Gerta Cami-Kobeci

A novel orvinol analog, BU08028, as a safe opioid analgesic without abuse liability in primates

Significance A potent opioid analgesic without addictive and respiratory adverse effects has been a predominant goal for opioid medicinal chemistry since the isolation of morphine from opium in the 19th century. Here we report a functional profile of a unique analog, BU08028, targeting a combination of a classical and nonclassical opioid receptors in monkeys. By examining behavioral, physiological, and pharmacologic factors, the present study demonstrates that BU08028 exhibits full antinociception and antihypersensitivity without reinforcing effects (i.e., abuse liability), respiratory depression, pruritus, adverse cardiovascular events, or acute physical dependence. Because monkey models provide the most phylogenetically appropriate evaluation of opioid receptor functions and drug effects, these findings provide a translational bridge for such ligands as effective analgesics without safety and abuse liability concerns. Despite the critical need, no previous research has substantiated safe opioid analgesics without abuse liability in primates. Recent advances in medicinal chemistry have led to the development of ligands with mixed mu opioid peptide (MOP)/nociceptin-orphanin FQ peptide (NOP) receptor agonist activity to achieve this objective. BU08028 is a novel orvinol analog that displays a similar binding profile to buprenorphine with improved affinity and efficacy at NOP receptors. The aim of this preclinical study was to establish the functional profile of BU08028 in monkeys using clinically used MOP receptor agonists for side-by-side comparisons in various well-honed behavioral and physiological assays. Systemic BU08028 (0.001–0.01 mg/kg) produced potent long-lasting (i.e., >24 h) antinociceptive and antiallodynic effects, which were blocked by MOP or NOP receptor antagonists. More importantly, the reinforcing strength of BU08028 was significantly lower than that of cocaine, remifentanil, or buprenorphine in monkeys responding under a progressive-ratio schedule of drug self-administration. Unlike MOP receptor agonists, BU08028 at antinociceptive doses and ∼10- to 30-fold higher doses did not cause respiratory depression or cardiovascular adverse events as measured by telemetry devices. After repeated administration, the monkeys developed acute physical dependence on morphine, as manifested by precipitated withdrawal signs, such as increased respiratory rate, heart rate, and blood pressure. In contrast, monkeys did not show physical dependence on BU08028. These in vivo findings in primates not only document the efficacy and tolerability profile of bifunctional MOP/NOP receptor agonists, but also provide a means of translating such ligands into therapies as safe and potentially abuse-free opioid analgesics.

Orvinols with Mixed Kappa/Mu Opioid Receptor Agonist Activity

Dual-acting kappa opioid receptor (KOR) agonist and mu opioid receptor (MOR) partial agonist ligands have been put forward as potential treatment agents for cocaine and other psychostimulant abuse. Members of the orvinol series of ligands are known for their high binding affinity to both KOR and MOR, but efficacy at the individual receptors has not been thoroughly evaluated. In this study, it is shown that a predictive model for efficacy at KOR can be derived, with efficacy being controlled by the length of the group attached to C20 and by the introduction of branching into the side chain. In vivo evaluation of two ligands with the desired in vitro profile confirms both display KOR, and to a lesser extent MOR, activity in an analgesic assay suggesting that, in this series, in vitro measures of efficacy using the [35S]GTPγS assay are predictive of the in vivo profile.

Structural Determinants of Opioid and NOP Receptor Activity in Derivatives of Buprenorphine

The unique pharmacological profile of buprenorphine has led to its considerable success as an analgesic and as a treatment agent for drug abuse. Activation of nociceptin/orphanin FQ peptide (NOP) receptors has been postulated to account for certain aspects of buprenorphines behavioral profile. In order to investigate the role of NOP activation further, a series of buprenorphine analogues has been synthesized with the aim of increasing affinity for the NOP receptor. Binding and functional assay data on these new compounds indicate that the area around C20 in the orvinols is key to NOP receptor activity, with several compounds displaying higher affinity than buprenorphine. One compound, 1b, was found to be a mu opioid receptor partial agonist of comparable efficacy to buprenorphine but with higher efficacy at NOP receptors.

