Synthesis of enantiomerically pure [14 C]-labelled morpholine derivatives for a class of trace amine-associate receptor 1 agonists.

Various agonists of the trace amine-associate receptor 1, under consideration as potential clinical development candidates, were labelled with carbon-14 for use in preclinical in vitro and in vivo drug metabolism studies. Herein, the [14 C]-radiosynthesis of 2-phenyl-substituted morpholines 1 is described. After evaluating and optimizing different synthetic routes, 4-iodonitrobenzene 3 was selected as starting material for the 14-step synthesis. Incorporation of carbon-14 into the acetyl moiety allowed a safe and efficient synthesis of [14 C]-labelled 4-nitroacetophenone 2 in five steps and 38% yield. Further transformation of 2 to the target compounds 1 was achieved in a 9-step synthesis. In a representative example, [14 C]-labelled 1 was obtained in an overall yield of 11% and was isolated in >99% radiochemical purity and a specific activity of 47 mCi/mmol.

Discovery and Characterization of 2-Aminooxazolines as Highly Potent, Selective, and Orally Active TAAR1 Agonists.

2-Aminooxazolines were discovered as a novel structural class of TAAR1 ligands. Starting from a known adrenergic compound 1, structural modifications were made to obtain highly potent and selective TAAR1 ligands such as 12 (RO5166017), 18 (RO5256390), 36 (RO5203648), and 48 (RO5263397). These compounds exhibit drug-like physicochemical properties, have good oral bioavailability, and display in vivo activity in a variety of animal models relevant for psychiatric diseases and addiction.

Brain-specific overexpression of trace amine-associated receptor 1 alters monoaminergic neurotransmission and decreases sensitivity to amphetamine.

Trace amines (TAs) such as ß-phenylethylamine, p-tyramine, or tryptamine are biogenic amines found in the brain at low concentrations that have been implicated in various neuropsychiatric disorders like schizophrenia, depression, or attention deficit hyperactivity disorder. TAs are ligands for the recently identified trace amine-associated receptor 1 (TAAR1), an important modulator of monoamine neurotransmission. Here, we sought to investigate the consequences of TAAR1 hypersignaling by generating a transgenic mouse line overexpressing Taar1 specifically in neurons. Taar1 transgenic mice did not show overt behavioral abnormalities under baseline conditions, despite augmented extracellular levels of dopamine and noradrenaline in the accumbens nucleus (Acb) and of serotonin in the medial prefrontal cortex. In vitro, this was correlated with an elevated spontaneous firing rate of monoaminergic neurons in the ventral tegmental area, dorsal raphe nucleus, and locus coeruleus as the result of ectopic TAAR1 expression. Furthermore, Taar1 transgenic mice were hyposensitive to the psychostimulant effects of amphetamine, as it produced only a weak locomotor activation and failed to alter catecholamine release in the Acb. Attenuating TAAR1 activity with the selective partial agonist RO5073012 restored the stimulating effects of amphetamine on locomotion. Overall, these data show that Taar1 brain overexpression causes hyposensitivity to amphetamine and alterations of monoaminergic neurotransmission. These observations confirm the modulatory role of TAAR1 on monoamine activity and suggest that in vivo the receptor is either constitutively active and/or tonically activated by ambient levels of endogenous agonist(s).

Optimisation of imidazole compounds as selective TAAR1 agonists: discovery of RO5073012.

A series of imidazole compounds has been identified which affords potent and selective partial and full agonists of the TAAR1 receptor. Starting from 2-benzyl-imidazoline screening hits, a series of structurally related 2-benzyl- and 4-benzyl-imidazoles was investigated first, but it proved highly challenging to obtain compounds having sufficient selectivity against the adrenergic alpha 2 receptor. This issue could be successfully addressed by modification of the linker region and SAR exploration led to the discovery of highly selective isopropyl-substituted 4-aminomethyl-imidazole compounds. The work culminated in the identification of the selective TAAR1 partial agonist RO5073012 (4-chlorophenyl)-(1H-imidazol-4-ylmethyl)-isopropyl-amine, 24), which has a good pharmacokinetic profile after oral administration in rodents. RO5073012 has been found to be active in a behavioural rat model which is considered indicative for schizophrenia.

