Multistage coupling of independent laser-plasma accelerators.

Laser-plasma accelerators (LPAs) are capable of accelerating charged particles to very high energies in very compact structures. In theory, therefore, they offer advantages over conventional, large-scale particle accelerators. However, the energy gain in a single-stage LPA can be limited by laser diffraction, dephasing, electron-beam loading and laser-energy depletion. The problem of laser diffraction can be addressed by using laser-pulse guiding and preformed plasma waveguides to maintain the required laser intensity over distances of many Rayleigh lengths; dephasing can be mitigated by longitudinal tailoring of the plasma density; and beam loading can be controlled by proper shaping of the electron beam. To increase the beam energy further, it is necessary to tackle the problem of the depletion of laser energy, by sequencing the accelerator into stages, each powered by a separate laser pulse. Here, we present results from an experiment that demonstrates such staging. Two LPA stages were coupled over a short distance (as is needed to preserve the average acceleration gradient) by a plasma mirror. Stable electron beams from a first LPA were focused to a twenty-micrometre radius--by a discharge capillary-based active plasma lens--into a second LPA, such that the beams interacted with the wakefield excited by a separate laser. Staged acceleration by the wakefield of the second stage is detected via an energy gain of 100 megaelectronvolts for a subset of the electron beam. Changing the arrival time of the electron beam with respect to the second-stage laser pulse allowed us to reconstruct the temporal wakefield structure and to determine the plasma density. Our results indicate that the fundamental limitation to energy gain presented by laser depletion can be overcome by using staged acceleration, suggesting a way of reaching the electron energies required for collider applications.

Uterine artery embolisation or myomectomy for women with uterine fibroids wishing to avoid hysterectomy: a cost-utility analysis of the FEMME trial.

OBJECTIVES: To assess the cost-effectiveness of uterine artery embolisation (UAE) and myomectomy for women with symptomatic uterine fibroids wishing to avoid hysterectomy. DESIGN: Economic evaluation alongside the FEMME randomised controlled trial. SETTING: 29 UK hospitals. POPULATION: Premenopausal women who had symptomatic uterine fibroids amenable to UAE or myomectomy wishing to avoid hysterectomy. 254 women were randomised to UAE (127) and myomectomy (127). METHODS: A within-trial cost-utility analysis was conducted from the perspective of the UK NHS. MAIN OUTCOME MEASURES: Quality-adjusted life years (QALYs) measured using the EuroQoL EQ-5D-3L, combined with costs to estimate cost-effectiveness over 2 and 4 years of follow-up. RESULTS: Over a 2-year time horizon, UAE was associated with higher mean costs (difference £645; 95% CI -1381 to 2580) and lower QALYs (difference -0.09; 95% CI -0.11 to -0.04) when compared with myomectomy. Similar results were observed over the 4-year time horizon. Thus, UAE was dominated by myomectomy. Results of the sensitivity analyses were consistent with the base case results for both years. Over 2 years, UAE was associated with higher costs (difference £456; 95% CI -1823 to 3164) and lower QALYs (difference -0.06; 95% CI -0.11 to -0.02). CONCLUSIONS: Myomectomy is a cost-effective option for the treatment of uterine fibroids. The differences in costs and QALYs are small. Women should be fully informed and have the option to choose between the two procedures. TWEETABLE ABSTRACT: Fully informed women with uterine fibroids should have a choice between uterine artery embolisation or myomectomy.

Premature ovarian insufficiency: the need for evidence on the effectiveness of hormonal therapy.

Premature ovarian insufficiency (POI) - the loss of ovarian function before the age of 40 years, a decade before natural menopause - is a life-changing diagnosis for women. POI causes significant short-term and long-term morbidity related to estrogen deficiency. The condition is managed by providing exogenous estrogen replacement, usually as the oral contraceptive pill or hormone therapy. These preparations have different estrogen formulations and may have differing benefits and risks. At present, there are no robust data to inform clinical recommendations and women's decision-making about treatment that they may be taking for many years. The POISE study (Premature Ovarian Insufficiency Study of Effectiveness of hormonal therapy) has been designed to determine whether hormone therapy is superior to combined oral contraceptives on important clinical outcomes and patient-reported symptoms, based on the hypothesis that hormone therapy provides more physiological continuous hormone supplementation with natural estrogens. The study is an open and pragmatic, parallel, randomized controlled trial. The primary outcome is absolute bone mineral density assessed by dual-energy X-ray absorptiometry of the lumbar spine after 2 years of treatment. The study will also investigate cardiovascular markers, symptom relief and acceptability of treatment, and will continue to collect long-term data on fractures and cardiovascular events. Results will inform future guidance on management of POI.

