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Multicenter phase I/II trial of the safety of allogeneic endothelial cell implants after the creation of arteriovenous access for hemodialysis use: The V-HEALTH study

      Objectives

      Vascular access dysfunction is the major cause of morbidity in patients on hemodialysis to treat end stage renal disease. Preclinical studies have demonstrated that the perivascular placement of implants containing allogeneic aortic endothelial cells (Vascugel) reduces thrombosis, inflammation, stenosis and increases lumen diameter in porcine models of arteriovenous fistulae (AVF) and arteriovenous grafts (AVG). We conducted a phase I/II clinical study to investigate the safety of Vascugel placement around the surgical anastomotic sites of newly constructed dialysis accesses.

      Methods

      From July 2006 to August 2006, eight patients (4 AVG, 4 AVF) were treated with two Vascugel sponges at the venous anastomosis in the open–label phase I trial. From January 2007 to August 2007 57 patients (30 AVG and 27 AVF) were randomized in a 2:1 fashion to receive either Vascugel or control matrices (placebo) at surgery. The phase II AVG patients had sponges placed at both the venous and arterial anastomoses. All patients were followed for 24 weeks. The primary objective of the study was to demonstrate the safety (incidence of infection, intervention, and thrombosis) of Vascugel compared with placebo within 30 days post-surgery. Secondary endpoints included assessments of patency, lumen diameter, and immunologic sensitization to human leukocyte antigens (HLA) determined by measurement of panel reactive antibodies (PRA).

      Results

      There was no difference in early complication rates between the Vascugel and placebo groups at 4 weeks (10.9% vs 21.1%, respectively). There were no statistically significant differences in primary or assisted primary patency between the intent to treat groups at 24 weeks. Vascugel treated AVG had a primary patency rate of 38% and an assisted primary patency rate of 72% (vs 23% and 58%, respectively, for placebo). Vascugel treated AVF had a primary patency rate of 60% at 24 weeks and an assisted primary patency rate of 96% (vs 62% and 88%, respectively, for placebo). A greater than 30% increase in PRA was detected in 9 of the 46 (19.5%) Vascugel treated patients and one of the 19 (5.2%) placebo patients (P = .26) and was not associated with any evidence of local or systemic complications.

      Conclusions

      Targeted local therapy with perivascular, allogeneic endothelial cells is a safe and novel therapeutic approach that may be ideally suited to control the response to injury at surgical anastomoses. Larger randomized trials are needed to determine if Vascugel can prolong AVG or AVF patency.
      Vascular access failure is a major complication in patients receiving hemodialysis to treat end stage renal disease (ESRD).
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      Methods

       Study design

      A single protocol was developed which encompassed a dual study approach, treatment of AVG and AVF. The Vascular intimal Hyperplasia: Extending Arterial and venous patency, Limiting vascular Trauma, and inhibiting Hyperplasia while re-establishing vascular health (V-HEALTH) protocol was a two-stage (phase I and II) design within each of the surgical treatment options. An initial limited phase I safety and feasibility trial of Vascugel enrolled four patients in each group, AVF and AVG (total of eight patients at three participating sites), with each patient receiving two implants placed adjacent to the venous anastomosis (Fig 1). The phase I patients were followed for 30 days, and their data were reviewed by an independent data monitoring committee (DMC, Appendix, online only), which recommended proceeding to the phase II portion of the study. The phase II study was a randomized, double-blind, study in patients undergoing creation of AVG or AVF. Patients were randomized 2:1 to receive either Vascugel or control matrices (placebo) immediately prior to surgery, using a computer-generated permuted block randomization. The proposed sample size of 30 patients in each of the AVG and AVF groups (20 Vascugel and 10 placebo) was considered appropriate for an exploratory phase I/II study to collect necessary information regarding the safety and activity of the investigational product for this indication.
      Figure thumbnail gr1
      Fig 1Schematic and images of sponge placement. A, Diagram of placement of two 1 × 4 × 0.3 cm sponges (arrows) adjacent to venous anastomosis and outflow segment in AVF patients. B, Diagram of placement of two 1 × 4 × 0.3 cm sponges adjacent to venous anastomosis and outflow segment (phase I and II) and one 1 × 4 × 0.3 cm sponge adjacent to arterial anastomosis (phase II) in AVG patients. C, Image of a 1 × 4 × 0.3 cm sponge used in the clinical trials. D, Image of placement around venous anastomosis and outflow vein in an AVG subject.

