David Beattie

The Identification of Indacaterol as an Ultralong-Acting Inhaled β2-Adrenoceptor Agonist

Following a lipophilicity-based hypothesis, an 8-hydroxyquinolinone 2-aminoindan derived series of beta(2)-adrenoceptor agonists have been prepared and evaluated for their potential as inhaled ultralong-acting bronchodilators. Determination of their activities at the human beta(2)-adrenoceptor receptor showed symmetrical substitution of the 2-aminoindan moiety at the 5- and 6-positions delivered the targeted intermediate potency and intrinsic-efficacy profiles relative to a series of clinical reference beta(2)-adrenoceptor agonists. Further assessment with an in vitro superfused electrically stimulated guinea-pig tracheal-strip assay established the onset and duration of action time courses, which could be rationalized by considering the lipophilicity, potency, and intrinsic efficacy of the compounds. From these studies the 5,6-diethylindan analogue indacaterol 1c was shown to possess a unique profile of combining a rapid onset of action with a long duration of action. Further in vivo profiling of 1c supported the long duration of action and a wide therapeutic index following administration to the lung, which led to the compound being selected as a development candidate.

The in vivo gastrointestinal activity of TD-5108, a selective 5-HT4 receptor agonist with high intrinsic activity

The in vivo preclinical pharmacodynamic profile of TD-5108, a selective 5-HT4 receptor agonist with high intrinsic activity, was compared to that of the clinically studied gastrointestinal pro-kinetic agents, tegaserod, cisapride and mosapride. The activity of TD-5108 was evaluated in guinea pig colonic transit, rat oesophageal relaxation and dog gastrointestinal smooth muscle contractility models. Subcutaneous administration of TD-5108, tegaserod, cisapride and mosapride increased guinea pig colonic transit (rank order of potencies: TD-5108 > tegaserod > cisapride > mosapride). Following intravenous and intraduodenal dosing, TD-5108, tegaserod, cisapride and mosapride produced dose-dependent relaxation of the rat oesophagus. On a molar basis, TD-5108 was approximately twofold less potent than tegaserod following intravenous dosing but 6- or 86-fold more potent than cisapride or mosapride, respectively, and 9- or 18-fold more potent than tegaserod or cisapride, respectively, after intraduodenal administration. Orally dosed TD-5108 increased the contractility of the canine antrum, duodenum and jejunum with higher potency than tegaserod. The selective 5-HT4 receptor agonist, TD-5108, demonstrates robust in vivo activity in the guinea pig, rat and dog gastrointestinal tracts.

The Pharmacology of TD-8954, a Potent and Selective 5-HT4 Receptor Agonist with Gastrointestinal Prokinetic Properties

This study evaluated the in vitro and in vivo pharmacological properties of TD-8954, a potent and selective 5-HT4 receptor agonist. TD-8954 had high affinity (pKi = 9.4) for human recombinant 5-HT4(c) (h5-HT4(c)) receptors, and selectivity (>2,000-fold) over all other 5-hydroxytryptamine (5-HT) receptors and non-5-HT receptors, ion channels, enzymes and transporters tested (n = 78). TD-8954 produced an elevation of cAMP in HEK-293 cells expressing the h5-HT4(c) receptor (pEC50 = 9.3), and contracted the guinea pig colonic longitudinal muscle/myenteric plexus preparation (pEC50 = 8.6). TD-8954 had moderate intrinsic activity in the in vitro assays. In conscious guinea pigs, subcutaneous administration of TD-8954 (0.03–3 mg/kg) increased the colonic transit of carmine red dye, reducing the time taken for its excretion. Following intraduodenal dosing to anesthetized rats, TD-8954 (0.03–10 mg/kg) evoked a dose-dependent relaxation of the esophagus. Following oral administration to conscious dogs, TD-8954 (10 and 30 μg/kg) produced an increase in contractility of the antrum, duodenum, and jejunum. In a single ascending oral dose study in healthy human subjects, TD-8954 (0.1–20 mg) increased bowel movement frequency and reduced the time to first stool. It is concluded that TD-8954 is a potent and selective 5-HT4 receptor agonist in vitro, with robust in vivo stimulatory activity in the gastrointestinal (GI) tract of guinea pigs, rats, dogs, and humans. TD-8954 may have clinical utility in patients with disorders of reduced GI motility.

