Imatinib-ULS-lysozyme: a proximal tubular cell-targeted conjugate of imatinib for the treatment of renal diseases

Lysozyme-targeted liposomes for enhanced tubular targeting in the treatment of acute kidney injury

Acute kidney injury (AKI) is defined by the release of pro-inflammatory factors, leading to structural damage in renal tubules and subsequent tubular cell injury and death. Delivering drugs specifically to renal tubules to mitigate tubular cell damage holds potential for AKI treatment. In this work, we developed functional liposomes (LZM-PLNPs-TP) designed to bypass the glomerular filtration barrier and target tubules by leveraging the unique structural and pathological characteristics of glomeruli and tubules. LZM-PLNPs-TP, incorporating lysozyme (LZM) and cationic liposome, and carrying the anti-inflammatory and antioxidant drug Triptolide (TP), demonstrated favorable stability, efficient drug release, and good cytocompatibility in wide TP concentrations (0-100 ng/mL). These liposomes exhibited the enhanced renal accumulation, tubular retention, and cellular targeting through endocytosis by peritubular capillary endothelial cells. The administration of LZM-PLNPs-TP at a minimal TP dosage (0.01 mg/kg) demonstrated significant protection through the mitigation of oxidative stress and inflammation in ischemia/reperfusion injury (IRI) mice, while the naked TP (0.01 mg/kg) exhibited lower efficacy. Following treatment with LZM-PLNPs-TP, levels of serum creatine, blood urea nitrogen, superoxide dismutase, malondialdehyde, as well as the inflammatory cytokines IL-1β and IL-6 in renal IRI mice were found to be significantly reduced by factors of 2.9, 1.7, 0.7, 1.3, 2.1, and 1.9, respectively, compared to mice treated with TP alone. In summary, this study presents an LZM-targeted drug delivery system that synergistically enhances tubular reabsorption and cellular uptake, offering a promising strategy for AKI treatment. STATEMENT OF SIGNIFICANCE: We have designed specialized liposomes (LZM-PLNPs-TP) with targeting capabilities towards renal tubules to enhance cellular internalization, offering a promising therapeutic strategy for AKI treatment. Our research confirms that the increased accumulation of LZM-PLNPs-TP in renal tubules is facilitated by peritubular capillary endothelial cells rather than glomerular filtration. LZM-PLNPs-TP demonstrated effective mitigation of oxidative stress, inflammation suppression, and significant improvement in kidney injury, ultimately leading to the restoration of renal function in murine models of AKI induced by ischemia/reperfusion. This study introduces LZM-targeted liposomes that enhance tubular reabsorption and cellular uptake synergistically, providing a promising therapeutic approach for AKI management.

Targeted therapeutic strategies for the kidney

INTRODUCTION

Kidney diseases impose a significant burden with high incidence and mortality rates. Current treatment options for kidney diseases are limited, necessitating urgent development of novel and effective therapeutic strategies to delay or reverse disease progression. Targeted therapies for the kidney hold promise in significantly enhancing treatment outcomes, offering hope to patients afflicted with renal disorders.

AREAS COVERED

This review summarized advances in kidney-targeted therapies including genes, peptides and proteins, cell-based, nanoparticles, and localized delivery routes. We also explored the potential clinical applications, prospects, and challenges of targeted therapies for renal disorders.

EXPERT OPINION

Advances in targeted therapies for renal conditions have enhanced therapeutic outcomes. Clinical application of kidney-targeted therapies is currently limited by renal structure and the scarcity of robust biomarkers. Bridging the gap from basic and pre-clinical research targeting the kidney to achieving clinical translation remains a formidable challenge.

