Global Phase 3 programme of vadadustat for treatment of anaemia of chronic kidney disease: rationale, study design and baseline characteristics of dialysis-dependent patients in the INNO2VATE trials

Background

Erythropoiesis-stimulating agents (ESAs) are currently the mainstay of treatment for anaemia of chronic kidney disease (CKD). Vadadustat is an investigational oral hypoxia-inducible factor prolyl-hydroxylase inhibitor that stimulates endogenous erythropoietin formation. The INNO₂VATE programme comprises two studies designed to evaluate the safety and efficacy of vadadustat versus the ESA darbepoetin alfa in ameliorating anaemia in patients with dialysis-dependent CKD (DD-CKD). Here we describe the trial design along with patient demographics and baseline characteristics.

Methods

Two Phase 3, open-label, sponsor-blind, active-controlled trials enrolled adults with anaemia of CKD who recently initiated dialysis and had limited ESA exposure (incident DD-CKD trial) or were receiving maintenance dialysis with ESA treatment (prevalent DD-CKD trial). Study periods include correction/conversion (Weeks 0–23), maintenance (Weeks 24–52), long-term treatment (Weeks 53 to end of treatment) and safety follow-up. The primary safety endpoint is the time to the first major adverse cardiovascular event and the primary efficacy endpoint is the change in haemoglobin (baseline to Weeks 24–36).

Results

A total of 369 and 3554 patients were randomized in the incident DD-CKD and prevalent DD-CKD trials, respectively. Demographics and baseline characteristics were similar among patients in both trials and comparable to those typically observed in DD-CKD.

Conclusions

The two INNO₂VATE trials will provide important information on the safety and efficacy of a novel approach for anaemia management in a diverse DD-CKD population. Demographics and baseline characteristics of enrolled patients suggest that study results will be representative for a large proportion of the DD-CKD population.

MO541HEMATOLOGIC EFFICACY OF VADADUSTAT FOR ANEMIA IN PATIENTS WITH NON--DIALYSIS-DEPENDENT CHRONIC KIDNEY DISEASE

Background and Aims

Vadadustat is a small-molecule inhibitor of hypoxia-inducible factor prolyl hydroxylases under development to treat anemia associated with chronic kidney disease (CKD). The vadadustat phase 3 program includes four efficacy and cardiovascular safety outcome trials of vadadustat versus the erythropoiesis-stimulating agent (ESA) darbepoetin alfa. Here we describe detailed results on hematologic efficacy in two phase 3, randomized trials (the PRO2TECT trials) in adult patients with non–dialysis-dependent (NDD) CKD and anemia, in which vadadustat met prespecified noninferiority criteria compared to darbepoetin alfa, with respect to hematologic efficacy (correction/maintenance of hemoglobin [Hb] target concentrations).

Method

The mean screening Hb level for the ESA-untreated NDD-CKD trial (NCT02648347) had to be <10.0 g/dL, and for the ESA-treated NDD-CKD trial (NCT02680574), the range had to be from 8.0-11.0 g/dL in the United States (US) and from 9.0-12.0 g/dL non-US. In the ESA-untreated trial, patients received no ESA within 8 weeks before randomization; in the ESA-treated trial, patients were maintained on ESA therapy, with ≥1 dose received within 6 weeks prior to or during screening. The vadadustat starting dose was 300 mg/day for all patients, whereas the initial darbepoetin alfa dose depended on each patient’s prior dose or the product label. Both vadadustat and darbepoetin alfa doses were titrated according to prespecified dosing algorithms to achieve target Hb concentrations (US: 10-11 g/dL; non-US: 10-12 g/dL) both during the primary (PEP; weeks 24-36) and secondary (SEP; weeks 40-52) evaluation periods. Herein, we present topline results from the PEP and SEP endpoints, in addition to more detailed erythrocyte parameters.

