Correlation between intraluminal oxygen gradient and radial partitioning of intestinal microbiota

BACKGROUND & AIMS

The gut microbiota is a complex and densely populated community in a dynamic environment determined by host physiology. We investigated how intestinal oxygen levels affect the composition of the fecal and mucosally adherent microbiota.

METHODS

We used the phosphorescence quenching method and a specially designed intraluminal oxygen probe to dynamically quantify gut luminal oxygen levels in mice. 16S ribosomal RNA gene sequencing was used to characterize the microbiota in intestines of mice exposed to hyperbaric oxygen, human rectal biopsy and mucosal swab samples, and paired human stool samples.

RESULTS

Average Po2 values in the lumen of the cecum were extremely low (<1 mm Hg). In altering oxygenation of mouse intestines, we observed that oxygen diffused from intestinal tissue and established a radial gradient that extended from the tissue interface into the lumen. Increasing tissue oxygenation with hyperbaric oxygen altered the composition of the gut microbiota in mice. In human beings, 16S ribosomal RNA gene analyses showed an increased proportion of oxygen-tolerant organisms of the Proteobacteria and Actinobacteria phyla associated with rectal mucosa, compared with feces. A consortium of asaccharolytic bacteria of the Firmicute and Bacteroidetes phyla, which primarily metabolize peptones and amino acids, was associated primarily with mucus. This could be owing to the presence of proteinaceous substrates provided by mucus and the shedding of the intestinal epithelium.

CONCLUSIONS

In an analysis of intestinal microbiota of mice and human beings, we observed a radial gradient of microbes linked to the distribution of oxygen and nutrients provided by host tissue.

A randomized phase III study evaluating the efficacy and safety of NEPA, a fixed-dose combination of netupitant and palonosetron, for prevention of chemotherapy-induced nausea and vomiting following moderately emetogenic chemotherapy

BACKGROUND

Antiemetic guidelines recommend co-administration of agents that target multiple molecular pathways involved in emesis to maximize prevention and control of chemotherapy-induced nausea and vomiting (CINV). NEPA is a new oral fixed-dose combination of 300 mg netupitant, a highly selective NK1 receptor antagonist (RA) and 0.50 mg palonosetron (PALO), a pharmacologically and clinically distinct 5-HT3 RA, which targets dual antiemetic pathways.

PATIENTS AND METHODS

This multinational, randomized, double-blind, parallel group phase III study (NCT01339260) in 1455 chemotherapy-naïve patients receiving moderately emetogenic (anthracycline-cyclophosphamide) chemotherapy evaluated the efficacy and safety of a single oral dose of NEPA versus a single oral dose (0.50 mg) of PALO. All patients also received oral dexamethasone (DEX) on day 1 only (12 mg in the NEPA arm and 20 mg in the PALO arm). The primary efficacy end point was complete response (CR: no emesis, no rescue medication) during the delayed (25-120 h) phase in cycle 1.

RESULTS

The percentage of patients with CR during the delayed phase was significantly higher in the NEPA group compared with the PALO group (76.9% versus 69.5%; P = 0.001), as were the percentages in the overall (0-120 h) (74.3% versus 66.6%; P = 0.001) and acute (0-24 h) (88.4% versus 85.0%; P = 0.047) phases. NEPA was also superior to PALO during the delayed and overall phases for all secondary efficacy end points of no emesis, no significant nausea and complete protection (CR plus no significant nausea). NEPA was well tolerated with a similar safety profile as PALO.

CONCLUSIONS

NEPA plus a single dose of DEX was superior to PALO plus DEX in preventing CINV following moderately emetogenic chemotherapy in acute, delayed and overall phases of observation. As a fixed-dose antiemetic drug combination, NEPA along with a single dose of DEX on day 1 offers guideline-based prophylaxis with a convenient, single-day treatment.

Cardiac Safety Data for Casopitant, a Neurokinin-1 Receptor Antagonist, Given with Anthracycline