Research Progress of Drug Delivery Systems Targeting the Kidneys

Chronic kidney disease (CKD) affects more than 10% of the global population, and its incidence is increasing, partially due to an increase in the prevalence of disease risk factors. Acute kidney injury (AKI) is an independent risk factor for CKD and end-stage renal disease (ESRD). The pathogenic mechanisms of CKD provide several potential targets for its treatment. However, due to off-target effects, conventional drugs for CKD typically require high doses to achieve adequate therapeutic effects, leading to long-term organ toxicity. Therefore, ideal treatments that completely cure the different types of kidney disease are rarely available. Several approaches for the drug targeting of the kidneys have been explored in drug delivery system research. Nanotechnology-based drug delivery systems have multiple merits, including good biocompatibility, suitable degradability, the ability to target lesion sites, and fewer non-specific systemic effects. In this review, the development, potential, and limitations of low-molecular-weight protein-lysozymes, polymer nanomaterials, and lipid-based nanocarriers as drug delivery platforms for treating AKI and CKD are summarized.

Protein and peptide-based renal targeted drug delivery systems

Renal diseases have become an increasingly concerned public health problem in the world. Kidney-targeted drug delivery has profound transformative potential on increasing renal efficacy and reducing extra-renal toxicity. Protein and peptide-based kidney targeted drug delivery systems have garnered more and more attention due to its controllable synthesis, high biocompatibility and low immunogenicity. At the same time, the targeting methods based on protein/peptide are also abundant, including passive renal targeting based on macromolecular protein and active targeting mediated by renal targeting peptide. Here, we review the application and the drug loading strategy of different proteins or peptides in targeted drug delivery, including the ferritin family, albumin, low molecular weight protein (LMWP), different peptide sequence and antibodies. In addition, we summarized the factors influencing passive and active targeting in drug delivery system, the main receptors related to active targeting in different kidney diseases, and a variety of nano forms of proteins based on the controllable synthesis of proteins.

Biopolymer-Based Nanosystems: Potential Novel Carriers for Kidney Drug Delivery

Kidney disease has become a serious public health problem throughout the world, and its treatment and management constitute a huge global economic burden. Currently, the main clinical treatments are not sufficient to cure kidney diseases. During its development, nanotechnology has shown unprecedented potential for application to kidney diseases. However, nanotechnology has disadvantages such as high cost and poor bioavailability. In contrast, biopolymers are not only widely available but also highly bioavailable. Therefore, biopolymer-based nanosystems offer new promising solutions for the treatment of kidney diseases. This paper reviews the biopolymer-based nanosystems that have been used for renal diseases and describes strategies for the specific, targeted delivery of drugs to the kidney as well as the physicochemical properties of the nanoparticles that affect the targeting success.

In Humanized Sickle Cell Mice, Imatinib Protects Against Sickle Cell-Related Injury

Drug repurposing is a valuable strategy for rare diseases. Sickle cell disease (SCD) is a rare hereditary hemolytic anemia accompanied by acute and chronic painful episodes, most often in the context of vaso-occlusive crisis (VOC). Although progress in the knowledge of pathophysiology of SCD have allowed the development of new therapeutic options, a large fraction of patients still exhibits unmet therapeutic needs, with persistence of VOCs and chronic disease progression. Here, we show that imatinib, an oral tyrosine kinase inhibitor developed for the treatment of chronic myelogenous leukemia, acts as multimodal therapy targeting signal transduction pathways involved in the pathogenesis of both anemia and inflammatory vasculopathy of humanized murine model for SCD. In addition, imatinib inhibits the platelet-derived growth factor-B-dependent pathway, interfering with the profibrotic response to hypoxia/reperfusion injury, used to mimic acute VOCs. Our data indicate that imatinib might be considered as possible new therapeutic tool for chronic treatment of SCD.

Delivery of sorafenib by myofibroblast-targeted nanoparticles for the treatment of renal fibrosis

