Cysteamine bitartrate delayed-release capsules control leukocyte cystine levels and promote statural growth and kidney health in an open-label study of treatment-naïve patients <6 years of age with nephropathic cystinosis.

Nephropathic cystinosis is a rare autosomal recessive lysosomal storage disease that is characterized by accumulation of cysteine and formation of crystals within cells of different organs and tissues causing systemic manifestations in childhood that include poor linear growth, ocular involvement, hypothyroidism, and progressive kidney disease. This study was a long-term, prospective open-label evaluation of twice-daily delayed release (DR) cysteamine capsules in cystinosis patients <6 years of age who were naïve to any form of cysteamine treatment. Fifteen treatment-naïve patients <6 years old (mean age 2.2 ± 1.0 years, 53% male, 73% White) were enrolled and treated with DR-cysteamine capsules for up to 18 months. Patients had clinically meaningful decreases in WBC cysteine concentration during treatment (3.2 ± 3.0 nmol ½ cystine/mg protein at Day 1 to 0.8 ± 0.8 nmol ½ cystine/mg protein at study exit), and anthropometric data improvements were consistently observed in height, weight and body surface area. Additionally, estimated glomerular filtration rate increased from 55.93 ± 22.43 ml/min/1.73 m2 at baseline to 63.79 ± 21.44 ml/min/1.73 m2 at study exit. Pharmacokinetic/Pharmacodynamic results support the use of the same starting, escalation, and maintenance doses according to body surface for children aged <6 years that are currently recommended in adults and older children. All patients experienced ≥1 adverse event(s) with vomiting (80%) and upper respiratory tract infection (53%) most frequently reported. Based on our study, patients <6 years of age with nephropathic cystinosis without prior treatment can safely and effectively initiate treatment with DR-cysteamine, a delayed-release form of cysteamine bitartrate that can be given every 12 h.

Teprotumumab Efficacy, Safety, and Durability in Longer-Duration Thyroid Eye Disease and Re-treatment: OPTIC-X Study.

PURPOSE: To evaluate teprotumumab safety/efficacy in patients with thyroid eye disease (TED) who were nonresponsive or who experienced a disease flare. DESIGN: The Treatment of Graves' Orbitopathy to Reduce Proptosis with Teprotumumab Infusions in an Open-Label Clinical Extension Study (OPTIC-X) is a teprotumumab treatment and re-treatment trial following the placebo-controlled teprotumumab Phase 3 Treatment of Graves' Orbitopathy (Thyroid Eye Disease) to Reduce Proptosis with Teprotumumab Infusions in a Randomized, Placebo-Controlled, Clinical Study (OPTIC) trial. PARTICIPANTS: Patients who previously received placebo (n = 37) or teprotumumab (n = 14) in OPTIC. METHODS: OPTIC nonresponders or those who flared (≥2-mm increase in proptosis, ≥2-point increase in clinical activity score [CAS], or both) during follow-up were treated for the first time (previous placebo patients) or re-treated with teprotumumab in OPTIC-X with 8 infusions over 24 weeks. MAIN OUTCOME MEASURES: Proptosis response and safety. Secondary outcomes included proptosis, CAS, subjective diplopia, and quality-of-life. RESULTS: Thirty-three of 37 placebo-treated OPTIC patients (89.2%) became proptosis responders (mean ± standard deviation, -3.5 ± 1.7 mm) when treated with teprotumumab in OPTIC-X. The responses were equivalent to the OPTIC study. In these responders, proptosis, CAS of 0 or 1, and diplopia responses were maintained in 29 of 32 patients (90.6%), 20 of 21 patients (95.2%), and 12 of 14 patients (85.7%), respectively, at follow-up week 48. The median TED duration was 12.9 months versus 6.3 months in those treated with teprotumumab in the OPTIC study. Of the 5 OPTIC teprotumumab nonresponders re-treated in OPTIC-X, 2 responded, 1 showed a proptosis reduction of 1.5 mm from OPTIC baseline, and 2 discontinued treatment early. Of the OPTIC teprotumumab responders who experienced flare, 5 of 8 patients (62.5%) responded when re-treated (mean proptosis reduction, 1.9 ± 1.2 mm from OPTIC-X baseline and 3.3 ± 0.7 mm from OPTIC baseline). Compared with published double-masked trials and their integrated follow-up, no new safety signals were identified. Mild hearing impairment was reported; 4 events occurred during the first course of treatment, and 2 events reoccurred after re-treatment. CONCLUSIONS: Patients with TED of longer disease duration responded similarly to those treated earlier in the disease course. Patients with an insufficient initial response or flare may benefit from additional teprotumumab therapy. No new safety risk was identified; however additional postmarketing pharmacovigilance is ongoing.