Objectives: The NK-1 receptor antagonist casopitant is a promising agent for the prevention of chemotherapy-related and postoperative nausea and vomiting. However, findings suggestive of cardiac damage were noted in animal studies of long-term administration of casopitant at supratherapeutic doses. Cardiac evaluation of the concomitant use of casopitant with anthracyclines was therefore of particular interest due to myocyte loss associated with anthracycline use.Methods: Chemotherapy-naïve patients receiving anthracyclines as part of a Phase III moderately emetogenic chemotherapy study regimen were randomized to receive ondansetron and dexamethasone plus one of the following casopitant regimens: single-dose 150-mg oral casopitant (ORAL1); 3-day IV/oral casopitant (90 mg IV/50 mg oral/50 mg oral) (IV/ORAL); 3-day oral casopitant (150/50/50 mg) (ORAL3); or placebo. Serial cardiac troponin (cTnI) levels were measured using the Beckman assay. Although this assay is generally considered reliable within the range of 0.04-0.5 ng/mL, levels below the limit of quantitation (LOQ) (&lt;0.04 ng/mL) were also evaluated in an attempt to identify patterns of change below LOQ. Further cardiac assessment consisting of left ventricular ejection fraction (LVEF) monitoring was conducted in patients with cTnI levels ³0.12 ng/mL.Results: In total, 611 patients were evaluated: 155 ORAL1, 145 IV/ORAL, 159 ORAL3, and 152 placebo; no risk factor variation between groups was observed. Adverse events were balanced across treatment groups. Cardiovascular adverse events occurred in 3% of patients in each of the placebo, ORAL1, and ORAL/IV groups and in 2% of the ORAL3 group. Three patients (0.5%) had cTnI &gt;0.12 ng/mL (1 each IV/ORAL, ORAL3, and placebo); all LVEF determinations were normal at follow-up, with the exception of 1 patient with mitral regurgitation but normal ejection fraction. A total of 59 patients (9.7%) had median cTnI 0.04-0.12 ng/mL. Of the remaining patients with cTnI below LOQ, median baseline levels across groups were similar (ORAL1 and IV/ORAL 0.008 ng/mL; ORAL3 0.01 ng/mL; placebo 0.009 ng/mL). After 4 cycles of anthracycline, median cTnI increased to 0.02 ng/mL in all groups, with no difference noted between casopitant and placebo groups.Conclusions: Thorough monitoring of cardiac-related toxicities including cardiac (S)AEs, ECG, and ejection fraction data showed no evidence of increased risk of cardiac damage in the casopitant groups compared with control. Subclinical elevations in cTnI occurred in patients receiving anthracyclines but were not considered to be related to or accentuated by simultaneous administration of casopitant. cTnI elevations were similar across treatment groups and were well below rates reported in the literature for a patient population receiving higher doses of anthracycline. Use of appropriate cardiac biomarkers in ranges below those commonly used to detect infarction may be valuable to detect or exclude subclinical toxicity of potentially cardiotoxic agents used in combination. Additional analysis is ongoing.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 1118.

Alterations in sex steroids and gonadotropins in post-menopausal women subsequent to long-term mifepristone administration

Long-term administration of progesterone antagonists (PAs) and progesterone receptor modulators (PRMs) has been proposed as a novel hormonal therapy for various hormone dependent maladies. We studied the long-term endocrine effects of mifepristone on the kinetics of estradiol (E(2)) and its precursors, and on gonadotropin levels in five postmenopausal women treated for unresectable meningioma with mifepristone [200 mg/day] for at least 15 months. Serum samples were analyzed for LH, FSH and SHBG with fluoroimmunoassay; androstenedione (A), testosterone (T), estrone (E(1)) and E(2) were measured with radioimmunoassay (RIA). Serum levels of mifepristone were measured using both RIA and high performance-liquid chromatography (HPLC). Serum levels (mean +/- SD) of LH and FSH were suppressed from pretreatment values of 32 +/- 16 and 65 +/- 30 IU/l to 13 +/- 7 and 33 +/- 16 IU/l at 6 months (P < 0.05), respectively. Serum (mean +/- SD) A, T, E(1), and E(2) were increased from initial values of 6.9 +/- 0.9 nmol/l, 1.2 +/- 0.3 nmol/l, 77 +/- 25 pmol/l, and 29 +/- 14 pmol/l to 6 month values of 13.1 +/- 5.6 nmol/l, 1.8 +/- 0.6 nmol/l, 178 +/- 60 pmol/l, and 45 +/- 22 pmol/l (n.s.). The correlation coefficients between the levels of A, T, E(1), and E(2) were statistically significant, whereas the ratios of T/A, E(1)/A, E(2)/E(1), and E(2)/T remained unchanged. The levels of SHBG remained stable, and ranged from 48 +/- 10 to 65 +/- 9 nmol/l (mean +/- SD). Thus, prolonged mifepristone treatment marginally increased the serum levels of A, T, E(1) and E(2). These effects of mifepristone are likely due to its antiglucocorticoid effect and thus increased secretion of adrenal A. Serum levels of LH and FSH declined. The serum levels of gonadotropins and those of T, E(1) and E(2) were inversely, yet significantly, correlated. Therefore the decrease in LH and FSH might reflect the slightly increased levels of T, E(1) and E(2). However, the lack of change in SHBG and the low E(2) levels suggest that enhanced systemic estrogen effects are unlikely during long-term mifepristone treatment.