Results

A total of 3,476 patients (1751 ESA-untreated and 1725 ESA-treated) were randomized 1:1 to vadadustat or darbepoetin alfa. In both trials, vadadustat was noninferior to darbepoetin alfa with regard to the difference of mean change in Hb concentrations between baseline and PEP, as well as between baseline and SEP. The respective proportions of patients (vadadustat vs. darbepoetin alfa) with an average Hb value within the geography-specific target range in the PEP and SEP were 50.4% versus 50.2% and 43.1% versus 43.5% in the ESA-untreated trial and 60.1% versus 60.7% and 50.7% versus 49.0% in the ESA-treated trial. The proportion of patients (vadadustat vs darbepoetin alfa) who achieved an Hb increase >1.0 g/dL from baseline to week 52 was assessed only for the ESA-untreated trial and was 87.7% (95% CI: 85.4%, 89.8%) for vadadustat versus 88.0% (95% CI: 85.6%, 90.0%) for darbepoetin alfa.

Hematologic parameters at time points within the PEP and SEP are presented in Table 1. In both the ESA-untreated and ESA-treated trials, the reticulocyte count trended up from baseline through week 52 for vadadustat and trended down from baseline for darbepoetin alfa. Trends in erythrocyte mean corpuscular volume and erythrocyte mean corpuscular Hb were largely unremarkable by week 52 in both treatment groups.

Conclusion

Vadadustat demonstrated similar profiles across erythrocyte parameters compared with darbepoetin alfa in the treatment of adults with anemia in CKD not on dialysis, whether ESA-untreated or ESA-treated at study entry.

MO539HEMATOLOGIC EFFICACY OF VADADUSTAT FOR ANEMIA IN PATIENTS WITH KIDNEY FAILURE ON DIALYSIS

Background and Aims

Vadadustat is a small-molecule inhibitor of hypoxia-inducible factor prolyl hydroxylase being developed for treatment of anemia associated with chronic kidney disease (CKD). The vadadustat phase 3 program includes four efficacy and cardiovascular safety outcome trials of vadadustat versus the erythropoiesis-stimulating agent (ESA) darbepoetin alfa. Here we describe detailed results on hematologic efficacy in two of the four phase 3, randomized, open-label, sponsor-blind trials (the INNO2VATE trials) in adult patients with dialysis-dependent (DD) CKD and anemia, where vadadustat met prespecified noninferiority criteria compared with darbepoetin alfa with respect to cardiovascular safety and correction/maintenance of hemoglobin (Hb) target concentrations.

Method

The mean screening Hb range for the incident DD-CKD trial (NCT02865850) was 8.0-11.0 g/dL; for the prevalent DD-CKD trial (NCT02892149), it was 8.0-11.0 g/dL in the United States (US) and 9.0-12.0 g/dL for non-US. Patients in the incident and prevalent DD-CKD trials had initiated dialysis within <16 weeks with limited or no prior ESA exposure and >12 weeks with established ESA treatment prior to screening, respectively. Vadadustat starting dose was 300 mg/day for all patients, whereas initial darbepoetin alfa dose depended on each patient’s prior dose or product label. Both vadadustat and darbepoetin alfa doses were titrated according to prespecified dosing algorithms to achieve target Hb concentrations (US: 10-11 g/dL; non-US: 10-12 g/dL) during the primary evaluation period (PEP; weeks 24-36) and the secondary evaluation period (SEP; weeks 40-52). Herein, we present topline results from PEP and SEP endpoints, as well as other, more detailed hematologic erythrocyte parameters.

Results

A total of 3923 patients (369 with incident DD-CKD and 3554 with prevalent DD-CKD) were randomized 1:1 to vadadustat or darbepoetin alfa. Vadadustat was noninferior to darbepoetin alfa in achieving target-range Hb concentrations (primary efficacy endpoint) among patients who were new to, or established on, dialysis. The respective proportions of patients (vadadustat vs. darbepoetin alfa) with an average Hb value within the geography-specific target range in the PEP and SEP were 43.6% versus 56.9% and 39.8% versus 41.0% in the incident trial and 49.2% versus 53.2% and 44.3% versus 50.9% in the prevalent dialysis trial. The proportion of patients who achieved an Hb increase >1.0 g/dL from baseline to week 52 was assessed only for the incident trial and was 84.0% (95% CI: 77.8%, 89.0%) for vadadustat versus 89.9% (95% CI: 84.7%, 93.8%) for darbepoetin alfa.