Teprotumumab for patients with active thyroid eye disease: a pooled data analysis, subgroup analyses, and off-treatment follow-up results from two randomised, double-masked, placebo-controlled, multicentre trials.

BACKGROUND: Thyroid eye disease manifests inflammation and treatment-resistant proptosis and diplopia. Teprotumumab, an insulin-like growth factor-1 receptor inhibiting monoclonal antibody, was approved in the USA on Jan 21, 2020, on the basis of two randomised trials. In this analysis we evaluated the short-term and long-term aggregate response to teprotumumab from the two trials, focusing on proptosis and diplopia. METHODS: We analysed integrated outcomes and follow-up data from two randomised, double-masked, placebo-controlled, multicentre, trials done at a total of 28 academic referral tertiary specialised centres offering joint thyroid eye clinics, or orbital clinics or practices, or both, in Europe and the USA. Participants were adult patients with a diagnosis of Graves' disease and active moderate-to-severe thyroid eye disease (clinical activity score [CAS] ≥4). Patients received eight intravenous infusions of either teprotumumab (10 mg/kg body weight for the first infusion, 20 mg/kg for subsequent infusions) or placebo every 3 weeks. The final study visit was at week 24, 3 weeks after the final infusion. In our analysis, the prespecified primary outcome was the between-group difference from baseline to week 24 in the proportion of patients with a proptosis response (≥2 mm reduction in the study eye without similar deterioration in the fellow eye at week 24) stratified by tobacco non-use and current use. Secondary endpoints at week 24 were the proportion of patients with improved diplopia (≥1 Bahn-Gorman grade), an overall response (reduction of ≥2 mm in proptosis and reduction of ≥2 points in CAS), mean change from baseline in proptosis measurement in the study eye, mean change from baseline in Graves' ophthalmopathy quality of life (GO-QOL) questionnaire scores (overall, visual functioning, and appearance), and the proportion of patients with disease inactivation (ie, a CAS score of 0 or 1). We also assessed data for the primary and secondary outcomes by patient subgroups (tobacco use; age <65 years or older; sex; time to diagnosis; CAS score 4 or 5, or 6 or 7; and thyrotropin binding inhibiting immunoglobulin [TBII] concentration <10 IU/L or ≥10 IU/L) versus placebo. Additional outcomes included short-term and long-term responses at 7 weeks and 51 weeks after the final dose, and post-hoc assessments of disease severity (more severe baseline disease defined as proptosis ≥3 mm or constant or inconstant diplopia, or both, as compared with all others), and an ophthalmic composite outcome (improvement in ≥1 eye from baseline without deterioration in either eye in ≥2 of the following: absence of eyelid swelling; CAS ≥2; proptosis ≥2 mm; lid aperture ≥2 mm; diplopia disappearance or grade change; or improvement of 8 degrees of globe motility). All outcome endpoint analyses were done by intention-to-treat (ITT) except where noted. FINDINGS: The pooled ITT population consisted of 84 patients assigned teprotumumab and 87 assigned placebo. More patients receiving teprotumumab achieved a reduction of at least 2 mm in proptosis at week 24 versus placebo (65 [77%] of 84 patients assigned teprotumumab vs 13 [15%] assigned placebo; stratified treatment difference 63%, 95% CI 51-75; p<0·0001). Numbers-needed-to-treat (NNT) were 1·6 for proptosis response, 2·5 for diplopia response (treatment difference 39%, 95% CI 23-55), 1·7 for overall response (treatment difference 60%, 48-72), and 2·5 for disease inactivation (treatment difference 40%, 27-53); all p <0·0001. The post-hoc assessment of the composite outcome showed that it was reached by 68 (81%) patients in the teprotumumab group and 38 (44%) in the placebo group (NNT 2·5, treatment difference 40%, 95% CI 26-53; p<0·0001). There were significantly more proptosis responders with teprotumumab in all subgroups at week 24; the number of diplopia responders was also significantly higher with teprotumumab for all subgroups except tobacco users and patients with TBII less than 10 IU/L at baseline. Integrated treatment differences for proptosis ranged from 47% in tobacco users (95% CI 21-73, p=0·0015; NNT=2·1) to 83% in patients aged 65 years and older (60-100, p<0·0001; NNT=1·2), and for diplopia ranged from 29% in tobacco users (95% CI -3 to 62, p=0·086; NNT=3·4) to 47% in those with baseline CAS of 6 or 7 (95% CI 23-71, p=0·0002; NNT=2·1). All other integrated subgroup results were p≤0·033. Integrated responses were observed at 7 weeks and 51 weeks after final dose for proptosis in 62 (87%) of 71 patients and 38 (67%) of 57 patients respectively; for diplopia in 38 (66%) of 58 and 33 (69%) of 48 respectively; and for the composite outcome in 66 (92%) of 72 and 48 (83%) of 58, respectively. During the 24-week study, compared with placebo, there were moderate-to-large improvements with teprotumumab for GO-QOL total scores (19 vs 6, p<0·0001), visual scores (20 vs 7, p=0·0003), and appearance scores (18 vs 6, p=0·0003), respectively, which were maintained during follow-up. Of all adverse events during the treatment period, 63 (94%) of 67 patients with teprotumumab and 59 (98%) of 60 patients with placebo were mild to moderate (grade 1 or 2), with three (4%) serious adverse events related or possibly related to teprotumumab of diarrhoea, infusion reaction, and Hashimoto's encephalopathy (co-incident with confusion) leading to study discontinuation. Of the most commonly reported adverse events with teprotumumab, muscle spasm (18%, 95% CI 7·3-28·7), hearing loss (10%), and hyperglycaemia (8%, 1·7-15·0) had the greatest risk difference from placebo. INTERPRETATION: Teprotumumab markedly improved the clinical course of thyroid eye disease in all patient subgroups examined from the two trials, with most patients maintaining responses in the long-term. Analyses of the effect of teprotumumab retreatment on non-responders and those who flare after response, as well as further studies in a broader population of thyroid eye disease are ongoing. FUNDING: Horizon Therapeutics.

