PKD2, mutations in which cause autosomal dominant polycystic kidney disease (ADPKD), encodes an integral membrane glycoprotein with similarity to calcium channel subunits. We induced two mutations in the mouse homologue Pkd2 (ref.4): an unstable allele (WS25; hereafter denoted Pkd2WS25) that can undergo homologous-recombination-based somatic rearrangement to form a null allele; and a true null mutation (WS183; hereafter denoted Pkd2-). We examined these mutations to understand the function of polycystin-2, the protein product of Pkd2, and to provide evidence that kidney and liver cyst formation associated with Pkd2 deficiency occurs by a two-hit mechanism. Pkd2-/- mice die in utero between embryonic day (E) 13.5 and parturition. They have structural defects in cardiac septation and cyst formation in maturing nephrons and pancreatic ducts. Pancreatic ductal cysts also occur in adult Pkd2WS25/- mice, suggesting that this clinical manifestation of ADPKD also occurs by a two-hit mechanism. As in human ADPKD, formation of kidney cysts in adult Pkd2WS25/- mice is associated with renal failure and early death (median survival, 65 weeks versus 94 weeks for controls). Adult Pkd2+/- mice have intermediate survival in the absence of cystic disease or renal failure, providing the first indication of a deleterious effect of haploinsufficiency at Pkd2on long-term survival. Our studies advance our understanding of the function of polycystin-2 in development and our mouse models recapitulate the complex human ADPKD phenotype.

Objective To evaluate the efficacy and safety of sarilumab in combination with methotrexate (MTX) for the treatment of rheumatoid arthritis (RA). Methods Adults with moderate‐to‐severe RA and an inadequate response to MTX were randomized (1:1:1) to receive sarilumab (doses of 150 mg or 200 mg) or placebo every 2 weeks in conjunction with weekly MTX for 52 weeks. Co–primary end points were the proportion of patients achieving American College of Rheumatology 20% (ACR20) improvement responses at week 24, change from baseline in the Health Assessment Questionnaire (HAQ) disability index (DI) at week 16, and change from baseline in the modified Sharp/van der Heijde score (SHS) of radiographic damage at week 52. Results Baseline characteristics were similar among the groups. For all 3 co–primary end points, the sarilumab 150 mg and 200 mg groups demonstrated statistically significant improvements as compared with the placebo group (ACR20 response rate at week 24, 58.0%, 66.4%, and 33.4%, respectively [P < 0.0001]; least squares mean change in HAQ DI at week 16, −0.53, −0.55, and −0.29, respectively [P < 0.0001]; and mean change in SHS at week 52, 0.90, 0.25, and 2.78, respectively [P < 0.0001]). The most common treatment‐emergent adverse event was infection. In the sarilumab 150 mg, sarilumab 200 mg, and placebo groups, the incidence of serious infections was 2.6%, 4.0%, and 2.3%, respectively. Elevations in alanine aminotransferase levels >3‐fold the upper limit of normal occurred in 9.5%, 8.0%, and 2.1% of patients, respectively; in 24 patients, this led to discontinuation of treatment. Elevated total cholesterol levels were observed in 36.8%, 43.0%, and 18.3% of patients, respectively. In patients receiving 150 mg and 200 mg sarilumab, neutrophil counts of 0.5 to <1.0 × 109/liter were observed in 5.1% and 7.8% of patients, respectively, while neutrophil counts of <0.5 × 109/liter were observed in 0.9% and 0.7% of patients, respectively; none of the patients receiving placebo experienced changes in neutrophil counts. Conclusion In RA patients treated with sarilumab (150 mg or 200 mg every 2 weeks) in combination with MTX, both doses provided sustained clinical efficacy, as shown by significant improvements in symptomatic, functional, and radiographic outcomes. Sarilumab was generally well tolerated. The adverse events observed in this study were consistent with the effects of interleukin‐6 signaling blockade.