Alterations in the pituitary-thyroid and pituitary-adrenal axes--consequences of long-term mifepristone treatment

The effects of short-term administration of the antiprogestin and antiglucocorticoid, mifepristone, have been well characterized. However, little is known about the effects of prolonged administration of mifepristone. We analyzed hormonal parameters in four female and three male patients with unresectable meningioma who were treated with mifepristone (200 mg/d) for 20 to 40 months. Serum samples were collected at monthly intervals approximately 24 hours following mifepristone ingestion. Serum thyrotropin (TSH), thyroxine (T4), free T4 (fT4), 3,5,3-triiodothyronine (T3), prolactin, and cortisol were analyzed by fluoroimmunoassay, and androstenedione by radioimmunoassay (RIA). Levels of mifepristone and its three most proximal metabolites were measured by high-performance liquid chromatography. TSH values increased significantly (P < .005, one-way ANOVA), with the most pronounced increase evident during the first 3 months of mifepristone treatment. Despite these changes, concentrations of TSH remained within the normal range throughout the treatment period. There were no significant changes in serum T4, fT4, T3 or prolactin; however, a transient decrease in serum T4 was noted at 2 to 3 months. Cortisol and androstenedione values increased significantly and in parallel (P < .05), suggesting an adrenal origin also for androstenedione. As during short-term administration, levels of mifepristone and its metabolites remained stable in the micromolar range. Individual levels of mifepristone were significantly correlated with those of TSH and cortisol. This suggests that the alterations in the pituitary-thyroid and -adrenal axes occurred in a concentration-dependent manner. It is concluded that long-term mifepristone treatment results in resetting of the pituitary-thyroid balance. As in the case with cortisol and androstenedione, it is likely that the alterations in serum TSH are due to the antiglucocorticoid properties of mifepristone. The clinical significance of these biochemical alterations in thyroid homeostasis remains to be determined. However, monitoring thyroid function during long-term mifepristone treatment appears to be warranted.

Platinum-DNA damage in leukocyte DNA of patients receiving carboplatin and cisplatin chemotherapy, measured by atomic absorption spectrometry

Previous studies have shown that platinum-DNA adduct level in leukocyte DNA (measured by antibody methodology) is directly related to disease response in ovarian cancer and testicular cancer. To determine if this principle could be more broadly applied, platinum-DNA damage was studied in a blinded fashion in leukocyte DNA of 21 cancer patients who received carboplatin (day 1) and cisplatin (day 3) in a phase 1 clinical trial. Fifteen different tumor types were included in this cohort. Using atomic absorption spectrometry with Zeeman background correction, DNA-bound platinum was measured during cycles 1 (C1) and 2 (C2) of therapy for most patients. For each of two cycles of therapy, most patients developed measurable levels of adduct after carboplatin, and in most patients adduct levels increased further after cisplatin, often in a supra-additive fashion. Total mg dose levels varied by less than 2-fold, whereas individual patients differed by as much as 10(3) in their adduct measurements after C1 and after C2, and by 29-fold after the very first carboplatin dose. All patients had refractory disease at the initiation of therapy, and 19 patients were evaluable for disease response. Adduct determinations were made 24 h after the first dose of platinum therapy in 17 of these individuals. Mean adduct levels after the first dose of carboplatin were higher in six responders (50 fmol/micrograms DNA +/- 26) than in 11 non-responders (14 fmol/micrograms DNA +/- 10); Wilcoxon two sample test two-sided P = 0.0071. The six responders were patients with pleural mesothelioma (2), breast cancer, buccal mucosa cancer, esophageal cancer and ovarian cancer. Adduct levels were consistently higher in the group of responders on each day that adduct was measured, with a summary two-sided P value of 0.00011. We conclude that analysis of platinum-DNA adduct formation may help determine whether pharmacogenetics are important in cancer drug resistance; and may help to determine the relationship between DNA damage in the peripheral blood compartment and internal organ response to in vivo exposures to DNA-damaging agents.

Dose-escalation study of carboplatin (day 1) and cisplatin (day 3): tolerance and relation to leukocyte and buccal cell platinum--DNA adducts

Carboplatin and cisplatin have similar antitumor activities but different toxicities. Combining these two analogs may be expected to balance the toxicities and allow higher doses of platinum compounds to be administered with tolerable toxicity. To test this concept, a Phase I trial of carboplatin in combination with cisplatin was performed. Thirty-three eligible patients received carboplatin doses ranging from 200-480 mg/m2 on day 1 and cisplatin doses ranging from 50-100 mg/m2 on day 3 of the 28 day cycle. A 2-day interval ensured no interference in renal excretion of carboplatin by cisplatin. Myelosuppression was the dose limiting toxicity. With the usual full dose of carboplatin, 480 mg/m2, patients tolerated 50 mg/m2 of cisplatin, without apparent additional toxicity. At 100 mg/m2 of cisplatin, non-hematologic as well as hematologic toxicities frequently precluded administration of more than 300 mg/m2 of carboplatin. Platinum-DNA adduct quantitation was done in leukocytes and buccal cells during cycle 1 in most patients. The adduct-specific immunosignal in buccal cells was always increased after carboplatin and in all but one after cisplatin. The level of adducts in buccal cells increased with increasing doses of carboplatin and cisplatin. In leukocytes, measurable levels of adducts were formed after carboplatin with further contribution made by cisplatin but not obviously in a dose dependent fashion. We conclude from the toxicities observed, that combinations of carboplatin with cisplatin may have advantages over either drug alone in certain clinical situations; and that further study of platinum-DNA adducts may shed light on platinum dose-response relationships.

Kartagener's syndrome

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