D. Kim Turgeon

Role of intestinal P-glycoprotein (mdr1) in interpatient variation in the oral bioavailability of cyclosporine

Interpatient differences in the oral clearance of cyclosporine (INN, ciclosporin) have been partially attributed to variation in the activity of a single liver enzyme termed CYP3A4. Recently it has been shown that small bowel also contains CYP3A4, as well as P‐glycoprotein, a protein able to transport cyclosporine. To assess the importance of these intestinal proteins, the oral pharmacokinetics of cyclosporine were measured in 25 kidney transplant recipients who each had their liver CYP3A4 activity quantitated by the intravenous [14C‐N‐methyl]‐erythromycin breath test and who underwent small bowel biopsy for measurement of CYP3A4 and P‐glycoprotein. Forward multiple regression revealed that 56% (i.e., r2 = 0.56) and 17% of the variability in apparent oral clearance [log (dose/area under the curve)] were accounted for by variation in liver CYP3A4 activity (p < 0.0001) and intestinal P‐glycoprotein concentration (p = 0.0059), respectively. For peak blood concentration, liver CYP3A4 activity accounted for 32% (p = 0.0002) and P‐glycoprotein accounted for an additional 30% (p = 0.0024) of the variability. Intestinal levels of CYP3A4, which varied tenfold, did not appear to influence any cyclosporine pharmacokinetic parameter examined. We conclude that intestinal P‐glycoprotein plays a significant role in the first‐pass elimination of cyclosporine, presumably by being a rate‐limiting step in absorption. Drug interactions with cyclosporine previously ascribed to intestinal CYP3A4 may instead be mediated by interactions with intestinal P‐glycoprotein.

Difluoromethylornithine plus sulindac for the prevention of sporadic colorectal adenomas: a randomized placebo-controlled, double-blind trial.

Abstract Preclinical studies of chemoprevention drugs given in combination at low doses show remarkable efficacy in preventing adenomas with little additional toxicities, suggesting a strategy to improve risk to benefit ratios for preventing recurrent adenomas. Three hundred seventy-five patients with history of resected (≥3 mm) adenomas were randomly assigned to receive oral difluoromethylornithine (DFMO) 500 mg and sulindac 150 mg once daily or matched placebos for 36 months, stratified by use of low-dose aspirin (81 mg) at baseline and clinical site. Follow-up colonoscopy was done 3 years after randomization or off-study. Colorectal adenoma recurrence was compared among the groups with log-binomial regression. Comparing the outcome in patients receiving placebos to those receiving active intervention, (a) the recurrence of one or more adenomas was 41.1% and 12.3% (risk ratio, 0.30; 95% confidence interval, 0.18-0.49; P < 0.001); (b) 8.5% had one or more advanced adenomas, compared with 0.7% of patients (risk ratio, 0.085; 95% confidence interval, 0.011-0.65; P < 0.001); and (c) 17 (13.2%) patients had multiple adenomas (>1) at the final colonoscopy, compared with 1 (0.7%; risk ratio, 0.055; 0.0074-0.41; P < 0.001). Serious adverse events (grade ≥3) occurred in 8.2% of patients in the placebo group, compared with 11% in the active intervention group (P = 0.35). There was no significant difference in the proportion of patients reporting hearing changes from baseline. Recurrent adenomatous polyps can be markedly reduced by a combination of low oral doses of DFMO and sulindac and with few side effects.

