Wilfried Hornberger

Inhibitors of GlyT1 affect glycine transport via discrete binding sites.

In the forebrain, synaptic glycine concentrations are regulated through the glycine transporter GlyT1. Because glycine is a coagonist of the N-methyl-d-aspartate (NMDA) receptor (NMDAR), which has been implicated in schizophrenia, inhibition of GlyT1 is thought to provide an option for the treatment of schizophrenia. In support of this hypothesis, GlyT1 inhibitors facilitate in vivo NMDAR function and demonstrate antipsychotic-like effects in animal models. Among the specific GlyT1 inhibitors, substituted N-methyl-glycine (sarcosine) derivatives (e.g., (R)-N[3-(4′fluorophenyl)-3-(4′phenyl-phenoxy)propyl]-sarcosine [NFPS], (R)-N[3-phenyl-3-(4′-(4-toluoyl)phenoxy)-propyl]sarcosine [(R)-NPTS], and (R,S)-(±)N-methyl-N-[(4-trifluoromethyl)phenoxy]-3-phenyl-propylglycine [Org24589]), and non-sarcosine-containing inhibitors, such as 2-chloro-N-[(S)-phenyl[(2S)-piperidin-2-yl] methyl]-3-trifluoromethyl benzamide, monohydrochloride (SSR504734), have been described. In the present study, we analyzed the mode of interaction of these compounds with GlyT1 by using electrophysiological measurements in Xenopus laevis oocytes, and with two binding assays, using [3H](R)-NPTS or 2-chloro-N-[(S)-phenyl[(2S)-N-methylpiperidin-2-yl]-methyl]-3-trifluoromethyl benzamide monohydrochloride ([3H]N-methyl-SSR504734) as radioligands. Inhibition of electrogenic glycine transport by sarcosine-based compounds was apparently irreversible and independent of glycine concentration. The latter indicates a noncompetitive mode of action. In contrast, both SSR504734 and N-methyl-SSR504734 exhibited reversible and competitive inhibition of glycine transport. In GlyT1-expressing membranes, the binding of the novel radioligand [3H]N-methyl-SSR504734 to a single site on GlyT1 was competitively displaced by glycine and SSR504734 but noncompetitively by sarcosine-based compounds. Inversely, [3H](R)-NPTS binding was competitively inhibited by sarcosine-based compounds, whereas glycine, SSR504734, and N-methyl-SSR504734 noncompetitively decreased maximal binding. Our data indicate that besides exerting an apparently irreversible or reversible inhibition, GlyT1 inhibitors differ by exhibiting either a noncompetitive or competitive mode of inhibition. The divergent modes of inhibition may significantly affect the efficacy and tolerability of these drugs.

Design, Synthesis and Biological Actmty of Novel Rigid Amidino-Phenylalanine Derivatives as Inhibitors of Thrombin

(3S)-(Naphthalene-2-sulfonylamino)-1-[2R-(4-amidinophenyl)-1- piperidinocarbonylethyl]-2-pyrrolidinone (1a) is a potent inhibitor of thrombin with an IC50 value by 112 times lower than that of NAPAP (racemate). The selectivity versus trypsin can be improved by incorporation of substituents on the naphthyl ring. The mode of binding of the compound was determined by X-ray crystallography.

Design and synthesis of 1,5- and 2,5-substituted tetrahydrobenzazepinones as novel potent and selective integrin α V β 3 antagonists

Abstract The design and synthesis of novel integrin αVβ3 antagonists based on a 1,5- or 2,5-substituted tetrahydrobenzaezpinone core is described. In vitro activity of respective compounds was determined via αVβ3 binding assay, and selected derivatives were submitted to further characterization in functional cellular assays. SAR was obtained by modification of the benzazepinone core, variation of the spacer linking guanidine moiety and core, and modification of the guanidine mimetic. These efforts led to the identification of novel αVβ3 inhibitors displaying potency in the subnanomolar range, selectivity versus αIIbβ3 and functional efficacy in relevant cellular assays. A method for the preparation of enantiomerically pure derivatives was developed, and respective enantiomers evaluated in vitro. Compounds 31 and 37 were assessed for metabolic stability, resorption in the Caco-2 assay and pharmacokinetics.

