have been generated by past blood transfusion studies. We report here that we have developed a method to produce enucleated cRBCs by differentiation of baboon induced pluripotent stem cells (iPSCs). This method will enable the use of baboons to evaluate therapeutic cRBCs and generate essential pre-clinical data in an immuno-competent, large animal model. Production of the enucleated baboon cRBCs was achieved by adapting the PSC-RED protocol that we previously developed for human cells. Baboon-PSC-RED is an efficient chemically-defined method to differentiate iPSCs into cRBCs that are about 40% to 50% enucleated. PSC-RED is relatively low cost because it requires no albumin and only small amounts of recombinant transferrin.

Red Blood Cell Membrane Processing for Biomedical Applications

Red blood cells (RBC) are actually exploited as innovative drug delivery systems with unconventional and convenient properties. Because of a long in vivo survival and a non-random removal from circulation, RBC can be loaded with drugs and/or contrasting agents without affecting these properties and maintaining the original immune competence. However, native or drug-loaded RBC, can be modified decorating the membrane with peptides, antibodies or small chemical entities so favoring the targeting of the processed RBC to specific cells or organs. Convenient modifications have been exploited to induce immune tolerance or immunogenicity, to deliver antibodies capable of targeting other cells, and to deliver a number of constructs that can recognize circulating pathogens or toxins. The methods used to induce membrane processing useful for biomedical applications include the use of crosslinking agents and bifunctional antibodies, biotinylation and membrane insertion. Another approach includes the expression of engineered membrane proteins upon ex vivo transfection of immature erythroid precursors with lentiviral vectors, followed by in vitro expansion and differentiation into mature erythrocytes before administration to a patient in need. Several applications have now reached the clinic and a couple of companies that take advantage from these properties of RBC are already in Phase 3 with selected applications. The peculiar properties of the RBC and the active research in this field by a number of qualified investigators, have opened new exciting perspectives on the use of RBC as carriers of drugs or as cellular therapeutics.

General Approach to Drug Delivery Systems (DDS)

The field of drug discovery drives to find out efficient, selective, stable and biocompatible new drugs. The purpose of drug delivery systems (DDS) is to reduce the side effects that treatments usually cause to mitigate some diseases, especially cancer. Cancer treatments are usually so strong and invasive that they end up weakening the patient, so the cure became as dangerous as the disease. That is the reason that DDS try to maximize the effectiveness of the drugs administered by wanting them to reach specifically to the area affected by the disease (High specificity). In this regard, the fruitfully use of liposome-, erythrocytes-, nanoparticles- or antibodies-based therapies became a choice for the treatment of a huge range of diseases, due to the biocompatibility that these macromolecular systems present. In the last five years, a broad range of DDS have been developed, and some of them, specifically four ADC´s are approved by the FDA and commercializing. In this work, we summarized the most important approach to DDS obtained through chemical conjugation, highlighting ADC´s like the most promising controlled release systems.

Biocompatible coupling of therapeutic fusion proteins to human erythrocytes

Carriage of drugs by red blood cells (RBCs) modulates pharmacokinetics, pharmacodynamics, and immunogenicity. However, optimal targets for attaching therapeutics to human RBCs and adverse effects have not been studied. We engineered nonhuman-primate single-chain antibody fragments (scFvs) directed to human RBCs and fused scFvs with human thrombomodulin (hTM) as a representative biotherapeutic cargo (hTM-scFv). Binding fusions to RBCs on band 3/glycophorin A (GPA; Wright b [Wr^b] epitope) and RhCE (Rh17/Hr0 epitope) similarly endowed RBCs with hTM activity, but differed in their effects on RBC physiology. scFv and hTM-scFv targeted to band 3/GPA increased membrane rigidity and sensitized RBCs to hemolysis induced by mechanical stress, while reducing sensitivity to hypo-osmotic hemolysis. Similar properties were seen for other ligands bound to GPA and band 3 on human and murine RBCs. In contrast, binding of scFv or hTM-scFv to RhCE did not alter deformability or sensitivity to mechanical and osmotic stress at similar copy numbers bound per RBCs. Contrasting responses were also seen for immunoglobulin G antibodies against band 3, GPA, and RhCE. RBC-bound hTM-scFv generated activated protein C (APC) in the presence of thrombin, but RhCE-targeted hTM-scFv demonstrated greater APC generation per bound copy. Both Wr^b- and RhCE-targeted fusion proteins inhibited fibrin deposition induced by tumor necrosis factor-α in an endothelialized microfluidic model using human whole blood. RhCE-bound hTM-scFv more effectively reduced platelet and leukocyte adhesion, whereas anti-Wr^b scFv appeared to promote platelet adhesion. These data provide a translational framework for the development of engineered affinity ligands to safely couple therapeutics to human RBCs.