Comparison of urinary 6‐β‐cortisol and the erythromycin breath test as measures of hepatic P450IIIA (CYP3A) activity

The production of 14CO2 in the breath from an intravenous dose of [14C‐N‐methyl] ‐erythromycin (the erythromycin breath test [ERMBT]) and the measurement of the ratio of 6‐β‐cortisol to free cortisol (6‐β‐F/FF) in the urine have each been proposed as means of measuring hepatic P450IIIA catalytic activity in patients. We found that there was a significant correlation between the results of each test (r = 0.59, p < 0.001) in 47 patients who were without liver disease and who were not taking medications believed to influence P450IIIA catalytic activity. In the 24 of these patients who were subsequently treated with the P450IIIA substrate cyclosporine, the ERMBT result was highly correlated with the mean trough cyclosporine blood level observed; however, there was no correlation between urinary 6‐β‐F/FF and the cyclosporine blood levels. In a separate study of a patient during the anhepatic phase of liver transplantation surgery, the ERMBT result decreased by greater than 85%, whereas urinary 6‐β‐F/FF decreased by just 50%. We conclude that the ERMBT and urinary 6‐β‐F/FF do not always provide similar information about P450IIIA catalytic activity in patients, possibly because of extrahepatic production of 6‐β‐F. Of the two tests, the ERMBT appears to provide the most relevant information for cyclosporine administration.

Missed Adenomas during Colonoscopic Surveillance in Individuals with Lynch Syndrome (Hereditary Nonpolyposis Colorectal Cancer)

Background and Aims: Lynch syndrome (also known as hereditary nonpolyposis colon cancer) is associated with an increased risk for colorectal cancer, which can arise despite frequent colonoscopic exams. We evaluated the adenoma miss rate of conventional colonoscopy in patients with Lynch syndrome, and compared the sensitivity of chromoendoscopy versus intensive inspection for detecting polyps missed by conventional colonoscopy. Methods: Fifty-four subjects with Lynch syndrome underwent tandem colonoscopies at four centers of the Great Lakes-New England Clinical Epidemiology and Validation Center of the Early Detection Research Network. All participants first had a conventional colonoscopy with removal of all visualized polyps. The second endoscopy was randomly assigned as either pancolonic indigo carmine chromoendoscopy or standard colonoscopy with intensive inspection lasting >20 minutes. Size, histology, and number of polyps detected on each exam were recorded. Results: After undergoing standard colonoscopy, 28 individuals were randomized to a second exam with chromoendoscopy and 26 underwent intensive inspection. The mean interval since last colonoscopy was 17.5 months. Seventeen polyps (10 adenomas and 7 hyperplastic polyps) were identified on the first standard colonoscopies. Twenty-three additional polyps (12 adenomas and 11 hyperplastic polyps) were found on the second exams, yielding an adenoma miss rate of 55%. Fifteen polyps (5 adenomas and 10 hyperplastic polyps) were found in subjects who had chromoendoscopy and 8 polyps (7 adenomas and 1 hyperplastic polyp) in those who had intensive inspection. Chromoendoscopy was associated with more normal tissue biopsies (11 versus 5) and longer procedure times compared with intensive inspection (29.8 ± 9.5 versus 25.3 ± 5.8 minutes; P = 0.04). Controlling for age, number of previous colonoscopies, procedure time, and prior colonic resection, chromoendoscopy detected more polyps (P = 0.04), but adenoma detection was not significantly different compared with intensive inspection (P = 0.27). Conclusions: Small adenomas are frequently missed in patients with Lynch syndrome. Although chromoendoscopy did not detect more missed adenomas than intensive inspection in this pilot study, larger trials are needed to determine optimal surveillance techniques in this high-risk population.

P450 3A activity and cyclosporine dosing in kidney and heart transplant recipients

