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

Is the proximal tubule the focus of tubulointerstitial fibrosis?

Tubulointerstitial fibrosis (TIF), a common end result of almost all progressive chronic kidney diseases (CKD), is also the best predictor of kidney survival. Almost all cells in the kidney are involved in the progression of TIF. Myofibroblasts, the primary producers of extracellular matrix, have previously received a great deal of attention; however, a large body of emerging evidence reveals that proximal tubule (PT) plays a central role in TIF progression. In response to injury, renal tubular epithelial cells (TECs) transform into inflammatory and fibroblastic cells, producing various bioactive molecules that drive interstitial inflammation and fibrosis. Here we reviewed the increasing evidence for the key role of the PT in promoting TIF in tubulointerstitial and glomerular injury and discussed the therapeutic targets and carrier systems involving the PT that holds particular promise for treating patients with fibrotic nephropathy.

Role of Nanotechnology and Their Perspectives in the Treatment of Kidney Diseases

Nanoparticles (NPs) are differing in particle size, charge, shape, and compatibility of targeting ligands, which are linked to improved pharmacologic characteristics, targetability, and bioavailability. Researchers are now tasked with developing a solution for enhanced renal treatment that is free of side effects and delivers the medicine to the active spot. A growing number of nano-based medication delivery devices are being used to treat renal disorders. Kidney disease management and treatment are currently causing a substantial global burden. Renal problems are multistep processes involving the accumulation of a wide range of molecular and genetic alterations that have been related to a variety of kidney diseases. Renal filtration is a key channel for drug elimination in the kidney, as well as a burgeoning topic of nanomedicine. Although the use of nanotechnology in the treatment of renal illnesses is still in its early phases, it offers a lot of potentials. In this review, we summarized the properties of the kidney and characteristics of drug delivery systems, which affect a drug’s ability should focus on the kidney and highlight the possibilities, problems, and opportunities.

Targeted Drug Delivery Systems for Kidney Diseases

Kidney diseases have gradually become a global health burden. Along with the development of nanotechnology, many hybrids or nanomaterials have been utilized to promote treatment efficiency with negligible side effects. These therapeutic agents have been successfully applied in many fields. In particular, some efforts have also been made to ameliorate the treatment of kidney diseases through targeted delivery nanomaterials. Though most of the delivery systems have not yet been transmitted into clinical use or even still at an early stage, they have shown great potential in carrying immunosuppressants like tacrolimus and triptolide, antioxidants, or siRNAs. Excitingly, some of them have achieved significant treatment effectiveness and reduced systemic side effect in kidney disease animal models. Here, we have reviewed the recent advances and presented nanotherapeutic devices designed for kidney targeted delivery.

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.

Antibody Fragment F(ab')2 Targeting Caveolae-Associated Protein PV1 for Selective Kidney Targeting and Retention

Targeted strategies to deliver and retain drugs to kidneys are needed to improve drug accumulation and efficacy in a myriad of kidney diseases. These drug delivery systems show potential for improving the therapeutic windows of drugs acting in the kidney. Biodistribution of antibody-based therapeutics in vivo is governed by several factors including binding affinity, size, and valency. Investigations of how the biophysical and biochemical properties of biologics enable them to overcome biological barriers and reach kidneys are therefore of interest. Although renal accumulation of antibody fragments in cancer diagnostics and treatment has been observed, reports on effective delivery of antibody fragments to the kidneys remain scarce. Previously, we demonstrated that targeting plasmalemma vesicle-associated protein (PV1), a caveolae-associated protein, can promote accumulation of antibodies in both the lungs and the kidneys. Here, by fine-tuning the binding affinity of an antibody toward PV1, we observe that the anti-PV1 antibody with reduced binding affinity lost the capability for kidney targeting while retaining the lung targeting activity, suggesting that binding affinity is a critical factor for kidney targeting of the anti-PV1 antibody. We next use the antibody fragment F(ab')₂ targeting PV1 to assess the dual effects of rapid kidney filtration and PV1 targeting on kidney-selective targeting. Ex vivo fluorescence imaging results demonstrated that after rapidly accumulating in kidneys at 4 h, PV1-targeted F(ab')₂ was continually retained in the kidney at 24 h, whereas the isotype control F(ab')₂ underwent urinary elimination with significantly reduced signaling in the kidney. Confocal imaging studies confirmed the localization of PV1-targeted F(ab')₂ in the kidney. In addition, the monovalent antibody fragment (Fab-C4) lost the capability for kidney homing, indicating that the binding avidity of anti-PV1 F(ab')₂ is important for kidney targeting. Our findings suggest that PV1-targeted F(ab')₂ might be useful as a drug carrier for renal targeting and highlight the importance of affinity optimization for tissue targeting antibodies.