       Study patients

      The institutional review board at each participating site approved the protocol and all study patients provided written informed consent. Individuals undergoing placement of new upper extremity fistula or grafts were eligible for enrollment in V-HEALTH if they were currently receiving maintenance therapy of ESRD with hemodialysis. Major exclusion criteria included patients on an active transplant list, more than one prior access in the target limb, chronic, systemic immunosuppressive therapy, CBC hematocrit <24%, platelet count <100 × 103/μL, white blood cell count < 4000/μL or > 12,000 μL, bleeding disorder or hypercoagulable condition, hepatitis B, hepatitis C, HIV/AIDS, two times lab control value of albumin, ALT (SGPT), alkaline phosphatase, AST/(SGOT) or total bilirubin, allergy to bovine or porcine products, allergy to collagen/gelatin products, panel reactive antibodies (PRA) >30%, pregnant, and current IV drug use. Patients also underwent preoperative vein mapping to identify blood vessels in the upper extremities that were suitable for AVG or AVF creation.

       Investigational product

      Vascugel is being developed as a novel cell therapy product for use following vascular access surgery and is composed of allogeneic aortic EC cultured in a gelatin (Gelfoam; Pfizer, New York, NY) matrix. The human EC, isolated from the aorta of single cadaver donors, are obtained from Lonza (Walkersville, Md) and tested extensively for endothelial cell purity; biological function (assays for secretion of HS, TGF-β1 and fibroblast growth factor, uptake of acetylated LDL as well the ability to inhibit cultured SMC proliferation), the presence of bacteria, fungi, known human pathogens, and other adventitious agents according to FDA proposed rules.
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      The cells are cryopreserved for later expansion and formulation in gelatin sponges. Vascugel was supplied to the clinical sites as sponges having dimensions of 1.0 × 4.0 × 0.3 cm. Prior to shipment to the clinic, in vitro cohorts of Vascugel sponges were assayed for cell number, viability, and secreted levels of HS and TGF-β1. Each sponge contained approximately 1.23 × 106 human aortic EC (≥90% viability) secreting levels of 0.69 ± 0.05 μg/mL/d HS and 566 ± 29 pg/mL/d TGF- β1. Placebo sponges were packaged identically and were of the same shape and size, but lacked EC.

       Study procedures

      Study patients underwent planned creation of surgical AV access using standard surgical and anesthetic techniques per practice of the local treating physicians. Sponges were placed at the conclusion of the procedure after all bleeding at the sites has been controlled and immediately before surgical closure. For all patients, implant administration consisted of two sponges placed adjacent to the venous anastomosis and outflow vein. Phase II AVG patients received a third sponge adjacent to the arterial anastomosis, for a total of three implanted sponges. Patients received implant application at the time of access placement and no repeat applications occurred during this study. All phase II study patients, investigators, and other members of the study team were blinded to treatment assignment. The use of medications such as antibiotics, heparin, and antithrombotics was at the discretion of the treating physician and not specified in the protocol.
      Following surgery, patients were seen and examined at 2, 4, 12, and 24 weeks to evaluate healing, access related complications, adverse reactions, hospitalizations, patency, and maturation. PRA were measured from serum samples obtained at screening, 2, 4, 12, and 24 weeks. Serum samples were screened for PRA using the LABScreen (One Lambda, Inc, Canoga Park, Calif) Luminex platform. The LABScreen Luminex method detects human leukocyte antigen (HLA) antibodies using flow cytometric technology. A number of exploratory analyses were also performed to evaluate vein remodeling in AVF by color-flow duplex ultrasound at 2, 4, 12, and 24 weeks and lumen diameter in AVG and AVF by protocol-mandated angiography at 12 and 24 weeks for AVG and 24 weeks for AVF (Appendix, online only). After the 24-week evaluation, patients were offered the option of entering an extension study, where safety and efficacy will continue to be assessed every 24 weeks for approximately 2.5 years (144 weeks).

       Safety monitoring and study outcomes

      The primary outcome of the trial was safety, assessed by the incidence of infection (local or systemic), need for revision, and development of thrombosis within 30 days after surgery. The medical monitor was responsible for reviewing the safety data for each patient enrolled in the study on an ongoing basis, and a Pharmacovigilance group (Appendix, online only) forwarded all serious adverse event (SAE) reports to the DMC. Secondary outcomes were loss of primary and assisted primary patency.
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      • et al.
      Recommended standards for reports dealing with arteriovenous hemodialysis accesses.
      In an attempt to focus the patency analysis to within the treatment zone, “anastomotic patency” was assessed by a blinded adjudication committee (Appendix, online only), which consisted of an interventional radiologist, a vascular surgeon, and a nephrologist. This committee used operative notes, radiology reports, and primary review of angiograms to determine if an access failure could be specifically determined to be related or unrelated to the treated anastomotic zone. If the occlusion or causative lesion was determined to be in the treatment area, or if no clear evidence existed to assign a culprit lesion, then the determination was made that an event occurred. If a specific causative lesion could be assigned outside of the treatment zone, then the determination was that an event did not occur. Additional secondary outcomes were measurements of immunological sensitization, defined as an increase in HLA antibodies using PRA testing after surgery >30% compared with screening levels; and time to first access use calculated as the time from the access placement to the first successful hemodialysis use.

