Discovering type I cis-AT polyketides through computational mass spectrometry and genome mining with Seq2PKS.

Type 1 polyketides are a major class of natural products used as antiviral, antibiotic, antifungal, antiparasitic, immunosuppressive, and antitumor drugs. Analysis of public microbial genomes leads to the discovery of over sixty thousand type 1 polyketide gene clusters. However, the molecular products of only about a hundred of these clusters are characterized, leaving most metabolites unknown. Characterizing polyketides relies on bioactivity-guided purification, which is expensive and time-consuming. To address this, we present Seq2PKS, a machine learning algorithm that predicts chemical structures derived from Type 1 polyketide synthases. Seq2PKS predicts numerous putative structures for each gene cluster to enhance accuracy. The correct structure is identified using a variable mass spectral database search. Benchmarks show that Seq2PKS outperforms existing methods. Applying Seq2PKS to Actinobacteria datasets, we discover biosynthetic gene clusters for monazomycin, oasomycin A, and 2-aminobenzamide-actiphenol.

"PROTAC" modified dihydroquinolizinones (DHQs) that cause degradation of PAPD-5 and inhibition of hepatitis A virus and hepatitis B virus, in vitro.

Dihydroquinolizinones (DHQs) that inhibit cellular polyadenylating polymerases 5 and 7 (PAPD5 & 7), such as RG7834, have been shown to inhibit both hepatitis A (HAV) and hepatitis B virus (HBV) in vitro and in vivo. In this report, we describe RG7834-based proteolysis-targeting chimeras (PROTACs), such as compound 12b, (6S)-9-((1-((2-(2,6-dioxopiperidin-3-yl)-1,3-dioxoisoindolin-4-yl)amino)-21-oxo-3,6,9,12,15,18-hexaoxa-22-azapentacosan-25-yl)oxy)-6-isopropyl-10-methoxy-2-oxo-6,7-dihydro-2H-pyrido[2,1-a]isoquinoline-3-carboxylic acid. The PROTAC DHQs described here inhibited an HAV reporter virus in vitro with an IC50 of 277 nM. Although the PROTAC DHQs were also inhibitory to HBV, their activities were substantially less potent against HBV in vitro, being in the 10 to 20 µM range, based on the reduction of HBsAg and HBV mRNA levels. Importantly, unlike RG7834, the incubation of cells in vitro with PROTAC DHQ 12b resulted in the degradation of PAPD5, as expected for a PROTAC compound, but curiously not PAPD7. PAPD5 polypeptide degradation was prevented when a proteasome inhibitor, epoxomicin, was used, indicating that proteasome mediated proteolysis was associated with the observed activities of 12b. Taken together, these data show that 12b is the first example of a PROTAC that suppresses both HAV and HBV that is based on a small molecule warhead. The possibility that it has mechanisms that differ from its parent compound, RG7834, and has clinical value, is discussed.

Identification of novel tetrahydroquinoxaline derived phenyl ureas as modulators of the hepatitis B virus nucleocapsid assembly.

A key step of hepatitis B virus (HBV) replication is the selective packaging of pregenomic RNA (pgRNA) by core protein (Cp) dimers, forming a nucleocapsid where the reverse transcriptional viral DNA replication takes place. One approach in the development of new anti-HBV drugs is to disrupt the assembly of HBV nucleocapsids by misdirecting Cp dimers to assemble morphologically normal capsids devoid of pgRNA. In this study, we built upon our previous discovery of benzamide-derived HBV capsid assembly modulators by exploring fused bicyclic scaffolds with an exocyclic amide that is ß, γ to the fused ring, and identified 1,2,3,4-tetrahydroquinoxaline derived phenyl ureas as a novel scaffold. Structure-activity relationship studies showed that a favorable hydrophobic substitution can be tolerated at the 2-position of the 1,2,3,4-tetrahydroquinoxaline core, and the resulting compound 88 demonstrated comparable or improved antiviral potencies in mouse and human hepatocyte-derived HBV-replicating cell lines compared to our previously reported benzamide compound, 38017 (8). In addition, a novel bis-urea series based on 1,2,3,4-tetrahydroquinoxaline was also found to inhibit HBV DNA replication with sub-micromolar EC50 values. The mode of action of these compounds is consistent with specific inhibition of pgRNA encapsidation into nucleocapsids in hepatocytes.

The Marine Compound Tartrolon E Targets the Asexual and Early Sexual Stages of Cryptosporidium parvum.