Interpatient differences in the kinetics of cyclosporine appear to result in part from interindividual differences in the catalytic activity of an enzyme termed P450 3A. We investigated the relationship between P450 3A activity, as measured by the erythromycin breath test (ERMBT), and the appropriate stable daily dose of cyclosporine as currently determined by physicians at our institution. The ERMBT was administered to kidney and heart allograft recipients who had attended at least two monthly clinic visits without having their daily cyclosporine dose changed. There was a significant positive correlation between the ERMBT result and the daily cyclosporine doses (in milligrams per kilogram) in both the heart (r = 0.68; p = 0.04; n = 9) and kidney (r = 0.68; p = 0.03; n = 10) recipients. To confirm our findings, we prospectively administered the ERMBT on multiple occasions to 20 patients who were undergoing kidney transplantation. Although the transplant physicians were blinded to the ERMBT results, the test predicted the stable daily doses of cyclosporine that they ultimately prescribed to the patients (r = 0.54; p = 0.015). When data from all 39 patients were pooled and subjected to multiple regression analysis, the ERMBT was the only variable examined that significantly correlated with the stable daily cyclosporine dose (r = 0.63; p < 0.001; n = 39). In the 20 patients prospectively studied, the prescribed daily dose of cyclosporine generally decreased during the months after surgery and the percentage changes in cyclosporine daily dose correlated with changes in P450 3A activity during this period (r = 0.47; p = 0.03). We conclude that interpatient and intrapatient differences in P450 3A activity in part account for the cyclosporine dosing practices of transplant physicians.

Erythromycin breath test predicts oral clearance of cyclosporine in kidney transplant recipients

It has been shown recently that cyclosporine is largely metabolized by P450IIIA (CYP3A), an enzyme whose catalytic activity varies significantly among patients. To determine whether heterogeneity in P450IIIA activity contributes to interpatient differences in cyclosporine dosing requirements, the oral pharmacokinetics of the drug were determined in 20 stable kidney transplant recipients. P450IIIA activity was then measured in each patient by use of the erythromycin breath test. In the 16 patients who were at steady state, the logarithm of the apparent oral clearance of cyclosporine correlated significantly with the rate of 14CO2 exhaled in breath after intravenous administration of [14C N‐methyl] erythromycin (r = 0.55, p = 0.03). No significant correlations existed between apparent oral clearance and age, high‐density lipoprotein cholesterol or low‐density lipoprotein cholesterol, or hematocrit in these patients. We conclude that heterogeneity in P450IIIA activity significantly contributes to interpatient differences in dosing requirements of cyclosporine in kidney transplant patients.

Chromoendoscopy detects more adenomas than colonoscopy using intensive inspection without dye spraying.

Conventional colonoscopy misses some neoplastic lesions. We compared the sensitivity of chromoendoscopy and colonoscopy with intensive inspection for detecting adenomatous polyps missed by conventional colonoscopy. Fifty subjects with a history of colorectal cancer or adenomas underwent tandem colonoscopies at one of five centers of the Great Lakes New England Clinical Epidemiology and Validation Center of the Early Detection Research Network. The first exam was a conventional colonoscopy with removal of all visualized polyps. The second exam was randomly assigned as either pan-colonic indigocarmine chromoendoscopy or standard colonoscopy with intensive inspection lasting >20 minutes. Size, histology, and numbers of polyps detected on each exam were recorded. Twenty-seven subjects were randomized to a second exam with chromoendoscopy and 23 underwent intensive inspection. Forty adenomas were identified on the first standard colonoscopies. The second colonoscopies detected 24 additional adenomas: 19 were found using chromoendoscopy and 5 were found using intensive inspection. Chromoendoscopy found additional adenomas in more subjects than did intensive inspection (44% versus 17%) and identified significantly more missed adenomas per subject (0.7 versus 0.2, P < 0.01). Adenomas detected with chromoendoscopy were significantly smaller (mean size 2.66 ± 0.97 mm) and were more often right-sided. Chromoendoscopy was associated with more normal tissue biopsies and longer procedure times than intensive inspection. After controlling for procedure time, chromoendoscopy detected more adenomas and hyperplastic polyps compared with colonoscopy using intensive inspection alone. Chromoendoscopy detected more polyps missed by standard colonoscopy than did intensive inspection. The clinical significance of these small missed lesions warrants further study.

Early detection of colon cancer: new tests on the horizon.