Pharmacokinetics and Exposure-Response Relationship of Teprotumumab, an Insulin-Like Growth Factor-1 Receptor-Blocking Antibody, in Thyroid Eye Disease.

BACKGROUND AND OBJECTIVE: Thyroid eye disease (TED) is characterized by inflammation/expansion of orbital tissues, proptosis, and diplopia. Teprotumumab is the first US Food and Drug Administration-approved therapy for TED, administered as an initial intravenous infusion of 10 mg/kg followed by 20 mg/kg every 3 weeks for an additional seven infusions. The objective of this article is to discuss the pharmacokinetics and exposure-response profile for teprotumumab in patients with TED. METHODS: A population pharmacokinetic analysis was performed to characterize pharmacokinetics and select dosing in patients with TED. Exposure-response was evaluated for efficacy (proptosis response, clinical activity score categorical response, and diplopia response) and safety (hyperglycemia, muscle spasms, and hearing impairment) parameters. RESULTS: Teprotumumab pharmacokinetics was linear in patients with TED, with low systemic clearance (0.334 L/day), low volume of distribution (3.9 and 4.2 L for the central and peripheral compartment, respectively), and a long elimination half-life (19.9 days). The approved dosing regimen provided > 20 µg/mL for > 90% insulin-like growth factor 1 receptor saturation throughout the dosing interval. Model-predicted mean (± standard deviation) steady-state area under the concentration-time curve, peak, and trough concentrations in patients with TED were 131 (± 30.9) mg∙h/mL, 643 (± 130) µg/mL, and 157 (± 50.6) µg/mL, respectively. Female patients had a 15% higher steady-state peak concentration but a similar steady-state area under the concentration-time curve vs male patients. No other covariates affected teprotumumab pharmacokinetics. No meaningful correlations between teprotumumab exposures and efficacy or safety parameters were observed. CONCLUSIONS: Teprotumumab pharmacokinetics was well characterized in patients with TED, and generally consistent with other IgG1 antibodies. Efficacy was consistent across the exposure range with a well-tolerated safety profile supporting the current dose regimen for patients with TED.

