• Novel Cholinergics for Treatment of Central Nervous System Disorders

      Johnson, Chad; Coop, Andrew; 0000-0001-7584-3000 (2019)
      Approximately 16% of Americans are diagnosed with major depressive disorder, a mental disorder thought be caused by a combination of characterized by genetic, biological, environmental, and psychological factors. It can be accompanied by low self-esteem, loss of interest in normally enjoyable activities, low energy, and diminished quality of life. Between 2-7% of adults with this disorder die by suicide. In addition, almost half of patients who are treated initially with an SSRI do not achieve complete remission, and nearly a third after four different treatment regimens (nimh.nih.gov). While counseling and antidepressant medication can be effective treatments, current selective serotonin re-uptake inhibitors (SSRI's) take weeks before therapeutic effects are observed. This "delay" period of action is not well understood and presents a significant challenge for medical professionals in the management of major depression. Mechanisms of anti-depressants have been a major focus of both current/past research in hopes of developing more effective and faster acting drugs. Directly related to this, clinical data (nimh.nih.gov) that oral and intravenous treatment with the muscarinic cholinergic antagonist scopolamine had rapid anti-depressant effects in humans--likely mediated through an antimuscarinic effect. Unfortunately, scopolamine can produce cognitive impairment including memory disturbances due to its anticholinergic properties. Since major depressive disorder is associated with deficits in cognition, this would produce an undesired additive effect that would only exacerbate the problem. It is our goal to identify a muscarinic antagonist that may be able to relieve depression and have little to no effect on memory or cognition. The 3-exo-1-azabicyclo[2.2.1]heptane, 1-azabicyclo[2.2.2]octane, 1-azabicyclo[3.2.1]octane, and N-methyltetrahydropyidine 3 (and 4)-substituted-1,2,4-oxadiazoles appear to be excellent chemical scaffolds for the generation of potent muscarinic agonists/antagonists. In order to probe the orthosteric site of the mAChRs we designed a large library of compounds and evaluated them via a battery of pharmacological assays to confirm both their antidepressant and cognitive effects. This resulted in the identification of lead compound (CJ2100) that showed potent antidepressant activity without cognitive impairment. (Supported by NIMH Grant 107499)
    • Opioid analgesics with reduced tolerance

      Cunningham, Christopher W.; Coop, Andrew (2008)
      Morphine is the gold-standard treatment for the management of severe pain. Despite its beneficial analgesic and euphoric effects, the profound development of analgesic tolerance limits its usefulness as a chronic pain therapeutic. Several mechanisms have been proposed, however it is unclear to what extent each contributes to tolerance development. First, the contribution of efflux transporters, such as P-glycoprotein (P-gp), has only recently been investigated, despite being implicated as a potential contributor by numerous studies. Most opioids possess some level of P-gp substrate activity, thus it is imperative to identify and design opioids which bypass this transporter in order to elucidate its effect on tolerance development. Second, it is well established that delta opioid receptor antagonists modulate the tolerance effects of mu receptor agonists, and several groups have attempted to exploit this phenomenon by producing ligands possessing this dual activity profile. To date, few studies have reported highly potent, orally available, small-molecule mu-agonist/delta-antagonist ligands, however recent advances in rational drug design have become crucial tools aiding their development. Combined, to target these mechanisms behind the rapid development of analgesic tolerance, small-molecule ligands have been designed, synthesized, and analyzed both in vitro and in vivo for opioid activity, as well as recognition by P-gp. First, a series of morphine analogs has been synthesized to elucidate the effect of hydrogen bonding of opioids on P-gp substrate activity. This led to the identification of 6-desoxymorphine as a potent opioid agonist with diminished recognition by P-gp. Second, the quantitative conformationally sampled pharmacophore (CSP) model describing delta opioid receptor ligands has been challenged by a structurally-diverse test set and applied toward designing novel, low-efficacy delta opioid ligands. These results facilitated the development of benzylideneoxymorphone (BOM), a small-molecule mu-partial agonist with low efficacy at delta receptors. Finally, based on the results of in silico CSP modeling studies, novel codeine cycloadducts have been synthesized through Diels-Alder condensation of codeine analogs with highly reactive dienes. These products are predicted to be low efficacy delta ligands which would act as probes toward understanding the effect of conformational flexibility on mu/delta receptor efficacy and selectivity. During the course of these procedures, the synthetic process presented unique challenges which were investigated. This has resulted in the optimization of novel synthetic methods which can be utilized for further transformations in opioid chemistry.
    • Phenylpropyloxyethylamines: Opioids lacking a tyrosine mimetic

