Bertrand Le Bourdonnec

Potent, Orally Bioavailable Delta Opioid Receptor Agonists for the Treatment of Pain : Discovery of N,N-Diethyl-4-(5-hydroxyspiro-[chromene-2,4'-piperidine]-4-yl)benzamide (ADL5859)

Selective delta opioid receptor agonists are promising potential therapeutic agents for the treatment of various types of pain conditions. A spirocyclic derivative was identified as a promising hit through screening. Subsequent lead optimization identified compound 20 (ADL5859) as a potent, selective, and orally bioavailable delta agonist. Compound 20 was selected as a clinical candidate for the treatment of pain.

Spirocyclic Delta Opioid Receptor Agonists for the Treatment of Pain: Discovery of N,N-Diethyl-3-hydroxy-4-(spiro[chromene-2,4'-piperidine]-4-yl) Benzamide (ADL5747)

Selective, nonpeptidic delta opioid receptor agonists have been the subject of great interest as potential novel analgesic agents. The discoveries of BW373U86 (1) and SNC80 (2) contributed to the rapid expansion of research in this field. However, poor drug-like properties and low therapeutic indices have prevented clinical evaluation of these agents. Doses of 1 and 2 similar to those required for analgesic activity produce convulsions in rodents and nonhuman primates. Recently, we described a novel series of potent, selective, and orally bioavailable delta opioid receptor agonists. The lead derivative, ADL5859 (4), is currently in phase II proof-of-concept studies for the management of pain. Further structure activity relationship exploration has led to the discovery of ADL5747 (36), which is approximately 50-fold more potent than 4 in an animal model of inflammatory pain. On the basis of its favorable efficacy, safety, and pharmacokinetic profile, 36 was selected as a clinical candidate for the treatment of pain.

δ-Opioid Mechanisms for ADL5747 and ADL5859 Effects in Mice: Analgesia, Locomotion, and Receptor Internalization

N,N-diethyl-4-(5-hydroxyspiro[chromene-2,4′-piperidine]-4-yl) benzamide (ADL5859) and N,N-diethyl-3-hydroxy-4-(spiro[chromene-2,4′-piperidine]-4-yl)benzamide (ADL5747) are novel δ-opioid agonists that show good oral bioavailability and analgesic and antidepressive effects in the rat and represent potential drugs for chronic pain treatment. Here, we used genetic approaches to investigate molecular mechanisms underlying their analgesic effects in the mouse. We tested analgesic effects of ADL5859 and ADL5747 in mice by using mechanical sensitivity measures in both complete Freunds adjuvant and sciatic nerve ligation pain models. We examined their analgesic effects in δ-opioid receptor constitutive knockout (KO) mice and mice with a conditional deletion of δ-receptor in peripheral voltage-gated sodium channel (Nav)1.8-expressing neurons (cKO mice). Both ADL5859 and ADL5747, and the prototypical δ agonist 4-[(R)-[(2S,5R)-4-allyl-2,5-dimethyl-piperazin-1-yl]-(3-methoxyphenyl)methyl]-N,N-diethyl-benzamide (SNC80) as a control, significantly reduced inflammatory and neuropathic pain. The antiallodynic effects of all three δ-opioid agonists were abolished in constitutive δ-receptor KO mice and strongly diminished in δ-receptor cKO mice. We also measured two other well described effects of δ agonists, increase in locomotor activity and agonist-induced receptor internalization by using knock-in mice expressing enhanced green fluorescence protein-tagged δ receptors. In contrast to SNC80, ADL5859 and ADL5747 did not induce either hyperlocomotion or receptor internalization in vivo. In conclusion, both ADL5859 and ADL5747 showed efficient pain-reducing properties in the two models of chronic pain. Their effects were mediated by δ-opioid receptors, with a main contribution of receptors expressed on peripheral Nav1.8-positive neurons. The lack of in vivo receptor internalization and locomotor activation, typically induced by SNC80, suggests agonist-biased activity at the receptor for the two drugs.

Medicinal Chemistry Strategies to Reduce CYP2D6 Inhibitory Activity of Lead Candidates

Among the various human cytochrome P450s (CYP450s) that catalyze the biotransformation of xenobiotics, CYP450 2D6 (CYP2D6) is one of the most important based on the number and wide variety of its drug substrates. CYP2D6 shows a high degree of interindividual variability, which is primarily due to the extensive genetic polymorphism that influences its expression and function. A number of drugs have been clinically implicated in major drug-drug interactions (DDI) via CYP2D6 inhibition. In order to avoid or minimize issues related to CYP2D6-mediated DDIs, pharmaceutical companies routinely screen for potential CYP2D6 liability of lead candidates in the early stage of the drug discovery process. This review summarizes the medicinal chemistry tactics employed to mitigate inhibitory activity at CYP2D6, identified through an extensive literature survey covering the 1998-2008 period.

Design and Synthesis of Imidazopyrimidine Derivatives as Potent iNOS Dimerization Inhibitors

A series of imidazopyrimidine derivatives with the general formula I was synthesized and identified as potent inhibitors of iNOS dimer formation, a prerequisite for proper functioning of the enzyme. Stille and Negishi coupling reactions were used as key steps to form the carbon-carbon bond connecting the imidazopyrimidine core to the central cycloalkenyl, cycloalkyl and phenyl ring templates.