Investigation of the influence of nephropathy on monoclonal antibody disposition: a pharmacokinetic study in a mouse model of diabetic nephropathy

Rodent models to study type 1 and type 2 diabetes induced human diabetic nephropathy

INTRODUCTION

Diabetic nephropathy (DN), an outcome of prolonged diabetes, has affected millions of people worldwide and every year the incidence and prevalence increase substantially. The symptoms may start with mild manifestations of the disease such as increased albuminuria, serum creatinine levels, thickening of glomerular basement membrane, expansion of mesangial matrix to severe pathological symptoms such as glomerular lesions and tubulointerstitial fibrosis which may further proceed to cardiovascular dysfunction or end-stage renal disease.

PERSPECTIVE

Numerous therapeutic interventions are being explored for the management of DN, however, these interventions do not completely halt the progression of this disease and hence animal models are being explored to identify critical genetic and molecular parameters which could help in tackling the disease. Rodent models which mostly include mice and rats are commonly used experimental animals which provide a wide range of advantages in understanding the onset and progression of disease in humans and also their response to a wide range of interventions helps in the development of effective therapeutics. Rodent models of type 1 and type 2 diabetes induced DN have been developed utilizing different platforms and interventions during the last few decades some of which mimic various stages of diabetes ranging from early to later stages. However, a rodent model which replicates all the features of human DN is still lacking. This review tries to evaluate the rodent models that are currently available and understand their features and limitations which may help in further development of more robust models of human DN.

CONCLUSION

Using these rodent models can help to understand different aspects of human DN although further research is required to develop more robust models utilizing diverse genetic platforms which may, in turn, assist in developing effective interventions to target the disease at different levels.

Immunoglobulin G Is a Novel Substrate for the Endocytic Protein Megalin

Therapeutic immunoglobulin G (IgG) antibodies comprise the largest class of protein therapeutics. Several factors that influence their overall disposition have been well-characterized, including target-mediated mechanics and convective flow. What remains poorly defined is the potential for non-targeted entry into various tissues or cell types by means of uptake via cell surface receptors at those sites. Megalin and cubilin are large endocytic receptors whose cooperative function plays important physiological roles at the tissues in which they are expressed. One such example is the kidney, where loss of either results in significant declines in proximal tubule protein reabsorption. Due to their diverse ligand profile and broad tissue expression, megalin and cubilin represent potential candidates for receptor-mediated uptake of IgG into various epithelia. Therefore, the objective of the current work was to determine if IgG was a novel ligand of megalin and/or cubilin. Direct binding was measured for human IgG with both megalin and the cubilin/amnionless complex. Additional work focusing on the megalin-IgG interaction was then conducted to build upon these findings. Cell uptake studies using megalin ligands for competitive inhibition or proximal tubule cells stably transduced with megalin-targeted shRNA constructs supported a role for megalin in the endocytosis of human IgG. Furthermore, a pharmacokinetic study using transgenic mice with a kidney-specific mosaic knockout of megalin demonstrated increased urinary excretion of human IgG in megalin knockout mice when compared to wild-type controls. These findings indicate that megalin is capable of binding and internalizing IgG via a high affinity interaction.

Understanding Inter-Individual Variability in Monoclonal Antibody Disposition

Monoclonal antibodies (mAbs) are currently the largest and most dominant class of therapeutic proteins. Inter-individual variability has been observed for several mAbs; however, an understanding of the underlying mechanisms and factors contributing to inter-subject differences in mAb disposition is still lacking. In this review, we analyze the mechanisms of antibody disposition and the putative mechanistic determinants of inter-individual variability. Results from in vitro, preclinical, and clinical studies were reviewed evaluate the role of the neonatal Fc receptor and Fc gamma receptors (expression and polymorphism), target properties (expression, shedding, turnover, internalization, heterogeneity, polymorphism), and the influence of anti-drug antibodies. Particular attention is given to the influence of co-administered drugs and disease, and to the physiological relevance of covariates identified by population pharmacokinetic modeling, as determinants of variability in mAb pharmacokinetics.

Investigation of the Influence of Protein-Losing Enteropathy on Monoclonal Antibody Pharmacokinetics in Mice

Protein losing enteropathy (PLE), which is characterized by substantial loss of plasma proteins into the gastrointestinal (GI) tract, is a complication of a variety of GI diseases, including inflammatory bowel disease. Clinical studies have found that the clearance of monoclonal antibodies (mAb) is often increased in subjects with diseases known to cause PLE; however, direct relationships between PLE and mAb pharmacokinetics have not been demonstrated. This study employed a murine model of colitis to examine the influence of PLE on mAb pharmacokinetics. Mice were given dextran sodium sulfate (DSS, 2% w/v) supplemented tap water as drinking source for 6 days to induce colitis and PLE. Mice were then intravenously injected with 8C2, a murine IgG1 mAb. 8C2 plasma concentrations were measured up to 14 days post injection. Fecal alpha-1-antitrypsin (A1AT) clearance was measured as biomarker for PLE. DSS-treated mice developed PLE of clinically relevant severity. They also showed a transient increase in 8C2 plasma clearance and a decrease in 8C2 plasma exposure. The area under the 8C2 plasma concentration-time curve for the length of the study (AUC_0-14d) reduced from 1368 ± 255 to 594 ± 224 day μg/ml following DSS treatment (p = 0.001). A quantitative relationship between A1AT clearance and 8C2 clearance was obtained via population pharmacokinetic modeling. DSS treatment substantially increased 8C2 clearance and reduced 8C2 exposure. Increased mAb plasma clearance was highly correlated with A1AT fecal clearance, suggesting the possible utility of A1AT fecal clearance as a mechanistic biomarker to predict the pharmacokinetics of therapeutic antibodies.