      Stavitskaya, Lidiya; Coop, Andrew (2011)
      The mu opioid agonist morphine is the standard for severe pain management. Despite the ability of morphine to treat severe pain, there are significant side effects which often cause undermedication in clinical settings. Such effects are respiratory depression, tolerance, constipation, and dependence. Accordingly, investigation of novel classes of opioid analgesics would provide great therapeutic benefits. 14-Phenylpropyloxymorphinans are agonists that exhibit extreme potency at mu receptors, suggesting that the 14-phenylpropyloxy group has a major effect on receptor binding and is responsible for the dramatic increase in potency. Our hypothesis is that both a basic amine and a phenylpropyloxy group alone are required for opioid activity, and the aromatic A-ring, that was historically considered essential, is not required. By removing the A-ring, this allows the skeleton to adopt an alternate binding mode with the receptor, thereby potentially causing alternate receptor trafficking events and post-receptor mechanisms, all of which are involved in the development of tolerance. During initial studies, a conformationally sampled pharmacophore approach was utilized to confirm that the aromatic moiety in the novel series does not mimic the A-ring. In order to further substantiate our hypothesis, a series of phenylpropyloxyethylamines and cinnamyloxyethylamines were synthesized, and analyzed for opioid receptor binding affinity. Opioid binding studies showed that the optimal N-substituent is the N-phenethyl, specifically analog 2-(cinnamyloxy)-N-methyl-N-phenethylethanamine which has an affinity of 1680 nM for mu opioid receptors. Subsequently, rings B, C, and D from the morphine skeleton were systematically re-introduced as ring-constrained analogs. Binding studies showed that the B-ring analog containing a N,N-dimethyl substituent produced the highest affinity of 2340 nM, while the C- and D-ring analogs were fully inactive. Furthermore, by combining the B-ring with the optimal N-substituent, phenethyl, we were able to achieve 1640 nM affinity at mu. Moreover, upon introduction of an indole group into the C-ring analog, N,N-dimethyl-1-(3-(3-phenylpropoxy)-2,3,4,9-tetrahydro-1H-carbazol-3-yl)methanamine, the affinity was increased to 1110 nM, which represents a viable lead compound for optimization studies.
    • Structure-based optimization of small molecule transcription therapy targeting the BCL6 oncoprotein

      Tsourounis, Marilyn; Coop, Andrew (2009)
      BCL6, a member of the BTB/Zinc finger family of proteins is a transcriptional repressor that is constitutively expressed in over 50% of patients with Diffuse Large B Cell Lymphomas (DLBCL). BCL6 is responsible for the repression of at least 14 different genes linked by roles in B cell activation, differentiation, inflammation, and cell cycle control. Prior to cell differentiation, normal BCL6 encourages apoptosis by repressing expression of anti-apoptotic BCL6 target genes in the germinal center. Specific mutations and translocations in the 5' regulatory region of the BCL6 gene have been implicated in the constitutive expression of BCL6. This results in the aberrant replication of B cells that can escape the germinal center and lead to the formation of lymphomas. Preliminary proof of principle experiments have illustrated that an interaction between the BTB domain of BCL6 and unique regulatory sequences of its critical corepressors NCoR and SMRT are responsible for the mechanism of transcriptional repression of BCL6 at a "lateral groove" motif. Peptides that block the BCL6-SMRT interface kill lymphoma cells in vitro and in vivo, without causing toxicity to normal tissues. Small molecule inhibitors based on the 3D BCL6-SMRT interface were discovered via a target based drug design approach utilizing computer aided chemical database screening. Lead compounds displaying the desired biological activity in biochemical and functional assays were identified and selected for chemical derivation. Over 70 compounds have been developed and synthesized and are currently being evaluated for BCL6 inhibitory activity, as a part of our successive chemical optimization process to improve binding affinity, selectivity, and solubility. Preliminary in vitro studies of our first generations of indolylidene inhibitor compounds have demonstrated that an N-carboxylic acid and nature of the central heterocyclic ring are significant for activity. These results are consistent with CADD results determination of an energetically favorable interaction between the carboxylic charged moieties of lead compounds identified from primary database screens and key Arginine and Histidine residues in the putative binding site of the BCl6 BTB domain. Other CADD identified lead candidates possessing a diarylheterocyclic based scaffold were selected for further optimization to generate a chemically diverse library of molecules for SAR investigation of BTB lateral groove blockade and are presented. As continuation of this work, the development of small molecule inhibitors to target a secondary binding site of the BTB domain is described. Our structure-based strategy for introducing chemical modifications to our existing small molecule inhibitors along with proposed synthetic methodology to develop targets achieving this unique biological profile are reported.
    • Synthesis and characterization of meperidine analogs at the P-glycoprotein efflux transporter

      Mercer, Susan L.; Coop, Andrew (2008)
      Chronic clinical pain remains poorly treated. The use of mu opioid analgesics is effective in treating chronic pain, but the rapid development of tolerance to the analgesic effects necessitates ever increasing doses to be administered. However, tolerance to the constipatory effects occurs at a slower rate, a condition we refer to as differential tolerance. There is a great need to develop opioids to which differential tolerance does not develop in order to reduce the severity of constipation. Our hypothesis is that the efflux transporter, P-glycoprotein (P-gp), contributes to the development of central tolerance by actively pumping morphine out of the CNS. P-gp is present at the BBB, morphine is a known P-gp substrate, and P-gp is up-regulated in morphine and oxycodone tolerant animals. As analgesia is primarily central and constipation is primarily peripheral, up-regulation of P-gp would be expected to lead to lower brain concentrations of morphine compared to naive animals; therefore, contributing to tolerance. The design of opioids with decreased activity as P-gp substrates is anticipated to produce analgesics with reduced differential tolerance and therefore, diminished constipation. Meperidine, a moderately potent mu opioid receptor agonist causes less constipation than morphine clinically and has lower P-gp substrate activity than morphine. We have worked towards the optimization of meperidine by (1) employing opioid N-substituent SAR to increase its potency similar to morphine, (2) synthesizing isosteric replacements of the 4-ester to increase duration of action, and (3) introducing steric hinderance into the piperidine ring at the 2- and 6-positions to eliminate toxic metabolite formation. All analogs were analyzed for opioid receptor binding and P-gp substrate affinity. Results showed the optimal N-substituent was N-methyl; the ester was superior in the 4-position, and the introduction of a m-OH into the phenyl ring increased P-gp substrate affinity. Progress towards introducing steric hindrance is reported along with the strategy for their completion. Additional work on the synthesis and development of (1) selective sigma-1 ligands for stimulant abuse; and (2) a dual profile inhibitor of the S100beta and p53 interaction involved in malignant melanoma is presented.