Hematologic erythrocyte parameters at time points within the PEP and SEP are presented in Table 1. In the incident trial, reticulocyte count was slightly increased from baseline at 28 and 52 weeks for vadadustat, whereas for darbepoetin alfa, reticulocyte count was slightly decreased or unchanged in both trials. Erythrocyte mean corpuscular volume and erythrocyte mean corpuscular Hb showed increases by week 52 for both groups.

Conclusion

Vadadustat demonstrated similar profiles across erythrocyte parameters compared with darbepoetin alfa in the treatment of anemia associated with CKD in adults in both incident dialysis and prevalent dialysis settings.

Effect of Moderate Hepatic Impairment on the Pharmacokinetics of Vadadustat, an Oral Hypoxia-Inducible Factor Prolyl Hydroxylase Inhibitor

Vadadustat is a hypoxia-inducible factor prolyl hydroxylase inhibitor in development for the treatment of anemia of chronic kidney disease. This phase 1, open-label, parallel-group, single-dose study evaluated the pharmacokinetics of 450-mg vadadustat in adults with moderate hepatic impairment (Child-Pugh class B) vs those with normal hepatic function. Primary end points were area under the plasma concentration-time curve (AUC) from dosing to last concentration and to infinity, as well as maximum concentration (C_max ); additional pharmacokinetic parameters included time to C_max (T_max ) and half-life. Safety and tolerability were also assessed. All enrolled participants (n = 16) completed the study. Demographics were similar in both groups (overall, 100% White; 62.5% female; mean age, 59.2 years). Vadadustat plasma exposure was higher in the moderate hepatic impairment group, whereas maximum concentration was similar between groups. Point estimates of the hepatic impairment : normal geometric mean ratios (90% confidence interval) for AUC from dosing to last concentration, AUC from dosing to infinity, and C_max were 1.05 (0.82-1.35), 1.06 (0.82-1.36), and 1.02 (0.79-1.32), respectively. Mean elimination half-life was 5.8 and 7.8 hours in the normal and hepatic impairment groups, respectively. Treatment-emergent adverse events were mostly mild in severity, and vadadustat was generally well tolerated. In conclusion, moderate hepatic impairment did not significantly impact vadadustat systemic exposure, and mild hepatic impairment is unlikely to alter vadadustat exposure.

Vadadustat, an oral hypoxia-inducible factor prolyl hydroxylase inhibitor, for treatment of anemia of chronic kidney disease: two randomized Phase 2 trials in Japanese patients

BACKGROUND

Vadadustat is an investigational, oral hypoxia-inducible factor prolyl hydroxylase inhibitor in development in Japan for the treatment of chronic kidney disease (CKD)-induced anemia.

METHODS

Two Phase 2, multicenter, double-blind, placebo-controlled studies randomized Japanese patients with nondialysis-dependent (NDD, n = 51) or dialysis-dependent (DD, n = 60) CKD-induced anemia to once-daily vadadustat (150, 300 or 600 mg) or placebo. A 6-week, fixed-dose primary efficacy period was followed by a 10-week vadadustat dose adjustment/maintenance period. The primary endpoint was the mean change in hemoglobin (Hb) level from pretreatment to Week 6.