Practitioner review: health anxiety in children and young people in the context of the COVID-19 pandemic.

Health-related fear is a normal and common response in the face of the global pandemic of COVID-19. Children and young people are frequently being exposed to messages about the threat to health, including from the media and authorities. Whilst for most, their anxiety will be proportionate to the threat, for some, existing pre-occupation with physical symptoms and illness will become more problematic. There is a growing body of evidence that health anxiety may occur in childhood, however much of the literature is taken from research using adult samples. This practitioner review aims to give an overview of the assessment and treatment of health-related worries in children and young people in the context of the COVID-19 pandemic. This review is based on the limited existing evidence in this population and the more substantial evidence base for treating health anxiety in adults. We consider the adaptations needed to ensure such interventions are developmentally appropriate.

Crop production in the USA is frequently limited by a lack of pollinators.

Most of the world's crops depend on pollinators, so declines in both managed and wild bees raise concerns about food security. However, the degree to which insect pollination is actually limiting current crop production is poorly understood, as is the role of wild species (as opposed to managed honeybees) in pollinating crops, particularly in intensive production areas. We established a nationwide study to assess the extent of pollinator limitation in seven crops at 131 locations situated across major crop-producing areas of the USA. We found that five out of seven crops showed evidence of pollinator limitation. Wild bees and honeybees provided comparable amounts of pollination for most crops, even in agriculturally intensive regions. We estimated the nationwide annual production value of wild pollinators to the seven crops we studied at over $1.5 billion; the value of wild bee pollination of all pollinator-dependent crops would be much greater. Our findings show that pollinator declines could translate directly into decreased yields or production for most of the crops studied, and that wild species contribute substantially to pollination of most study crops in major crop-producing regions.

Pravastatin for early-onset pre-eclampsia: a randomised, blinded, placebo-controlled trial.

OBJECTIVE: Women with pre-eclampsia have elevated circulating levels of soluble fms-like tyrosine kinase-1 (sFlt-1). Statins can reduce sFlt-1 from cultured cells and improve pregnancy outcome in animals with a pre-eclampsia-like syndrome. We investigated the effect of pravastatin on plasma sFlt-1 levels during pre-eclampsia. DESIGN: Blinded (clinician and participant), proof of principle, placebo-controlled trial. SETTING: Fifteen UK maternity units. POPULATION: We used a minimisation algorithm to assign 62 women with early-onset pre-eclampsia (24+0 -31+6  weeks of gestation) to receive pravastatin 40 mg daily (n = 30) or matched placebo (n = 32), from randomisation to childbirth. PRIMARY OUTCOME: Difference in mean plasma sFlt-1 levels over the first 3 days following randomisation. RESULTS: The difference in the mean maternal plasma sFlt-1 levels over the first 3 days after randomisation between the pravastatin (n = 27) and placebo (n = 29) groups was 292 pg/ml (95% CI -1175 to 592; P = 0.5), and over days 1-14 was 48 pg/ml (95% CI -1009 to 913; P = 0.9). Women who received pravastatin had a similar length of pregnancy following randomisation compared with those who received placebo (hazard ratio 0.84; 95% CI 0.50-1.40; P = 0.6). The median time from randomisation to childbirth was 9 days (interquartile range [IQR] 5-14 days) for the pravastatin group and 7 days (IQR 4-11 days) for the placebo group. There were three perinatal deaths in the placebo-treated group and no deaths or serious adverse events attributable to pravastatin. CONCLUSIONS: We found no evidence that pravastatin lowered maternal plasma sFlt-1 levels once early-onset pre-eclampsia had developed. Pravastatin appears to have no adverse perinatal effects. TWEETABLE ABSTRACT: Pravastatin does not improve maternal plasma sFlt-1 or placental growth factor levels following a diagnosis of early preterm pre-eclampsia #clinicaltrial finds.

The cost-effectiveness of progesterone in preventing miscarriages in women with early pregnancy bleeding: an economic evaluation based on the PRISM trial.

