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[This corrects the article DOI: 10.1093/gastro/gow048.][This corrects the article DOI: 10.1093/gastro/gow048.].

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There is growing evidence that methane production, predominantly by Methanobrevibacter smithii, in the intestines is a cause of constipation, pain, and bloating in irritable bowel syndrome with constipation (IBS-C). M smithii resides primarily in the large intestine but can also colonize the small intestine. In vitro studies found that the prodrug lactone form of lovastatin, found in cholesterol-lowering drugs, inhibited methane production in stool samples from patients with IBS-C. However, the cholesterol-lowering lovastatin ß-hydroxyacid was ineffective at inhibiting methane production in this system. A considerable amount of lovastatin is converted to hydroxyacid in the stomach and is absorbed. It was hypothesized that galenic innovations could protect lovastatin from the stomach and allow release in 2 strategic locations, the duodenum and the ileocecal region, to reach M smithii. The desired release profile was achieved by developing an oral dosage form containing lovastatin and coated with 2 different enteric polymers that enabled a pH-dependent "dual pulse" drug release. Combinations of the 2 coated tablets were encapsulated together to deliver the desired amount of lovastatin to the targeted intestinal locations. The capsules have been tested in vitro and in vivo and show promise in treating IBS-C.

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BACKGROUND: Levels of breath methane, together with breath hydrogen, are determined by means of repeated collections of both, following ingestion of a carbohydrate substrate, at 15-20 minutes intervals, until 10 samples have been obtained. The frequent sampling is required to capture a rise of hydrogen emissions, which typically occur later in the test: in contrast, methane levels are typically elevated at baseline. If methane emissions represent the principal objective of the test, a spot methane test (i.e. a single-time-point sample taken after an overnight fast without administration of substrate) may be sufficient. METHODS: We analysed 10-sample lactulose breath test data from 11 674 consecutive unique subjects who submitted samples to Commonwealth Laboratories (Salem, MA, USA) from sites in all of the states of the USA over a one-year period. The North American Consensus (NAC) guidelines criteria for breath testing served as a reference standard. RESULTS: The overall prevalence of methane-positive subjects (by NAC criteria) was 20.4%, based on corrected methane results, and 18.9% based on raw data. In our USA dataset, the optimal cut-off level to maximize sensitivity and specificity was ≥4 ppm CH4, 94.5% [confidential interval (CI): 93.5-95.4%] and 95.0% (CI: 94.6-95.5%), respectively. The use of a correction factor (CF) (5% CO2 as numerator) led to reclassifications CH4-high to CH4-low in 0.7 % and CH4-low to CH4-high in 2.1%. CONCLUSIONS: A cut-off value for methane at baseline of either ≥4 ppm, as in our USA dataset, or ≥ 5 ppm, as described in a single institution study, are both highly accurate in identifying subjects at baseline that would be diagnosed as 'methane-positive' in a 10-sample lactulose breath test for small intestinal bacterial overgrowth.

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UNLABELLED: Methane produced by the methanoarchaeon Methanobrevibacter smithii ( M. smithii) has been linked to constipation, irritable bowel syndrome with constipation (IBS-C), and obesity. Lovastatin, which demonstrates a cholesterol-lowering effect by the inhibition of HMG-CoA reductase, may also have an anti-methanogenesis effect through direct inhibition of enzymes in the archaeal methanogenesis pathway. We conducted protein-ligand docking experiments to evaluate this possibility. Results are consistent with recent clinical findings. METHODS: F420-dependent methylenetetrahydromethanopterin dehydrogenase ( mtd), a key methanogenesis enzyme was modeled for two different methanogenic archaea: M. smithii and Methanopyrus kandleri. Once protein models were developed, ligand-binding sites were identified. Multiple ligands and their respective protonation, isomeric and tautomeric representations were docked into each site, including F420-coenzyme (natural ligand), lactone and ß-hydroxyacid forms of lovastatin and simvastatin, and other co-complexed ligands found in related crystal structures. RESULTS: 1) Generally, for each modeled site the lactone form of the statins had more favorable site interactions compared to F420; 2) The statin lactone forms generally had the most favorable docking scores, even relative to the native template PDB ligands; and 3) The statin ß-hydroxyacid forms had less favorable docking scores, typically scoring in the middle with some of the F420 tautomeric forms. Consistent with these computational results were those from a recent phase II clinical trial ( NCT02495623) with a proprietary, modified-release lovastatin-lactone (SYN-010) in patients with IBS-C, which showed a reduction in symptoms and breath methane levels, compared to placebo. CONCLUSION: The lactone form of lovastatin exhibits preferential binding over the native-F420 coenzyme ligand in silico and thus could inhibit the activity of the key M. smithii methanogenesis enzyme mtd in vivo. Statin lactones may thus exert a methane-reducing effect that is distinct from cholesterol lowering activity, which requires HMGR inhibition by statin ß-hydroxyacid forms.

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BACKGROUND: ONT-093 is an orally bioavailable inhibitor of P-glycoprotein (P-gp). In pre-clinical studies, ONT-093 could inhibit P-gp and reverse multidrug resistance at nM concentrations with no effect on paclitaxel pharmacokinetics. Phase I trials of ONT-093 in normal human volunteers showed no dose-limiting toxicities at serum concentrations associated with biologic activity achieved with doses ranging from 300 to 500 mg. METHODS: Phase I pharmacokinetic trial of ONT-093 in doses from 300 to 500 mg administered before and after intravenous paclitaxel doses of 150 to 175 mg/m(2) repeated every 21 days. All patients received paclitaxel alone on cycle 1. RESULTS: 18 patients were enrolled onto 4 dose levels. Toxicity of the combination included neutropenia, arthralgia, myalgia, and peripheral neuropathy. Four of 6 patients receiving 500 mg doses of ONT-093 and paclitaxel at 175 mg/m(2) (dose level 4) had higher-grade neutropenia with cycle 2, with 1 patient experiencing febrile neutropenia. Plasma pharmacokinetic parameters of paclitaxel were unchanged between cycle 1 and 2 for dose levels 1 to 3, but at dose level 4, 45-65% increases in paclitaxel AUC were observed in 4 of the 6 patients. Mean C(max) of ONT-093 was 9 microM (range 5-15 microM) which were 3- to 5-fold higher than in single agent studies of ONT-093. CONCLUSIONS: Doses of ONT-093 achieving serum concentrations associated with biological activity were well tolerated in combination with standard doses of paclitaxel. Toxicities of the combination in this schedule were mainly attributable to paclitaxel and dose-limiting toxicity was limited to febrile neutropenia. There was an apparent pharmacokinetic interaction between paclitaxel and ONT-093, possibly related in part to the excipient, Cremophor, present in the paclitaxel formulation.

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