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INTRODUCTIONAcute kidney injury and chronic kidney disease (CKD) are common in hospitalized patients. To inform clinical decision making, more accurate information regarding risk of long-term progression to kidney failure is required.METHODSWe enrolled 1538 hospitalized patients in a multicenter, prospective cohort study. Monocyte chemoattractant protein 1 (MCP-1/CCL2), uromodulin (UMOD), and YKL-40 (CHI3L1) were measured in urine samples collected during outpatient follow-up at 3 months. We followed patients for a median of 4.3 years and assessed the relationship between biomarker levels and changes in estimated glomerular filtration rate (eGFR) over time and the development of a composite kidney outcome (CKD incidence, CKD progression, or end-stage renal disease). We paired these clinical studies with investigations in mouse models of renal atrophy and renal repair to further understand the molecular basis of these markers in kidney disease progression.RESULTSHigher MCP-1 and YKL-40 levels were associated with greater eGFR decline and increased incidence of the composite renal outcome, whereas higher UMOD levels were associated with smaller eGFR declines and decreased incidence of the composite kidney outcome. A multimarker score increased prognostic accuracy and reclassification compared with traditional clinical variables alone. The mouse model of renal atrophy showed greater Ccl2 and Chi3l1 mRNA expression in infiltrating macrophages and neutrophils, respectively, and evidence of progressive renal fibrosis compared with the repair model. The repair model showed greater Umod expression in the loop of Henle and correspondingly less fibrosis.CONCLUSIONSBiomarker levels at 3 months after hospitalization identify patients at risk for kidney disease progression.FUNDINGNIH.

Pseudohypoaldosteronism type II (PHAII) is a rare Mendelian syndrome featuring hypertension and hyperkalemia resulting from constitutive renal salt reabsorption and impaired K ⁺ secretion. Recently, mutations in Kelch-like 3 (KLHL3) and Cullin 3 (CUL3), components of an E3 ubiquitin ligase complex, were found to cause PHAII, suggesting that loss of this complex’s ability to target specific substrates for ubiquitination leads to PHAII. By MS and coimmunoprecipitation, we show that KLHL3 normally binds to WNK1 and WNK4, members of WNK (with no lysine) kinase family that have previously been found mutated in PHAII. We show that this binding leads to ubiquitination, including polyubiquitination, of at least 15 specific sites in WNK4, resulting in reduced WNK4 levels. Dominant disease-causing mutations in KLHL3 and WNK4 both impair WNK4 binding, ubiquitination, and degradation. WNK4 normally induces clearance of the renal outer medullary K ⁺ channel (ROMK) from the cell surface. We show that WT but not mutant KLHL3 inhibits WNK4-induced reduction of ROMK level. We show that PHAII-causing mutations in WNK4 lead to a marked increase in WNK4 protein levels in the kidney in vivo. These findings demonstrate that CUL3–RING (really interesting new gene) ligases that contain KLHL3 target ubiquitination of WNK4 and thereby regulate WNK4 levels, which in turn regulate levels of ROMK. These findings reveal a specific role of CUL3 and KLHL3 in electrolyte homeostasis and provide a molecular explanation for the effects of disease-causing mutations in both KLHL3 and WNK4.

Background Fibrosis is the unifying pathway leading to chronic kidney disease. Identifying biomarkers of fibrosis may help predict disease progression. Methods We performed a systematic review to evaluate the reliability of blood and urine biomarkers in identifying fibrosis on biopsy as well as predicting renal outcomes. Using MEDLINE and EMBASE, a two-stage search strategy was implemented. Stage I identified a library of biomarkers correlating with fibrosis on biopsy. Stage II evaluated the association between biomarkers identified in stage I, and renal outcomes. Only biomarkers with moderate positive correlation with fibrosis ( r  > 0.40) or acceptable area under the curve (AUC >0.65) advanced to stage II. Results Stage I identified 17 studies and 14 biomarkers. Five biomarkers met criteria to advance to stage II, but only three were independently associated with renal outcomes. Transforming growth factor β (TGF-β) correlated with fibrosis ( r  = 0.60), and was associated with 1.7–3.9 times the risk of worsening renal function in 426 patients. Monocyte chemoattractant protein-1 (MCP-1) diagnosed fibrosis with AUC of 0.66 and was associated with 2.3–11.0 times the risk of worsening renal function in 596 patients. Matrix metalloproteinase-2 (MMP-2) correlated with fibrosis ( r  = 0.41), and was associated with 2.5 times the risk of worsening renal function. Conclusions Given the heterogeneity of the data due to diverse patient populations along with differing renal outcomes, a meta-analysis could not be conducted. Nonetheless we can conclude from the published data that TGF-β, MCP-1 and MMP-2 may identify patients at risk for renal fibrosis and hence worse renal outcomes.