This year, the American Cancer Society reported that the rate of decline in both the incidence and mortality of colorectal cancer has increased over the last two decades. This success is felt to be attributable to the early detection and treatment of colonic adenomas and early-stage colorectal cancers. However, the current recommended ‘menu of options’ for screening is limited by poor patient acceptance, low sensitivity, and both high cost and poor accessibility for application to a large general screening population (colonoscopy). Computerized tomography and magnetic resonance colonography offer an alternative method for the identification of polyps and early lesions in certain patients, but have cost, access, and acceptance limitations that are similar to those of colonoscopy; thus, they present similar barriers to their use in broad population screening. These limitations provide a strong rationale for the development of early colorectal cancer detection biomarkers that are simple to use and are cost effective.A successful biomarker or biomarker panel, coupled with the colonoscopic follow-up of only those patients with positive results, would reduce the burden and morbidity associated with the screening of colonoscopy. This would most likely result in enhanced adherence to colorectal screening, as well as a dramatic reduction in the incidence and mortality rates of colorectal cancer. In this paper, we review recent advances in the discovery of potential colorectal cancer biomarkers. Their applicability to clinical population screening will require large prospective validation.

Phase II Study of the Effects of Ginger Root Extract on Eicosanoids in Colon Mucosa in People at Normal Risk for Colorectal Cancer

Inhibitors of COX indicate that upregulation of inflammatory eicosanoids produced by COX, and in particular prostaglandin E2 (PGE2), are early events in the development of colorectal cancer (CRC). Ginger has shown downregulation of COX in vitro and decreased incidence/multiplicity of adenomas in rats. This study was conducted to determine if 2.0 g/d of ginger could decrease the levels of PGE2, 13-hydroxy-octadecadienoic acids, and 5-, 12-, and 15-hydroxyeicosatetraenoic acid (5-, 12-, and 15-HETE), in the colon mucosa of healthy volunteers. To investigate this aim, we randomized 30 subjects to 2.0 g/d ginger or placebo for 28 days. Flexible sigmoidoscopy at baseline and day 28 was used to obtain colon biopsies. A liquid chromatography mass spectrometry method was used to determine eicosanoid levels in the biopsies, and levels were expressed per protein or per free arachidonic acid. There were no significant differences in mean percent change between baseline and day 28 for any of the eicosanoids, when normalized to protein. There was a significant decrease in mean percent change in PGE2 (P = 0.05) and 5-HETE (P = 0.04), and a trend toward significant decreases in 12-HETE (P = 0.09) and 15-HETE (P = 0.06) normalized to free arachidonic acid. There was no difference between the groups in terms of total adverse events P = 0.55). On the basis of these results, it seems that ginger has the potential to decrease eicosanoid levels, perhaps by inhibiting their synthesis from arachidonic acid. Ginger also seemed to be tolerable and safe. Further investigation in people at high risk for CRC seems warranted. Cancer Prev Res; 4(11); 1929–37. ©2011 AACR.

Multimodal endoscope can quantify wide-field fluorescence detection of Barrett's neoplasia.

BACKGROUND AND STUDY AIMS To demonstrate the clinical use of a multimodal endoscope with a targeted fluorescently labeled peptide for quantitative detection of Barretts neoplasia. PATIENTS AND METHODS We studied 50 patients with Barretts esophagus using a prototype multimodal endoscope with a fluorescently labeled peptide. Co-registered fluorescence and reflectance images were converted to ratios to correct for differences in distance and geometry over the image field of view. The ratio images were segmented using a unique threshold that maximized the variance between high and low intensities to localize regions of high grade dysplasia (HGD) and esophageal adenocarcinoma (EAC). RESULTS Early neoplasia (HGD and EAC) was identified with 94 % specificity and 96 % positive predictive value at a threshold of 1.49. The mean results for HGD and EAC were significantly greater than those for squamous/Barretts esophagus and low grade dysplasia by one-way analysis of variance (ANOVA). The receiver operator characteristic curve for detection of early neoplasia had an area under the curve of 0.884. No adverse events associated with the endoscope or peptide were found. CONCLUSION A multimodal endoscope can quantify fluorescence images from targeted peptides to localize early Barretts neoplasia. (ClinicalTrials.gov number NCT01630798.).