Acute Inhibition of 11β-Hydroxysteroid Dehydrogenase Type-1 Improves Memory in Rodent Models of Cognition

Mounting evidence suggests excessive glucocorticoid activity may contribute to Alzheimers disease (AD) and age-associated memory impairment. 11β-hydroxysteroid dehydrogenase type-1 (HSD1) regulates conversion of glucocorticoids from inactive to active forms. HSD1 knock-out mice have improved cognition, and the nonselective inhibitor carbenoxolone improved verbal memory in elderly men. Together, these data suggest that HSD1 inhibition may be a potential therapy for cognitive deficits, such as those associated with AD. To investigate this, we characterized two novel and selective HSD1 inhibitors, A-918446 and A-801195. Learning, memory consolidation, and recall were evaluated in mouse 24 h inhibitory avoidance. Inhibition of brain cortisol production and phosphorylation of cAMP response element-binding protein (CREB), a transcription factor involved in cognition, were also examined. Rats were tested in a short-term memory model, social recognition, and in a separate group cortical and hippocampal acetylcholine release was measured via in vivo microdialysis. Acute treatment with A-801195 (10–30 mg/kg) or A-918446 (3–30 mg/kg) inhibited cortisol production in the ex vivo assay by ∼35–90%. Acute treatment with A-918446 improved memory consolidation and recall in inhibitory avoidance and increased CREB phosphorylation in the cingulate cortex. Acute treatment with A-801195 significantly improved short-term memory in rat social recognition that was not likely due to alterations of the cholinergic system, as acetylcholine release was not increased in a separate set of rats. These studies suggest that selective HSD1 inhibitors work through a novel, noncholinergic mechanism to facilitate cognitive processing.

Potent and selective oxindole-based vasopressin 1b receptor antagonists with improved pharmacokinetic properties

Herein we report the discovery of a novel series of vasopressin 1b (V1b) receptor antagonists, starting from potent but metabolically labile oxindole SSR149415. Masking the proline N,N-dimethyl amide moiety as an oxazole and attaching a benzylic amine moiety to the northern phenyl ring resulted in potent and selective V1b receptor antagonists with improved metabolic stability and improved pharmacokinetic properties in rat. Compound 18c was found to be efficacious in a rat model of anti-depressant activity.

Synthesis and SAR of N-substituted dibenzazepinone derivatives as novel potent and selective αVβ3 antagonists

Abstract Synthesis and SARs of new integrin α V β 3 antagonists based on an N -substituted dibenzazepinone scaffold are described. Variation of spacer and guanidine mimetic led to potent compounds exhibiting an IC 50 towards α V β 3 in the nanomolar range, high selectivity versus integrin α IIb β 3 and efficacy in functional cellular assays.

D-Phe-Pro-Arg type thrombin inhibitors: unexpected selectivity by modification of the P1 moiety.

Synthesis of thrombin inhibitors and their binding mode to thrombin is described. Modification of the P1 moiety leads to an increased selectivity versus trypsin. The observed selectivity is discussed in view of their thrombin-inhibitor complex X-ray structures.

Highly potent and selective αVβ3-receptor antagonists: solid-phase synthesis and SAR of 1-substituted 4-amino-1H-pyrimidin-2-ones

Abstract Solid-phase synthesis and SAR of αVβ3-receptor antagonists based on a N1-substituted 4-amino-1H-pyrimidin-2-one scaffold are described. The most potent compounds exhibited IC50 values towards αVβ3 in the nano- to subnanomolar range and high selectivity versus related integrins like αIIbβ3. For selected examples efficacy in functional cellular assays was demonstrated.

Discovery of Novel and Highly Selective Inhibitors of Calpain for the Treatment of Alzheimer’s Disease: 2-(3-Phenyl-1H-pyrazol-1-yl)-nicotinamides

Calpain overactivation has been implicated in a variety of pathological disorders including ischemia/reperfusion injury, cataract formation, and neurodegenerative diseases such as Alzheimers disease (AD). Herein we describe our efforts leading to the identification of ketoamide-based 2-(3-phenyl-1H-pyrazol-1-yl)nicotinamides as potent and reversible inhibitors of calpain with high selectivity versus related cysteine protease cathepsins, other proteases, and receptors. Broad efficacy in a set of preclinical models relevant to AD suggests that inhibition of calpain represents an attractive approach with potential benefit for the treatment of AD.

Discovery of Novel Aminotetralines and Aminochromanes as Selective and Competitive Glycine Transporter 1 (GlyT1) Inhibitors

The glycine transporter 1 (GlyT1) has emerged as a key novel target for the treatment of schizophrenia. Herein, we report the synthesis and biological evaluation of aminotetralines and aminochromanes as novel classes of competitive GlyT1 inhibitors. Starting from a high-throughput screening hit, structure-activity relationship studies led first to the discovery of aminotetralines displaying high GlyT1 potency and selectivity, with favorable pharmacokinetic properties. Systematic investigations of various parameters (e.g., topological polar surface area, number of hydrogen bond donors) guided by ex vivo target occupancy evaluation resulted in lead compounds possessing favorable brain penetration properties as for (7 S,8 R)-27a. Further optimization revealed compounds with reduced efflux liabilities as for aminochromane 51b. In an in vivo efficacy model (7 S,8 R)-27a, dose-dependently reversed L-687,414 induced hyperlocomotion in mice with an ED50 of 0.8 mg/kg. All these results suggest (7 S,8 R)-27a and 51b as new GlyT1 inhibitors worthy of further profiling.