New therapeutic agents for cryptosporidiosis are a critical medical need. The marine organic compound, tartrolon E (trtE), is highly effective against multiple apicomplexan parasites, including Cryptosporidium. Understanding the mechanism of action of trtE is required to advance in the drug development pipeline. Here, we validate using Nluc C. parvum parasites for the study of trtE and pinpoint the life stage targeted by trtE. Results show that trtE kills Nluc and wild type C. parvum with equal efficiency, confirming the use of the Nluc C. parvum to study this compound. Results revealed that trtE kills the parasite within an hour of treatment and while the compound has no effect on viability of sporozoites, trtE does inhibit establishment of infection. Targeting treatment at particular life cycle stages demonstrated that trtE is effective against asexual of the parasite but has reduced efficacy against mature sexual stages. Gene expression analysis shows that trtE inhibits the early sexual stage of the parasite. Results from these studies will aid the development of trtE as a therapeutic for cryptosporidiosis.

4-Oxooctahydroquinoline-1(2H)-carboxamides as hepatitis B virus (HBV) capsid core protein assembly modulators.

Hepatitis B virus (HBV) core protein, the building block of the HBV capsid, plays multiple roles in viral replication, and is an attractive target for development of antiviral agents with a new mechanism of action. In addition to the heteroaryldihydropyrimidines (HAPs), sulfamoylbenzamides (SBAs), dibenzothiazepine derivatives (DBTs), and sulfamoylpyrrolamides (SPAs) that inhibit HBV replication by modulation of viral capsid assembly and are currently under clinical trials for the treatment of chronic hepatitis B (CHB), other chemical structures with activity to modulate HBV capsid assembly have also been explored. Here we describe our continued optimization of a benzamide originating from our high throughput screening. A new bicyclic carboxamide lead featuring an electron deficient non-planar core structure was discovered. Evaluations of its ADMET (absorption, distribution, metabolism, excretion and toxicity) and pharmacokinetic (PK) profiles demonstrate improved metabolic stability and good bioavailability.

A comparison of outcomes between open and endovascular arteriovenous access creation for hemodialysis.

OBJECTIVE: Preliminary outcomes for percutaneous endovascular autogenous access (endoAVF) have shown promising results; however, comparisons with surgical cohorts in dialysis populations are lacking. This study compares autogenous arteriovenous access created with the EverlinQ endoAVF system with accesses created by conventional surgical technique with respect to functional and patency related outcomes. METHODS: This is a multicenter, retrospective review of autogenous arteriovenous accesses entered into a prospective database. Patients receiving radiocephalic, brachiocephalic, or endoAVF arteriovenous accesses between 2014 and 2019 were included. Autogenous access maturation, primary patency, secondary patency, steal syndrome, and reinterventions were collected and analyzed using standard statistical and survival analyses. RESULTS: A total of 369 accesses were created during the study period, including 61 endovascular accesses, 171 radiocephalic accesses, and 137 brachiocephalic accesses (median follow-up, 17 months; range, 1-71 months). Maturation failure at the end of follow-up was 27% ± 6%, 27% ± 5%, and 18% ± 4% for endovascular, radiocephalic, and brachiocephalic accesses, respectively (P = .049 for brachiocephalic vs endovascular accesses). Primary patencies at 12 and 24 months were 42% ± 5% and 32% ± 7% for endovascular accesses, 43% ± 4% and 24% ± 4% for radiocephalic accesses, and 42% ± 4% and 29% ± 4% for brachiocephalic accesses (P = .906). Secondary patencies at 12 and 24 months were 68% ± 6% and 60% ± 7% for endovascular accesses, 75% ± 3% and 67% ± 4% for radiocephalic accesses, and 91% ± 3% and 81% ± 4% for brachiocephalic accesses (P = .006 for brachiocephalic vs endovascular accesses). There were no statistically significant differences in ischemic steal syndrome (3.3%, 4.1%, and 8.0%; P = .229) or total reinterventions/year (1.0 ± 3.1, 0.9 ± 1.8, and 1.2 ± 1.8; P = .289) for endovascular, radiocephalic, or brachiocephalic arteriovenous accesses, respectively. CONCLUSIONS: EndoAVF compare favorably with respect to maturation and patency compared with surgically created accesses in a real-world cohort. Outcomes and reintervention rates are similar to conventional radiocephalic arteriovenous accesses, but are inferior with respect to patency and maturation to brachiocephalic accesses.

