Marta Calbet

The sphingosine-1-phosphate receptor-1 antagonist, W146, causes early and short-lasting peripheral blood lymphopenia in mice

Agonists of the sphingosine-1-phosphate (S1P) receptors, like fingolimod (FTY720), are a novel class of immunomodulators. Administration of these compounds prevents the egress of lymphocytes from primary and secondary lymphoid organs causing peripheral blood lymphopenia. Although it is well established that lymphopenia is mediated by S1P receptor type 1 (S1P1), the exact mechanism is still controversial. The most favored hypothesis states that S1P1 agonists cause internalization and loss of the cell surface receptor on lymphocytes, preventing them to respond to S1P. Hence, S1P1 agonists would behave in vivo as functional antagonists of the receptor. For this hypothesis to be valid, a true S1P1 antagonist should also induce lymphopenia. However, it has been reported that S1P1 antagonists fail to show this effect, arguing against the concept. Our study demonstrates that a S1P1 antagonist, W146, induces a significant but transient blood lymphopenia in mice and a parallel increase in CD4+ and CD8+ lymphocytes in lymph nodes. Treatment with W146 also causes the accumulation of mature T cells in the medulla of the thymus and moreover, it induces lung edema. We show that both the S1P1 antagonist and a S1P1 agonist cause lymphopenia in vivo in spite of their different effects on receptor expression in vitro. Although the antagonist purely blocks the receptor and the agonist causes its disappearance from the cell surface, the response to the endogenous ligand is prevented in both cases. Our results support the hypothesis that lymphopenia evoked by S1P1 agonists is due to functional antagonism of S1P1 in lymphocytes.

Structure-activity relationships (SAR) and structure-kinetic relationships (SKR) of pyrrolopiperidinone acetic acids as CRTh2 antagonists.

Pyrrolopiperidinone acetic acids (PPAs) were identified as highly potent CRTh2 receptor antagonists. In addition, many of these compounds displayed slow-dissociation kinetics from the receptor. Structure-kinetic relationship (SKR) studies allowed optimisation of the kinetics to give potent analogues with long receptor residence half-lives of up to 23 h. Low permeability was a general feature of this series, however oral bioavailability could be achieved through the use of ester prodrugs.

2-(1H-Pyrazol-4-yl)acetic acids as CRTh2 antagonists

High throughput screening identified the pyrazole-4-acetic acid substructure as CRTh2 receptor antagonists. Optimisation of the compounds uncovered a tight SAR but also identified some low nanomolar inhibitors.

2-(1H-Pyrazol-1-yl)acetic acids as chemoattractant receptor-homologous molecule expressed on Th2 lymphocytes (CRTh2) antagonists

In this manuscript, the synthesis and biological activity of a series of pyrazole acetic acid derivatives as CRTh2 antagonists is presented. Biological evaluation in vitro revealed that the pyrazole core showed in several cases a different structure-activity relationship (SAR) to that of related indole acetic acid. A potent series of ortho-sulfonyl benzyl substituents was found, from which compounds 27 and 63 were advanced to in vivo profiling.

Structure-activity relationships (SAR) and structure-kinetic relationships (SKR) of bicyclic heteroaromatic acetic acids as potent CRTh2 antagonists III: the role of a hydrogen-bond acceptor in long receptor residence times.

The correct positioning and orientation of an hydrogen bond acceptor (HBA) in the tail portion of the biaryl series of CRTh2 antagonists is a requirement for long receptor residence time. The HBA in combination with a small steric substituent in the core section (R(core) ≠ H) gives access to compounds with dissociation half-lives of ⩾ 24h.

Pharmacological characterization of CRTh2 antagonist LAS191859: Long receptor residence time translates into long-lasting in vivo efficacy.

