Hamed Aissaoui

Promotion of sleep by targeting the orexin system in rats, dogs and humans

Orexins are hypothalamic peptides that play an important role in maintaining wakefulness in mammals. Permanent deficit in orexinergic function is a pathophysiological hallmark of rodent, canine and human narcolepsy. Here we report that in rats, dogs and humans, somnolence is induced by pharmacological blockade of both orexin OX1 and OX2 receptors. When administered orally during the active period of the circadian cycle, a dual antagonist increased, in rats, electrophysiological indices of both non-REM and, particularly, REM sleep, in contrast to GABAA receptor modulators; in dogs, it caused somnolence and increased surrogate markers of REM sleep; and in humans, it caused subjective and objective electrophysiological signs of sleep. No signs of cataplexy were observed, in contrast to the rodent, dog or human narcolepsy syndromes. These results open new perspectives for investigating the role of endogenous orexins in sleep-wake regulation.

N-Glycine-sulfonamides as potent dual orexin 1/orexin 2 receptor antagonists.

A series of dual OX(1)R/OX(2)R orexin antagonists was prepared based on a N-glycine-sulfonamide core. SAR studies of a screening hit led to compounds with low nanomolar affinity for both receptors and good oral bioavailability. One of these compounds, 47, has demonstrated in vivo activity in rats following oral administration.

Tetrahydroisoquinolines as orexin receptor antagonists: Strategies for lead optimization by solution-phase chemistry

Different techniques can be applied for the automated production of small and large compound collections. Large libraries that are often generated and tested during the lead-finding stage of a project are typically produced by solid-phase chemistry. Libraries that are significantly smaller in size are often synthesized in solution. Chemistry in solution is rather versatile, offers numerous advantages and is therefore often the method of choice for generating small libraries during a lead optimization process. Fast and reliable purification procedures are required to yield compounds of high quality that can be immediately used in biological as well as pharmacological assays. Solution-phase chemistry combined with automated purification was applied to optimize initial lead inhibitors for the two human orexin receptors OX1 and OX2. Starting from a submicro-molar OX1 selective lead compound, low nanomolar analogues with improved physico-chemical properties were synthesized that antagonize either one or both orexin receptors.

Identification of a New Chemical Class of Antimalarials

The increasing spread of drug-resistant malaria strains underscores the need for new antimalarial agents with novel modes of action (MOAs). Here, we describe a compound representative of a new class of antimalarials. This molecule, ACT-213615, potently inhibits in vitro erythrocytic growth of all tested Plasmodium falciparum strains, irrespective of their drug resistance properties, with half-maximal inhibitory concentration (IC(50)) values in the low single-digit nanomolar range. Like the clinically used artemisinins, the compound equally and very rapidly affects all 3 asexual erythrocytic parasite stages. In contrast, microarray studies suggest that the MOA of ACT-213615 is different from that of the artemisinins and other known antimalarials. ACT-213615 is orally bioavailable in mice, exhibits activity in the murine Plasmodium berghei model and efficacy comparable to that of the reference drug chloroquine in the recently established P. falciparum SCID mouse model. ACT-213615 represents a new class of potent antimalarials that merits further investigation for its clinical potential.

Novel in vivo active anti-malarials based on a hydroxy-ethyl-amine scaffold

A novel series of anti-malarials, based on a hydroxy-ethyl-amine scaffold, initially identified as peptidomimetic protease inhibitors is described. Combination of the hydroxy-ethyl-amine anti-malarial phramacophore with the known Mannich base pharmacophore of amodiaquine (57) resulted in promising in vivo active novel derivatives.

Structure–Activity Relationship, Biological, and Pharmacological Characterization of the Proline Sulfonamide ACT-462206: a Potent, Brain-Penetrant Dual Orexin 1/Orexin 2 Receptor Antagonist

The orexin system consists of two G‐protein‐coupled receptors, the orexin 1 and orexin 2 receptors, widely expressed in diverse regions of the brain, and two peptide agonists, orexin A and orexin B, which are produced in a small assembly of neurons in the lateral hypothalamus. The orexin system plays an important role in the maintenance of wakefulness. Several compounds (almorexant, SB‐649868, suvorexant) have been in advanced clinical trials for treating primary insomnia. ACT‐462206 is a new, potent, and selective dual orexin receptor antagonist (DORA) that inhibits the stimulating effects of the orexin peptides at both the orexin 1 and 2 receptors. It decreases wakefulness and increases non‐rapid eye movement (non‐REM) and REM sleep while maintaining natural sleep architectures in rat and dog electroencephalography/electromyography (EEG/EMG) experiments. ACT‐462206 shows anxiolytic‐like properties in rats without affecting cognition and motor function. It is therefore a potential candidate for the treatment of insomnia.

Novel pyrazolo-tetrahydropyridines as potent orexin receptor antagonists.

A novel series of dual orexin receptor antagonists was prepared by heteroaromatic five-membered ring system replacement of the dimethoxyphenyl moiety contained in the tetrahydroisoquinoline core skeleton of almorexant. Thus, replacement of the dimethoxyphenyl by a substituted pyrazole and additional optimization of the substitution pattern of the phenethyl motif allowed the identification of potent antagonists with low nanomolar affinity for hOX(1)R and hOX(2)R. The synthesis and structure-activity relationship of these novel antagonists will be discussed in this communication. These investigations furnished several suitable candidates for further evaluation in in vivo studies in rats.

Discovery of substituted lactams as novel dual orexin receptor antagonists. Synthesis, preliminary structure–activity relationship studies and efforts towards improved metabolic stability and pharmacokinetic properties. Part 1

Starting from a thiazolidin-4-one HTS hit, a novel series of substituted lactams was identified and developed as dual orexin receptor antagonists. In this Letter, we describe our initial efforts towards the improvement of potency and metabolic stability. These investigations delivered optimized lead compounds with CNS drug-like properties suitable for further optimization.

Substituted pyrrolidin-2-ones: Centrally acting orexin receptor antagonists promoting sleep. Part 2.

Starting from advanced pyrrolidin-2-one lead compounds, this novel series of small-molecule orexin receptor antagonists was further optimized by fine-tuning of the C-3 substitution at the γ-lactam ring. We discuss our design to align in vitro potency with metabolic stability and improved physicochemical/pharmacokinetic properties while avoiding P-glycoprotein-mediated efflux. These investigations led to the identification of the orally active 3-hydroxypyrrolidin-2-one 46, a potent and selective orexin-2 receptor antagonist, that achieved good brain exposure and promoted physiological sleep in rats.

UV-triggered Affinity-Capture Identifies Interactions Between the Plasmodium falciparum Multidrug Resistance Protein 1 (PfMDR1) and Antimalarial Agents in Live Parasitized Cells

Background: We have previously identified potent novel antimalarial compounds with an unknown mode of action. Results: A photo-reactive affinity capture method was used to identify parasite proteins that interact with these antimalarials. Conclusion: ACT-213615 interacts with Plasmodium falciparum multidrug resistance protein 1 (PfMDR1). Significance: This photo-reactive affinity capture method can be generally used to identify drug targets in live cells. A representative of a new class of potent antimalarials with an unknown mode of action was recently described. To identify the molecular target of this class of antimalarials, we employed a photo-reactive affinity capture method to find parasite proteins specifically interacting with the capture compound in living parasitized cells. The capture reagent retained the antimalarial properties of the parent molecule (ACT-213615) and accumulated within parasites. We identified several proteins interacting with the capture compound and established a functional interaction between ACT-213615 and PfMDR1. We surmise that PfMDR1 may play a role in the antimalarial activity of the piperazine-containing compound ACT-213615.