With-no-lysine kinase 4 (WNK4) regulates electrolyte homeostasis and blood pressure. WNK4 phosphorylates the kinases SPAK (Ste20-related proline alanine-rich kinase) and OSR1 (oxidative stress responsive kinase), which then phosphorylate and activate the renal Na-Cl cotransporter (NCC). WNK4 levels are regulated by binding to Kelch-like 3, targeting WNK4 for ubiquitylation and degradation. Phosphorylation of Kelch-like 3 by PKC or PKA downstream of AngII or vasopressin signaling, respectively, abrogates binding. We tested whether these pathways also affect WNK4 phosphorylation and activity. By tandem mass spectrometry and use of phosphosite-specific antibodies, we identified five WNK4 sites (S47, S64, S1169, S1180, S1196) that are phosphorylated downstream of AngII signaling in cultured cells and in vitro by PKC and PKA. Phosphorylation at S64 and S1196 promoted phosphorylation of the WNK4 kinase T-loop at S332, which is required for kinase activation, and increased phosphorylation of SPAK. Volume depletion induced phosphorylation of these sites in vivo, predominantly in the distal convoluted tubule. Thus, AngII, in addition to increasing WNK4 levels, also modulates WNK4 kinase activity via phosphorylation of sites outside the kinase domain.

Hypertension contributes to the global burden of cardiovascular disease. Increased dietary K ⁺ reduces blood pressure; however, the mechanism has been obscure. Human genetic studies have suggested that the mechanism is an obligatory inverse relationship between renal salt reabsorption and K ⁺ secretion. Mutations in the kinases with-no-lysine 4 (WNK4) or WNK1, or in either Cullin 3 (CUL3) or Kelch-like 3 (KLHL3)—components of an E3 ubiquitin ligase complex that targets WNKs for degradation—cause constitutively increased renal salt reabsorption and impaired K ⁺ secretion, resulting in hypertension and hyperkalemia. The normal mechanisms that regulate the activity of this ubiquitin ligase and levels of WNKs have been unknown. We posited that missense mutations in KLHL3 that impair binding of WNK4 might represent a phenocopy of the normal physiologic response to volume depletion in which salt reabsorption is maximized. We show that KLHL3 is phosphorylated at serine 433 in the Kelch domain (a site frequently mutated in hypertension with hyperkalemia) by protein kinase C in cultured cells and that this phosphorylation prevents WNK4 binding and degradation. This phosphorylation can be induced by angiotensin II (AII) signaling. Consistent with these in vitro observations, AII administration to mice, even in the absence of volume depletion, induces renal KLHL3 S⁴³³ phosphorylation and increased levels of both WNK4 and the NaCl cotransporter. Thus, AII, which is selectively induced in volume depletion, provides the signal that prevents CUL3/KLHL3-mediated degradation of WNK4, directing the kidney to maximize renal salt reabsorption while inhibiting K ⁺ secretion in the setting of volume depletion. Significance Aldosterone produces distinct adaptive responses in volume depletion and hyperkalemia. Mutations in with-no-lysine (WNK) kinases or ubiquitin ligases containing Cullin 3 (CUL3) and Kelch-like 3 (KLHL3) cause a Mendelian disease featuring hypertension and hyperkalemia due to constitutive renal salt reabsorption and inhibited K ⁺ secretion. WNKs modulate activities of aldosterone-regulated electrolyte flux pathways, and WNK levels are regulated by CUL3/KLHL3; disease-causing mutations prevent WNK degradation. This manuscript shows that angiotensin II (AII), a hormone produced only in volume depletion, induces PKC-mediated phosphorylation of KLHL3, preventing WNK degradation and phenocopying KLHL3 mutations. These findings provide a mechanism by which AII signaling alters WNK4, promoting increased renal salt reabsorption and reduced K ⁺ secretion.