Percutaneous arteriovenous fistula creation with the 4F WavelinQ EndoAVF System.

BACKGROUND: Percutaneous devices for creation of native arteriovenous fistulae offer an alternative to traditional open surgical techniques. The 4F WavelinQ EndoAVF System was developed as a lower profile alternative to facilitate access through smaller vessels and minimize access site complications; The current report is the original first experience of this device, assessing outcome in 120 patients followed for 6 months. METHODS: The use of the 4F WavelinQ system in three studies, EASE (32 patients), EASE-2 (24 patients), and the EU postmarket clinical follow-up study (64 patients) was aggregated and analyzed. Patients were followed with duplex ultrasound at discharge and follow-up visits at 1, 3, and 6 months. Primary, assisted primary, and secondary patency rates were evaluated as Kaplan-Meier estimates and standard errors. Time to maturity and time to successful cannulation were defined as the mean ± standard deviation days from the procedure in patients enrolled on dialysis. RESULTS: Procedural success was achieved in 116 patients (96.7%). Primary, assisted-primary, and secondary 6-month patency rates were 71.9% ± 4.5%, 80.7% ± 4.1%, and 87.8% ± 3.3%, respectively. Time to maturity averaged 41 ± 17 days. Time to successful cannulation averaged 68 ± 51 days. Device-related serious adverse events were reported in 3 of 120 patients (2.5%) and procedure-related serious adverse events occurred in 7 of 120 patients (5.8%). Arterial or venous access complications were not reported in any of the patients. Access circuit reinterventions were performed in 23 patients (19.2%), split between those performed for EndoAVF maturation (13/120 [10.8%]) and maintenance (11/120 [9.2%]). CONCLUSIONS: Percutaneous creation of native dialysis fistulae with the 4F WavelinQ EndoAVF System is safe and effective, with favorable durability and a low rate of serious complications and reinterventions through 6-month follow-up. Use of the 4F device allows for percutaneous fistula creation between the radial artery and radial vein or the ulnar artery and ulnar vein. These findings suggest that the 4F device is a useful percutaneous alternative to open surgical AVF or endovascular AVF with larger bore devices.

Identification of a 3-ß-homoalanine conjugate of brusatol with reduced toxicity in mice.

Brusatol, a quassinoid natural product, is effective against multiple diseases including hematologic malignancies, as we reported recently by targeting the PI3Kγ isoform, but toxicity limits its further development. Herein, we report the synthesis of a series of conjugates of brusatol with amino acids and short peptides at its enolic hydroxyl at C-3. A number of conjugates with smaller amino acids and peptides demonstrated activities comparable to brusatol. Through in vitro and in vivo evaluations, we identified UPB-26, a conjugate of brusatol with a L- ß-homoalanine, which exhibits good chemical stability at physiological pH's (SGF and SIF), moderate rate of conversion to brusatol in both human and rat plasmas, improved mouse liver microsomal stability, and most encouragingly, enhanced safety compared to brusatol in mice upon IP administration.

The Inhibitory Effect of Plant Extracts on Growth of the Foodborne Pathogen, Listeria monocytogenes.

Listeria monocytogenes is a foodborne pathogen responsible for about 1600 illnesses each year in the United States (US) and about 2500 confirmed invasive human cases in European Union (EU) countries. Several technologies and antimicrobials are applied to control the presence of L. monocytogenes in food. Among these, the use of natural antimicrobials is preferred by consumers. This is due to their ability to inhibit the growth of foodborne pathogens but not prompt negative safety concerns. Among natural antimicrobials, plant extracts are used to inactivate L. monocytogenes. However, there is a large amount of these types of extracts, and their active compounds remain unexplored. The aim of this study was to evaluate the antibacterial activity against L. monocytogenes of about 800 plant extracts derived from plants native to different countries worldwide. The minimal inhibitory concentrations (MICs) were determined, and scanning electron microscopy (SEM) was used to verify how the plant extracts affected L. monocytogenes at the microscopic level. Results showed that 12 of the plant extracts had inhibitory activity against L. monocytogenes. Future applications of this study could include the use of these plant extracts as new preservatives to reduce the risk of growth of pathogens and contamination in the food industry from L. monocytogenes.

Galtonosides A-E: Antiproliferative and Antiplasmodial Cholestane Glycosides from Galtonia regalis.