       Statistical methods

      The primary and secondary safety outcome analyses were performed on all enrolled patients (safety population). The secondary efficacy outcome analyses were performed on the intent-to-treat population (ITT), which included all randomized patients who were confirmed to have received Vascugel or placebo, excluding the four AVG patients enrolled in the phase I portion of the study because they received a different dose of product. Secondary efficacy outcomes were also analyzed for the modified intent-to-treat population (mITT), which was prespecified in the protocol and defined in accordance with The National Kidney Foundation Kidney Disease Outcomes Quality Initiative (KDOQI) guidelines as the subset of ITT patients who had successful hemodialysis initiation within the first 2 months of creation of the AVG or within the first 3 months of creation of the AVF. The primary endpoint of infection (local wound or systemic), need for revision, and development of thrombosis within 30 days, the secondary efficacy endpoint of positive lumen diameter changes at the anastomotic sites for graft patients, and the secondary safety endpoint of PRA >30% , were analyzed as discrete outcomes. The two treatment groups were compared using Fisher exact test. The secondary safety endpoint (PRA) and the angiogram change analyses at each location compared the two treatment groups using a Wilcoxon rank sum test.
      Secondary endpoint patency rates were described in a continuous fashion, from the day of access placement until the day of intervention or abandonment (an event) or the subject's last day on study (censored). Overall duration of patency was analyzed using the Kaplan-Meier product limit method. Results were summarized descriptively using Q25, median (95% CI), and Q75. Time to first use was calculated as the time from the access placement to the first successful hemodialysis use and analyzed in the same fashion as for patency durations. For all secondary time-to-event endpoints inferential comparisons were made using the log-rank statistic.

      Results

       Patient population

      A total of 109 patients were screened with eight enrolled in the phase I portion of the study and 57 randomized, 38 to receive Vascugel and 19 to receive placebo (Fig 2), in the phase II portion of the study. Baseline characteristics in the two treatment groups were similar (Table I). Perioperative antibiotics were given in 52.2% of Vascugel patients and in 52.6% of placebo patients. Heparin was administered during the surgical procedure in 36.9% of Vascugel patients and in 26.3% of placebo patients. The number of patients who died, were lost to follow-up, or withdrew consent during the course of the trial was eight (17.4%) in the Vascugel group and two (10.5%) in the placebo group. The target of 2:1 randomization was achieved in the AVG group with a total of 23 patients in the Vascugel group and 11 patients in the placebo group. Randomization in the AVF group was 3:1 with 23 patients in the Vascugel group and eight patients in the placebo group. The imbalance in randomization between study arms occurred secondary to several patients undergoing AVG placement based on intraoperative findings, after having been initially assigned to the planned AVF group.
      Figure thumbnail gr2
      Fig 2Phase I and phase II combined participant flow. Secondary outcome analysis for the AVG population was performed on 19 Vascugel patients in the ITT group and 14 in the mITT group; 11 placebo patients in the ITT group and eight in the mITT group. Two of the 23 Vascugel (8.7%) and two of the 11 placebo (18%) AVG were never used for dialysis during the 24-week follow-up period. Secondary outcome analysis for the AVF population was performed on 23 Vascugel patients in the ITT group and 12 in the mITT group; eight placebo patients in the ITT group and six in the mITT group. Three of the 23 Vascugel (13%) and one of the eight placebo (12.5%) AVF were never used for dialysis during the 24-week follow-up period.
      Table IBaseline characteristics of the participants
      No statistically significant differences observed in baseline characteristics between groups.
      AVGAVF
      CharacteristicVascugelPlaceboVascugelPlacebo
      N = 23N = 11N = 23N = 8
      Age, years59.9 ± 15.759.5 ± 19.253.2 ± 17.957.8 ± 18.1
      Male, %52.263.656.562.5
      Black, %73.972.734.825.0
      Cardiovascular disease, %100100100100
      Diabetes mellitus, %69.563.652.250
      Body mass index, (kg/m2)29.7 ± 7.927.9 ± 4.226.3 ± 6.728.7 ± 4.1
      Systolic blood pressure (mm Hg)145.2 ± 27.4143.5 ± 36.7127.8 ± 21.2144.4 ± 24.5
      Diastolic blood pressure (mm Hg)79.2 ± 11.178.8 ± 19.276.6 ± 14.276.9 ± 18.1
      Prior AV access in index arm
      One Vascugel AVF subject had two previous accesses, one AVG and one AVF.
       Prior AVG (%)4 (17.4)01 (4.3)0
       Prior AVF (%)12 (52.2)5 (45.5)5 (21.7)1 (12.5)
       No prior access7 (30)6 (55)18 (78)7 (88)
      Antithrombotic use, %91.381.878.362.5
       Antiplatelet use, %73.963.660.962.5
       Anticoagulant use, %47.845.552.250.0
      Statin use, %39.136.456.537.5
      Hemoglobin, g/dL12.7 ± 2.112.2 ± 2.513.3 ± 1.913.9 ± 1.7
      % Panel reactive antibodies1.6 ± 4.24.0 ± 7.30.43 ± 1.20.88 ± 2.5
      Hemodialysis initiated before study access creation, %100100100100
      Study access
      Study patients underwent planned creation of surgical AVG or AVF per standard practice and guidelines of the local treating physicians.
       Forearm, %1 (4.3)1 (9.1)2 (8.7)1 (12.5)
       Upper arm, %22 (95.7)10 (90.9)21 (91.3)7 (87.5)
      AVG, Arteriovenous graft; AVF, arteriovenous fistulae.
      a No statistically significant differences observed in baseline characteristics between groups.
      b One Vascugel AVF subject had two previous accesses, one AVG and one AVF.
      c Study patients underwent planned creation of surgical AVG or AVF per standard practice and guidelines of the local treating physicians.