BU08073 a buprenorphine analogue with partial agonist activity at μ‐receptors in vitro but long‐lasting opioid antagonist activity in vivo in mice

Buprenorphine is a potent analgesic with high affinity at μ, δ and κ and moderate affinity at nociceptin opioid (NOP) receptors. Nevertheless, NOP receptor activation modulates the in vivo activity of buprenorphine. Structure activity studies were conducted to design buprenorphine analogues with high affinity at each of these receptors and to characterize them in in vitro and in vivo assays.

Anti-inflammatory effect of dual nociceptin and opioid receptor agonist, BU08070, in experimental colitis in mice

Endogenous opioid and nociceptin systems are widely distributed in the gastrointestinal tract where they seem to play a crucial role in maintaining the intestinal homeostasis. The aim of our study was to assess whether activation of nociceptin (NOP) and µ-opioid (MOP) receptors by a mixed NOP/MOP receptor agonist, BU08070, induces anti-inflammatory response in experimental colitis. The anti-inflammatory effect of BU08070 (1 mg/kg i.p.) was characterized in the mouse model of 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced colitis, based on the assessment of the macroscopic and microscopic total damage scores and determination of myeloperoxidase (MPO) activity and TNF-α level in the colon. The effect of BU08070 on cell viability and NF-κB was characterized in THP-1 Blue cell line. The antinociceptive activity of BU08070 was examined in mustard oil-induced mouse model of abdominal pain. A potent anti-inflammatory effect of BU08070 (1 mg/kg i.p.) was observed as indicated by decrease in macroscopic damage score (1.88±0.39 vs. 5.19±0.43 units in TNBS alone treated mice), MPO activity (2.29±0.37 vs. 9.64±2.55 units) and TNF-α level in the colon (35.85±2.45 vs. 49.79±3.81 pg/ml). The anti-inflammatory effect of BU08070 was reversed by selective NOP and MOP receptor antagonists. BU08070 produced concentration-dependent inhibition of TNF-α and LPS-induced NF-κB activation. BU08070 exerted antinociceptive action in mice with experimental colitis. In conclusion, BU08070 significantly reduced the severity of colitis in TNBS-treated mice compared with controls. These results suggest that BU08070 is a potential therapeutic agent for inflammatory bowel diseases therapy.

Mixed κ/μ Opioid Receptor Agonists: The 6β-Naltrexamines

Ligands from the naltrexamine series have consistently demonstrated agonist activity at kappa opioid receptors (KOR), with varying activity at the mu opioid receptor (MOR). Various 6 beta-cinnamoylamino derivatives were made with the aim of generating ligands with a KOR agonist/MOR partial agonist profile, as ligands with this activity may be of interest as treatment agents for cocaine abuse. The ligands all displayed the desired high affinity, nonselective binding in vitro and in the functional assays were high efficacy KOR agonists with some partial agonist activity at MOR. Two of the new ligands (12a, 12b) have been evaluated in vivo, with 12a acting as a KOR agonist and therefore somewhat similar to the previously evaluated analogues 3-6, while 12b displayed predominant MOR agonist activity.

Methyl-orvinol—Dual activity opioid receptor ligand inhibits gastrointestinal transit and alleviates abdominal pain in the mouse models mimicking diarrhea-predominant irritable bowel syndrome