An extract of Galtonia regalis from the Natural Products Discovery Institute showed moderate antiplasmodial activity, with an IC50 value less than 1.25 µg/mL. The two known cholestane glycosides 1 and 2 and the five new cholestane glycosides galtonosides A-E (3-7) were isolated after bioassay-directed fractionation. The structures of the new compounds were determined by interpretation of their NMR and mass spectra. Among these compounds, galtonoside B (4) displayed the most potent antiplasmodial activity, with an IC50 value of 0.214 µM against the drug-resistant Dd2 strain of Plasmodium falciparum.

Anibamine and Its Analogues: Potent Antiplasmodial Agents from Aniba citrifolia.

In our continuing search for novel natural products with antiplasmodial activity, an extract of Aniba citrifolia was found to have good activity, with an IC50 value less than 1.25 µg/mL. After bioassay-directed fractionation, the known indolizinium alkaloid anibamine (1) and the new indolizinium alkaloid anibamine B (2) were isolated as the major bioactive constituents, with antiplasmodial IC50 values of 0.170 and 0.244 µM against the drug-resistant Dd2 strain of Plasmodium falciparum. The new coumarin anibomarin A (3), the new norneolignan anibignan A (5), and six known neolignans (7-12) were also obtained. The structures of all the isolated compounds were determined based on analyses of 1D and 2D NMR spectroscopic and mass spectrometric data, and the absolute configuration of anibignan A (5) was assigned from its ECD spectrum. Evaluation of a library of 28 anibamine analogues (13-40) indicated that quaternary charged analogues had IC50 values as low as 58 nM, while uncharged analogues were inactive or significantly less active. Assessment of the potential effects of anibamine and its analogues on the intraerythrocytic stages and morphological development of P. falciparum revealed substantial activity against ring stages for compounds with two C-10 side chains, while those with only one C-10 side chain exhibited substantial activity against trophozoite stages, suggesting different mechanisms of action.

Endovascular Creation of Arteriovenous Fistulae for Hemodialysis Access with a 4 Fr Device: Clinical Experience from the EASE Study.

BACKGROUND: The use of arteriovenous fistula (AVF) is hampered by long surgical wait times, slow maturation, and upwards of 60% that do not mature. We describe our clinical experience in using a system with a 4F catheter profile for endovascular AVF creation in patients on hemodialysis. METHODS: This was a multioperator, single-center, single-arm, prospective study intended to evaluate safety and efficacy of a 4 Fr endovascular AVF (endoAVF) system for the creation of vascular access in hemodialysis patients. The study was performed after institutional review board approval at Italian Hospital (Asuncion, Paraguay). Patients were followed up at regular intervals through 6 months to determine procedural, maturation, and cannulation success as well as intervention rate and patency. RESULTS: From May to November 2016, 32 patients underwent the endoAVF procedure with no device-related adverse events. An endoAVF was successfully created in the proximal forearm for all 32 patients (20 between the radial artery and radial vein; 12 between the ulnar artery and ulnar vein). Wrist access was used for 72% (23/32) of the procedures for the arterial catheter and 59% (19/32) of the procedures for the venous catheter. The device successfully created an endoAVF in every patient for a technical success rate of 100% (32/32). The device- or procedure-related serious adverse event rate was 3% (1/32); one patient experienced a venous guidewire perforation successfully managed with a stent graft. Primary and cumulative patency rates through 6 months were 83% and 87%, respectively, with an intervention rate of 0.21 per patient-year. Physiological suitability, as defined by target flow rates ≥500 ml/min and cannulation vessel diameters ≥4 mm, was achieved in 91% (29/32) of patients by 90 days. Successful 2-needle cannulation was achieved in 78% (21/27) by 90 days, with mean time to cannulation of 43 ± 14 days. Functional cannulation, as defined by successful 2-needle cannulation for two-thirds of the dialysis sessions within 1 month, was achieved in 95% (20/21) of the patients who were successfully cannulated for an overall rate of 74% (20/27). All patients who achieved functional cannulation had their central venous catheters (CVCs) removed before the 90-day follow-up for a CVC removal rate of 74% (20/27). CONCLUSIONS: The 4 Fr endoAVF system allowed for multiple access and fistula creation site options to tailor the procedure to individual patient anatomy. Furthermore, the outcomes are comparable to previous generation endoAVF technology, with a potentially improved safety profile because of the use of arteries at the wrist for access.

Antiplasmodial flavanones and a stilbene from Carpha glomerata.

