Discovery of orally bioavailable NK1 receptor antagonists

Chronic pruritus: from pathophysiology to drug design

Pruritus, the most common symptom in dermatology, is an innate response capable of protecting skin against irritants. Nonetheless, when it lasts more than six weeks it is assumed to be a chronic pathology having a negative impact on people's lives. Chronic pruritus (CP) can occur in common and rare skin diseases, having a high prevalence in global population. The existing therapies are unable to counteract CP or are associated with adverse effects, so the development of effective treatments is a pressing issue. The pathophysiological mechanisms underlying CP are not yet completely dissected but, based on current knowledge, involve a wide range of receptors, namely neurokinin 1 receptor (NK1R), Janus kinase (JAK), and transient receptor potential (TRP) ion channels, especially transient receptor potential vanilloid 1 (TRPV1) and transient receptor potential ankyrin 1 (TRPA1). This review will address the relevance of these molecular targets for the treatment of CP and molecules capable of modulating these receptors that have already been studied clinically or have the potential to possibly alleviate this pathology. According to scientific and clinical literature, there is an increase in the expression of these molecular targets in the lesioned skin of patients experiencing CP when compared with non-lesioned skin, highlighting their importance for the development of potential efficacious drugs through the design of antagonists/inhibitors.

Design, optimization, and in vivo evaluation of a series of pyridine derivatives with dual NK1 antagonism and SERT inhibition for the treatment of depression

A series of substituted pyridines, ether linked to a phenylpiperidine core were optimized for dual NK(1)/SERT affinity. Optimization based on NK(1)/SERT binding affinities, and minimization of off-target ion channel activity lead to the discovery of compound 44. In vivo evaluation of 44 in the gerbil forced swim test (a depression model), and ex-vivo NK(1)/SERT receptor occupancy data support the potential of a dual acting compound for the treatment of depression.

Synthesis and initial PET imaging of new potential NK1 receptor radioligands 1-[2-(3,5-bis-trifluoromethyl-benzyloxy)-1-phenyl-ethyl]-4-[11C]methyl-piperazine and {4-[2-(3,5-bis-trifluoromethyl-benzyloxy)-1-phenyl-ethyl]-piperazine-1-yl}-acetic acid [11C]methyl ester

The NK(1) receptor radioligands 1-[2-(3,5-bis-trifluoromethyl-benzyloxy)-1-phenyl-ethyl]-4-[(11)C]methyl-piperazine ([(11)C]BMP, [(11)C]) and {4-[2-(3,5-bis-trifluoromethyl-benzyloxy)-1-phenyl-ethyl]-piperazine-1-yl}-acetic acid [(11)C]methyl ester ([(11)C]BME, [(11)C]) were synthesized for evaluation as new potential PET imaging agents for brain NK(1) receptors. The new tracers [(11)C]BMP and [(11)C]BME were prepared by N-[(11)C]methylation and O-[(11)C]methylation of corresponding precursors 1-[2-(3,5-bis-trifluoromethyl-benzyloxy)-1-phenyl-ethyl]-piperazine and {4-[2-(3,5-bis-trifluoromethyl-benzyloxy)-1-phenyl-ethyl]-piperazine-1-yl}-acetic acid using [(11)C]methyl triflate and isolated by solid-phase extraction (SPE) purification procedure with 40-55% radiochemical yields, decay corrected to end of bombardment, and a synthesis time of 15-20 min. The initial PET dynamic studies of the tracers [(11)C] and [(11)C] in rats were performed using an animal PET scanner, IndyPET-II, developed in our laboratory. The results show the tracer [(11)C]BMP had better uptake in the animal brain than the tracer [(11)C]BME and gave higher quality rat brain images. Blocking studies by intravenous coinjection of hot tracer [(11)C]BMP with cold drug BMP had no effect on [(11)C]BMP-PET rat brain imaging. Likewise, blocking studies by intravenous coinjection of hot tracer [(11)C]BME with cold drug BME also showed no effect on [(11)C]BME-PET rat brain imaging. These results suggest that the localization of [(11)C]BMP and [(11)C]BME in rat brain is mediated by nonspecific processes, and the visualization of [(11)C]BMP-PET and [(11)C]BME-PET on rat brain is related to nonspecific binding.