RESULTS

Statistically significant (P < 0.01) dose-dependent increases in mean Hb values were observed at Week 6 in all vadadustat groups versus placebo [placebo and vadadustat 150, 300 and 600 mg: -0.47, 0.43, 1.13 and 1.62 (NDD-CKD) and -1.48, -0.28, 0.08 and 0.41 (DD-CKD), respectively]. By Week 16, 91% (NDD-CKD) and 71% (DD-CKD) of vadadustat-treated participants achieved target Hb levels (10.0-12.0 g/dL) and significant dose-dependent changes in iron utilization and mobilization biomarkers were observed with vadadustat. During the primary efficacy period, the incidence of treatment-emergent adverse events (AEs) with placebo and vadadustat 150, 300 and 600 mg was 36, 33, 58 and 54% (NDD-CKD) and 40, 53, 73 and 40% (DD-CKD), respectively. The most common AEs during the primary efficacy period were nausea and hypertension (NDD-CKD) and diarrhea, nasopharyngitis and shunt stenosis (DD-CKD). Of 23 serious AEs in 18 patients, 1 was deemed related (hepatic function abnormal); no deaths were reported.

CONCLUSIONS

The efficacy and safety results from these studies support the development of vadadustat for the treatment of anemia in patients with CKD.

SO050DIFFERENT FERRIC CITRATE DOSE REGIMENS IN THE TREATMENT OF IRON DEFICIENCY ANAEMIA IN PATIENTS WITH NON-DIALYSIS-DEPENDENT CKD: THE COMPASS TRIAL

Background and Aims

Ferric citrate (FC) is approved in the US as oral iron replacement for the treatment of iron deficiency anaemia (IDA) in adult patients with non-dialysis dependent (NDD) chronic kidney disease (CKD) and for the treatment of hyperphosphatemia in adult patients with dialysis dependent CKD. For IDA, a starting dose FC of 1 tablet three times daily (TID) is recommended with titration to maintain haemoglobin (Hb) at goal. This study was designed to investigate the possibility of dosing FC twice daily (BID) for flexibility in clinical practice. The efficacy and safety of different FC dosing regimens for the treatment of IDA were examined in adults with NDD-CKD.

Method

In this 48-wk, Phase 4, randomized, open-label, multicentre study, subjects with IDA of NDD-CKD (stage 3-5) were randomized 1:1 to receive 1 FC tablet (1gm containing 210mg ferric iron) TID or 2 tablets BID. At wk 12, subjects whose Hb increased &lt;0.5 g/dL from baseline (BL) or was &lt;10 g/dL had their dose increased to either 2 tablets TID or 3 tablets BID consistent with their original dosing regimen. This prespecified analysis reports data through wk 24. The primary endpoint was mean change in Hb from BL to wk 24. Secondary endpoints included mean change in transferrin saturation (TSAT), ferritin, and phosphate to wk 24.

Results

206 subjects were randomized, 183 were included in this analysis after completing the 24-wk dose titration period. Groups were well matched with mean age of 69.5 +/- 10.32 years, 64% female and 54% had diabetes as a cause of CKD. Mean BL eGFR was 33.6 +/- 10.85 ml/min/1.73m2 and Hb 10.45 +/-0.744 g/dL. In subjects who did not require an increase in the FC dose at wk 12, mean changes in Hb at wk 24 were 1.05 and 1.24 g/dL in the 1 tablet TID and 2 tablet BID dosage groups, respectively. In subjects who required an increase in the FC dose at wk 12, mean changes in Hb at wk 24 were 0.41 and 0.13 g/dL in the 2 tablet TID and 3 tablet BID groups, respectively. Mean changes in TSAT, ferritin and phosphate are presented in the Table. The incidence of TEAEs was 78.2% and 75.0% in the BID and TID groups, respectively. The most common AEs reported were diarrhoea, stool discoloration and constipation. The incidence of SAEs was 13.9% and 17.3% in the BID and TID groups, respectively. Five deaths were reported, none were deemed related to FC per the investigator.