       Primary safety outcome

      Comparison of the Vascugel group and the placebo group in the safety population as well as in each AVG and AVF safety subpopulation showed no statistical difference between the two groups in the incidence of local wound infection, access intervention or the incidence of acute thrombosis within 30 days postsurgery (Table II). The Vascugel group demonstrated an excellent safety profile. Separate analysis of wound infection, access intervention and incidence of acute thrombosis in the AVG ITT population that received three Vascugel sponges showed no increase in early complications at 4 weeks due to the addition of the third sponge (10.5% for Vascugel vs 36.4% for placebo). A summary of adverse events by system organ class is presented in Table III. The majority of these events were unrelated to treatment as determined by the investigator at each site; 8.7% of Vascugel patients and 26.3% of placebo patients experienced events that were considered possibly related. Events considered possibly related in the placebo group included cellulitis, AVG thrombosis, and venous stenosis. Events considered possibly related in the Vascugel group included AVG thrombosis and venous stenosis. None of the events was considered probably or definitely related.
      Table IIPrimary endpoint summary at 30 days: Safety population
      Safety PopulationAVGAVF
      AssessmentVascugelPlaceboVascugelPlaceboVascugelPlacebo
      N = 46N = 19N = 23N = 11N = 23N = 8
      Local wound infection,
      Local infection was defined as wound dehiscence with access exposure; graft removal for confirmed graft infection; purulent drainage with positive gram stain or cultures; or as four of the five following criteria: (1) need for intravenous antibiotics, (2) fever (>100.5), (3) increased WBC count (>12,000/μL), (4) significant erythema, or (5) wound dehiscence without access exposure.
      access intervention or Thrombosis
      Total number of subjects who experienced any event (%).
      5 (10.9%)
      P = .430.
      4 (21.1%)3 (13%)
      P = .178.
      4 (36.4%)2 (8.7%)
      P > .999.
      0
      • Local wound infection
      Individual subjects who experienced the specific event (%).
      2 (4.3%)2 (10.5%)1 (4.3%)2 (18.2%)1 (4.3%)0
      • Access intervention
      Individual subjects who experienced the specific event (%).
      2 (4.3%)1 (5.3%)1 (4.3%)1 (9.1%)1 (4.3%)0
      • Thrombosis
      Individual subjects who experienced the specific event (%).
      2 (4.3%)2 (10.5%)2 (8.7%)2 (18.2%)00
      AVG, Arteriovenous graft; AVF, arteriovenous fistulae.
      a Local infection was defined as wound dehiscence with access exposure; graft removal for confirmed graft infection; purulent drainage with positive gram stain or cultures; or as four of the five following criteria: (1) need for intravenous antibiotics, (2) fever (>100.5), (3) increased WBC count (>12,000/μL), (4) significant erythema, or (5) wound dehiscence without access exposure.
      b Total number of subjects who experienced any event (%).
      c P = .430.
      d P = .178.
      e P > .999.
      f Individual subjects who experienced the specific event (%).
      Table IIIAdverse event by system organ class
      System organ classVascugel
      Number of subjects (%).
      Placebo
      Number of subjects (%).
      n = 46n = 19
      Blood and lymphatic system disorders4 (8.7%)2 (10.5%)
      Cardiac disorders9 (19.6%)4 (21.1%)
      Gastrointestinal disorders13 (28.3%)5 (26.3%)
      General disorders/administration site conditions14 (30.4%)7 (36.8%)
      Infections (systemic and access)18 (39.1%)9 (47.4%)
      Procedural and access complications20 (43.5%)8 (42.1%)
      Abnormal lab values3 (6.5%)2 (10.5%)
      Musculoskeletal/connective tissue disorders7 (15.2%)3 (15.8%)
      Nervous system disorders5 (10.9%)2 (10.5%)
      Renal and urinary disorders2 (4.3%)0
      Respiratory and thoracic disorders9 (19.6%)3 (15.8%)
      Skin and subcutaneous tissue disorders9 (19.6%)2 (10.5%)
      Vascular disorders16 (34.8%)9 (47.4%)
      a Number of subjects (%).
      SAEs were recorded from the time of consent for all patients enrolled in the study who received Vascugel or placebo. The majority of events were expected as typical comorbidities in the ESRD patient population. The majority of these events were unrelated to treatment as determined by the investigator at each site as well as the study medical monitor; 4.3% patients in the Vascugel group and none of the patients in the placebo group experienced events that were considered possibly related. Events considered possibly related were AVG thrombosis. Overall, 38 patients (58% of the patients enrolled) reported a total of 73 SAEs. There was no statistically significant difference between groups in the number of SAEs reported.