Bioassay-guided fractionation of an extract of Carpha glomerata (Cyperaceae) led to the isolation of seven compounds. Compounds 1 (carphorin A), 3 (carphorin C), 4 (carphorin D), and 5 (carphabene) are new compounds, and compound 2 (8-(3″-hydroxyisoamyl)-naringenin) was isolated for the first time as a natural product. All structures were elucidated based on analyses of their HR-ESIMS and 1D and 2D NMR data. Compounds 1, 2, and 6, which have prenyl or hydroxyprenyl side chains, exhibited antiplasmodial activities with IC50 values of 5.2 ±â€¯0.6, 3.4 ±â€¯0.4, and 6.7 ±â€¯0.8 µM against the drug-resistant Dd2 strain of Plasmodium falciparum. In addition the prenylated stilbene 5 also showed good activity, with IC50 5.8 ±â€¯0.7 µM.

Antiplasmodial Chromanes and Chromenes from the Monotypic Plant Species Koeberlinia spinosa.

Nine new compounds containing either a chromane or chromene ring moiety were isolated from the monotypic plant Koeberlinia spinosa. Compounds 1-4 are chromanes with all possible E and Z isomers of the isoprenoid side chain, with compound 5 a methylated derivative of 1. Compounds 6 and 7 were assigned as diastereomeric cyclized derivatives of 2 and were probably artifacts formed during the extraction or the isolation processes. Compounds 8 and 9 were characterized as new chromenes. Structure elucidation of 1-9 was conducted via 1D and 2D NMR spectroscopic data interpretation, and absolute configurations were determined by ECD spectroscopic analysis. Compounds 2, 5, 6, and 7 had weak antiplasmodial activity, while none of the compounds exhibited antiproliferative activity. The isolation, structure elucidation, and biological evaluation of these compounds are presented.

Antiplasmodial alkaloids from bulbs of Amaryllis belladonna Steud.

A bioassay-guided fractionation and chemical investigation of Amaryllis belladonna Steud. bulbs resulted in the isolation and identification of the new crinane alkaloid 1,4-dihydroxy-3-methoxy powellan (1), along with the 3 known crinane alkaloids 2-4 and the two lycorane alkaloids 5-6. The structures were elucidated by interpretation of combined HR-ESIMS, CD and 2D NMR spectroscopic data. Among these isolated compounds the lycorane-type alkaloid acetylcaranine (5) exhibited strong antiplasmodial activity, while compounds 3 and 4 were moderately active, and compounds 1 and 6 were inactive.

Canvass: A Crowd-Sourced, Natural-Product Screening Library for Exploring Biological Space.

Natural products and their derivatives continue to be wellsprings of nascent therapeutic potential. However, many laboratories have limited resources for biological evaluation, leaving their previously isolated or synthesized compounds largely or completely untested. To address this issue, the Canvass library of natural products was assembled, in collaboration with academic and industry researchers, for quantitative high-throughput screening (qHTS) across a diverse set of cell-based and biochemical assays. Characterization of the library in terms of physicochemical properties, structural diversity, and similarity to compounds in publicly available libraries indicates that the Canvass library contains many structural elements in common with approved drugs. The assay data generated were analyzed using a variety of quality control metrics, and the resultant assay profiles were explored using statistical methods, such as clustering and compound promiscuity analyses. Individual compounds were then sorted by structural class and activity profiles. Differential behavior based on these classifications, as well as noteworthy activities, are outlined herein. One such highlight is the activity of (-)-2(S)-cathafoline, which was found to stabilize calcium levels in the endoplasmic reticulum. The workflow described here illustrates a pilot effort to broadly survey the biological potential of natural products by utilizing the power of automation and high-throughput screening.

Endovascular Proximal Forearm Arteriovenous Fistula for Hemodialysis Access: Results of the Prospective, Multicenter Novel Endovascular Access Trial (NEAT).