A physical properties based approach for the exploration of a 4-hydroxybenzothiazolone series of β2-adrenoceptor agonists as inhaled long-acting bronchodilators

The chiral synthesis of a 4-hydroxybenzothiazolone based series of beta(2)-adrenoceptor agonists is described. Using this methodology a library of N-substituted analogues were prepared for the rapid identification of leads with the potential to be fast onset and long-acting inhaled bronchodilators with improved therapeutic margins. The design of the library to achieve the targeted profile was based upon lipophilicity and metabolism based hypotheses. This approach identified beta-phenethyl, alpha-substituted cyclopentyl and monoterpene N-substituents to be of particular interest for further evaluation, as exemplified by structures 19, 29 and 33, respectively.

The in vivo pharmacodynamics of the novel opioid receptor antagonist, TD-1211, in models of opioid-induced gastrointestinal and CNS activity

The in vivo preclinical pharmacodynamic profile of TD-1211, a selective opioid receptor antagonist currently under development for the treatment of opioid-induced constipation, was compared to that of the clinically studied opioid antagonists, naltrexone, alvimopan, and ADL 08-0011 (the primary active metabolite of alvimopan). The oral activity of TD-1211 was evaluated in models of gastrointestinal (GI) and central nervous system (CNS) function in the rat and dog. Oral administration of TD-1211, naltrexone, and ADL 08-0011 reversed loperamide-induced inhibition of gastric emptying and castor oil-induced diarrhea in rats and nonproductive GI circular smooth muscle contractility in dogs. Alvimopan was only efficacious in the castor oil model. Oral administration of naltrexone and ADL 08-0011, but not TD-1211 or alvimopan, was associated with a CNS withdrawal response in morphine-dependent mice, inhibition of morphine-induced anti-nociception in rat and dog hot plate tests, and hypothermia and sedation in dogs. It is concluded that TD-1211 has potent in vivo GI activity, consistent with opioid receptor antagonism, but has no significant CNS activity. The data from these studies support the clinical development of TD-1211 as a novel treatment for opioid-induced GI dysfunction.

Discovery, oral pharmacokinetics and in vivo efficacy of velusetrag, a highly selective 5-HT4 receptor agonist that has achieved proof-of-concept in patients with chronic idiopathic constipation

Utilization of Theravances multivalent approach to drug discovery towards 5-HT(4) receptor agonists with a focus on identification of neutral (non-charged at physiological pH) secondary binding groups is described. Optimization of a quinolone-tropane primary binding group with a chiral 2-propanol linker to a range of neutral secondary binding group motifs, for binding affinity and functional potency at the 5-HT(4) receptor, selectivity over the 5-HT(3) receptor, oral pharmacokinetics, and in vivo efficacy in models of GI motility, afforded velusetrag (TD-5108). Velusetrag has achieved proof-of-concept in patients with chronic idiopathic constipation.

The in vitro pharmacological profile of TD-1211, a neutral opioid receptor antagonist