       Secondary efficacy outcomes - AVG cohort

      Treatment with Vascugel did not significantly prolong unassisted or assisted primary AVG patency compared to placebo in the ITT or mITT populations (Fig 3). At 24 weeks, the primary patency rate for ITT patients who received Vascugel was 38% vs 23% for placebo. Similarly, primary patency in the mITT group was 49% vs 25% for Vascugel and placebo, respectively. Vascugel assisted primary patency rates were 72% for ITT and 78% for mITT, vs 58% and 50%, respectively, for the placebo group. Adjudication of graft events to determine anastomotic patency did not result in significant differences in patency rates (data not shown), due to the difficulty in determining the presence and/or location of the causative lesion in the grafts, especially after interventional procedures performed to treat thrombosed grafts. There was no statistically significant difference in time to first AVG use between the Vascugel and placebo groups.
      Figure thumbnail gr3
      Fig 3AVG secondary outcome of patency analyzed using the Kaplan Meier product limit method. A, ITT primary patency; B, mITT primary patency; C, ITT assisted primary patency; D, mITT assisted primary patency. Comparison of the two treatment groups was made using the log-rank test.
      Quantitative angiography data (methods in Appendix, online only) showed no significant differences between groups in lumen diameter changes from 12-24 weeks (data not shown). There was no observable difference in minimal lumen diameter (MLD).

       Secondary efficacy outcomes - AVF cohort

      Treatment with Vascugel did not significantly prolong unassisted or assisted primary fistula patency compared with placebo in the ITT or mITT populations (Fig 4). At 24 weeks, the primary patency rates for ITT patients who received Vascugel were 60% vs 62% for placebo. Primary patency in the mITT group was 75% vs 65%, for Vascugel and placebo, respectively. Assisted primary patency rates for ITT were 96% vs 88% for Vascugel and placebo, respectively. Assisted primary patency in the mITT population was 100% in both treatment groups. Blinded adjudication of fistula events was more straightforward and resulted in a primary anastomotic patency in the ITT Vascugel group of 73% at 24 weeks compared with 58% in the placebo group and 92% vs 64% for Vascugel vs placebo in the mITT group (Fig 4). Decisions to adjudicate an event as unrelated to the anastomotic treatment area included cases of angioplasty of central venous stenosis outside of the treatment area and ligation of collateral venous branches without stenosis. There was no statistically significant difference in time to first AVF use between the Vascugel and placebo groups. Angiography was performed only at 24 weeks in AVF patients and analysis showed no significant differences between groups (data not shown). By ultrasound, positive changes in venous lumen diameter were observed over time in both groups (5.57 ± 1.64 mm and 5.71 ± 1.11 mm at 2 weeks, 5.93 ± 1.89 mm and 5.31 ± 1.24 mm at 4 weeks, 6.92 ± 2.47 mm and 5.86 ± 1.92 mm at 12 weeks, 7.01 ± 2.66 mm and 7.41 ± 2.844 mm at 24 weeks for Vascugel and placebo, respectively).
      Figure thumbnail gr4
      Fig 4AVF secondary outcome of patency analyzed using the Kaplan Meier product limit method. A, ITT primary patency; B, ITT primary anastomotic patency; C, mITT primary patency; D, mITT primary anastomotic patency. Comparison of the two treatment groups was made using the log-rank test.

