Design,Synthesis And Bioactivity Evaluation Of Indoline Piperidine Amides As Novel MOR Agonist/TRPV1-Antagonist Dual-Target Compouds

Pain is a common disease in clinical treatment that affects the quality of life of many people.However,it is also a necessary warning signal that can trigger protective reactions.Among them,chronic pain not only has no protective effect on the human body,but is actually harmful to the body.At present,common single target analgesic drugs in clinical practice,such as opioid analgesics and non-steroidal antiinflammatory drugs,are often not ideal in terms of efficacy and side effects,limiting their clinical use.Compared with the therapeutic effects of single target drugs,multi target drugs can manipulate two(or more)targets involving different molecular pathways of diseases,and have been proven to be a reliable treatment strategy for complex diseases.Therefore,the development of multi target analgesic drugs may provide new opportunities for the treatment of pain.MOR(μ-Opioid),as a member of the G protein coupled receptor superfamily,is currently considered to be the most effective analgesic target,but its application has been greatly limited due to adverse reactions such as analgesia tolerance,respiratory depression and dependence.Transient receptor potential vanillic acid subtype 1(TRPV1)can be activated by various stimuli and plays a crucial role in pain transmission.It is a highly validated pain target,and its agonists and antagonists are potential analgesics in clinical trials.More and more studies have shown that the TRPV1 mediated signaling pathway can reduce the adverse reactions of opioid analgesics and improve the therapeutic effect of morphine in acute or bone cancer pain models.Therefore,we aim to develop a dual target analgesic drug that simultaneously acts on opioid receptors and TRPV1 receptors,in order to achieve better analgesic effects.AZD1386 is a classical TRPV1 antagonist,which has a potent but short-lasting analgesic effect and causes an increase in body temperature.Additionally Johnson & Johnson pharmaceuticals and Purdue pharmaceuticals have developed a series of piperidine urea TRPV1 antagonists such as compound B,and structure-activity relationship studies have shown that the piperidine urea moiety is its basic pharmacophore.To deeply investigate the structure-activity relationship,in this work,we used the strategy of pharmacophore fusion to expand the five membered imidazolone ring linked to indoline in compound AZD1386 to a six membered piperidine ring and designed and synthesized 25 single target compounds(5a-5y)antagonizing TRPV1 by introducing aromatic rings and aromatic heterocycles with different substituents through urea group.In order to further develop new analgesic drugs,based on the functional crosstalk between MOR and TRPV1,we simultaneously attempted to develop dual active ligands targeting MOR and TRPV1,and compared them with the first series of single target compounds.Fentanyl,a typical anilino piperidine MOR receptor agonist,has strong analgesic activity,but is prone to tolerance and addiction and other adverse effects.On the basis of the above structures of single target TRPV1 antagonists,we further introduced a propionyl group at the indoline nitrogen atom in an attempt to obtain analgesic compounds that simultaneously acted on mor and TRPV1 targets.We preserved the anilino piperidine structure required for fentanyl agonism of MOR targets and antagonism of the essential pharmacophore piperidine urea moiety of TRPV1 and designed and synthesized multiple dual target compounds(8a-8y)that could simultaneously act on TRPV1 and MOR by introducing aromatic and aromatic heterocycles with different substituents through the urea group.In vitro analgesic activity experiments,compounds 5e,5l,5m,8i,and 8m showed potent analgesic activity.Moreover,compounds 5e and 8m showed more excellent target affinities as tested by competitive binding of the compounds to TRPV1 and MOR targets.In the evaluation of analgesic activity in vivo,compound 8m exhibited superior analgesic efficacy than the control BCTC(TRPV1 antagonist)and the first series of single target compounds in both the first phase(acute pain)and the second phase(chronic pain)of formalin induced pain,significantly reducing the licking time of mice.In addition,target engagement experiments proved that compound 8m was an analgesic agent by mediating TRPV1 and MOR receptors.Finally,in molecular modeling docking studies,compound 8m formed more interaction forces than BCTC and fentanyl in TRPV1(PDB ID: 5IS0)and MOR(PDB ID: 5C1M)hydrophobic pockets and could effectively bind in the hydrophobic pockets of TRPV1 and MOR,further verifying our rational for dual target drug design ideas.In result,the dual target compound 8m possessed relatively superior analgesic activity and possessed potential clinical applications.