OBJECTIVES: To assess the cost-effectiveness of progesterone compared with placebo in preventing pregnancy loss in women with early pregnancy vaginal bleeding. DESIGN: Economic evaluation alongside a large multi-centre randomised placebo-controlled trial. SETTING: Forty-eight UK NHS early pregnancy units. POPULATION: Four thousand one hundred and fifty-three women aged 16-39 years with bleeding in early pregnancy and ultrasound evidence of an intrauterine sac. METHODS: An incremental cost-effectiveness analysis was performed from National Health Service (NHS) and NHS and Personal Social Services perspectives. Subgroup analyses were carried out on women with one or more and three or more previous miscarriages. MAIN OUTCOME MEASURES: Cost per additional live birth at ≥34 weeks of gestation. RESULTS: Progesterone intervention led to an effect difference of 0.022 (95% CI -0.004 to 0.050) in the trial. The mean cost per woman in the progesterone group was £76 (95% CI -£559 to £711) more than the mean cost in the placebo group. The incremental cost-effectiveness ratio for progesterone compared with placebo was £3305 per additional live birth. For women with at least one previous miscarriage, progesterone was more effective than placebo with an effect difference of 0.055 (95% CI 0.014-0.096) and this was associated with a cost saving of £322 (95% CI -£1318 to £673). CONCLUSIONS: The results suggest that progesterone is associated with a small positive impact and a small additional cost. Both subgroup analyses were more favourable, especially for women who had one or more previous miscarriages. Given available evidence, progesterone is likely to be a cost-effective intervention, particularly for women with previous miscarriage(s). TWEETABLE ABSTRACT: Progesterone treatment is likely to be cost-effective in women with early pregnancy bleeding and a history of miscarriage.

Petawatt Laser Guiding and Electron Beam Acceleration to 8 GeV in a Laser-Heated Capillary Discharge Waveguide.

Guiding of relativistically intense laser pulses with peak power of 0.85 PW over 15 diffraction lengths was demonstrated by increasing the focusing strength of a capillary discharge waveguide using laser inverse bremsstrahlung heating. This allowed for the production of electron beams with quasimonoenergetic peaks up to 7.8 GeV, double the energy that was previously demonstrated. Charge was 5 pC at 7.8 GeV and up to 62 pC in 6 GeV peaks, and typical beam divergence was 0.2 mrad.

The effect of the EP3 antagonist DG-041 on male mice with diet-induced obesity.

BACKGROUND/AIMS: The prostaglandin E2 (PGE2) EP3 receptor has a multifaceted role in metabolism. Drugs targeting EP3 have been proposed as therapeutics for diabetes; however, studies utilizing global EP3 knockout mice suggest that EP3 blockade increases obesity and insulin resistance. The present studies attempt to determine the effect of acute EP3 antagonist treatment on the diabetic phenotype. METHODS: DG-041 was confirmed to be a high affinity antagonist at the mouse EP3 receptor by competition radioligand binding and by blockade of EP3-mediated responses. DG-041 pharmacokinetic studies were performed to determine the most efficacious route of administration. Male C57BL/6 × BALB/c (CB6F1) mice were fed diets containing 10%, 45%, or 60% calories from fat to induce obesity. Changes to the metabolic phenotype in these mice were evaluated after one week treatment with DG-041. RESULTS: Subcutaneous injections of DG-041 at 20 mg/kg blocked the sulprostone-evoked rise in mean arterial pressure confirming the efficacy of this administration regime. Seven day treatment with DG-041 had minimal effect on body composition or glycemic control. DG-041 administration caused a reduction in skeletal muscle triglyceride content while showing a trend toward increased hepatic triglycerides. CONCLUSION: Short term EP3 administration of DG-041 produced effective blockade of the EP3 receptor and decreased skeletal muscle triglyceride content but had no significant effects on the diabetic phenotype.

Discovery of 4-alkoxy-6-methylpicolinamide negative allosteric modulators of metabotropic glutamate receptor subtype 5.

This letter describes the further chemical optimization of VU0424238 (auglurant), an mGlu5 NAM clinical candidate that failed in non-human primate (NHP) 28 day toxicology due to accumulation of a species-specific aldehyde oxidase (AO) metabolite of the pyrimidine head group. Here, we excised the pyrimidine moiety, identified the minimum pharmacophore, and then developed a new series of saturated ether head groups that ablated any AO contribution to metabolism. Putative back-up compounds in this novel series provided increased sp3 character, uniform CYP450-mediated metabolism across species, good functional potency and high CNS penetration. Key to the optimization was a combination of matrix and iterative libraries that allowed rapid surveillance of multiple domains of the allosteric ligand.