       Secondary safety outcome

      A secondary safety endpoint of the study was to measure the development of PRA over time. PRA testing determines the presence of anti- HLA antibodies in serum samples and is reported as a percentage. No statistically significant increases were observed in class II anti-HLA antibodies (data not shown). At 2 weeks, more AVG placebo patients had an elevation in class I antibodies compared with Vascugel patients (P < .005, Fig 5). No statistically significant differences were observed at any of the other time points or in AVF patients. An increase >30% compared with baseline levels in class I anti-HLA antibodies was observed in four Vascugel AVG patients, in one placebo AVG subject, and in five AVF Vascugel patients and none of the placebo AVF patients (P = .26, Fig 5). In all of the Vascugel patients who experienced PRA elevations, one or more of the antibodies were specific to the donor EC HLA antigens. Statistical analysis revealed no relationship between an increase in PRA and either access patency or the incidence of adverse events at 24 weeks. Larger trials and longer time points are needed to confirm this observation.
      Figure thumbnail gr5
      Fig 5Bar graph of increase in % PRA at 2, 4, 12, and 24 weeks. A, At 2 weeks, more AVG placebo patients had an elevation in class I anti-HLA antibodies compared with Vascugel patients. No statistically significant differences were observed at any of the other time points. B, Time course of PRA response in four AVG Vascugel patients (02-016, 08-009, 09-003, and 09-009) and one AVG placebo subject (02-011). Only baseline and 12-week PRA were obtained for 02-016 and therefore the complete time course could not be assessed. C, No statistically significant differences were observed between AVF placebo and Vascugel patients at any of the time points. D, Time course of PRA response in five Vascugel patients. Increases of PRA ≥30% in either AVG or AVF patients did not reach statistical significance when the two treatment groups were compared (P = .26). The presence of HLA antibodies in serum samples was determined using the LABScreen Luminex platform which utilizes a panel of color-coded micro-beads coated with purified class I or class II HLA antigens and preoptimized reagents for the detection of class I or class II HLA antibodies in human sera and the LABScan 100 flow analyzer for data acquisition and analysis.