Efficacy of a Selective Binder of αVβ3 Integrin Linked to the Tyrosine Kinase Inhibitor Sunitinib in Ovarian Carcinoma Preclinical Models

Ovarian carcinoma, the most lethal gynecological cancer, is characterized by late diagnosis, with drug resistance limiting the efficacy of platinum-based therapy. Since some integrins are upregulated in cancer, including ovarian carcinoma, they represent a potential target for drug delivery. Receptor tyrosine kinases are also deregulated in cancer and their expression has been associated with drug resistance. Here, the antitumor effects of three conjugates possessing a selective binder of the extracellular portion of integrin α_Vβ₃ covalently linked to the tyrosine kinase inhibitor sunitinib were investigated in cisplatin-sensitive and -resistant ovarian carcinoma cells expressing both tyrosine kinase VEGFR2 and α_Vβ₃ at different levels. We found that one of the three compounds was active in inhibiting the growth of both drug-sensitive and -resistant cells in the micromolar range with a slightly increased potency in resistant cells as compared to sunitinib. The same compound markedly impaired cell migratory and invasive abilities and reduced paxillin phosphorylation. Antitumor activity studies in IGROV-1/Pt1 cells xenografted in nude mice revealed a striking activity of this conjugate versus sunitinib. Taken together, our results support the interest of integrin-targeted sunitinib conjugates for the treatment of drug-resistant tumors.

Renal fibrosis: Primacy of the proximal tubule

Tubulointerstitial fibrosis (TIF) is the hallmark of chronic kidney disease and best predictor of renal survival. Many different cell types contribute to TIF progression including tubular epithelial cells, myofibroblasts, endothelia, and inflammatory cells. Previously, most of the attention has centered on myofibroblasts given their central importance in extracellular matrix production. However, emerging data focuses on how the response of the proximal tubule, a specialized epithelial segment vulnerable to injury, plays a central role in TIF progression. Several proximal tubular responses such as de-differentiation, cell cycle changes, autophagy, and metabolic changes may be adaptive initially, but can lead to maladaptive responses that promote TIF both through autocrine and paracrine effects. This review discusses the current paradigm of TIF progression and the increasingly important role of the proximal tubule in promoting TIF both in tubulointerstitial and glomerular injuries. A better understanding and appreciation of the role of the proximal tubule in TIF has important implications for therapeutic strategies to halt chronic kidney disease progression.

Nanomedicines for renal disease: current status and future applications

Treatment and management of kidney disease currently presents an enormous global burden, and the application of nanotechnology principles to renal disease therapy, although still at an early stage, has profound transformative potential. The increasing translation of nanomedicines to the clinic, alongside research efforts in tissue regeneration and organ-on-a-chip investigations, are likely to provide novel solutions to treat kidney diseases. Our understanding of renal anatomy and of how the biological and physico-chemical properties of nanomedicines (the combination of a nanocarrier and a drug) influence their interactions with renal tissues has improved dramatically. Tailoring of nanomedicines in terms of kidney retention and binding to key membranes and cell populations associated with renal diseases is now possible and greatly enhances their localization, tolerability, and efficacy. This Review outlines nanomedicine characteristics central to improved targeting of renal cells and highlights the prospects, challenges, and opportunities of nanotechnology-mediated therapies for renal diseases.

Novel Therapies for Diabetic Kidney Disease: Storied Past and Forward Paths

IN BRIEF Current therapeutic approaches are only moderately efficacious at preventing the progression of diabetic kidney disease (DKD). As the number of people with DKD continues to rise worldwide, there is an urgent need for novel therapies. A better understanding of the root causes and molecular mechanisms of DKD pathogenesis has enabled the identification of numerous new therapeutic targets, including advanced glycation end products, reactive oxygen species, protein kinase C, and serum amyloid A. Although experimental studies have illustrated the potential of such approaches, challenges in clinical translation remain a barrier in therapeutic development. Advances in preclinical safety and efficacy evaluations and improved delivery systems may aid in clinical translation of novel DKD therapies.

Kidney-targeted drug delivery systems

Kidney-targeted drug delivery systems represent a promising technology to improve drug efficacy and safety in the treatment of renal diseases. In this review, we summarize the strategies that have been employed to develop kidney-targeted drug delivery systems. We also describe how macromolecular carriers and prodrugs play crucial roles in targeting drugs to particular target cells in the kidney. New technologies render it possible to create renal targeting conjugates and other delivery systems including nanoparticles and liposomes present promising strategies to achieve the goal of targeting drugs to the kidney.