SAR inspired by aldehyde oxidase (AO) metabolism: Discovery of novel, CNS penetrant tricyclic M4 PAMs.

This letter describes progress towards an M4 PAM preclinical candidate inspired by an unexpected aldehyde oxidase (AO) metabolite of a novel, CNS penetrant thieno[2,3-c]pyridine core to an equipotent, non-CNS penetrant thieno[2,3-c]pyrdin-7(6H)-one core. Medicinal chemistry design efforts yielded two novel tricyclic cores that enhanced M4 PAM potency, regained CNS penetration, displayed favorable DMPK properties and afforded robust in vivo efficacy in reversing amphetamine-induced hyperlocomotion in rats.

mGlu5 positive allosteric modulation normalizes synaptic plasticity defects and motor phenotypes in a mouse model of Rett syndrome.

Rett syndrome (RS) is a neurodevelopmental disorder that shares many symptomatic and pathological commonalities with idiopathic autism. Alterations in protein synthesis-dependent synaptic plasticity (PSDSP) are a hallmark of a number of syndromic forms of autism; in the present work, we explore the consequences of disruption and rescue of PSDSP in a mouse model of RS. We report that expression of a key regulator of synaptic protein synthesis, the metabotropic glutamate receptor 5 (mGlu5) protein, is significantly reduced in both the brains of RS model mice and in the motor cortex of human RS autopsy samples. Furthermore, we demonstrate that reduced mGlu5 expression correlates with attenuated DHPG-induced long-term depression in the hippocampus of RS model mice, and that administration of a novel mGlu5 positive allosteric modulator (PAM), termed VU0462807, can rescue synaptic plasticity defects. Additionally, treatment of Mecp2-deficient mice with VU0462807 improves motor performance (open-field behavior and gait dynamics), corrects repetitive clasping behavior, as well as normalizes cued fear-conditioning defects. Importantly, due to the rationale drug discovery approach used in its development, our novel mGlu5 PAM improves RS phenotypes and synaptic plasticity defects without evoking the overt adverse effects commonly associated with potentiation of mGlu5 signaling (i.e. seizures), or affecting cardiorespiratory defects in RS model mice. These findings provide strong support for the continued development of mGlu5 PAMs as potential therapeutic agents for use in RS, and, more broadly, for utility in idiopathic autism.

Discovery of 6-(pyrimidin-5-ylmethyl)quinoline-8-carboxamide negative allosteric modulators of metabotropic glutamate receptor subtype 5.

Based on previous work that established fused heterocycles as viable alternatives for the picolinamide core of our lead series of mGlu5 negative allosteric modulators (NAMs), we designed a novel series of 6-(pyrimidin-5-ylmethyl)quinoline-8-carboxamide mGlu5 NAMs. These new quinoline derivatives also contained carbon linkers as replacements for the diaryl ether oxygen atom common to our previously published chemotypes. Compounds were evaluated in a cell-based functional mGlu5 assay, and an exemplar analog 27 was >60-fold selective versus the other seven mGlu receptors. Selected compounds were also studied in metabolic stability assays in rat and human S9 hepatic fractions and exhibited a mixture of P450- and non-P450-mediated metabolism.

A novel in vitro allometric scaling methodology for aldehyde oxidase substrates to enable selection of appropriate species for traditional allometry.

1. Failure to predict human pharmacokinetics of aldehyde oxidase (AO) substrates using traditional allometry has been attributed to species differences in AO metabolism. 2. To identify appropriate species for predicting human in vivo clearance by single-species scaling (SSS) or multispecies allometry (MA), we scaled in vitro intrinsic clearance (CLint) of five AO substrates obtained from hepatic S9 of mouse, rat, guinea pig, monkey and minipig to human in vitro CLint. 3. When predicting human in vitro CLint, average absolute fold-error was ≤2.0 by SSS with monkey, minipig and guinea pig (rat/mouse >3.0) and was <3.0 by most MA species combinations (including rat/mouse combinations). 4. Interspecies variables, including fraction metabolized by AO (Fm,AO) and hepatic extraction ratios (E) were estimated in vitro. SSS prediction fold-errors correlated with the animal:human ratio of E (r2 = 0.6488), but not Fm,AO (r2 = 0.0051). 5. Using plasma clearance (CLp) from the literature, SSS with monkey was superior to rat or mouse at predicting human CLp of BIBX1382 and zoniporide, consistent with in vitro SSS assessments. 6. Evaluation of in vitro allometry, Fm,AO and E may prove useful to guide selection of suitable species for traditional allometry and prediction of human pharmacokinetics of AO substrates.

