ABSTRACT
We identified, via high-throughput screening using a FLIPR® calcium assay, compound 1, which incorporated a dihydroquinolinyl-2-oxoethylsulfanyl-(1H,5H)-pyrimidinedione core and activated the µ-opioid receptor (MOR) in the presence of naloxone or naltrexone. A structure-activity relationship study of the analogs of 1 led to the design of compound 21, which activated MOR in the presence of naloxone with an EC50 of 3.3 ± 0.2 µM. MOR activation by the compound 21-antagonist pair was antagonist-dependent. Compound 21 did not affect the potency of the orthosteric agonist, morphine, toward MOR, indicating that it affected the function of MOR antagonists rather than that of the agonists. Computer modeling of the compound 21-MOR-naloxone complex revealed major interactions between compound 21 and MOR, including hydrogen bonding with Ser196, π-π stacking with Tyr149, and sulfur-aromatic interaction with Trp192. This study may pave the way for developing agents capable of safe and effective MOR modulation.
Subject(s)
Naloxone , Naltrexone , Analgesics, Opioid , Imidazoles , Naloxone/pharmacology , Naltrexone/pharmacology , Receptors, Opioid , Sulfonamides , ThiophenesABSTRACT
Indoleamine 2,3-dioxygenase-1 (IDO1) is a potential target for the next generation of cancer immunotherapies. We describe the development of two series of IDO1 inhibitors incorporating a N-hydroxy-thiophene-carboximidamide core generated by knowledge-based drug design. Structural modifications to improve the cellular activity and pharmacokinetic (PK) properties of the compounds synthesized, including extension of the side chain of the N-hydroxythiophene-2-carboximidamide core, resulted in compound 27a, a potent IDO1 inhibitor which demonstrated significant (51%) in vivo target inhibition on IDO1 in a human SK-OV-3 ovarian xenograft tumor mouse model. This strategy is expected to be applicable to the discovery of additional IDO1 inhibitors for the treatment of other diseases susceptible to modulation of IDO1.
Subject(s)
Amides/chemistry , Drug Design , Enzyme Inhibitors/chemistry , Indoleamine-Pyrrole 2,3,-Dioxygenase/antagonists & inhibitors , Amides/metabolism , Animals , Binding Sites , Cell Line, Tumor , Enzyme Inhibitors/metabolism , Enzyme Inhibitors/therapeutic use , Half-Life , Humans , Indoleamine-Pyrrole 2,3,-Dioxygenase/metabolism , Mice , Mice, Inbred ICR , Molecular Docking Simulation , Neoplasms/drug therapy , Structure-Activity Relationship , Thiophenes/chemistry , Transplantation, HeterologousABSTRACT
Morphine is widely used for the treatment of severe pain. This analgesic effect is mediated principally by the activation of µ-opioid receptors (MOR). However, prolonged activation of MOR also results in tolerance, dependence, addiction, constipation, nausea, sedation, and respiratory depression. To address this problem, we sought alternative ways to activate MOR - either by use of novel ligands, or via a novel activation mechanism. To this end, a series of compounds were screened using a sensitive CHO-K1/MOR/Gα15 cell-based FLIPR® calcium high-throughput screening (HTS) assay, and the bithiazole compound 5a was identified as being able activate MOR in combination with naloxone. Structural modifications of 5a resulted in the discovery of lead compound 5j, which could effectively activate MOR in combination with the MOR antagonist naloxone or naltrexone. In vivo, naloxone in combination with 100â¯mg/kg of compound 5j elicited antinociception in a mouse tail-flick model with an ED50 of 17.5⯱â¯4â¯mg/kg. These results strongly suggest that the mechanism by which the 5j/naloxone combination activates MOR is worthy of further study, as its discovery has the potential to yield an entirely novel class of analgesics.