ROCK: the Roche medicinal chemistry knowledge application - design, use and impact.

Medicinal chemistry is a complex science that lies at the interface of many fields of research and at the very heart of drug discovery, with property relationships based on chemical structure at its core. It is clear that the effective capture and dissemination of medicinal chemistry knowledge and experience will be a key differentiator among pharmaceutical organizations and crucial for the future success in delivering effective and safe drug candidates. Therefore, in 2005 we developed ROCK (Roche medicinal chemistry knowledge), an internal user-friendly and peer-reviewed Wiki-like application to capture, browse and search tacit knowledge, key discoveries and property effects related to chemical structure, which is used as a primary source for addressing challenges faced in drug design.

Attenuated Abeta42 responses to low potency gamma-secretase modulators can be overcome for many pathogenic presenilin mutants by second-generation compounds.

Sequential processing of the ß-amyloid precursor protein by ß- and γ-secretase generates the amyloid ß-peptide (Aß), which is widely believed to play a causative role in Alzheimer disease. Selective lowering of the pathogenic 42-amino acid variant of Aß by γ-secretase modulators (GSMs) is a promising therapeutic strategy. Here we report that mutations in presenilin (PS), the catalytic subunit of γ-secretase, display differential responses to non-steroidal anti-inflammatory drug (NSAID)-type GSMs and more potent second-generation compounds. Although many pathogenic PS mutations resisted lowering of Aß(42) generation by the NSAID sulindac sulfide, the potent NSAID-like second-generation compound GSM-1 was capable of lowering Aß(42) for many but not all mutants. We further found that mutations at homologous positions in PS1 and PS2 can elicit differential Aß(42) responses to GSM-1, suggesting that a positive GSM-1 response depends on the spatial environment in γ-secretase. The aggressive pathogenic PS1 L166P mutation was one of the few pathogenic mutations that resisted GSM-1, and Leu-166 was identified as a critical residue with respect to the Aß(42)-lowering response of GSM-1. Finally, we found that GSM-1-responsive and -resistant PS mutants behave very similarly toward other potent second-generation compounds of different structural classes than GSM-1. Taken together, our data show that a positive Aß(42) response for PS mutants depends both on the particular mutation and the GSM used and that attenuated Aß(42) responses to low potency GSMs can be overcome for many PS mutants by second generation GSMs.

Substituted 2-oxo-azepane derivatives are potent, orally active gamma-secretase inhibitors.

A hydroxamic acid screening hit 1 was elaborated to 5,5-dimethyl-2-oxoazepane derivatives exhibiting low nanomolar inhibition of gamma-secretase, a key proteolytic enzyme involved in Alzheimer's disease. Early ADME data showed a high metabolic clearance for the geminal dimethyl analogs which could be overcome by replacement with the bioisosteric geminal difluoro group. Synthesis and structure-activity relationship are discussed and in vivo active compounds are presented.

Novel orally active, dibenzazepinone-based gamma-secretase inhibitors.

Structural modifications of the gamma-secretase inhibitor, LY411575, led to a malonamide analogue (S),(S)-1 with potent inhibitory activity in vitro, but disappointing activity in a mouse model of Alzheimer's disease. Identification and replacement of a metabolically labile position provided an improved compound (R/S),(S)-13 with high in vitro activity (IC(50)=1.7 nM), and in vivo activity after oral administration (MED=3 mg/kg). Further modifications gave an equipotent carbamate analogue 14 with improved molecular properties.

Design and synthesis of a novel, achiral class of highly potent and selective, orally active neurokinin-1 receptor antagonists.

The discovery of a novel, achiral pyridine class of potent and orally active neurokinin-1 (NK(1)) receptor antagonists is described. The evaluation of this class is briefly outlined, leading to the identification of netupitant 21 and befetupitant 29, two new proprietary chemical entities with high affinity and excellent CNS penetration.