Allosteric activation of M4 muscarinic receptors improve behavioral and physiological alterations in early symptomatic YAC128 mice.

Mutations that lead to Huntington's disease (HD) result in increased transmission at glutamatergic corticostriatal synapses at early presymptomatic stages that have been postulated to set the stage for pathological changes and symptoms that are observed at later ages. Based on this, pharmacological interventions that reverse excessive corticostriatal transmission may provide a novel approach for reducing early physiological changes and motor symptoms observed in HD. We report that activation of the M4 subtype of muscarinic acetylcholine receptor reduces transmission at corticostriatal synapses and that this effect is dramatically enhanced in presymptomatic YAC128 HD and BACHD relative to wild-type mice. Furthermore, chronic administration of a novel highly selective M4 positive allosteric modulator (PAM) beginning at presymptomatic ages improves motor and synaptic deficits in 5-mo-old YAC128 mice. These data raise the exciting possibility that selective M4 PAMs could provide a therapeutic strategy for the treatment of HD.

Adjuvant psychological therapy in long-term endocrine conditions.

Consideration of psychological distress in long-term endocrine conditions is of vital importance given the prevalence of anxiety and depression in such disorders. Poor mental health can lead to compromised self-care, higher utilization of health services, lower rates of adherence, reduced quality of life and ultimately poorer outcomes. Adjuvant psychological therapy offers an effective resource to reduce distress in endocrine conditions. While the vast majority of work in this area has focused on psychological screening and intervention in diabetes, identification and recognition of psychological distress are equally important in other endocrinological conditions, with supportive evidence in polycystic ovary syndrome and Addison's disease. Referral pathways and recommendations set out by UK guidelines and the Department of Health mandate requires greater attention across a wider range of long-term endocrine conditions to facilitate improved quality of life and health outcome.

Discovery of imidazo[1,2-a]-, [1,2,4]triazolo[4,3-a]-, and [1,2,4]triazolo[1,5-a]pyridine-8-carboxamide negative allosteric modulators of metabotropic glutamate receptor subtype 5.

Based on a hypothesis that an intramolecular hydrogen bond was present in our lead series of picolinamide mGlu5 NAMs, we reasoned that an inactive nicotinamide series could be modified through introduction of a fused heterocyclic core to generate potent mGlu5 NAMs. In this Letter, we describe the synthesis and evaluation of compounds that demonstrate the viability of that approach. Selected analogs were profiled in a variety of in vitro assays, and two compounds were evaluated in rat pharmacokinetic studies and a mouse model of obsessive-compulsive disorder. Ancillary pharmacology screening revealed that members of this series exhibited moderate inhibition of the dopamine transporter (DAT), and SAR was developed that expanded the selectivity for mGlu5 versus DAT.

Ultrasound bladder wall thickness and detrusor overactivity: a multicentre test accuracy study.

OBJECTIVE: Women with overactive bladder (OAB) often undergo urodynamics before invasive treatments are considered. Ultrasound measurement of bladder wall thickness (BWT) is a less invasive, less expensive and widely available test. It has the potential to diagnose the presence of detrusor overactivity (DO). We aimed to evaluate the accuracy of BWT in the diagnosis of DO. DESIGN: Prospective cohort study. SETTING: Twenty-two UK clinics (university and district general hospitals). METHODS: Consecutive eligible women with OAB symptoms had transvaginal ultrasound to estimate BWT (index test). The reference standard for the diagnosis of DO was urodynamic testing with multichannel subtracted cystometry. MAIN OUTCOME MEASURES: The sensitivity, specificity and likelihood ratios using a BWT threshold of ≥5 mm were used to indicate the presence of DO, and the area under the receiver operating characteristics (ROC) curve to give an overall estimate of BWT accuracy. RESULTS: Between March 2011 and 2013, 644/687 (94%) women recruited had both tests. The mean age was 52.7 years (standard deviation 13.9) and DO was diagnosed in 399/666 (60%) women. BWT had a sensitivity of 43% [95% confidence interval (CI) 38-48%], specificity of 62% (95% CI 55-68%), and likelihood ratios of 1.11 (95% CI 0.92-1.35) and 0.93 (95% CI 0.82-1.06) for positive and negative tests, respectively. The area under the ROC curve was 0.53 (95% CI 0.48-0.57). Extensive sensitivity analyses and subgroup analyses were carried out, but did not alter the interpretation. CONCLUSIONS: BWT is not a good replacement test for urodynamics in women with overactive bladder. TWEETABLE ABSTRACT: Bladder wall thickness is not a good replacement test for urodynamics in women with overactive bladder.