Conclusion

FC was effective and generally well tolerated in the treatment of IDA in this NDD-CKD population. Subjects who had per protocol FC dose increases at wk 12 had less pronounced iron deficiency at BL and smaller increases in Hb suggesting an additional underlying cause of anaemia. Mean changes in Hb, TSAT, ferritin, and phosphate and AE profiles were similar in the BID and TID regimens as well as in 3 g/day and 4 g/day dosing groups supporting the potential for dosing flexibility with FC.

Clinicaltrials.gov identifier NCT03236246

Funding provided by Akebia Therapeutics, Inc.

Abstract 752: The effect of food on the pharmacokinetics of tivozanib

Background: Tivozanib, a potent, selective, long-half-life tyrosine kinase inhibitor of vascular endothelial growth factor receptors 1, 2, and 3, has demonstrated antitumor activity in a Phase II study in patients with renal cell carcinoma (RCC), and is currently being studied in clinical trials in patients with RCC and other solid tumors. The goal of this study was to investigate the effect of food on the pharmacokinetics (PK) of a single 1.5 mg dose of tivozanib in healthy subjects. Methods: This was a single-center, open-label, randomized, two-period, crossover Phase I trial. Subjects were admitted to the clinical research unit (CRU) 1 day before dosing, fasted ∼10 hours, and were randomized to fed (standard high-fat breakfast)/fasted or fasted/fed sequence. In each phase of the sequence, subjects received a single oral dose of tivozanib 1.5 mg with a 6-week washout period between doses. Subjects remained at the CRU for at least 48 hours post dose for blood sample collection and safety monitoring, and were assessed on an outpatient basis for up to 504 hours post dose. PK data were analyzed by non-compartmental methods. The effect of food on PK was assessed using standard criteria for bioequivalence based on the exposure parameters AUC0-α and Cmax. If the 90% confidence intervals for the fed/fasted AUC0-α and Cmax fell within the range of 80% to 125%, it was concluded that food had no effect on exposure. Results: Thirty healthy volunteers were enrolled (19M/11F; mean age 39 years [range 22-53 years]). There was no significant difference in AUC0-α of serum tivozanib between the fed and fasted states (107.4%; Table 1). Food caused a significant decrease in serum tivozanib levels vs fasted state (Cmax: 77.5%). Conclusions: These results indicate that dosing tivozanib with food decreases maximal concentrations by ∼ 23%, but does not affect overall exposure. As tivozanib is dosed chronically in oncology patients and accumulates ∼6 to 7 times single-dose levels when at steady-state, these results are not likely to affect dosing.

A phase I QTc study of tivozanib in patients with advanced solid tumors

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Background: Tivozanib is a potent and selective tyrosine kinase inhibitor of vascular endothelial growth factor receptors-1, -2, and -3 that is currently being tested in a Phase III study in patients with renal cell carcinoma and Phase I/II studies of other solid tumors. Preclinical and retrospective electrocardiogram (ECG) analyses suggest no effect of tivozanib on QTc, although this has not been prospectively assessed according to ICH E14 Cardiac Assessment of New Drugs Guidelines. This open-label, non-randomized, single-arm study prospectively investigated the effect of tivozanib on the QTcF interval and its morphology on the ECG and ECG-pharmacokinetic (PK) relationship in patients with advanced solid tumors.

Methods: Patients with advanced solid tumors, an ECOG score ≤1 and life expectancy ≥3 months were eligible. Patients received 1.5 mg of tivozanib orally, once daily for 21 days. Serial blood samples and time-matched, triplicate, 12-lead ECGs were collected on: Day 1 20-30 minutes pre-dose (no blood sample collected), immediately pre-dose, and at 2.5, 4, 5, 6, 8, and 10 hours post dose; Day 2 pre-dose evaluation was taken approximately 24 hours post Day 1 dose; Day 8 (±1 day) pre-dose, and at 2.5, 5, and 8 hours post dose; Day 21 pre-dose and at 2.5, 4, 5, 6, 8, and 10 hours post dose; and Day 22 at approximately 24 hours post Day 21 dose. Additional safety parameters were evaluated by assessing clinical laboratory tests, physical examinations, vital signs, and recording of adverse events.