Fibrosis is an excessive accumulation of the extracellular matrix within solid organs in response to injury and a common pathway that leads functional failure. No clinically approved agent is available to reverse or even prevent this process. Herein, we report a nanotechnology-based approach that utilizes a drug carrier to deliver a therapeutic cargo specifically to fibrotic kidneys, thereby improving the antifibrotic effect of the drug and reducing systemic toxicity. We first adopted in vitro-in vivo combinatorial phage display technology to identify peptide ligands that target myofibroblasts in mouse unilateral ureteral obstruction (UUO)-induced fibrotic kidneys. We then engineered lipid-coated poly(lactic-co-glycolic acid) nanoparticles (NPs) with fibrotic kidney-homing peptides on the surface and sorafenib, a potent antineoplastic multikinase inhibitor, encapsulated in the core. Sorafenib loaded in the myofibroblast-targeted NPs significantly reduced the infiltration of α-smooth muscle actin-expressing myofibroblasts and deposition of collagen I in UUO-treated kidneys and enhanced renal plasma flow measured by Technetium-99m mercaptoacetyltriglycine scintigraphy. This study demonstrates the therapeutic potential of the newly identified peptide fragments as anchors to target myofibroblasts and represents a strategic advance for selective delivery of sorafenib to treat renal fibrosis. SIGNIFICANCE STATEMENT: Renal fibrosis is a pathological feature accounting for the majority of issues in chronic kidney disease (CKD), which may progress to end-stage renal disease (ESRD). This manuscript describes a myofibroblast-targeting drug delivery system modified with phage-displayed fibrotic kidney-homing peptides. By loading the myofibroblast-targeting nanoparticles (NPs) with sorafenib, a multikinase inhibitor, the NPs could suppress collagen synthesis in cultured human myofibroblasts. When given intravenously to mice with UUO-induced renal fibrosis, sorafenib loaded in myofibroblast-targeting NPs significantly ameliorated renal fibrosis. This approach provides an efficient therapeutic option to renal fibrosis. The myofibroblast-targeting peptide ligands and nanoscale drug carriers may be translated into clinical application in the future.

Folate decorated polymeric micelles for targeted delivery of the kinase inhibitor dactolisib to cancer cells

One of the main challenges in clinical translation of polymeric micelles is retention of the drug in the nanocarrier system upon its systemic administration. Core crosslinking and coupling of the drug to the micellar backbone are common strategies to overcome these issues. In the present study, polymeric micelles were prepared for tumor cell targeting of the kinase inhibitor dactolisib which inhibits both the mammalian Target of Rapamycin (mTOR) kinase and phosphatidylinositol-3-kinase (PI3K). We employed platinum(II)-based linker chemistry to couple dactolisib to the core of poly(ethylene glycol)-b-poly(acrylic acid) (PEG-b-PAA) polymeric micelles. The formed dactolisib-PEG-PAA unimers are amphiphilic and self-assemble in an aqueous milieu into core-shell polymeric micelles. Folate was conjugated onto the surface of the micelles to yield folate-decorated polymeric micelles which can target folate receptor over-expressing tumor cells. Fluorescently labeled polymeric micelles were prepared using a lissamine-platinum complex linked in a similar manner as dactolisib. Dactolisib polymeric micelles showed good colloidal stability in water and released the coupled drug in buffers containing chloride or glutathione. Folate decorated micelles were avidly internalized by folate-receptor-positive KB cells and displayed targeted cellular cytotoxicity at 50-75 nM IC₅₀. In conclusion, we have prepared a novel type of folate-receptor targeted polymeric micelles in which platinum(II) linker chemistry modulates drug retention and sustained release of the coupled inhibitor dactolisib.

Design, Synthesis, and Renal Targeting of Methylprednisolone-Lysozyme

Methylprednisolone (MP) is often used in the treatment of various kidney diseases, but overcoming the systemic side effects caused by its nonspecific distribution in the body is a challenge. This article reports the design, synthesis, and renal targeting of methylprednisolone–lysozyme (MPS–LZM). This conjugate was obtained by covalently linking MP with the renal targeting carrier LZM through a linker containing an ester bond, which could utilize the renal targeting of LZM to deliver MP to renal proximal tubular epithelial cells and effectively release MP. The reaction conditions for the preparation of the conjugate were mild, and the quality was controllable. The number of drug payloads per LZM was 1.1. Cell-level studies have demonstrated the safety and endocytosis of the conjugate. Further pharmacokinetic experiments confirmed that, compared with that of free MP, the conjugate increased the renal exposure (AUC_0–t) of active MP from 17.59 to 242.18 h*ng/mL, and the targeting efficiency improved by approximately 14 times. Tissue and organ imaging further revealed that the conjugate could reach the kidneys quickly, and fluorescence could be detected in the kidneys for up to 12 h. This study preliminarily validates the feasibility of a renal targeting design strategy for MPS–LZM, which is expected to provide a new option for improving kidney-specific distribution of glucocorticoids.