Teprotumumab for the Treatment of Active Thyroid Eye Disease.

BACKGROUND: Thyroid eye disease is a debilitating, disfiguring, and potentially blinding periocular condition for which no Food and Drug Administration-approved medical therapy is available. Strong evidence has implicated the insulin-like growth factor I receptor (IGF-IR) in the pathogenesis of this disease. METHODS: In a randomized, double-masked, placebo-controlled, phase 3 multicenter trial, we assigned patients with active thyroid eye disease in a 1:1 ratio to receive intravenous infusions of the IGF-IR inhibitor teprotumumab (10 mg per kilogram of body weight for the first infusion and 20 mg per kilogram for subsequent infusions) or placebo once every 3 weeks for 21 weeks; the last trial visit for this analysis was at week 24. The primary outcome was a proptosis response (a reduction in proptosis of ≥2 mm) at week 24. Prespecified secondary outcomes at week 24 were an overall response (a reduction of ≥2 points in the Clinical Activity Score plus a reduction in proptosis of ≥2 mm), a Clinical Activity Score of 0 or 1 (indicating no or minimal inflammation), the mean change in proptosis across trial visits (from baseline through week 24), a diplopia response (a reduction in diplopia of ≥1 grade), and the mean change in overall score on the Graves' ophthalmopathy-specific quality-of-life (GO-QOL) questionnaire across trial visits (from baseline through week 24; a mean change of ≥6 points is considered clinically meaningful). RESULTS: A total of 41 patients were assigned to the teprotumumab group and 42 to the placebo group. At week 24, the percentage of patients with a proptosis response was higher with teprotumumab than with placebo (83% [34 patients] vs. 10% [4 patients], P<0.001), with a number needed to treat of 1.36. All secondary outcomes were significantly better with teprotumumab than with placebo, including overall response (78% of patients [32] vs. 7% [3]), Clinical Activity Score of 0 or 1 (59% [24] vs. 21% [9]), the mean change in proptosis (-2.82 mm vs. -0.54 mm), diplopia response (68% [19 of 28] vs. 29% [8 of 28]), and the mean change in GO-QOL overall score (13.79 points vs. 4.43 points) (P≤0.001 for all). Reductions in extraocular muscle, orbital fat volume, or both were observed in 6 patients in the teprotumumab group who underwent orbital imaging. Most adverse events were mild or moderate in severity; two serious events occurred in the teprotumumab group, of which one (an infusion reaction) led to treatment discontinuation. CONCLUSIONS: Among patients with active thyroid eye disease, teprotumumab resulted in better outcomes with respect to proptosis, Clinical Activity Score, diplopia, and quality of life than placebo; serious adverse events were uncommon. (Funded by Horizon Therapeutics; OPTIC ClinicalTrials.gov number, NCT03298867, and EudraCT number, 2017-002763-18.).

Single-dose, subcutaneous recombinant phenylalanine ammonia lyase conjugated with polyethylene glycol in adult patients with phenylketonuria: an open-label, multicentre, phase 1 dose-escalation trial.

