ABSTRACT
Our group has recently shown that brain-penetrant ataxia telangiectasia-mutated (ATM) kinase inhibitors may have potential as novel therapeutics for the treatment of Huntington's disease (HD). However, the previously described pyranone-thioxanthenes (e.g., 4) failed to afford selectivity over a vacuolar protein sorting 34 (Vps34) kinase, an important kinase involved with autophagy. Given that impaired autophagy has been proposed as a pathogenic mechanism of neurodegenerative diseases such as HD, achieving selectivity over Vps34 became an important objective for our program. Here, we report the successful selectivity optimization of ATM over Vps34 by using X-ray crystal structures of a Vps34-ATM protein chimera where the Vps34 ATP-binding site was mutated to approximate that of an ATM kinase. The morpholino-pyridone and morpholino-pyrimidinone series that resulted as a consequence of this selectivity optimization process have high ATM potency and good oral bioavailability and have lower molecular weight, reduced lipophilicity, higher aqueous solubility, and greater synthetic tractability compared to the pyranone-thioxanthenes.
Subject(s)
Ataxia Telangiectasia Mutated Proteins/antagonists & inhibitors , Pyridones/chemistry , Pyrimidinones/chemistry , Animals , Ataxia Telangiectasia Mutated Proteins/metabolism , Binding Sites , Brain/metabolism , Class III Phosphatidylinositol 3-Kinases/antagonists & inhibitors , Class III Phosphatidylinositol 3-Kinases/metabolism , Crystallography, X-Ray , Drug Design , Half-Life , Humans , Huntington Disease/drug therapy , Male , Mice , Mice, Inbred C57BL , Molecular Dynamics Simulation , Morpholinos/chemistry , Pyridones/metabolism , Pyridones/therapeutic use , Pyrimidinones/metabolism , Pyrimidinones/therapeutic use , Structure-Activity RelationshipABSTRACT
Replacement of the core heterocycle of a defined series of chromen-4-one DNA-PK inhibitors by the isomeric chromen-2-one (coumarin) and isochromen-1-one (isocoumarin) scaffolds was investigated. Structure-activity relationships for DNA-PK inhibition were broadly consistent, albeit with a reduction of potency compared with the parent chromenone.
Subject(s)
Adenosine Triphosphate/metabolism , Coumarins/antagonists & inhibitors , DNA-Activated Protein Kinase/chemistry , Isocoumarins/antagonists & inhibitors , Antineoplastic Agents , Binding Sites , Chromones , DNA-Activated Protein Kinase/metabolism , Humans , Inhibitory Concentration 50 , Structure-Activity RelationshipABSTRACT
Substitution at the 3-position of the dibenzothiophen-4-yl ring of 8-(dibenzo[b,d]thiophen-4-yl)-2-morpholino-4H-chromen-4-one NU7441, a potent and selective DNA-dependent protein kinase (DNA-PK) inhibitor, with propyl, allyl or methyl enabled the separation by chiral HPLC of atropisomers. This is a consequence of restricted rotation about the dibenzothiophene-chromenone bond. Biological evaluation against DNA-PK of the pairs of atropisomers showed a marked difference in potency, with only one enantiomer being biologically active.
Subject(s)
DNA-Activated Protein Kinase/antagonists & inhibitors , DNA-Activated Protein Kinase/metabolism , Protein Kinase Inhibitors/chemistry , Protein Kinase Inhibitors/pharmacology , Thiophenes/chemistry , Thiophenes/pharmacology , Chromatography, High Pressure Liquid , Isomerism , Protein Kinase Inhibitors/chemical synthesis , Thiophenes/chemical synthesisABSTRACT
Selective activation of peripheral cannabinoid CB1 receptors has the potential to become a valuable therapy for chronic pain conditions as long as central nervous system effects are attenuated. A new class of cannabinoid ligands was rationally designed from known aminoalkylindole agonists and showed good binding and functional activities at human CB1 and CB2 receptors. This has led to the discovery of a novel CB1/CB2 dual agonist, naphthalen-1-yl-(4-pentyloxynaphthalen-1-yl)methanone (13), which displays good oral bioavailability, potent antihyperalgesic activity in animal models, and limited brain penetration.
Subject(s)
Analgesics/chemical synthesis , Brain/metabolism , Hyperalgesia/drug therapy , Naphthalenes/chemical synthesis , Receptor, Cannabinoid, CB1/agonists , Receptor, Cannabinoid, CB2/agonists , Administration, Oral , Analgesics/pharmacokinetics , Analgesics/pharmacology , Animals , Biological Availability , Cricetinae , Cricetulus , Cyclic AMP/biosynthesis , Humans , In Vitro Techniques , Microsomes, Liver/metabolism , Naphthalenes/pharmacokinetics , Naphthalenes/pharmacology , Radioligand Assay , Rats , Rats, Wistar , Structure-Activity RelationshipABSTRACT
CT-3 (ajulemic acid) is a synthetic analogue of a metabolite of Delta9-tetrahydrocannabinol that has reported analgesic efficacy in neuropathic pain states in man. Here we show that CT-3 binds to human cannabinoid receptors in vitro, with high affinity at hCB1 (Ki 6 nM) and hCB2 (Ki 56 nM) receptors. In a functional GTP-gamma-S assay CT-3 was an agonist at both hCB1 and hCB2 receptors (EC50 11 and 13.4 nM, respectively). In behavioural models of chronic neuropathic and inflammatory pain in the rat, oral administration of CT-3 (0.1-1 mg/kg) produced up to 60% reversal of mechanical hyperalgesia. In both models the antihyperalgesic activity was prevented by the CB1-antagonist SR141716A but not the CB2-antagonist SR144528. In the tetrad of tests for CNS activity, CT-3 (1-10 mg/kg, po) produced dose-related catalepsy, deficits in locomotor performance, hypothermia, and acute analgesia. Comparison of 50% maximal effects in the tetrad and chronic pain assays produced an approximate therapeutic index of 5-10. Pharmacokinetic analysis showed that CT-3 exhibits significant but limited brain penetration, with a brain/plasma ratio of 0.4 measured following oral administration, compared to ratios of 1.0-1.9 measured following subcutaneous administration of WIN55,212-2 or Delta9-THC. These data show that CT-3 is a cannabinoid receptor agonist and is efficacious in animal models of chronic pain by activation of the CB1 receptor. Whilst it shows significant cannabinoid-like CNS activity, it exhibits a superior therapeutic index compared to other cannabinoid compounds, which may reflect a relatively reduced CNS penetration.