BACKGROUND: Hemodialysis arteriovenous fistulas (AVFs) are suboptimally used primarily due to problems with maturation, early thrombosis, and patient nonacceptance. An endovascular approach to fistula creation without open surgery offers another hemodialysis vascular access option. STUDY DESIGN: Prospective, single-arm, multicenter study (Novel Endovascular Access Trial [NEAT]). SETTINGS & PARTICIPANTS: Consecutive adult non-dialysis-dependent and dialysis-dependent patients referred for vascular access creation at 9 centers in Canada, Australia, and New Zealand. INTERVENTION: Using catheter-based endovascular technology and radiofrequency energy, an anastomosis was created between target vessels, resulting in an endovascular AVF (endoAVF). OUTCOMES: Safety, efficacy, functional usability, and patency end points. MEASUREMENTS: Safety as percentage of device-related serious adverse events; efficacy as percentage of endoAVFs physiologically suitable (brachial artery flow ≥ 500mL/min, vein diameter ≥ 4mm) for dialysis within 3 months; functional usability of endoAVFs to provide prescribed dialysis via 2-needle cannulation; primary and cumulative endoAVF patencies per standardized definitions. RESULTS: 80 patients were enrolled (20 roll-in and 60 participants in the full analysis set; the latter are reported). EndoAVFs were created in 98% of participants; 8% had a serious procedure-related adverse event (2% device related). 87% were physiologically suitable for dialysis (eg, mean brachial artery flow, 918mL/min; endoAVF vein diameter, 5.2mm [cephalic vein]). EndoAVF functional usability was 64% in participants who received dialysis. 12-month primary and cumulative patencies were 69% and 84%, respectively. LIMITATIONS: Due to the unique anatomy and vessels used to create endoAVFs, this was a single-arm study without a surgical comparator. CONCLUSIONS: An endoAVF can be reliably created using a radiofrequency magnetic catheter-based system, without open surgery and with minimal complications. The endoAVF can be successfully used for hemodialysis and demonstrated high 12-month cumulative patencies. It may be a viable alternative option for achieving AVFs for hemodialysis patients in need of vascular access.

Cytotoxic oplopane sesquiterpenoids from Arnoglossum atriplicifolium.

Pale Indian plantain (Arnoglossum atriplicifolium (L.) H. Rob.) is a plant with traditional medicinal usage among the Cherokee Native American tribe for treating cancer. Two oplopane sesquiterpenoids were isolated from an extract of A. atriplicifolium from Western North Carolina. The compounds were isolated by bioassay-guided fractionation using an MCF-7 breast tumour cell line assay. The known compound (1S,6R,7R,8R)-1-acetoxy-6,7-diangeloxy-8,10-epoxy-2-oxo-oplopa-3,14Z,11,12-dien-13-al (1) had an EC50 value of 9.0 µM against MCF-7 cells, while the new compound (1S,3R,6R,7R,8R,11S)-1-acetoxy-6,7-diangeloxy-8,10,11,13-bisepoxyoplopan-2-one (2) had an EC50 value of 96 µM. The compounds were characterised by 1D and 2D NMR spectroscopy and by comparison with literature values in the case for 1. Based on NOESY analysis, a correction of the relative configuration for 1 is presented. The presence of these compounds may help to explain the folk remedy usage of this plant as an anticancer agent.

Risk factors associated with arteriovenous fistula failure after first radiologic intervention.

PURPOSE: Improving arteriovenous fistula (AVF) patency is an integral part of the care of hemodialysis patients, often requiring procedures such as percutaneous transluminal angioplasty (PTA). However, these interventions may fail to reduce AVF dysfunction and failure. The purpose of this study was to determine predictive factors for subsequent AVF failure post-PTA. METHODS: Data from 155 consecutive AVFs in 155 patients at a single institution who had undergone a first PTA and had at least 1 year of follow-up data were analyzed. Using survival analysis, we assessed primary and secondary patency, and identified predictive factors taking into account competing risks. RESULTS: Of the 155 patients, 52% required multiple subsequent PTAs; 32% of the AVFs were not in use prior to the first PTA. At first PTA, 83% had outflow vein stenosis (OVS), 26% had multiple stenoses and 43% of stenoses were longer than 2 cm. During follow-up, 1-, 2-, 3-year postintervention primary patency was 41%, 32%, 32% and secondary patency was 80%, 71% and 68%. AVFs with stenoses greater than 2 cm or OVS were at higher risk of requiring multiple PTAs (p = 0.04, 0.006). Factors associated with requiring a second PTA included stenosis greater than 2 cm (hazard ratio (HR) = 1.8, 95% confidence interval (CI) = 1.2-2.9), OVS (HR = 2.5, 95% CI = 1.1-5.4) and primary renal diagnosis of diabetes or renal vascular diseases (HR = 1.8, 95% CI = 1.1-2.9); after adjustments for competing risks, OVS and stenosis length remained associated with requiring subsequent PTAs. CONCLUSIONS: The location and size of the AVF stenosis at first PTA appear to be consistent factors associated with worse postintervention primary patency.