Interplay between HSP90 and Nrf2 pathways in diabetes-associated atherosclerosis

INTRODUCTION

Oxidative stress and inflammation are determinant processes in the development of diabetic vascular complications. Heat shock protein 90 (HSP90) overexpression in atherosclerotic plaques plays a role in sustaining inflammatory mechanisms, and its specific inhibition prevents atherosclerosis. The present work investigates, in a mouse model of diabetes-driven atherosclerosis, whether atheroprotection by pharmacological HSP90 inhibition is accomplished by bolstering antioxidant defense mechanisms headed by nuclear factor erythroid-derived 2-like 2 (Nrf2).

METHODS

Streptozotocin-induced diabetic apolipoprotein E-deficient mice were randomized to receive vehicle or HSP90 inhibitor (17-dimethylaminoethylamino-17-demethoxygeldanamycin, 4mg/kg) for 10 weeks. Aortic root sections were analyzed for plaque size and composition, transcription factor activity, and expression of inflammatory and antioxidant markers. In vitro studies were performed in murine macrophages cultured under hyperglycemic conditions.

RESULTS

Treatment with HSP90 inhibitor promoted the activation of Nrf2 in the aortic tissue of diabetic mice (predominantly localized in macrophages and smooth muscle cells) and also in cultured cells. Nrf2 induction was associated with a concomitant inhibition of nuclear factor-κB (NF-κB) in atherosclerotic plaques, thus resulting in a significant reduction in lesion size and inflammatory component (leukocytes and cytokines). Furthermore, atheroprotection by HSP90 inhibition was linked to the induction of cytoprotective HSP70, antioxidant enzymes (heme oxygenase-1, superoxide dismutase and catalase) and autophagy machinery (LC3 and p62/SQSTM1) in aortic tissue.

CONCLUSION

HSP90 inhibition protects from atherosclerosis in experimental diabetes through the induction of Nrf2-dependent cytoprotective mechanisms, reinforcing its therapeutic potential.

Targeting HSP90 Ameliorates Nephropathy and Atherosclerosis Through Suppression of NF-κB and STAT Signaling Pathways in Diabetic Mice

Heat shock proteins (HSPs) are induced by cellular stress and function as molecular chaperones that regulate protein folding. Diabetes impairs the function/expression of many HSPs, including HSP70 and HSP90, key regulators of pathological mechanisms involved in diabetes complications. Therefore, we investigated whether pharmacological HSP90 inhibition ameliorates diabetes-associated renal damage and atheroprogression in a mouse model of combined hyperglycemia and hyperlipidemia (streptozotocin-induced diabetic apolipoprotein E-deficient mouse). Treatment of diabetic mice with 17-dimethylaminoethylamino-17-demethoxygeldanamycin (DMAG, 2 and 4 mg/kg, 10 weeks) improved renal function, as evidenced by dose-dependent decreases in albuminuria, renal lesions (mesangial expansion, leukocyte infiltration, and fibrosis), and expression of proinflammatory and profibrotic genes. Furthermore, DMAG significantly reduced atherosclerotic lesions and induced a more stable plaque phenotype, characterized by lower content of lipids, leukocytes, and inflammatory markers, and increased collagen and smooth muscle cell content. Mechanistically, the renoprotective and antiatherosclerotic effects of DMAG are mediated by the induction of protective HSP70 along with inactivation of nuclear factor-κB (NF-κB) and signal transducers and activators of transcription (STAT) and target gene expression, both in diabetic mice and in cultured cells under hyperglycemic and proinflammatory conditions. In conclusion, HSP90 inhibition by DMAG restrains the progression of renal and vascular damage in experimental diabetes, with potential implications for the prevention of diabetes complications.

Effect of Type 2 Diabetes Mellitus and Diabetic Nephropathy on IgG Pharmacokinetics and Subcutaneous Bioavailability in the Rat

The objective of this research was to assess the effects of type 2 diabetes mellitus (T2DM) and diabetic nephropathy (DN) on the pharmacokinetics of human IgG (hIgG), an antibody isotype, in Zucker diabetic fatty (ZDF) rats. Furthermore, the specific role of T2DM in the altered disposition of hIgG was evaluated by treating diabetic rats with pioglitazone, while the role of chronic kidney disease (CKD) was assessed using 5/6 nephrectomized Sprague Dawley rats. ZDF male (lean non-diabetic control and obese diabetic) and pioglitazone-treated ZDF rats were studied at ages 12-13 weeks (only DM was present), and at ages 29-30 weeks (progression to DN). All animals were dosed with 1 mg/kg of hIgG intravenously (IV) or subcutaneously (SC). ZDF rats had significantly higher blood glucose concentrations and urinary albumin excretion compared to control rats. Significant increases in total clearance (2.5-fold) and renal clearance (100-fold) of hIgG were observed; however the major increase in total clearance was due to increased non-renal clearance. Greater changes in urinary albumin excretion and total and renal clearances of IgG (3.5-fold and 300-fold, respectively) were observed with progression to DN. SC bioavailability of hIgG in all animal groups was similar (>84%). With pioglitazone-treatment, diabetic animals remained euglycemic and treatment was able to reverse the clearance changes, although incompletely. In the CKD group, no difference in hIgG clearance was observed when compared with controls. In conclusion, the increased clearance of hIgG in ZDF diabetic animals, reversal by pioglitazone treatment and lack of effect of CKD, demonstrate the influence of T2DM on hIgG pharmacokinetics.