Since the introduction of the Fast Track designation in 1988, the number of special regulatory programs available for the approval of new drugs and biologics by the US Food and Drug Administration (FDA) has increased, offering the agency flexibility with respect to evidentiary requirements. To characterize pivotal efficacy trials supporting the approval of new drugs and biologics during the past 3 decades. This cross-sectional study included 273 new drugs and biologics approved by the FDA for 339 indications from 1995 to 1997, from 2005 to 2007, and from 2015 to 2017. Therapeutics were classified by product type and therapeutic area as well as orphan designation and use of special regulatory programs, such as Priority Review and Accelerated Approval. Pivotal trials were characterized by use of randomization, blinding, types of comparators, primary end points, number of treated patients, and trial duration, both individually and aggregated by each indication approval. A total of 273 new drugs and biologics were approved by the FDA in these 3 periods (107 [39.2%] in 1995-1997; 57 [20.9%] in 2005-2007; and 109 [39.9%] in 2015-2017), representing 339 indications (157 [46.3%], 64 [18.9%], and 118 [34.8%], respectively). The proportion of therapeutic approvals using at least 1 special regulatory program increased (37 [34.6%] in 1995-1997; 33 [57.9%] in 2005-2007; and 70 [64.2%] in 2015-2017), as did indication approvals receiving an orphan designation (20 [12.7%] in 1995-1997; 17 [26.6%] in 2005-2007, and 45 [38.1%] in 2015-2017). The most common therapeutic areas differed over time (infectious disease, 53 [33.8%] in 1995-1997 vs cancer, 32 [27.1%] in 2015-2017). When considering the aggregate pivotal trials supporting each indication approval, the proportion of indications supported by at least 2 pivotal trials decreased (80.6% [95% CI, 72.6%-87.2%] in 1995-1997; 60.3% [95% CI, 47.2%-72.4%] in 2005-2007; and 52.8% [95% CI, 42.9%-62.6%] in 2015-2017; P < .001). The proportion of indications supported by only single-group pivotal trials increased (4.0% [95% CI, 1.3%-9.2%] in 1995-1997; 12.7% [95% CI, 5.6%-23.5%] in 2005-2007; and 17.0% [95% CI, 10.4%-25.5%] in 2015-2017; P = .001), whereas the proportion supported by at least 1 pivotal trial of 6 months' duration increased (25.8% [95% CI, 18.4%-34.4%] in 1995-1997; 34.9% [95% CI, 23.3%-48.0%] in 2005-2007; and 46.2% [95% CI, 36.5%-56.2%] in 2015-2017; P = .001). In this study, more recent FDA approvals of new drugs and biologics were based on fewer pivotal trials, which, when aggregated by indication, had less rigorous designs but longer trial durations, suggesting an ongoing need for continued evaluation of therapeutic safety and efficacy after approval.