Results: Fifty patients with advanced solid tumors (males, 17; median age, 63 years; 94% white) who received ≥ 1 dose of tivozanib were evaluable. Preliminary data showed that there were no clinically significant changes in QTcF from baseline. Further analysis will be completed, and final safety and ECG-PK modeling will be presented.

Conclusions: Preliminary data suggest that tivozanib 1.5 mg/d over a 21-day period does not cause clinically significant QT/QTc prolongation over baseline, suggesting that its safety and PK profile is similar to that observed in previous studies, including ECG evaluation in a monkey telemetry study.

Abstract C123: A phase 1 study to evaluate the absorption, metabolism, and excretion of the vascular endothelial growth factor receptor (VEGFR) tyrosine kinase inhibitor (TKI) tivozanib

Background: Tivozanib is a potent, selective, long half-life tyrosine kinase inhibitor (TKI) of vascular endothelial growth factor receptors (VEGFR)-1, -2, and -3. Tivozanib has demonstrated antitumor activity in a Phase II study in subjects with renal cell carcinoma. This study was conducted to determine the absorption, metabolism, and excretion of a single 1.5 mg dose of [14C]-tivozanib administered to healthy male subjects.

Methods: This study was approved by an independent institutional review board and enrolled 8 healthy male subjects; each received a single 1.5 mg (∼160 μCi) dose of oral [14C]-tivozanib. Whole blood, serum, urine, and feces were collected for up to 28 days post dose for assessment of total radioactivity and/or for determination of [14C]-tivozanib concentrations. All subjects were kept confined as inpatients for the duration of the study. Safety assessments included laboratory tests, electrocardiograms, physical examinations, vital signs, and recording of adverse events. Pharmacokinetic data were analyzed by noncompartmental methods.

Results: Subjects had a mean age of 32 years (range 19 to 46 years) and mean body mass index of 25 kg/m2 (range: 23 to 29 kg/m2). Of the 8 subjects enrolled, 7 completed the study. [14C]-tivozanib and total radioactivity were slowly absorbed and eliminated from serum; median Tmax was 10.0 hours, and mean (±SD) t1/2 for [14C]-tivozanib and total radioactivity in serum was 89.3 hours (± 23.5 hours) and 99.1 hours (± 32.5 hours), respectively. Mean (±SD) Cmax and AUC0−∞ values for [14C]-tivozanib were 12.1 ng/mL (±46.9 ng/mL) and 1084 ng*hr/mL (±417 ng*hr/mL), respectively; these values were approximately 93% and 80% of the values for total radioactivity in serum, respectively. Mean blood to serum concentration ratios ranged from 0.495 to 0.615 through 312 hours post dose, indicating minimal association of radioactivity with red blood cells. Overall, mean (±SD) recovery of total radioactivity was 91.1% (±11.0%), with 11.8% (±4.6%) recovered in urine and 79.3% (±8.8%) recovered in feces. No unchanged tivozanib was found in the urine. A single therapeutic dose of tivozanib was well tolerated in healthy subjects.

Conclusion: These results indicate that after an oral dose of 1.5 mg (∼160 μCi) of [14C]-tivozanib, the majority of circulating drug in the systemic circulation was unchanged tivozanib. The main route of elimination of [14C]-tivozanib was via feces, with at least 11.8% of the administered total radioactive dose being absorbed into systemic circulation. No unchanged tivozanib was found in the urine, indicating that tivozanib does not undergo renal excretion. In this study, the mean half-life of [14C]- tivozanib was 89.3 hours, one of the longest half-lives among VEGF TKIs. Tivozanib is currently being tested in a Phase III study in subjects with RCC and Phase I/II studies in other solid tumors.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr C123.