Harnessing Biology to Deliver Therapeutic and Imaging Entities via Cell-Based Methods

The accumulation of therapeutic and imaging agents at sites of interest is critical to their efficacy. Similarly, off-target effects (especially toxicity) are a major liability for these entities. For this reason, the use of delivery vehicles to improve the distribution characteristics of bio-active agents has become ubiquitous in the field. However, the majority of traditionally employed, cargo-bearing platforms rely on passive accumulation. Even in cases where "targeting" functionalities are used, the agents must first reach the site in order for the ligand-receptor interaction to occur. The next stage of vehicle development is the use of "recruited" entities, which respond to biological signals produced in the tissues to be targeted, resulting in improved specificities. Recently, many advances have been made in the utilization of cells as delivery agents. They are biocompatible, exhibit excellent circulation lifetimes and tissue penetration capabilities, and respond to chemotactic signals. In this Minireview, we will explore various cell types, modifications, and applications where cell-based delivery agents are used.

Efficacy and safety of native versus pegylated Escherichia coli asparaginase for treatment of adults with high-risk, Philadelphia chromosome-negative acute lymphoblastic leukemia

Native or pegylated (PEG) asparaginase (ASP) are commonly used in treatment of acute lymphoblastic leukemia (ALL), but have been scarcely compared in the same trial in adult patients. Native vs. PEG-ASP administered according to availability in each center were prospectively evaluated in adults with high-risk ALL. Ninety-one patients received native ASP and 35 PEG-ASP in induction. No significant differences were observed in complete remission, minimal residual disease levels after induction and after consolidation, disease-free survival, and overall survival. No significant differences in grades 3-4 toxicity were observed in the induction period, although a trend for higher hepatic toxicity was observed in patients receiving PEG-ASP. In this trial the type of ASP did not influence patient response and outcome.

A protease-resistant Escherichia coli asparaginase with outstanding stability and enhanced anti-leukaemic activity in vitro

L-Asparaginases (ASNases) have been used as first line drugs for paediatric Acute Lymphoblastic Leukaemia (ALL) treatment for more than 40 years. Both the Escherichia coli (EcAII) and Erwinia chrysanthemi (ErAII) type II ASNases currently used in the clinics are characterized by high in vivo instability, short half-life and the requirement of several administrations to obtain a pharmacologically active concentration. Moreover, they are sensitive to proteases (cathepsin B and asparagine endopeptidase) that are over-expressed by resistant leukaemia lymphoblasts, thereby impairing drug activity and pharmacokinetics. Herein, we present the biochemical, structural and in vitro antiproliferative characterization of a new EcAII variant, N24S. The mutant shows completely preserved asparaginase and glutaminase activities, long-term storage stability, improved thermal parameters, and outstanding resistance to proteases derived from leukaemia cells. Structural analysis demonstrates a modification in the hydrogen bond network related to residue 24, while Normal Mode-based geometric Simulation and Molecular Dynamics predict a general rigidification of the monomer as compared to wild-type. These improved features render N24S a potential alternative treatment to reduce the number of drug administrations in vivo and to successfully address one of the major current challenges of ALL treatment: spontaneous, protease-dependent and immunological inactivation of ASNase.