ObjectivesTo compare efficacy and safety of sarilumab monotherapy with adalimumab monotherapy in patients with active rheumatoid arthritis (RA) who should not continue treatment with methotrexate (MTX) due to intolerance or inadequate response.MethodsMONARCH was a randomised, active-controlled, double-blind, double-dummy, phase III superiority trial. Patients received sarilumab (200 mg every 2 weeks (q2w)) or adalimumab (40 mg q2w) monotherapy for 24 weeks. The primary end point was change from baseline in 28-joint disease activity score using erythrocyte sedimentation rate (DAS28-ESR) at week 24.ResultsSarilumab was superior to adalimumab in the primary end point of change from baseline in DAS28-ESR (−3.28 vs −2.20; p<0.0001). Sarilumab-treated patients achieved significantly higher American College of Rheumatology 20/50/70 response rates (sarilumab: 71.7%/45.7%/23.4%; adalimumab: 58.4%/29.7%/11.9%; all p≤0.0074) and had significantly greater improvement in Health Assessment Questionnaire-Disability Index (p=0.0037). Importantly, at week 24, more patients receiving sarilumab compared with adalimumab achieved Clinical Disease Activity Index remission (7.1% vs 2.7%; nominal p=0.0468) and low disease activity (41.8% vs 24.9%; nominal p=0.0005, supplemental analysis). Adverse events occurred in 63.6% (adalimumab) and 64.1% (sarilumab) of patients, the most common being neutropenia and injection site reactions (sarilumab) and headache and worsening RA (adalimumab). Incidences of infections (sarilumab: 28.8%; adalimumab: 27.7%) and serious infections (1.1%, both groups) were similar, despite neutropenia differences.ConclusionsSarilumab monotherapy demonstrated superiority to adalimumab monotherapy by improving the signs and symptoms and physical functions in patients with RA who were unable to continue MTX treatment. The safety profiles of both therapies were consistent with anticipated class effects.Trial registration numberNCT02332590.

ObjectiveTo evaluate the efficacy and safety of sarilumab plus conventional synthetic disease‐modifying antirheumatic drugs (DMARDs) in patients with active moderate‐to‐severe rheumatoid arthritis (RA) who had an inadequate response or intolerance to anti–tumor necrosis factor (anti‐TNF) therapy.MethodsPatients were randomly allocated to receive sarilumab 150 mg, sarilumab 200 mg, or placebo every 2 weeks for 24 weeks with background conventional synthetic DMARDs. The co‐primary end points were the proportion of patients achieving a response according to the American College of Rheumatology 20% criteria for improvement (ACR20) at week 24, and change from baseline in the Health Assessment Questionnaire disability index (HAQ DI) at week 12. Each sarilumab dose was evaluated against placebo; differences between the 2 sarilumab doses were not assessed.ResultsThe baseline characteristics of the treatment groups were similar. The ACR20 response rate at week 24 was significantly higher with sarilumab 150 mg and sarilumab 200 mg every 2 weeks compared with placebo (55.8%, 60.9%, and 33.7%, respectively; P < 0.0001). The mean change from baseline in the HAQ DI score at week 12 was significantly greater for sarilumab (least squares mean change: for 150 mg, −0.46 [P = 0.0007]; for 200 mg, −0.47 [P = 0.0004]) versus placebo (−0.26). Infections were the most frequently reported treatment‐emergent adverse events. Serious infections occurred in 1.1%, 0.6%, and 1.1% of patients receiving placebo, sarilumab 150 mg, and sarilumab 200 mg, respectively. Laboratory abnormalities included decreased absolute neutrophil count and increased transaminase levels in both sarilumab groups compared with placebo. In this study, reductions in the absolute neutrophil count were not associated with an increased incidence of infections or serious infections.ConclusionSarilumab 150 mg and sarilumab 200 mg every 2 weeks plus conventional synthetic DMARDs improved the signs and symptoms of RA and physical function in patients with an inadequate response or intolerance to anti‐TNF agents. Safety data were consistent with interleukin‐6 receptor blockade and the known safety profile of sarilumab.