The chemoattractant receptor-homologous molecule expressed on T-helper type 2 cells (CRTh2) is a G protein-coupled receptor expressed on the leukocytes most closely associated with asthma and allergy like eosinophils, mast cells, Th2-lymphocytes and basophils. At present it is clear that CRTh2 mediates most prostaglandin D2 (PGD2) pro-inflammatory effects and as a result antagonists for this receptor have reached asthma clinical studies showing a trend of lung function improvement. The challenge remains to identify compounds with improved clinical efficacy when administered once a day. Herein we described the pharmacological profile of LAS191859, a novel, potent and selective CRTh2 antagonist. In vitro evidence in GTPγS binding studies indicate that LAS191859 is a CRTh2 antagonist with activity in the low nanomolar range. This potency is also maintained in cellular assays performed with human eosinophils and whole blood. The main differentiation of LAS191859 vs other CRTh2 antagonists is in its receptor binding kinetics. LAS191859 has a residence time half-life of 21h at CRTh2 that translates into a long-lasting in vivo efficacy that is independent of plasma levels. We believe that the strategy behind this compound will allow optimal efficacy and posology for chronic asthma treatment.

Structure–activity relationships (SAR) and structure–kinetic relationships (SKR) of bicyclic heteroaromatic acetic acids as potent CRTh2 antagonists II: Lead optimization

Extensive structure-activity relationship (SAR) and structure-kinetic relationship (SKR) studies in the bicyclic heteroaromatic series of CRTh2 antagonists led to the identification of several molecules that possessed both excellent binding and cellular potencies along with long receptor residence times. A small substituent in the bicyclic core provided an order of magnitude jump in dissociation half-lives. Selected optimized compounds demonstrated suitable pharmacokinetic profiles.

Structure–activity relationships (SAR) and structure–kinetic relationships (SKR) of bicyclic heteroaromatic acetic acids as potent CRTh2 antagonists I

A knowledge-based design strategy led to the discovery of several new series of potent and orally bioavailable CRTh2 antagonists where a bicyclic heteroaromatic ring serves as the central core. Structure-kinetic relationships (SKR) opened up the possibility of long receptor residence times.

PI3K, p38 and JAK/STAT signalling in bronchial tissue from patients with asthma following allergen challenge

BackgroundInhaled allergen challenges are often used to evaluate novel asthma treatments in early phase clinical trials. Current novel therapeutic targets in asthma include phosphoinositide 3-kinases (PI3K) delta and gamma, p38 mitogen-activated protein kinase (p38) and Janus kinase/Signal Transducer and Activator of Transcription (JAK/STAT) signalling pathways. The activation of these pathways following allergen exposure in atopic asthma patients it is not known.MethodsWe collected bronchial biopsies from 11 atopic asthma patients at baseline and after allergen challenge to investigate biomarkers of PI3K, p38 MAPK and JAK/STAT activation by immunohistochemistry. Cell counts and levels of eosinophil cationic protein and interleukin-5 were also assessed in sputum and bronchoalvelar lavage.ResultsBiopsies collected post-allergen had an increased percentage of epithelial cells expressing phospho-p38 (17.5 vs 25.6%, p = 0.04), and increased numbers of sub-epithelial cells expressing phospho-STAT5 (122.2 vs 540.6 cells/mm2, p = 0.01) and the PI3K marker phospho-ribosomal protein S6 (180.7 vs 777.3 cells/mm2,p = 0.005). Type 2 inflammation was increased in the airways post allergen, with elevated levels of eosinophils, interleukin-5 and eosinophil cationic protein.ConclusionsFuture clinical trials of novel kinase inhibitors could use the allergen challenge model in proof of concept studies, while employing these biomarkers to investigate pharmacological inhibition in the lungs.

Discovery of a novel inhaled PI3Kδ inhibitor for the treatment of respiratory diseases

Oral PI3Kδ inhibitors such as Idelalisib and Duvelisib have shown efficacy as anticancer agents and Idelalisib has been approved for the treatment of three B-cell cancers. However, Idelalisib has a black box warning on its product label regarding the risks of fatal and serious toxicities including hepatic toxicity, severe diarrhea, colitis, pneumonitis, infections, and intestinal perforation. Some of these side effects are mechanism-related and could hinder the development of Idelalisib for less severe conditions. For respiratory diseases, compounds administered by inhalation are delivered directly to the site of action and may improve the therapeutic index of a drug, minimizing undesired side effects. This work describes the discovery and optimization of inhaled PI3Kδ inhibitors intended for the treatment of severe asthma and COPD. Once the potency was in the desired range, efforts were focused on identifying the particular physicochemical properties that could translate into better lung retention. This medicinal chemistry exercise led to the identification of LAS195319 as a candidate for clinical development.