BACKGROUND Diarrhea-predominant irritable bowel syndrome (IBS-D) is a functional disorder of the gastrointestinal (GI) tract. The major IBS-D symptoms include diarrhea, abdominal pain and discomfort. High density of opioid receptors (ORs) in the GI tract and their participation in the maintenance of GI homeostasis make ORs ligands an attractive option for developing new anti-IBS-D treatments. The aim of this study was to characterize the effect of methyl-orvinol on the GI motility and secretion and in mouse models mimicking symptoms of IBS-D. METHODS In vitro, the effects of methyl-orvinol on electrical field stimulated smooth muscle contractility and epithelial ion transport were characterized in the mouse colon. In vivo, the following tests were used to determine methyl-orvinol effect on mouse GI motility: colonic bead expulsion, whole GI transit and fecal pellet output. An antinociceptive action of methyl-orvinol was assessed in the mouse model of visceral pain induced by mustard oil. RESULTS Methyl-orvinol (10-10 to 10-6M) inhibited colonic smooth muscle contractions in a concentration-dependent manner. This effect was reversed by naloxone (non-selective opioid antagonist) and β-funaltrexamine (selective MOP antagonist). Experiments with a selective KOP receptor agonist, U50488 revealed that methyl-orvinol is a KOP receptor antagonist in the GI tract. Methyl-orvinol enhanced epithelial ion transport. In vivo, methyl-orvinol inhibited colonic bead expulsion and prolonged GI transit. Methyl-orvinol improved hypermotility and reduced abdominal pain in the mouse models mimicking IBS-D symptoms. CONCLUSION Methyl-orvinol could become a promising drug candidate in chronic therapy of functional GI diseases such as IBS-D.

Synthesis, Biological Evaluation, and SAR Studies of 14β-phenylacetyl Substituted 17-cyclopropylmethyl-7, 8-dihydronoroxymorphinones Derivatives: Ligands With Mixed NOP and Opioid Receptor Profile

A series of 14β-acyl substituted 17-cyclopropylmethyl-7,8-dihydronoroxymorphinone compounds has been synthesized and evaluated for affinity and efficacy for mu (MOP), kappa (KOP), and delta (DOP) opioid receptors and nociceptin/orphanin FQ peptide (NOP) receptors. The majority of the new ligands displayed high binding affinities for the three opioid receptors, and moderate affinity for NOP receptors. The affinities for NOP receptors are of particular interest as most classical opioid ligands do not bind to NOP receptors. The predominant activity in the [35S]GTPγS assay was partial agonism at each receptor. The results are consistent with our prediction that an appropriate 14β side chain would access a binding site within the NOP receptor and result in substantially higher affinity than displayed by the parent compound naltrexone. Molecular modeling studies, utilizing the recently reported structure of the NOP receptor, are also consistent with this interpretation.

CHAPTER 8:The Therapeutic Potential of Small-molecule Modulators of the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) Cl− Channel

The cystic fibrosis transmembrane conductance regulator (CFTR) plays a pivotal role in fluid and electrolyte movements across ducts and tubes lined by epithelia. Loss of CFTR function causes the common life-limiting genetic disease cystic fibrosis (CF) and a spectrum of disorders termed CFTR-related diseases, while unphysiological CFTR activity characterises secretory diarrhoea and autosomal dominant polycystic kidney disease (ADPKD). The prevalence of these disorders argues persuasively that small-molecule CFTR modulators have significant therapeutic potential. Here, we discuss how knowledge and understanding of the CFTR Cl− channel, its physiological role and malfunction in disease led to the development of the CFTR potentiator ivacaftor, the first small molecule targeting CFTR approved as a treatment for CF. We consider the prospects for developing other therapeutics targeting directly CFTR including CFTR correctors to rescue the apical membrane expression of CF mutants, CFTR corrector-potentiators, dual-acting small-molecules to correct the processing and gating defects of F508del-CFTR, the commonest CF mutant and CFTR inhibitors to prevent fluid and electrolyte loss in secretory diarrhoea and cyst swelling in ADPKD. The success of ivacaftor provides impetus to other CFTR drug development programmes and a paradigm for the creation of therapeutics targeting the root cause of other genetic disorders.

Substrate Activation: Indirect β-Bromination of Alcohols

The reversible oxidation of an alcohol into a ketone provides access to enol/enolate chemistry. Preliminary results have applied this principle to the beta-bromination of alcohols.