The clinical efficacy of opioid receptor antagonists for the treatment of opioid-induced constipation (OIC) is established. Peripherally selective antagonists are intended to provide OIC symptom relief without compromising the analgesic effects of centrally penetrant opioid agonists. We describe the in vitro profile of a novel opioid receptor antagonist, TD-1211, at recombinant (human μ and δ, and guinea pig κ) and rodent native opioid receptors. TD-1211 bound with high affinity to human recombinant μ and δ, and guinea pig κ receptors expressed in CHO-K1 cells (pKd = 9.7, 8.6, and 9.9, respectively). The in vitro receptor selectivity of TD-1211 (μ ≈ κ > δ) is similar to that for the peripherally-selective opioid receptor antagonist methylnaltrexone, but contrasts with the μ selectivity of alvimopan. Functionally, TD-1211 behaved as an antagonist at all three receptor types in both recombinant expression systems (pKb = 9.6, 8.8 and 9.5, at μ, δ, and κ, respectively) and rodent native tissue preparations (μ and κ pA2s = 10.1 and 8.8, respectively (guinea pig ileum), and δ pKb = 8.4 (hamster vas deferens)). TD-1211 displayed a high degree of selectivity for opioid receptors over a broad panel of cellular targets. These in vitro data justified investigation of the preclinical in vivo activity of TD-1211 (Armstrong et al., Naunyn-Schmiedeberg’s Arch Pharm, 2013).

Discovery, oral pharmacokinetics and in vivo efficacy of a highly selective 5-HT4 receptor agonist: clinical compound TD-2749.

Further application of our multivalent approach to drug discovery directed to 5-HT(4) receptor agonists is described. Optimization of the linker and secondary binding amine in the indazole-tropane primary binding group series, for binding affinity and functional potency at the 5-HT(4) receptor, selectivity over the 5-HT(3) receptor, oral pharmacokinetics, and in vivo efficacy in models of GI motility, resulted in the identification of clinical compound TD-2749.

Discovery of TD-8954, a clinical stage 5-HT(4) receptor agonist with gastrointestinal prokinetic properties.

The discovery of a series of 5-HT4 receptor agonists based on a novel 2-alkylbenzimidazole aromatic core is described. Optimization of the 2-substituent of the benzimidazole ring led to a series of agonists with subnanomolar binding affinity and moderate-to-high intrinsic activity relative to that of 5-HT. Consistent with our previously described multivalent design approach to this target, subsequent optimization of the linker and secondary binding group regions of the series afforded compound 18 (TD-8954), a potent and selective 5-HT4 receptor agonist in vitro with demonstrated prokinetic activity in multiple species.

Intestinally-restricted Janus Kinase inhibition: a potential approach to maximize the therapeutic index in inflammatory bowel disease therapy

BackgroundAn unmet need remains for safe and effective treatments to induce and maintain remission in inflammatory bowel disease (IBD) patients. The Janus kinase (JAK) inhibitor, tofacitinib, has demonstrated robust efficacy in ulcerative colitis patients although, like other systemic immunosuppressants, there may be safety concerns associated with its use. This preclinical study evaluated whether modulating intestinal inflammation via local JAK inhibition can provide efficacy without systemic immunosuppression.MethodsThe influence of tofacitinib, dosed orally or intracecally, on oxazolone-induced colitis, oxazolone or interferon-γ (IFNγ)-induced elevation of colonic phosphorylated signal transducer and activator of transcription1 (pSTAT1) levels, and basal splenic natural killer (NK) cell counts was investigated in mice.ResultsTofacitinib, dosed orally or intracecally, inhibited, with similar efficacy, oxazolone-induced colitis, represented by improvements in the disease activity index and its sub-scores (body weight, stool consistency and blood content). Intracecal dosing of tofacitinib resulted in a higher colon:plasma drug exposure ratio compared to oral dosing. At equieffective oral and intracecal doses, colonic levels of tofacitinib were similar, while the plasma levels for the latter were markedly lower, consistent with a lack of effect on splenic NK cell counts. Tofacitinib, dosed orally, intracecally, or applied to the colonic lumen in vitro, produced dose-dependent, and maximal inhibition of oxazolone or IFNγ-induced STAT1 phosphorylation in the colon.ConclusionsLocalized colonic JAK inhibition, by intracecal delivery of tofacitinib, provides colonic target engagement and efficacy in a mouse colitis model at doses which do not impact splenic NK cell counts. Intestinal targeting of JAK may permit separation of local anti-inflammatory activity from systemic immunosuppression, and thus provide a larger therapeutic index compared to systemic JAK inhibitors.