Gastroesophageal reflux disease (GERD) affects Ͼ10% of the Western population. Conventionally, GERD is treated by reducing gastric acid secretion, which is effective in most patients but inadequate in a significant minority. We describe a new therapeutic approach for GERD, based on inhibition of transient lower esophageal sphincter relaxation (TLESR) with a proposed peripherally acting GABA B receptor agonist, (R)-(3-amino-2-fluoropropyl)phosphinic acid (AZD3355). AZD3355 potently stimulated recombinant human GABA B receptors and inhibited TLESR in dogs, with a biphasic dose-response curve. In mice, AZD3355 produced considerably less central side effects than the prototypical GABA B receptor agonist baclofen but evoked hypothermia at very high doses (blocked by a GABA B receptor antagonist and absent in GABA B Ϫ/Ϫ mice). AZD3355 and baclofen differed markedly in their distribution in rat brain; AZD3355, but not baclofen, was concentrated in circumventricular organs as a result of active uptake (shown by avid intracellular sequestration) and related to binding of AZD3355 to native GABA transporters in rat cerebrocortical membranes. AZD3355 was also shown to be transported by all four recombinant human GABA transporters. AR-H061719 [(R/S)-(3-amino-2-fluoropropyl)phosphinic acid], (the racemate of AZD3355) inhibited the response of ferret mechanoreceptors to gastric distension, further supporting its peripheral site of action on TLESR. In summary, AZD3355 probably inhibits TLESR through stimulation of peripheral GABA B receptors and may offer a potential new approach to treatment of GERD.The GABA B receptor was originally defined pharmacologically by virtue of its insensitivity to the GABA A receptor antagonist bicuculline and its sensitivity to the GABA analog baclofen (Bowery et al., 1980). The GABA B receptor, a member of family C of the G protein-coupled receptors, is characterized by its large, ligand-binding extracellular N-terminal domain. It couples negatively to adenylyl cyclase and to voltage-gated calcium channels and positively to inwardly rectifying potassium channels (Bettler et al., 2004).Based on a wealth of preclinical data, the GABA B receptor has been proposed as a therapeutic target for several dis-

Purpose Janus kinase 1 (JAK1) is implicated in multiple inflammatory pathways that are critical for the pathogenesis of asthma, including the interleukin (IL)-4, IL-5, IL-13, and thymic stromal lymphopoietin cytokine signaling pathways, which have previously been targeted to treat allergic asthma. Here, we describe the development of AZD0449 and AZD4604, two novel and highly selective JAK1 inhibitors with promising properties for inhalation. Methods The effects of AZD0449 and AZD4604 in JAK1 signaling pathways were assessed by measuring phosphorylation of signal transducer and activator of transcription (STAT) proteins and chemokine release using immunoassays of whole blood from healthy human volunteers and rats. Pharmacokinetic studies performed on rats evaluated AZD0449 at a lung deposited dose of 52 μg/kg and AZD4604 at 30 µg/kg. The efficacy of AZD0449 and AZD4604 was assessed by evaluating lung inflammation (cell count and cytokine levels) and the late asthmatic response (average enhanced pause [Penh]). Results Both compounds inhibited JAK1-dependent cytokine signaling pathways in a dose-dependent manner in human and rat leukocytes. After intratracheal administration in rats, both compounds exhibited low systemic exposures and medium-to-long terminal lung half-lives (AZD0449, 34 hours; AZD4604, 5 hours). Both compounds inhibited STAT3 and STAT5 phosphorylation in lung tissue from ovalbumin (OVA)-challenged rats. AZD0449 and AZD4604 also inhibited eosinophilia in the lung and reduced the late asthmatic response, measured as Penh in the OVA rat model. Conclusion AZD0449 and AZD4604 show potential as inhibitors of signaling pathways involved in asthmatic immune responses, with target engagement demonstrated locally in the lung. These findings support the clinical development of AZD0449 and AZD4604 for the treatment of patients with asthma.