      Discussion

      The V-HEALTH trial represents the first use of a novel allogeneic endothelial implant in AV access patients. The primary outcome of the trial, safety, was met. There was no difference in the incidence of early complications for the Vascugel group compared with placebo. There was no evidence of local or systemic safety concerns for the Vascugel group based on analysis of reported adverse events and SAEs. The adverse events observed were expected as typical vascular access related complications or comorbidities associated with the ESRD patient population. The present study was not powered to detect efficacy of Vascugel, and thus, larger trials will be necessary to detect statistical differences in patency between treatment groups. A subset of V-HEALTH patients entered into an extension study where patency and access survival will continue to be assessed. Results from the extension study will be the subject of a follow-up report. The results of the present study support further clinical investigation of Vascugel in the setting of dialysis access surgery to explore efficacy, optimal treatment dose, and potential consequences of repeat administration.
      A major challenge in caring for patients undergoing hemodialysis for kidney failure is maintaining a functioning vascular access. The current therapy for a failing vascular access is either surgical revision or percutaneous interventions.
      • Gibson K.D.
      • Gillen D.L.
      • Caps M.T.
      • Kohler T.R.
      • Sherrard D.J.
      • Stehman-Breen C.O.
      Vascular access survival and incidence of revisions: a comparison of prosthetic grafts, simple autogenous fistulas, and venous transposition fistulas from the United States Renal Data System Dialysis Morbidity and Mortality Study.
      Although the exact causes of AVF and AVG stenosis and thrombosis are not completely understood, they are likely encompassed within the paradigm of the vessel wall injury response. Loss of endothelial integrity followed by platelet activation, inflammation, and the migration and proliferation of fibroblasts and SMC characterize this generalized response.
      • Roy-Chaudhury P.
      • Kelly B.S.
      • Narayana A.
      • Desai P.
      • Melhem M.
      • Munda R.
      • et al.
      Hemodialysis vascular access dysfunction from basic biology to clinical intervention.
      Dramatic changes in biomechanical stresses also occur as a result of the high-flow environment. Preclinical studies have shown that when placed outside a blood vessel, at the adventitia, EC decrease thrombosis, stenosis and negative remodeling
      • Nugent H.M.
      • Sjin R.T.
      • White D.
      • Milton L.G.
      • Manson R.J.
      • Lawson J.H.
      • et al.
      Adventitial endothelial implants reduce matrix metalloproteinase-2 expression and increase luminal diameter in porcine arteriovenous grafts.
      • Nugent M.A.
      • Nugent H.M.
      • Iozzo R.V.
      • Sanchack K.
      • Edelman E.R.
      Perlecan is required to inhibit thrombosis after deep vascular injury and contributes to endothelial cell-mediated inhibition of intimal hyperplasia.
      and provide the scientific basis for the clinical development of Vascugel as a locally applied perivascular therapy to improve healing at sites of vascular interventions. Both Vascugel and Gelfoam degrade in vivo between 4 to 6 weeks, however, animal data have demonstrated beneficial effects of the perivascular EC several months after degradation.
      • Nugent H.M.
      • Groothuis A.
      • Seifert P.
      • Guerraro J.L.
      • Nedelman M.
      • Mohanakumar T.
      • et al.
      Perivascular endothelial implants inhibit intimal hyperplasia in a model of arteriovenous fistulae: a safety and efficacy study in the pig.
      • Nugent H.M.
      • Edelman E.R.
      Endothelial implants provide long-term control of vascular repair in a porcine model of arterial injury.
      The use of allogeneic EC has multiple benefits on the manufacturing process, product release and quality assurance. The use of qualified cell banks from single donors is amenable to strict viral as well as functional testing prior to formulation of the final product. Patients with cardiovascular disease and diabetes (100% and 59% of the V-HEALTH population, respectively) are thought to have dysfunctional endothelium and circulating auto-antibodies making use of autologous EC from these patients less desirable.
      • Brevetti G.
      • Schiano V.
      • Chiariello M.
      Endothelial dysfunction: a key to the pathophysiology and natural history of peripheral arterial disease?.
      • Rask-Madsen C.
      • King G.L.
      Mechanisms of disease: endothelial dysfunction in insulin resistance and diabetes.
      • Mannarino E.
      • Pirro M.
      Endothelial injury and repair: a novel theory for atherosclerosis.
      • Zimering M.B.
      • Pan Z.
      Auto-antibodies in type 2 diabetes induce stress fiber formation and apoptosis in endothelial cells.
      However, the use of allogeneic EC in patients that may undergo kidney transplant required that we monitor for immunosensitization. An elevation in PRA over the course of the study, defined as a 30% increase over baseline, was observed in 19.5% of the Vascugel group (9/46) and in 5.2% of the placebo group (1/19). The majority of elevations observed in the Vascugel patients were class I and donor specific. There was no relationship between the presence of PRA, access patency, or adverse events. Outside of the context of this trial, sensitization is not an uncommon clinical finding. Sensitization occurs in most people through exposure to a foreign alloantigen, which can occur through pregnancy, blood transfusions or prior transplantation of solid organs or bone marrow.
      • Chhaya S.U.
      • Vazifdar G.N.
      • Rajadhyaksha S.B.
      Panel reactive antibodies in patients with neoplasia and hematological disorders.
      • MacPherson B.R.
      • Hammond P.B.
      • Maniscalco C.A.
      Alloimmunization to public HLA antigens in multi-transfused platelet recipients.
      • Taaning E.
      • Skibsted L.
      The frequency of platelet alloantibodies in pregnant women and the occurrence and management of neonatal alloimmune thrombocytopenic purpura.
      The implications of PRA increases or sensitization for potential kidney transplant candidates are twofold: an increase in time on the transplant wait list until a suitable donor is found
      US Organ Procurement and Transplantation Network and the Scientific Registry of Transplant Recipients
      2007 OPTN/SRTR Annual Report: Transplant Data 1997-2006.
      and if transplanted, an increase in risk of antibody mediated rejection may occur,
      • Terasaki P.I.
      • Ozawa M.
      Predicting kidney graft failure by HLA antibodies: a prospective trial.
      • Halloran P.F.
      • Wadgymar A.
      • Ritchie S.
      • Falk J.
      • Solez K.
      • Srinivasa N.S.
      The significance of the anti-class I antibody response. I Clinical and pathologic features of anti-class I-mediated rejection.
      which can be ameliorated with programs such as paired kidney exchange, immunosuppression, or desensitization protocols.
      • Vo A.A.
      • Toyoda M.
      • Peng A.
      • Bunnapradist S.
      • Lukovsky M.
      • Jordan S.C.
      Effect of induction therapy protocols on transplant outcomes in crossmatch positive renal allograft recipients desensitized with IVIG.
      The V-HEALTH study was conducted in dialysis patients who were not under consideration for transplantation at the time of enrollment and therefore the results of transplantation in V-HEALTH patients are unknown at this time. Additional PRA data will continue to be collected in the extension study.
      The present study had several limitations. It was designed as a small safety and feasibility study of a novel cellular implant and therefore, not powered to detect therapeutic benefit. The treatment of both AVG and AVF allowed for patients to be enrolled and not lost due to last minute decisions made concerning the type of access and for safety to be assessed in both AVF and AVG. However, this approach made efficacy analysis more difficult. In addition, a number of interventions that affected AVG primary patency were triggered by the 12-week protocol-mandated angiogram (30% of the Vascugel and 12% of the placebo group). This observation is reflected in 24-week AVG primary patency rates in the control group that are somewhat lower than those reported in the literature.
      • Hayashi R.
      • Huang E.
      • Nissenson A.R.
      Vascular access for hemodialysis.
      • Rotmans J.I.
      • Pasterkamp G.
      • Verhagen H.J.
      • Pattynama P.M.
      • Blankestijn P.J.
      • Stroes E.S.
      Hemodialysis access graft failure: time to revisit an unmet clinical need?.
      Design of future trials in which patency is a primary endpoint should not specify an angiogram unless indicated by clinical events. Targeted local therapy with tissue engineered endothelial cell implants is a novel therapeutic approach that is safe and may be ideally suited to control the response to injury and inhibit clinical vascular dysfunction. Larger, randomized trials will need to be performed to determine if there is a benefit of Vascugel on AV access patency, maturation and survival.

