ABSTRACT
Nicotinic acetylcholine receptors (nAChRs) are longstanding targets for a next generation of pain therapeutics, but the nAChR subtypes that govern analgesia remain unknown. We tested a series of nicotinic agonists, including many molecules used or tried clinically, on a panel of cloned neuronal nAChRs for potency and selectivity using patch-clamp electrophysiology and a live cell-based fluorescence assay. Nonselective nicotinic agonists as well as compounds selective either for alpha4beta2 or for alpha7 nAChRs were then tested in the formalin and complete Freund's adjuvant models of pain. Nonselective nAChR agonists ABT-594 and varenicline were effective analgesics. By contrast, the selective alpha4beta2 agonist ispronicline and a novel alpha4beta2-selective potentiator did not appear to produce analgesia in either model. alpha7-selective agonists reduced the pain-related endpoint, but the effect could be ascribed to nonspecific reduction of movement rather than to analgesia. Neither selective nor nonselective alpha7 nicotinic agonists affected the release of pro-inflammatory cytokines in response to antigen challenge. Electrophysiological recordings from spinal cord slice showed a strong nicotine-induced increase in inhibitory synaptic transmission that was mediated partially by alpha4beta2 and only minimally by alpha7 subtypes. Taken with previous studies, the results suggest that agonism of alpha4beta2 nAChRs is necessary but not sufficient to produce analgesia, and that the spinal cord is a key site where the molecular action of nAChRs produces analgesia.
Subject(s)
Analgesics/administration & dosage , Hyperalgesia/drug therapy , Hyperalgesia/physiopathology , Nicotinic Agonists/administration & dosage , Pain Measurement/drug effects , Animals , Chronic Disease , Humans , Hyperalgesia/diagnosis , Male , Rats , Rats, Sprague-Dawley , Treatment OutcomeABSTRACT
Deregulation of the receptor tyrosine kinase c-Met has been implicated in several human cancers and is an attractive target for small molecule drug discovery. We previously showed that O-linked triazolopyridazines can be potent inhibitors of c-Met. Herein, we report the discovery of a related series of N-linked triazolopyridazines which demonstrate nanomolar inhibition of c-Met kinase activity and display improved pharmacodynamic profiles. Specifically, the potent time-dependent inhibition of cytochrome P450 associated with the O-linked triazolopyridazines has been eliminated within this novel series of inhibitors. N-linked triazolopyridazine 24 exhibited favorable pharmacokinetics and displayed potent inhibition of HGF-mediated c-Met phosphorylation in a mouse liver PD model. Once-daily oral administration of 24 for 22days showed significant tumor growth inhibition in an NIH-3T3/TPR-Met xenograft mouse efficacy model.
Subject(s)
Angiogenesis Inhibitors/pharmacology , Apoptosis/physiology , Neovascularization, Physiologic/physiology , Protein Kinase Inhibitors/pharmacology , Proto-Oncogene Proteins c-met/antagonists & inhibitors , Animals , Cell Survival , Humans , Mice , Mice, Nude , Phosphorylation , Xenograft Model Antitumor AssaysABSTRACT
The discovery of a series of small molecule alpha4beta2 nAChR potentiators is reported. The structure-activity relationship leads to potent compounds selective against nAChRs including alpha3beta2 and alpha3beta4 and optimized for CNS penetrance. Compounds increased currents through recombinant alpha4beta2 nAChRs, yet did not compete for binding with the orthosteric ligand cytisine. High potency and efficacy on the rat channel combined with good PK properties will allow testing of the alpha4beta2 potentiator mechanism in animal models of disease.
Subject(s)
Central Nervous System/drug effects , Nicotinic Agonists/pharmacology , Piperidines/chemical synthesis , Piperidines/pharmacology , Receptors, Nicotinic/drug effects , Animals , Combinatorial Chemistry Techniques , Disease Models, Animal , Humans , Molecular Structure , Piperidines/chemistry , Rats , Receptors, Nicotinic/chemistry , Structure-Activity RelationshipABSTRACT
The synthesis and structure-activity relationship of a series of carbamate potentiators of alpha4beta2 nAChR is reported herein. These compounds were highly selective for alpha4beta2 over other nAChR subtypes. In addition, compounds increased the response of alpha4beta2 nAChRs to acetylcholine, as measured with patch-clamp electrophysiology.
Subject(s)
Chemistry, Pharmaceutical/methods , Receptors, Nicotinic/chemistry , Acetylcholine/chemistry , Calcium/chemistry , Carbamates/chemistry , Drug Design , Humans , Models, Chemical , Nervous System/metabolism , Neurons/metabolism , Patch-Clamp Techniques , Pyrazoles/chemistry , Pyridines/chemistry , Receptors, Nicotinic/metabolism , Structure-Activity RelationshipABSTRACT
Checkpoint kinase-1 (Chk1, CHEK1) is a Ser/Thr protein kinase that mediates the cellular response to DNA-damage. A novel class of 2-ureido thiophene carboxamide urea (TCU) Chk1 inhibitors is described. Inhibitors in this chemotype were optimized for cellular potency and selectivity over Cdk1.
Subject(s)
Chemistry, Pharmaceutical/methods , Protein Kinase Inhibitors/chemical synthesis , Protein Kinase Inhibitors/pharmacology , Protein Kinases/chemistry , Amides/chemistry , Apoptosis , Carbon/chemistry , Cell Cycle , Checkpoint Kinase 1 , DNA Damage , Drug Design , Humans , Inhibitory Concentration 50 , Models, Chemical , Phenyl Ethers/chemistry , Thiophenes/chemistry , Urea/chemistryABSTRACT
Tumorigenesis is a multistep process in which oncogenes play a key role in tumor formation, growth, and maintenance. MET was discovered as an oncogene that is activated by its ligand, hepatocyte growth factor. Deregulated signaling in the c-Met pathway has been observed in multiple tumor types. Herein we report the discovery of potent and selective triazolopyridazine small molecules that inhibit c-Met activity.
