Drug Repurposing: The Anthelmintics Niclosamide and Nitazoxanide Are Potent TMEM16A Antagonists That Fully Bronchodilate Airways.

There is an unmet need in severe asthma where approximately 40% of patients exhibit poor ß-agonist responsiveness, suffer daily symptoms and show frequent exacerbations. Antagonists of the Ca2+-activated Cl- channel, TMEM16A, offers a new mechanism to bronchodilate airways and block the multiple contractiles operating in severe disease. To identify TMEM16A antagonists we screened a library of ∼580,000 compounds. The anthelmintics niclosamide, nitazoxanide, and related compounds were identified as potent TMEM16A antagonists that blocked airway smooth muscle depolarization and contraction. To evaluate whether TMEM16A antagonists resist use- and inflammatory-desensitization pathways limiting ß-agonist action, we tested their efficacy under harsh conditions using maximally contracted airways or airways pretreated with a cytokine cocktail. Stunningly, TMEM16A antagonists fully bronchodilated airways, while the ß-agonist isoproterenol showed only partial effects. Thus, antagonists of TMEM16A and repositioning of niclosamide and nitazoxanide represent an important additional treatment for patients with severe asthma and COPD that is poorly controlled with existing therapies. It is of note that drug repurposing has also attracted wide interest in niclosamide and nitazoxanide as a new treatment for cancer and infectious disease. For the first time we identify TMEM16A as a molecular target for these drugs and thus provide fresh insights into their mechanism for the treatment of these disorders in addition to respiratory disease.

Differential Roles for Interleukin-23 and Interleukin-17 in Intestinal Immunoregulation.

Interleukin-23 (IL-23) and IL-17 are cytokines currently being targeted in clinical trials. Although inhibition of both of these cytokines is effective for treating psoriasis, IL-12 and IL-23 p40 inhibition attenuates Crohn's disease, whereas IL-17A or IL-17 receptor A (IL-17RA) inhibition exacerbates Crohn's disease. This dichotomy between IL-23 and IL-17 was effectively modeled in the multidrug resistance-1a-ablated (Abcb1a(-/-)) mouse model of colitis. IL-23 inhibition attenuated disease by decreasing colonic inflammation while enhancing regulatory T (Treg) cell accumulation. Exacerbation of colitis by IL-17A or IL-17RA inhibition was associated with severe weakening of the intestinal epithelial barrier, culminating in increased colonic inflammation and accelerated mortality. These data show that IL-17A acts on intestinal epithelium to promote barrier function and provide insight into mechanisms underlying exacerbation of Crohn's disease when IL-17A or IL-17RA is inhibited.

Predictability of peripheral lymphocyte reduction of novel S1P1 agonists by in vitro GPCR signaling profile.

Surrogate readouts of G-protein-coupled receptor signaling pathways using highly engineered systems are often employed in the drug discovery process. However, accumulating data have demonstrated the importance of selecting relevant biological activity rather than technically facile assays to support high-throughout screening and subsequent structure-activity relationship studies. Here we report a case study using sphingosine-1-phosphate receptor 1 (S1P(1)) as the model system to compare compound activity in six different in vitro assays with their ability to predict in vivo efficacy. S1P(1) has long been validated as a therapeutic target for autoimmune diseases. In this article, in vivo and in vitro studies on 19 S1P1 agonists are reported. In vitro activities of these S1P(1) agonists, together with S1P and FTY720p, on Ca(2+) mobilization, adenylyl cyclase inhibition, extracellular signal-related kinase (ERK) phosphorylation, ß-arrestin recruitment, and receptor internalization, were determined. The in vitro potency of these compounds was correlated with their ability to induce peripheral lymphocyte reduction. The results revealed that inhibition of adenylyl cyclase and induction of ß-arrestin recruitment and receptor internalization are good indicators to predict in vivo efficacy, whereas induction of Ca(2+) mobilization through G(qi/5) coupling and ERK phosphorylation is irrelevant. This study demonstrated the importance of identifying an appropriate in vitro assay to predict in vivo activity based on the biological relevance in the drug discovery setting.

Isoform-selective thiazolo[5,4-b]pyridine S1P1 agonists possessing acyclic amino carboxylate head-groups.

Replacement of the azetidine carboxylate of an S1P(1) agonist development candidate, AMG 369, with a range of acyclic head-groups led to the identification of a novel, S1P(3)-sparing S1P(1) agonist, (-)-2-amino-4-(3-fluoro-4-(5-(1-phenylcyclopropyl)thiazolo[5,4-b]pyridin-2-yl)phenyl)-2-methylbutanoic acid (8c), which possessed good in vivo efficacy and pharmacokinetic properties. A 0.3mg/kg oral dose of 8c produced a statistically significant reduction in blood lymphocyte counts 24h post-dosing in female Lewis rats.

Novel 5- and 6-subtituted benzothiazoles with improved physicochemical properties: potent S1P1 agonists with in vivo lymphocyte-depleting activity.

An SAR campaign designed to increase polarity in the 'tail' region of benzothiazole 1 resulted in two series of structurally novel 5-and 6-substituted S1P(1) agonists. Structural optimization for potency ultimately delivered carboxamide (+)-11f, which in addition to possessing improved physicochemical properties relative to starting benzothiazole 1, also displayed good S1P(3) selectivity and acceptable in vivo lymphocyte-depleting activity.

Discovery of a Potent, S1P3-Sparing Benzothiazole Agonist of Sphingosine-1-Phosphate Receptor 1 (S1P1).

Optimization of a benzofuranyl S1P1 agonist lead compound (3) led to the discovery of 1-(3-fluoro-4-(5-(2-fluorobenzyl)benzo[d]thiazol-2-yl)benzyl)azetidine-3-carboxylic acid (14), a potent S1P1 agonist with minimal activity at S1P3. Dosed orally at 0.3 mg/kg, 14 significantly reduced blood lymphocyte counts 24 h postdose and attenuated a delayed type hypersensitivity (DTH) response to antigen challenge.

Discovery of AMG 369, a Thiazolo[5,4-b]pyridine Agonist of S1P1 and S1P5.

The optimization of a series of thiazolopyridine S1P1 agonists with limited activity at the S1P3 receptor is reported. These efforts resulted in the discovery of 1-(3-fluoro-4-(5-(1-phenylcyclopropyl)thiazolo-[5,4-b]pyridin-2-yl)benzyl)azetidine-3-carboxylic acid (5d, AMG 369), a potent dual S1P1/S1P5 agonist with limited activity at S1P3 and no activity at S1P2/S1P4. Dosed orally at 0.1 mg/kg, 5d is shown to reduce blood lymphocyte counts 24 h postdose and delay the onset and reduce the severity of experimental autoimmune encephalomyelitis in rat.