1 The effects of the novel GABA analogue (2R)-(3-amino-2-fluoropropyl)sulphinic acid (AFPSiA) on transient lower oesophageal sphincter relaxations (TLOSRs) were studied in the dog. In addition, the GABA A /GABA B selectivity was determined in vitro and in vivo, and the pharmacokinetics and the metabolism of the compound were studied in the dog and rat. 2 TLOSRs were reduced by 5578% after intragastric administration of AFPSiA at 14 mmol kg À1 and did not decrease further at higher doses. When evaluated 2 and 4 h after administration, the effect declined to 3776 and 1679%, respectively. Spontaneous swallowing was only significantly inhibited at 100 mmol kg À1 . 3 The oral availability of AFPSiA was 52717 and 7174% in the dog and rat, respectively. A fraction of AFPSiA was oxidised to the corresponding sulphonate, (2R)-(3-amino-2-fluoropropyl)-sulphonic acid (AFPSoA) after oral administration to the rat and dog. 4 In rat brain membranes, AFPSiA was found to have ten times higher affinity for rat brain GABA B (K i ¼ 4774.4 nM) compared to GABA A (K i ¼ 430746 nM) binding sites. The compound was a full agonist at human recombinant GABA B(1a,2) receptors (EC 50 ¼ 130710 nM). In contrast, the metabolite AFPSoA was considerably more selective for binding to rat brain GABA A (K i ¼ 3773.1 nM) vs GABA B (K i ¼ 68007280 nM) receptors. 5 In the mouse, high doses (1-8 mmol kg À1 ) of AFPSiA induced a rapid and mild hypothermia followed by a profound and sustained hypothermia at the higher doses tested (6 and 8 mmol kg À1 ). This effect was unaffected by the selective GABA B receptor antagonist CGP62349. AFPSoA (1 and 2 mmol kg À1 ) produced transient and moderate hypothermia while the hypothermic response was considerably larger at 4 mmol kg À1 . 6 It is concluded that AFPSiA inhibits but does not abolish TLOSRs in the dog. High doses of the compound induce hypothermia in the mouse, which probably is attributable to activation of the GABA A receptor. The latter effect may be caused both by AFPSiA and its oxidised sulphonic acid metabolite AFPSoA.

During preclinical and early phase clinical studies of drug candidates, exposure to metabolites should be monitored to determine whether safety conclusions drawn from studies in animals can be extrapolated to humans. Metabolites accounting for more than 10% of total exposure to drug-related material (DRM) in humans are of regulatory concern, and for any such metabolites, adequate exposure should be demonstrated in animals before large-scale phase 3 clinical trials are conducted. We have previously identified six metabolites, M1-M6, of the gastroesophageal reflux inhibitor lesogaberan. In this study, we measured exposure in humans, rats, and beagle dogs to lesogaberan and these metabolites. Plasma samples were taken at various time points after lesogaberan dosing in two clinical and three preclinical studies. Concentrations of lesogaberan and its metabolites were measured, and exposures during a single dosing interval were calculated. The parent compound and metabolites M1, M2, M4, and M5 were together shown to constitute all significant exposure to DRM in humans. Only M4 and M5 were present at levels of regulatory concern (10.6% and 18.9% of total exposure to DRM, respectively, at steady state). Absolute exposure to M5 was greater in rats during toxicology studies than the highest absolute exposure observed in humans at steady state (117.0 mmol 3 h/liter vs. 52.2 mmol 3 h/liter). In contrast, exposure to M4 in rats was less than 50% of the highest absolute exposure observed in humans. Further safety testing of this metabolite may therefore be required.

Objective: The aim of this study was to evaluate the pharmacokinetic profile of lesogaberan in healthy subjects after single oral and intravenous administration of 14C-labeled lesogaberan and non-14C-labeled lesogaberan.Study Design: This was an open-label, single-center, randomized, two-way crossover, phase I study.Participants: Ten healthy male subjects took part in the study.Intervention: Volunteers were randomized to receive a single dose of either orally dosed (100 mg) or intravenously infused (20 mg) non-14C-labeled lesogaberan, and then orally (100 mg) or intravenously (20 mg) administered 14C-labeled lesogaberan in a crossover design. Treatment periods were separated by a washout period of at least 7 days.Main Outcome Measures Analyses of the rate and route of excretion, dose recovery, area under the plasma concentration versus time curve (AUC), AUC to the last quantifiable concentration, maximal plasma concentration (Cmax), time to Cmax, the apparent elimination half-life, bioavailability, total clearance, renal clearance, fraction of the bioavailable dose excreted unchanged in the urine, cumulative amount of drug excreted unchanged in urine, and the apparent volume of distribution at steady state of lesogaberan.Results: Lesogaberan was rapidly and extensively absorbed from the gastrointestinal tract and Cmax was achieved within 1–2 hours of oral dosing. The terminal half-life of lesogaberan was between 11 and 13 hours. Renal clearance accounted for approximately 22% of total body clearance. Based on the recovery of administered radioactivity, approximately 84% of the dose was excreted into the urine either as the parent compound or as water-soluble metabolite(s). There were no safety concerns raised during the study.Conclusion: Orally administered lesogaberan is rapidly absorbed with high bioavailability and the majority of the dose is excreted by the kidneys either as the parent compound or as metabolites. The major elimination pathway for lesogaberan in man is metabolism.