Burden of Proof for Tolvaptan in ADPKD: Did REPRISE Provide the Answer?

Targeting the ADPKD methylome using nanoparticle-mediated combination therapy

DNA methylation aberrancies are found in autosomal dominant polycystic kidney disease (ADPKD), which suggests the methylome to be a promising therapeutic target. However, the impact of combining DNA methylation inhibitors (DNMTi) and ADPKD drugs in treating ADPKD and on disease-associated methylation patterns has not been fully explored. To test this, ADPKD drugs, metformin and tolvaptan (MT), were delivered in combination with DNMTi 5-aza-2'-deoxycytidine (Aza) to 2D or 3D cystic Pkd1 heterozygous renal epithelial cells (PKD1-Het cells) as free drugs or within nanoparticles to enable direct delivery for future in vivo applications. We found Aza synergizes with MT to reduce cell viability and cystic growth. Reduced representation bisulfite sequencing (RRBS) was performed across four groups: PBS, Free-Aza (Aza), Free-Aza+MT (F-MTAza), and Nanoparticle-Aza+MT (NP-MTAza). Global methylation patterns showed that while Aza alone induces a unimodal intermediate methylation landscape, Aza+MT recovers the bimodality reminiscent of somatic methylomes. Importantly, site-specific methylation changes associated with F-MTAza and NP-MTAza were largely conserved including hypomethylation at ADPKD-associated genes. Notably, we report hypomethylation of cancer-associated genes implicated in ADPKD pathogenesis as well as new target genes that may provide additional therapeutic effects. Overall, this study motivates future work to further elucidate the regulatory mechanisms of observed drug synergy and apply these combination therapies in vivo.

1-Indanone retards cyst development in ADPKD mouse model by stabilizing tubulin and down-regulating anterograde transport of cilia

Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited kidney disease. Cyst development in ADPKD involves abnormal epithelial cell proliferation, which is affected by the primary cilia-mediated signal transduction in the epithelial cells. Thus, primary cilium has been considered as a therapeutic target for ADPKD. Since ADPKD exhibits many pathological features similar to solid tumors, we investigated whether targeting primary cilia using anti-tumor agents could alleviate the development of ADPKD. Twenty-four natural compounds with anti-tumor activity were screened in MDCK cyst model, and 1-Indanone displayed notable inhibition on renal cyst growth without cytotoxicity. This compound also inhibited cyst development in embryonic kidney cyst model. In neonatal kidney-specific Pkd1 knockout mice, 1-Indanone remarkably slowed down kidney enlargement and cyst expansion. Furthermore, we demonstrated that 1-Indanone inhibited the abnormal elongation of cystic epithelial cilia by promoting tubulin polymerization and significantly down-regulating expression of anterograde transport motor protein KIF3A and IFT88. Moreover, we found that 1-Indanone significantly down-regulated ciliary coordinated Wnt/β-catenin, Hedgehog signaling pathways. These results demonstrate that 1-Indanone inhibits cystic cell proliferation by reducing abnormally prolonged cilia length in cystic epithelial cells, suggesting that 1-Indanone may hold therapeutic potential to retard cyst development in ADPKD.

Natural-derived compounds and their mechanisms in potential autosomal dominant polycystic kidney disease (ADPKD) treatment

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) is a monogenic kidney disorder that impairs renal functions progressively leading to kidney failure. The disease affects between 1:400 and 1:1000 ratio of the people worldwide. It is caused by the mutated PKD1 and PKD2 genes which encode for the defective polycystins. Polycystins mimic the receptor protein or protein channel and mediate aberrant cell signaling that causes cystic development in the renal parenchyma. The cystic development is driven by the increased cyclic AMP stimulating fluid secretion and infinite cell growth. In recent years, natural product-derived small molecules or drugs targeting specific signaling pathways have caught attention in the drug discovery discipline. The advantages of natural products over synthetic drugs enthusiast researchers to utilize the medicinal benefits in various diseases including ADPKD.

CONCLUSION

Overall, this review discusses some of the previously studied and reported natural products and their mechanisms of action which may potentially be redirected into ADPKD.

Per-Treatment Post Hoc Analysis of Clinical Trial Outcomes With Tolvaptan in ADPKD

Introduction

In pivotal trials of patients with autosomal dominant polycystic kidney disease at risk of rapid progression, tolvaptan slowed estimated glomerular filtration rate (eGFR) decline in early-to-moderate (TEMPO 3:4 [NCT00428948]) and moderate- to late-stage (REPRISE [NCT02160145]) chronic kidney disease (CKD). Discontinuation was less frequent in REPRISE (15.0%) than TEMPO 3:4 (23.0%), given that in REPRISE, only subjects who tolerated tolvaptan 60/30 mg daily initiated the double-blind phase. We evaluated whether the greater treatment effect in REPRISE was attributable to different completion rates.

Methods

We conducted post hoc analyses of TEMPO 3:4 and REPRISE completers, defined as subjects who took trial drug to the end of the treatment period in TEMPO 3:4 (3 years) or REPRISE (1 year). Efficacy (rate of change in eGFR for tolvaptan vs. placebo) was analyzed as in each trial. Subjects from TEMPO 3:4 and REPRISE were also matched by propensity score for age, gender, and baseline eGFR to explore potential additional determinants of treatment effect.

Results

The annualized tolvaptan treatment effect in TEMPO 3:4 completers (difference vs. placebo of 0.98 ml/min per 1.73 m²/y) and REPRISE completers (difference of 1.23) was similar to that of the respective total trial populations (TEMPO 3:4: 0.94; REPRISE: 1.27). The treatment effect of tolvaptan was also similar between matched subjects.

Conclusion

Greater treatment completion rate did not drive greater treatment effect in REPRISE. The more advanced CKD of REPRISE subjects may be more relevant. More rapid decline in kidney function in later-stage CKD enabled the effects of tolvaptan to be more easily discerned.

Advances in Autosomal Dominant Polycystic Kidney Disease: A Clinical Review

Polycystic kidney disease (PKD) is a multiorgan disorder resulting in fluid-filled cyst formation in the kidneys and other systems. The replacement of kidney parenchyma with an ever-increasing volume of cysts eventually leads to kidney failure. Recently, increased understanding of the pathophysiology of PKD and genetic advances have led to new approaches of treatment targeting physiologic pathways, which has been proven to slow the progression of certain types of the disease. We review the pathophysiologic patterns and recent advances in the clinical pharmacotherapy of autosomal dominant PKD. A multipronged approach with pharmacologic and nonpharmacologic treatments can be successfully used to slow down the rate of progression of autosomal dominant PKD to kidney failure.