After US Food and Drug Administration (FDA) approval of a new drug, sponsors can submit additional clinical data to obtain supplemental approval for use for new indications. To characterize pivotal trials supporting recent supplemental new indication approvals of drugs and biologics by the FDA and to compare them with pivotal trials that supported these therapeutics' original indication approvals. This is a cross-sectional study characterizing pivotal trials supporting supplemental indication approvals by the FDA between 2017 and 2019 and pivotal trials that supported these therapeutics' original indication approvals. Data analysis was performed from August to October 2020. Number and design of pivotal trials supporting both supplemental and original indication approvals. From 2017 to 2019, the FDA approved 146 supplemental indications for 107 therapeutics on the basis of 181 pivotal efficacy trials. The median (interquartile range) number of trials per supplemental indication was 1 (1-1). Most trials used either placebo (77 trials [42.5%; 95% CI, 35.6%-49.8%]) or active comparators (65 trials [35.9%; 95% CI, 29.3%-43.1%]), and most of these multigroup trials were randomized (141 trials [99.3%; 95% CI, 96.0%-100.0%]) and double-blinded (106 trials [74.5%; 95% CI, 66.6%-81.0%]); 80 trials (44.2%; 95 CI, 37.2%-51.5%) used clinical outcomes as the primary efficacy end point. There was no difference between oncology therapies and those approved for other therapeutic areas to have supplemental indication approvals be based on at least 2 pivotal trials (11.5% vs 20.6%; difference, 9.1%; 95% CI, 2.9%-21.0%; P = .10). Similarly, there was no difference in use of randomization (98.3% vs 100.0%; difference, 1.7%; 95% CI, 1.6%-5.0%; P = .43) among multigroup trials, although these trials were less likely to be double-blinded (50.8% vs 92.3%; difference, 41.5%; 95% CI, 27.4%-55.5%; P < .001); overall, these trials were less likely to use either placebo or active comparators (64.9% vs 86.7%; difference, 21.8% 95% CI, 9.8%-33.9%; P < .001) or to use clinical outcomes as their primary efficacy end point (27.5% vs 61.1%; difference, 33.6%; 95% CI, 14.1%-40.9%; P < .001) and were longer (median [interquartile range], 17 [6-48] weeks vs 95 [39-146] weeks). Original approvals were more likely than supplemental indication approvals to be based on at least 2 pivotal trials (44.0% [95% CI, 33.7%-42.6%] vs 15.8% [95% CI, 10.7%-22.5%]; difference, 28.2%; 95% CI, 17.6%-39.6%; P < .001) and less likely to be supported by at least 1 trial of 12 months' duration (27.6% [95% CI, 17.9%-35.0%] vs 54.8% [95% CI, 46.7%-62.6%]; difference, 27.2%; 95% CI, 14.5%-37.8%; P < .001). Pivotal trial designs were otherwise not significantly different. These findings suggest that the number and design of the pivotal trials supporting supplemental indication approvals by the FDA varied across therapeutic areas, with the strength of evidence for cancer indications weaker than that for other indications. There was little difference in the design characteristics of the pivotal trials supporting supplemental indication and original approvals.

The Right to Try Act of 2017 allows patients with life-threatening conditions to access investigational medicines outside clinical trials without oversight from the US Food and Drug Administration (FDA). A better understanding of existing expanded access programs can inform the consideration and implementation of both the federal Right to Try Act and state right-to-try laws. To determine the timing and duration of expanded access programs for investigational medicines initiated prior to FDA approval. This cross-sectional study examined expanded access and compassionate use programs registered through August 1, 2017, identified from ClinicalTrials.gov and publicly available FDA documents. Start date of each program and 3 key regulatory dates (investigational new drug application activation, initial new drug application submission, and FDA approval), and timing and duration of expanded access availability in relation to new drug application submission and FDA approval. Through ClinicalTrials.gov, 92 FDA-approved drugs and biologics with associated expanded access programs initiated prior to FDA approval were identified. These programs were initiated between September 1996 and June 2017 for medicines that were most commonly used to treat cancer (n = 46 [50.0%]); metabolic, endocrine, and genetic diseases (n = 16 [17.4%]); and infectious diseases (n = 14 [15.2%]). The median (interquartile range) premarket expanded access availability was 10.0 (6.0-19.5) months, constituting a median (interquartile range) of 14% (7%-25%) of the premarket clinical development period (investigational new drug application activation to FDA approval). Of 92 expanded access programs, 64 (69.6%) were initiated just before or after new drug application submission: 24 (26.1%) were initiated during the 6-month period before, and 40 (43.5%) in the 6 months after. Over the past 2 decades, expanded access programs have provided access to investigational medicines for which evidence of safety and effectiveness was established. For medicines that ultimately receive FDA approval, these findings suggest that the FDA and pharmaceutical industry have established a balance between investigational new drug access and protection of patients from therapies without established safety. This balance may be compromised by policy makers seeking to speed access to investigational medicines through the Right to Try Act.