BACKGROUND: Phenylketonuria is an inherited disease caused by impaired activity of phenylalanine hydroxylase, the enzyme that converts phenylalanine to tyrosine, leading to accumulation of phenylalanine and subsequent neurocognitive dysfunction. Phenylalanine ammonia lyase is a prokaryotic enzyme that converts phenylalanine to ammonia and trans-cinnamic acid. We aimed to assess the safety, tolerability, pharmacokinetic characteristics, and efficacy of recombinant Anabaena variabilis phenylalanine ammonia lyase (produced in Escherichia coli) conjugated with polyethylene glycol (rAvPAL-PEG) in reducing phenylalanine concentrations in adult patients with phenylketonuria. METHODS: In this open-label, phase 1, multicentre trial, single subcutaneous injections of rAvPAL-PEG were given in escalating doses (0·001, 0·003, 0·010, 0·030, and 0·100 mg/kg) to adults with phenylketonuria. Participants aged 18 years or older with blood phenylalanine concentrations of 600 µmol/L or higher were recruited from among patients attending metabolic disease clinics in the USA. The primary endpoints were safety and tolerability of rAvPAL-PEG. Secondary endpoints were the pharmacokinetic characteristics of the drug and its effect on concentrations of phenylalanine. Participants and investigators were not masked to assigned dose group. This study is registered with ClinicalTrials.gov, number NCT00925054. FINDINGS: 25 participants were recruited from seven centres between May 6, 2008, and April 15, 2009, with five participants assigned to each escalating dose group. All participants were included in the safety population. The most frequently reported adverse events were injection-site reactions and dizziness, which were self-limited and without sequelae. Two participants had serious adverse reactions to intramuscular medroxyprogesterone acetate, a drug that contains polyethylene glycol as an excipient. Three of five participants given the highest dose of rAvPAL-PEG (0·100 mg/kg) developed a generalised skin rash. By the end of the study, all participants had developed antibodies against polyethylene glycol, and some against phenylalanine ammonia lyase as well. Drug concentrations peaked about 89-106 h after administration of the highest dose. Treatment seemed to be effective at reducing blood phenylalanine in all five participants who received the highest dose (mean reduction of 54·2% from baseline), with a nadir about 6 days after injection and an inverse correlation between drug and phenylalanine concentrations in plasma. Phenylalanine returned to near-baseline concentrations about 21 days after the injection. INTERPRETATION: Subcutaneous administration of rAvPAL-PEG in a single dose of up to 0·100 mg/kg was fairly safe and well tolerated in adult patients with phenylketonuria. At the highest dose tested, rAvPAL-PEG reduced blood phenylalanine concentrations. In view of the development of antibodies against polyethylene glycol (and in some cases against phenylalanine ammonia lyase), future studies are needed to assess the effect of repeat dosing. FUNDING: BioMarin Pharmaceutical.

CLCNKB-T481S and essential hypertension in a Ghanaian population.

OBJECTIVE: Prior to the discovery of chloride channel Kb with a variant threonine change to serine at position 481 (CLCNKB-T481S) there were no variants or clinical disorders associated with gain-of-function defects in thick ascending limb of the kidney channels or transporters. CLCNKB-T481S is a novel gain-of-function variant that has been associated with essential hypertension. This finding has not been replicated until our current study. In this study, we re-examined CLCNKB-T481S using a large homogenous population from Ghana, and coupled genetic analyses with the functional characterization of this polymorphism using a mammalian expression system. METHODS: We genotyped CLCNKB-T481S in four ethnically defined control populations and a homogenous cohort of normotensive and hypertensive Ghanaians. Functional analysis was performed by whole-cell patch-clamp recording of tsA201 cells (a cell line derived from the human renal cell line, HEK-293) transiently transfected with ClC-Kb and barttin. RESULTS: CLCNKB-T481S was found more commonly in the African and Caucasian-Americans when compared with the Asian and Hispanic American populations, having minor allele frequencies of 0.20, 0.15, 0.06 and 0.01 respectively. Additionally, CLCNKB-T481S was significantly associated with hypertension in Ghanaian males. In stratified logistic regression analysis with Ghanaian males, we observed a significant odds ratio of 3.29 (1.17-9.20 95% confidence interval, P=0.024) in the recessive model (TT versus AT&TT). Unlike previous results obtained in Xenopus oocytes, coexpression of CLCNKB-T481S with the obligatory accessory subunit barttin in tsA201 cells did not generate larger currents than coexpression of the wild-type allele. CONCLUSIONS: We conclude that CLCNKB-T481S is associated with essential hypertension in males within the Ghanaian population; however, further studies are needed to understand its sex and ethnic segregation as well as to identify cellular factors that account for the divergent functional expression of ClC-Kb-T481S plus barttin in Xenopus oocytes and mammalian cells.