Expression of naked plasmid DNA injected into the afferent and efferent vessels of rodent and dog livers

A variety of reporter genes within plasmid constructs were injected into the afferent and efferent vessels of the liver in mice, rats, and dogs. Efficient plasmid expression was obtained following delivery via the portal vein, the hepatic vein, and the bile duct. The use of hyperosmotic injection solutions and occlusion of the blood outflow from the liver substantially increased the expression levels. Combining these surgical approaches with improved plasmid vectors enabled uncommonly high levels of foreign gene expression in which over 15 microg of luciferase protein/liver was produced in mice and over 50 microg in rats. Equally high levels of beta-galactosidase (beta-Gal) expression were obtained, in that over 5% of the hepatocytes had intense blue staining. Expression of luciferase or beta-Gal was evenly distributed in hepatocytes throughout the entire liver when either of the three routes were injected. Peri-acinar hepatocytes were preferentially transfected when the portal vein was injected in rats. These levels of foreign gene expression are among the highest levels obtained with nonviral vectors. Repetitive plasmid administration through the bile duct led to successive events of foreign gene expression. The integration of these findings into laboratory and clinical protocols is discussed.

FN18-CRM9 immunotoxin promotes tolerance in primate renal allografts

BACKGROUND

Transplant tolerance, rather than immunity, may be favored in the setting of a lower mature lymphoid mass in the recipient induced by anti-T cell agents. A novel immunosuppressive agent, FN18-CRM9, known to specifically kill T cells with great potency, was evaluated in a transplant model.

METHODS

In order to ablate recipient T cells, the immunotoxin FN18-CRM9 was administered to rhesus monkey recipients of MHC-mismatched renal allografts. Donor lymphocytes were injected intrathymically into some animals.

RESULTS

All monkeys with T-cell depletion by immunotoxin had prolonged allograft survival, and tolerance confirmed by skin grafting has been confirmed in five of six long-surviving recipients.

CONCLUSIONS

In this clinically relevant model, profound but transient T-cell depletion by a single agent substantially promotes tolerance.

Free-tissue transfer with the aid of loupe magnification: experience with 251 procedures

Eight years ago, the principal author (Shenaq) began employing high-power ocular loupes for microvascular anastomoses. Subsequently, 251 free-tissue transfers were performed with loupes as the sole means of magnification. Procedures included free flaps, toe-to-hand transfers, and digital replantations, with the external diameter of the vascular pedicles averaging 1.5 mm. Analysis of the series revealed a 97.2 percent overall success rate, a 1.2 percent partial flap necrosis rate, and an 8.3 percent revision rate for anastomoses (during the initial operative procedure), which compare favorably with the success rates frequently cited for microscope-assisted procedures. The most favorable results were achieved with free flaps and toe-to-hand transfers with 98.5 and 96.4 percent success rates, respectively. The 79.2 percent survival rate achieved with digital replantation falls within the range (74.0 to 94.2 percent) reported in the literature. This experience indicates that in practiced hands, high-power ocular loupes provide an alternative to the operating microscope for microvascular anastomosis of vessels 1.0 mm or greater in diameter. Loupe use is advocated on the grounds of cost-effectiveness, portability, and operator freedom.

How to help diabetic patients avoid amputation. Prevention and management of foot ulcers

Foot ulcers are a weighty complication of diabetes whose significance is often underestimated. They are associated with a high degree of morbidity and mortality, and treatment is laborious and costly. The problem of susceptibility to foot ulceration is best addressed through a prevention program emphasizing patient education, pedal hygiene, regular follow-up visits, and lifestyle modification. Such programs are most efficiently administered by a healthcare team. When ulcers do occur, it is important to take a systematic approach to management, stressing infection control, metabolic stabilization, thorough debridement, and meticulous wound care.