Recent advances in nanotechnology-based drug delivery systems for the kidney

The application of nanotechnology in medicine has the potential to make a great impact on human health, ranging from prevention to diagnosis and treatment of disease. The kidneys are the main organ of the human urinary system, responsible for filtering the blood, and concentrating metabolic waste into urine by means of the renal glomerulus. The glomerular filtration apparatus presents a barrier against therapeutic agents based on charge and/or molecular size. Therefore, drug delivery to the kidneys faces significant difficulties resulting in treatment failure in several renal disorders. Accordingly, different strategies have recently being explored for enhancing the delivery of therapeutic agents across the filtration barrier of the glomerulus. Nanosystems with different physicochemical properties, including size, shape, surface, charge, and possessing biological features such as high cellular internalization, low cytotoxicity, controllable pharmacokinetics and biodistribution, have shown promising results for renal therapy. Different types of nanoparticles (NPs) have been used to deliver drugs to the kidney. In this review, we discuss nanotechnology-based drug delivery approaches for acute kidney injury, chronic kidney disease, renal fibrosis, renovascular hypertension and kidney cancer.

Cellular Senescence and the Kidney: Potential Therapeutic Targets and Tools

Chronic kidney disease (CKD) is an increasing health burden (affecting approximately 13.4% of the population). Currently, no curative treatment options are available and treatment is focused on limiting the disease progression. The accumulation of senescent cells has been implicated in the development of kidney fibrosis by limiting tissue rejuvenation and through the secretion of pro-fibrotic and pro-inflammatory mediators termed as the senescence-associated secretory phenotype. The clearance of senescent cells in aging models results in improved kidney function, which shows promise for the options of targeting senescent cells in CKD. There are several approaches for the development of “senotherapies”, the most rigorous of which is the elimination of senescent cells by the so-called senolytic drugs either newly developed or repurposed for off-target effects in terms of selectively inducing apoptosis in senescent cells. Several chemotherapeutics and checkpoint inhibitors currently used in daily oncological practice show senolytic properties. However, the applicability of such senolytic compounds for the treatment of renal diseases has hardly been investigated. A serious concern is that systemic side effects will limit the use of senolytics for kidney fibrosis. Specifically targeting senescent cells and/or targeted drug delivery to the kidney might circumvent these side effects. In this review, we discuss the connection between CKD and senescence, the pharmacological options for targeting senescent cells, and the means to specifically target the kidney.

Folate-dactolisib conjugates for targeting tubular cells in polycystic kidneys

The aim of the present study was to develop folic acid (FA) conjugates which can deliver the kinase inhibitor dactolisib to the kidneys via folate receptor-mediated uptake in tubular epithelial cells. Dactolisib is a dual inhibitor of phosphatidylinositol 3-kinase (PI3K) and mammalian target of rapamycin (mTOR) and is considered an attractive agent for treatment of polycystic kidney disease. The ethylenediamine platinum(II) linker, herein called Lx, was employed to couple dactolisib via coordination chemistry to thiol-containing FA-spacer adducts to yield FA-Lx-dactolisib conjugates. The dye lissamine was coupled via similar linker chemistry to folate to yield fluorescent FA-Lx-lissamine conjugates. Three different spacers (PEG₅-Cys, PEG₂₇-Cys or an Asp-Arg-Asp-Asp-Cys peptide spacer) were used to compare the influence of hydrophilicity and charged groups in the spacer on interaction with target cells and in vivo organ distribution of the final conjugates. The purity and identity of the final products were confirmed by UPLC and LC-MS analysis, respectively. FA-Lx-dactolisib conjugates were stable in serum and culture medium, while dactolisib was released from the conjugates in the presence of glutathione. All three type of conjugates were internalized efficiently by HK-2 cells and uptake could be blocked by an excess of folic acid in the medium, demonstrating FR mediated uptake. FA-Lx-dactolisib conjugates showed nanomolar inhibition of the PI3K pathway (Akt phosphorylation) and mTOR pathway (S6 phosphorylation) in cultured kidney epithelial cells (HK-2 cells). After intraperitoneal administration, all three types conjugates accumulated extensively in kidneys of iKsp-Pkd1^del mice with polycystic kidney disease. In conclusion, folate conjugates were successfully prepared by platinum(II) coordination chemistry and accumulated in a target-specific manner in kidney cells and polycystic kidneys. The folate conjugate of dactolisib thus may have potential for targeted therapy of polycystic kidney disease.