A likelihood ratio test of population Hardy-Weinberg equilibrium for case-control studies.

Testing Hardy-Weinberg equilibrium (HWE) in the control group is commonly used to detect genotyping errors in genetic association studies. We propose a likelihood ratio test for testing HWE in the study population using both case and control samples. This test incorporates underlying association models. Another feature is that, when we infer the disease-genotype association, we explicitly incorporate HWE or a possible departure from Hardy-Weinberg equilibrium (DHWE) into the model. Our unified framework enables us to infer the disease-genotype association when a detected DHWE needs to be part of the model after causes for the DHWE are explored. Real data sets are used to illustrate the application of the methodology and its implication in genetic association studies. Our analysis and interpretation touch on issues such as genotyping errors, population selection, population stratification, or the study sampling plan, that all could be the cause of DHWE.

Dipeptidyl peptidase IV in angiotensin-converting enzyme inhibitor associated angioedema.

Angioedema is a potentially life-threatening adverse effect of angiotensin-converting enzyme inhibitors. Bradykinin and substance P, substrates of angiotensin-converting enzyme, increase vascular permeability and cause tissue edema in animals. Studies indicate that amino-terminal degradation of these peptides, by aminopeptidase P and dipeptidyl peptidase IV, may be impaired in individuals with angiotensin-converting enzyme inhibitor-associated angioedema. This case-control study tested the hypothesis that dipeptidyl peptidase IV activity and antigen are decreased in sera of patients with a history of angiotensin-converting enzyme inhibitor-associated angioedema. Fifty subjects with a history of angiotensin-converting enzyme inhibitor-associated angioedema and 176 angiotensin-converting enzyme inhibitor-exposed control subjects were ascertained. Sera were assayed for angiotensin-converting enzyme activity, aminopeptidase P activity, aminopeptidase N activity, dipeptidyl peptidase IV activity, and antigen and the ex vivo degradation half-lives of bradykinin, des-Arg(9)-bradykinin, and substance P in a subset. The prevalence of smoking was increased and of diabetes decreased in case versus control subjects. Overall, dipeptidyl peptidase IV activity (26.6+/-7.8 versus 29.6+/-7.3 nmol/mL per minute; P=0.026) and antigen (465.8+/-260.8 versus 563.1+/-208.6 ng/mL; P=0.017) were decreased in sera from individuals with angiotensin-converting enzyme inhibitor-associated angioedema compared with angiotensin-converting enzyme inhibitor-exposed control subjects without angioedema. Dipeptidyl peptidase IV activity (21.5+/-4.9 versus 29.8+/-6.7 nmol/mL per minute; P=0.001) and antigen (354.4+/-124.7 versus 559.8+/-163.2 ng/mL; P=0.003) were decreased in sera from cases collected during angiotensin-converting enzyme inhibition but not in the absence of angiotensin-converting enzyme inhibition. The degradation half-life of substance P correlated inversely with dipeptidyl peptidase IV antigen during angiotensin-converting enzyme inhibition. Environmental or genetic factors that reduce dipeptidyl peptidase IV activity may predispose individuals to angioedema.

Haplotype diversity in four genes (CLCNKA, CLCNKB, BSND, NEDD4L) involved in renal salt reabsorption.