VU0477573: Partial Negative Allosteric Modulator of the Subtype 5 Metabotropic Glutamate Receptor with In Vivo Efficacy.

Negative allosteric modulators (NAMs) of metabotropic glutamate receptor subtype 5 (mGlu5) have potential applications in the treatment of fragile X syndrome, levodopa-induced dyskinesia in Parkinson disease, Alzheimer disease, addiction, and anxiety; however, clinical and preclinical studies raise concerns that complete blockade of mGlu5 and inverse agonist activity of current mGlu5 NAMs contribute to adverse effects that limit the therapeutic use of these compounds. We report the discovery and characterization of a novel mGlu5 NAM, N,N-diethyl-5-((3-fluorophenyl)ethynyl)picolinamide (VU0477573) that binds to the same allosteric site as the prototypical mGlu5 NAM MPEP but displays weak negative cooperativity. Because of this weak cooperativity, VU0477573 acts as a "partial NAM" so that full occupancy of the MPEP site does not completely inhibit maximal effects of mGlu5 agonists on intracellular calcium mobilization, inositol phosphate (IP) accumulation, or inhibition of synaptic transmission at the hippocampal Schaffer collateral-CA1 synapse. Unlike previous mGlu5 NAMs, VU0477573 displays no inverse agonist activity assessed using measures of effects on basal [(3)H]inositol phosphate (IP) accumulation. VU0477573 acts as a full NAM when measuring effects on mGlu5-mediated extracellular signal-related kinases 1/2 phosphorylation, which may indicate functional bias. VU0477573 exhibits an excellent pharmacokinetic profile and good brain penetration in rodents and provides dose-dependent full mGlu5 occupancy in the central nervous system (CNS) with systemic administration. Interestingly, VU0477573 shows robust efficacy, comparable to the mGlu5 NAM MTEP, in models of anxiolytic activity at doses that provide full CNS occupancy of mGlu5 and demonstrate an excellent CNS occupancy-efficacy relationship. VU0477573 provides an exciting new tool to investigate the efficacy of partial NAMs in animal models.

Evaluating the Disposition of a Mixed Aldehyde Oxidase/Cytochrome P450 Substrate in Rats with Attenuated P450 Activity.

Marketed drugs cleared by aldehyde oxidase (AO) are few, with no known clinically relevant pharmacokinetic drug interactions associated with AO inhibition, whereas cytochrome P450 (P450) inhibition or induction mediates a number of clinical drug interactions. Little attention has been given to the consequences of coadministering a P450 inhibitor with a compound metabolized by both AO and P450. Upon discovering that VU0409106 (1) was metabolized by AO (to M1) and P450 enzymes (to M4-M6), we sought to evaluate the in vivo disposition of 1 and its metabolites in rats with attenuated P450 activity. Male rats were orally pretreated with the pan-P450 inactivator, 1-aminobenzotriazole (ABT), before an i.p. dose of 1. Interestingly, the plasma area under the curve (AUC) of M1 was increased 15-fold in ABT-treated rats, indicating a metabolic shunt toward AO resulted from the drug interaction condition. The AUC of 1 also increased 7.8-fold. Accordingly, plasma clearance of 1 decreased from 53.5 to 15.3 ml/min per kilogram in ABT-pretreated rats receiving an i.v. dose of 1. Consistent with these data, M1 formation in hepatic S9 increased with NADPH-exclusion to eliminate P450 activity (50% over reactions containing NADPH). These studies reflect possible consequences of a drug interaction between P450 inhibitors and compounds cleared by both AO and P450 enzymes. Notably, increased exposure to an AO metabolite may hold clinical relevance for active metabolites or those mediating toxicity at elevated concentrations. The recent rise in clinical drug candidates metabolized by AO underscores the importance of these findings and the need for clinical studies to fully understand these risks.