Targeting renal fibrosis: Mechanisms and drug delivery systems

Renal fibrosis is the common outcome of many chronic kidney diseases (CKD) independent of the underlying etiology. Despite a host of promising experimental data, currently available strategies only ameliorate or delay the progression of CKD but do not reverse fibrosis. One of the major impediments of translating novel antifibrotic strategies from bench to bedside is due to the intricacies of the drug delivery process. In this review, we briefly describe mechanisms of renal fibrosis and methods of drug transfer into the kidney. Various tools used in gene therapy to administer nucleic acids in vivo are discussed. Furthermore, we review the modes of action of protein- or peptide-based drugs with target-specific antibodies and cytokines incorporated in hydrogels. Additionally, we assess an intriguing new method to deliver drugs specifically to tubular epithelial cells via conjugation with ligands binding to the megalin receptor. Finally, plant-derived compounds with antifibrotic properties are also summarized.

Arg tyrosine kinase modulates TGF-β1 production in human renal tubular cells under high-glucose conditions

Renal tubular cells are involved in the tubular interstitial fibrosis observed in diabetic nephropathy. It is debated whether epithelial-mesenchymal transition (EMT) affects tubular cells, which under high-glucose conditions overproduce transforming growth factor-β (TGF-β), a fibrogenic cytokine involved in interstitial fibrosis development. Our study investigated the involvement of non-receptor tyrosine kinase Arg (also called Abl2) in TGF-β production. Human primary tubular cell cultures exposed to high-glucose conditions were used. These cells showed an elongated morphology, stress fibers and vimentin increment but maintained most of the epithelial marker expression and distribution. In these cells exposed to high glucose, which overexpressed and secreted active TGF-β1, Arg protein and activity was downregulated. A further TGF-β1 increase was induced by Arg silencing with siRNA, as with the Arg tyrosine kinase inhibitor Imatinib. In the cells exposed to high glucose, reactive oxygen species (ROS)-dependent Arg kinase downregulation induced both RhoA activation, through p190RhoGAPA (also known as ARHGAP35) modulation, and proteasome activity inhibition. These data evidence a new specific involvement of Arg kinase into the regulation of TGF-β1 expression in tubular cells under high-glucose conditions and provide cues for new translational approaches in diabetic nephropathy.

A platinum-based hybrid drug design approach to circumvent acquired resistance to molecular targeted tyrosine kinase inhibitors

Three molecular targeted tyrosine kinase inhibitors (TKI) were conjugated to classical platinum-based drugs with an aim to circumvent TKI resistance, predominately mediated by the emergence of secondary mutations on oncogenic kinases. The hybrids were found to maintain specificity towards the same oncogenic kinases as the original TKI. Importantly, they are remarkably less affected by TKI resistance, presumably due to their unique structure and the observed dual mechanism of anticancer activity (kinase inhibition and DNA damage). The study is also the first to report the application of a hybrid drug approach to switch TKIs from being efflux transporter substrates into non-substrates. TKIs cannot penetrate into the brain for treating metastases because of efflux transporters at the blood brain barrier. The hybrids were found to escape drug efflux and they accumulate more than the original TKI in the brain in BALB/c mice. Further development of the hybrid compounds is warranted.