OBJECTIVE: Differences exist among various populations with regards to hypertension prevalence, severity, progression and response to therapy. Such differences may be due to genetic or environmental factors. We characterized the genetic variation and haplotype diversity of four hypertension candidate genes (CLCNKA, CLCNKB, BSND, NEDD4L) in four different ethnic groups (Caucasian Americans, African-Americans, Han Chinese, and Mexican-Americans). METHODS: We genotyped 42 single nucleotide polymorphisms across the four genes in equal numbers of each ethnically defined population, then tested for linkage disequilibrium, computed allelic and haplotype frequencies, and compared data across the different ethnic groups. RESULTS: We identified significant genotype and allele frequency differences among ethnic groups. The strongest differences were observed between African-American and Mexican-Americans and between Caucasian and Mexican-Americans. In addition, haplotype blocks were defined for BSND, CLCNKA_B and NEDD4L in the four populations examined. Completely mismatched ('yin yang') haplotypes were also observed. We found that the number of inferred halpotypes varied gene to gene and in some instances between the populations for a given gene indicating substantial haplotype diversity. The haplotype diversity among the various ethnic populations observed in our study was greater than that reported in Perlegen database. CONCLUSIONS: Haplotype diversity in hypertension candidate genes has important implications for designing and evaluating candidate gene or genome-wide blood pressure association studies that consider these genes.

Functional BSND variants in essential hypertension.

BACKGROUND: Defects in the handling of renal salt reabsorption may contribute to interindividual differences in blood-pressure regulation and susceptibility to hypertension. Sodium chloride reabsorption in the thick ascending limb (TAL) is dependent in part on the chloride channel, ClC-Kb (encoded by CLCNKB), and its accessory subunit, barttin (encoded by BSND). METHODS: We investigated genetic variations in BSND in a screening population, and genotyped a homogenous cohort of normotensive and hypertensive Ghanaian subjects, in addition to four ethnically defined control populations. Functional consequences of the identified BSND variants were examined using a heterologous expression system. RESULTS: Three novel, nonsynonymous coding-sequence single-nucleotide polymorphisms were identified (V43I, E255Q, and G284D) in the screening population. BSND-V43I was identified in African American, Asian, and Hispanic subjects, with minor allele frequencies of 0.14, 0.18, and 0.01, respectively, but it was absent in the Caucasian population. BSND-E225Q and BSND-G284D were rare variants. Two of these variants (V43I and G284D) exhibited partial loss-of-function phenotypes when heterologously expressed with ClC-Kb chloride channels in cultured cells. In logistic regression analyses, we observed no association between hypertension and BSND-I43 in our study population. However, we did observe significant deviation from Hardy-Weinberg equilibrium in the normotensive population. CONCLUSIONS: We conclude that BSND-V43I, a common variant conferring partial loss of function, exhibits significant deviation from Hardy-Weinberg equilibrium in the Ghanaian normotensive control population. However, it does not independently confer protection against hypertension.

Molecular physiology of renal ClC chloride channels/transporters.

PURPOSE OF REVIEW: Recent findings relevant to the renal ClC chloride channels/transporters are reviewed with a focus on structure-function relationships, regulation of trafficking, role in blood pressure control, and pharmacology. RECENT FINDINGS: The ClC proteins include plasma membrane Cl channels and vesicular Cl/H exchangers. Recent experiments have revealed further details regarding the structure and mechanism of the permeation path. X-ray crystallographic and electrophysiological studies have identified two glutamate residues required for gated Cl movement and proton permeation in bacterial and two mammalian (ClC-4, ClC-5) ClC transporters. In renal ClC channels (ClC-Ka, ClC-Kb), both glutamate residues are replaced by valine, leading to speculation about critical differences between transporter and channel members of the ClC family. New information about the physiological regulation of renal ClC proteins has implicated the Nedd4 ubiquitin ligases and serum and glucocorticoid-inducible kinases in controlling functional levels of ClC-5 and ClC-K/barttin in renal cells. SUMMARY: ClC proteins are critical for many clinically relevant physiological events. New insights into fundamental structure-function relationships, mechanisms of ion translocation, cellular regulation, and roles in human disease have increased attention on ClC proteins as important potential therapeutic targets.