Autosomal dominant polycystic kidney disease (ADPKD) is a common human genetic disease characterized by cyst formation in kidney tubules and other ductular epithelia. Cells lining the cysts have abnormalities in cell proliferation and cell polarity. The majority of ADPKD cases are caused by mutations in the PKD1 gene, which codes for polycystin-1, a large integral membrane protein of unknown function that is expressed on the plasma membrane of renal tubular epithelial cells in fetal kidneys. Because signaling from cell-cell and cell-matrix adhesion complexes regulates cell proliferation and polarity, we speculated that polycystin-1 might interact with these complexes. We show here that polycystin-1 colocalized with the cell adhesion molecules E-cadherin and α-, β-, and γ-catenin. Polycystin-1 coprecipitated with these proteins and comigrated with them on sucrose density gradients, but it did not colocalize, coprecipitate, or comigrate with focal adhesion kinase, a component of the focal adhesion. We conclude that polycystin-1 is in a complex containing E-cadherin and α-, β-, and γ-catenin. These observations raise the question of whether the defects in cell proliferation and cell polarity observed in ADPKD are mediated by E-cadherin or the catenins.

ObjectivesTo evaluate safety and efficacy of weekly (qw) and every other week (q2w) dosing of sarilumab, a fully human anti-interleukin 6 receptor α (anti-IL-6Rα) monoclonal antibody, for moderate-to-severe rheumatoid arthritis (RA).MethodsIn this dose-ranging study, patients (n=306) with active RA, despite methotrexate, were randomly assigned to placebo or one of five subcutaneous doses/regimens of sarilumab: 100 mg q2w, 150 mg q2w, 100 mg qw, 200 mg q2w, 150 mg qw for 12 weeks, plus methotrexate. The primary end point was ACR20 at Week 12. Secondary endpoints included ACR50, ACR70, Disease Activity Score in 28 joints (C reactive protein). Safety, pharmacokinetics, pharmacodynamics and efficacy in population subgroups were assessed.ResultsThe proportion of patients achieving an ACR20 response compared with placebo was significantly higher for sarilumab 150 mg qw (72.0% vs 46.2%, multiplicity adjusted p=0.0203). Higher ACR20 responses were also attained with 150 mg q2w (67%; unadjusted (nominal) p=0.0363) and 200 mg q2w (65%; unadjusted p=0.0426) versus placebo. Sarilumab ≥150 mg q2w reduced C reactive protein, which did not return to baseline between dosing intervals. Infections were the most common adverse event; none were serious. Changes in laboratory values (neutropenia, transaminases and lipids) were consistent with reports with other IL-6Rα inhibitors.ConclusionsSarilumab improved signs and symptoms of RA over 12 weeks in patients with moderate-to-severe RA with a safety profile similar to reports with other IL-6 inhibitors. Sarilumab 150 mg and sarilumab 200 mg q2w had the most favourable efficacy, safety and dosing convenience and are being further evaluated in Phase III.

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The contents of endocytic vesicles and other intracellular organelles (such as Golgi and microsomes) are acidified by an electrogenic proton-translocating ATPase that is remarkably similar to that found in urinary epithelia. We recently found that the number of H+ ATPases in the apical plasma membrane of these epithelia is regulated by exocytotic insertion of endocytic vesicles whose membranes contain this H+ pump. Carbon dioxide, a major stimulus for urinary acidification, causes rapid fusion of these vesicles with the luminal membrane, thereby inserting these pumps there and increasing the rate of net transepithelial H+ secretion; CO2 also inhibits endocytic retrieval of the pumps from the luminal membrane. Such reciprocal regulation of endocytosis and exocytosis by a physiological modulator makes this system particularly attractive for studying the cellular events regulating membrane fusion. Here we present evidence that CO2 induces exocytosis by a cascade of events, the first step of which is cytoplasmic acidification. Cell acidification then increases calcium activity, which causes the fusion event.