Diverse origins of the myofibroblast—implications for kidney fibrosis

Fibrosis is the common end point of chronic kidney disease. The persistent production of inflammatory cytokines and growth factors leads to an ongoing process of extracellular matrix production that eventually disrupts the normal functioning of the organ. During fibrosis, the myofibroblast is commonly regarded as the predominant effector cell. Accumulating evidence has demonstrated a diverse origin of myofibroblasts in kidney fibrosis. Proposed major contributors of myofibroblasts include bone marrow-derived fibroblasts, tubular epithelial cells, endothelial cells, pericytes and interstitial fibroblasts; the published data, however, have not yet clearly defined the relative contribution of these different cellular sources. Myofibroblasts have been reported to originate from various sources, irrespective of the nature of the initial damage responsible for the induction of kidney fibrosis. Here, we review the possible relevance of the diversity of myofibroblast progenitors in kidney fibrosis and the implications for the development of novel therapeutic approaches. Specifically, we discuss the current status of preclinical and clinical antifibrotic therapy and describe targeting strategies that might help support resident and circulating cells to maintain or regain their original functional differentiation state. Such strategies might help these cells resist their transition to a myofibroblast phenotype to prevent, or even reverse, the fibrotic state.

Epac-Rap signaling reduces oxidative stress in the tubular epithelium

Activation of Rap1 by exchange protein activated by cAMP (Epac) promotes cell adhesion and actin cytoskeletal polarization. Pharmacologic activation of Epac-Rap signaling by the Epac-selective cAMP analog 8-pCPT-2'-O-Me-cAMP during ischemia-reperfusion (IR) injury reduces renal failure and application of 8-pCPT-2'-O-Me-cAMP promotes renal cell survival during exposure to the nephrotoxicant cisplatin. Here, we found that activation of Epac by 8-pCPT-2'-O-Me-cAMP reduced production of reactive oxygen species during reoxygenation after hypoxia by decreasing mitochondrial superoxide production. Epac activation prevented disruption of tubular morphology during diethyl maleate-induced oxidative stress in an organotypic three-dimensional culture assay. In vivo renal targeting of 8-pCPT-2'-O-Me-cAMP to proximal tubules using a kidney-selective drug carrier approach resulted in prolonged activation of Rap1 compared with nonconjugated 8-pCPT-2'-O-Me-cAMP. Activation of Epac reduced antioxidant signaling during IR injury and prevented tubular epithelial injury, apoptosis, and renal failure. Our data suggest that Epac1 decreases reactive oxygen species production by preventing mitochondrial superoxide formation during IR injury, thus limiting the degree of oxidative stress. These findings indicate a new role for activation of Epac as a therapeutic application in renal injury associated with oxidative stress.

Targeting of a platinum-bound sunitinib analog to renal proximal tubular cells

Background

Activated proximal tubular cells play an important role in renal fibrosis. We investigated whether sunitinib and a kidney-targeted conjugate of sunitinib were capable of attenuating fibrogenic events in tubulointerstitial fibrosis.

Methods

A kidney-targeted conjugate was prepared by linkage of a sunitinib analog (named 17864) via a platinum-based linker to the kidney-specific carrier lysozyme. Pharmacological activity of 17864-lysozyme was evaluated in human kidney proximal tubular cells (HK-2); the capability of the kidney-directed conjugate to accumulate in the kidneys was studied in mice. Potential antifibrotic effects of a single-dose treatment were evaluated in the unilateral ureteral obstruction (UUO) model in mice.

Results

The 17864-lysozyme conjugate and its metabolites strongly inhibited tyrosine kinase activity. Upon intravenous injection, 17864-lysozyme rapidly accumulated in the kidneys and provided sustained renal drug levels for up to 3 days after a single dose. Renal drug level area under the curve was increased 28-fold versus an equimolar dose of sunitinib malate. Daily treatment of UUO mice with a high dose of sunitinib malate (50 mg/kg) resulted in antifibrotic responses, but also induced drug-related toxicity. A single dose of 17864-lysozyme (equivalent to 1.8 mg/kg sunitinib) was safe but showed no antifibrotic effects.

Conclusion

Multikinase inhibitors like sunitinib can be of benefit in the treatment of fibrotic diseases, provided that their safety can be improved by strategies as presented in this paper, and sustained renal levels can be achieved.