      Author contributions

      • Conception and design: MC, HN, PR-C, JL
      • Analysis and interpretation: MC, HN, PG, IG, PR-C, JL
      • Data collection: IG
      • Writing the article: MC, HN, JL
      • Critical revision of the article: MC, HN, PG, IG, PR-C, JL
      • Final approval of the article: MC, HN, PG, IG, PR-C, JL
      • Statistical analysis: PG, HN
      • Obtained funding: HN, MC, P R-C, JL
      • Overall responsibility: MC, HN, JL
      The authors acknowledge the expert technical assistance of Bechara Mfarrej of Harvard Medical School and are grateful to Mohamed H. Sayegh for careful review of the PRA data and manuscript. The authors thank for their support and commitment John Wilson, Molly Rosano, and Laurie Ridener of Pervasis Therapeutics. The authors also thank Jack Harvey of Pervasis Therapeutics and Barbara Seymour, Cynthia Provencher, and Michael Maria of Genzyme for their involvement in Vascugel production.

      APPENDIX, online only

       Participating Centers

      • Legacy Good Samaritan Hospital, Portland, Oregon, Principal Investigator (PI): Earl Schuman, MD
      • Department of Surgery, University of Miami, Miami, Florida, PI: A. Frederick Schild, MD
      • Bamberg Community Hospital, Bamberg, South Carolina, PI: John Ross, MD
      • St. Mary's Hospital, Tucson, Arizona, PI: Scott Berman, MD
      • Norfolk Sentara Health System, Norfolk, Virginia, Marc Glickman, MD
      • Cincinnati Dialysis Program, University of Cincinnati, Cincinnati, Ohio, PI: Prabir Roy-Chaudhury, MD, PhD
      • Department of Surgery, Duke University Medical Center, Durham, North Carolina, PI: Jeffrey H. Lawson, MD, PhD
      • Brigham and Women's Hospital, Harvard School of Medicine, Boston, Massachusetts, PI: Michael S. Conte, MD

       Committees

      • Clinical Adjudication Committee
      • Ziv J. Haskell, MD, Division of Vascular and Interventional Radiology NewYork-Presbyterian Hospital/Columbia University Medical Center, New York, New York
      • Larry A. Scher, MD, Department of Vascular Surgery, Montefiore Medical Center, Bronx, New York
      • Jack Work, MD, Department of Medicine, Renal Division, Emory University School of Medicine, Atlanta, Georgia
      • Data Monitoring Committee (DMC)
      • Bradley Dixon, MD, Department of Internal Medicine, Division of Nephrology, University of Iowa, Iowa City, Iowa
      • Edward Lakatos, PhD, BiostatHaven, Inc, Croton-on-Hudson, New York
      • Michael Miller, MD, Vascular and Interventional Radiology, Duke University Medical Center, Durham, North Carolina
      • Mohammed Sayegh, MD, Transplant Research Center, Brigham and Women's Hospital and Children's Hospital Boston, Boston, Massachusetts
      • Samuel Eric Wilson, MD, Department of Surgery, University of California Irvine, Orange County, California

       Pharmacovigilance group

      • PPD, Inc
      • 3900 Paramount Parkway
      • Morrisville, NC 27560

       Immunology Core Lab

      • Laboratory of Immunogenetics and Transplantation
      • Brigham & Women's Hospital and Children's Hospital
      • Nephrology Division
      • Harvard Medical School
      • 75 Francis Street
      • Boston, MA 02115

       Imaging Core Lab

      • RadPharm
      • 103 Carnegie Center, Suite 300A
      • Princeton, NJ 08540

      Methods

       Ultrasound and Angiography Lumen Diameter Measurements

      All lumen diameter measurements were performed by a blinded interventional radiologist provided by a core Imaging Lab (RadPharm). Venous lumen diameters for AVF patients were obtained by US at 1 cm, 3 cm and 5 cm from the venous anastomosis. Diameters at each location were averaged to obtain one venous measurement per patient at each time point. Venous and arterial lumen diameters were obtained by angiography at the anastomosis and up to 5 cm from the anastomosis at 0.5 cm increments. Graft lumen diameters were obtained up to 5 cm into the graft from either the venous or arterial anastomosis in 0.5 cm increments. Minimum lumen diameter was calculated for each patient by taking the smallest measured diameter over the 5 cm length of vessel. The frequency of positive venous diameter changes was determined by determining the distribution of patients with either positive or negative changes at each of the distances measured (ie, at the anastomosis, at the 10 distances measured between 0.5 and 5.0 cm into the venous outflow segment).

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