The pharmacodynamics of torsemide in patients with congestive heart failure

The pharmacodynamics of torsemide (a new loop diuretic of the pyridine sulfonylurea class) was studied in 16 subjects who had compensated congestive heart failure and had been receiving stable diuretic therapy. Oral doses of 50, 100, and 200 mg were studied by use of a randomized crossover design. The results of this study show that the pharmacokinetics of torsemide is linear up to at least a dose of 200 mg in patients with congestive heart failure. Approximately 20% of each of the three doses was excreted unchanged, consistent with previous findings in healthy volunteers. A hyperbolic relationship between diuretic effect and drug excretion rate was defined. The maximum urinary sodium excretion rate attained was about 0.6 mEq/min, which is about 20% of that in healthy subjects, indicating diuretic resistance in these patients. Although there was no saturation of the urinary excretory pathway with doses as high as 200 mg, the upper plateau of the dose-response curve was reached with doses of 50 mg, indicating that this dose represents a ceiling dose in patients with New York Heart Association class II and III congestive heart failure.

Reaction of enzyme-bound 5-deazaflavin with peroxides. Pyrimidine ring contraction via an epoxide intermediate

Reaction of peroxides with 5-deazaflavin bound to glucose oxidase, lactate oxidase, or D-amino acid oxidase results in the formation of 5-deazaflavin 4a, 5-epoxide. The reaction of D-amino acid oxidase with m-chloroperoxybenzoate is an exception since the reagent reacts rapidly with the protein moiety to form m-chlorobenzoate which then binds noncovalently near the unmodified coenzyme. Epoxide bound to glucose oxidase is converted to deazaFAD X X in a reaction similar to that observed previously with oxynitrilase and glycolate oxidase. With lactate oxidase the epoxide is quite stable in the absence of light. With D-amino acid oxidase, denaturation of the protein is accompanied by the release of the epoxide into solution where it decomposes in a manner similar to that observed with model epoxide compounds at neutral pH. Reaction of deazaFAD X X with phosphodiesterase and alkaline phosphatase yields deazariboflavin X X. The same compound has been formed in model studies by exposing 5-deazariboflavin 4a,5-epoxide to alkaline conditions. Structural studies indicate that this reaction involves contraction of the pyrimidine ring to yield 4-ribityl-6,7-dimethyloxazolo[ 4,5-b ]quinolin-2(4H)-one. Model reaction studies are consistent with a mechanism initiated by alkaline hydrolysis of the pyrimidine ring at position 4 followed by two additional steps which proceed at neutral pH. A similar mechanism for the enzyme reactions appears likely since analogous intermediates are detected in the glycolate oxidase and the model reactions. The results suggest that position 4 of the coenzyme in oxynitrilase, glycolate oxidase, and glucose oxidase must be accessible to solvent and that the protein moiety must facilitate the initial hydrolysis of the pyrimidine ring since the enzyme reactions occur at neutral pH. Failure to observe formation of deazaFMN X X with lactate oxidase is attributed, at least in part, to the inaccessibility of the pyrimidine ring to solvent.

Faecal bacterial flora in cancer of the colon

Selective aerobic and anaerobic plate media were employed to isolate the predominant faecal flora of patients with cancer of the colon (CC), cancer with non-gastrointestinal involvement (NGI), and with non-malignant diseases (N). The CC and N groups did not differ significantly in either total aerobic or anaerobic counts. The CC group did have a significantly lower anaerobic/aerobic ratio compared with the N group (2.42 vs. 2.96, P less than 0.05). This was the result of a greater predominance of aerobic bacteria and a decrease in anaerobic cocci, Eubacterium and Fusobacterium in the CC group. Previous studies report that aerobic organisms have a greater ability to produce amines than non-spore forming anaerobes. If the intestinal flora can produce carcinogenic nitrosamines in vivo from amines and nitrites, the aerobic bacterium in the faeces may be of importance in supplying the amine substrate for nitrosation. The comparison of the NGI group with the N group showed a significant variation in the total anaerobic count (11.02 vs. 11.41, P less than 0.05) and in the composition of the faecal flora. This indicates that discretion must be used in analysing the data obtained from cancer patients, as the presence of a carcinoma may be responsible for changes in bacterial flora.