In Vitro and In Vivo Mechanistic Studies toward Understanding the Role of 1-Aminobenzotriazole in Rat Drug-Drug Interactions.

1-Aminobenzotriazole (ABT) is regularly used in vivo as a nonspecific and irreversible cytochrome P450 inhibitor to elucidate the role of metabolism on the pharmacokinetic profile of xenobiotics. However, few reports have considered the recent findings that ABT can alter drug absorption or have investigated the possible differential inhibition of ABT on intestinal and hepatic metabolism. To address these uncertainties, pharmacokinetic studies under well controlled and defined ABT pretreatment conditions (50 mg/kg, 1 hour ABT i.v. and 16 hours ABT p.o.) were conducted prior to the oral administration of metoprolol, a permeable P450 probe that undergoes extensive intestinal and hepatic metabolism. The pharmacokinetic profile of metoprolol was affected differently by the two ABT pretreatments. An increase in area under the curve of 16-fold with ABT p.o. and 6.5-fold with ABT i.v. was observed compared with control. Based on in vitro studies, this difference could not be attributed to a differential inhibition of intestinal and hepatic metabolism. In the ABT i.v. pretreatment group, the increase in area under the curve was also associated with a prolonged time at maximal concentration (24-fold versus control), suggesting a delay in absorption. This was further confirmed by the administration of a charcoal meal, which resulted in a 7-fold increase in stomach weights in the 1-hour ABT pretreated groups compared with the untreated or 16-hour ABT pretreated rats. Based on these results, we recommend pretreating rats with ABT p.o. 16 hours before the administration of a test compound to preserve the inhibitory effect on intestinal and hepatic metabolism and avoid the confounding effect on drug absorption.

Design and synthesis of potent, isoxazole-containing renin inhibitors.

The design and optimization of a novel isoxazole S(1) linker for renin inhibitor is described herein. This effort culminated in the identification of compound 18, an orally bioavailable, sub-nanomolar renin inhibitor even in the presence of human plasma. When compound 18 was found to inhibit CYP3A4 in a time dependent manner, two strategies were pursued that successfully delivered equipotent compounds with minimal TDI potential.

Applying the pro-drug approach to afford highly bioavailable antagonists of P2Y(14).

Our series of competitive antagonists against the G-protein coupled receptor P2Y(14) were found to be highly shifted in the presence of serum (>99% protein bound). A binding assay using 2% human serum albumin (HSA) was developed to guide further SAR studies and led to the identification of the zwitterion 2, which is substantially less shifted (18-fold) than our previous lead compound 1 (323-fold). However, as the bioavailability of 2 was low, a library of ester pro-drugs was prepared (7a-7j) and assessed in vitro. The most interesting candidates were then profiled in vivo and led to the identification of the pro-drug 7j, which possesses a substantially improved pharmacokinetic profile.

Renin inhibitors for the treatment of hypertension: design and optimization of a novel series of spirocyclic piperidines.

The discovery and SAR of a novel series of spirocyclic renin inhibitors are described herein. It was found that by restricting the northern aromatic plate to the bioactive conformation through spirocyclization, increase in renin potency and decrease in hERG affinity could both be realized. When early members of this series were found to be potent time-dependent CYP3A4 inhibitors, two distinct strategies to address this liability were explored and this effort culminated in the identification of compound 31 as an optimized renin inhibitor.

Azaindoles as potent CRTH2 receptor antagonists.

A new class of 7-azaindole analogs of MK-7246 as potent and selective CRTH2 antagonists is reported. The SAR leading to the identification of the optimal azaindole regioisomer as well as the pharmacokinetics and off-target activities of the most potent antagonists are disclosed.

A novel series of potent and selective EP(4) receptor ligands: facile modulation of agonism and antagonism.

A novel series of EP(4) ligands, based on a benzyl indoline scaffold, has been discovered. It was found that agonism and antagonism in this series can be easily modulated by minor modifications on the benzyl group. The pharmacokinetic, metabolic and pharmacological profiles of these compounds was explored. It was found that these compounds show good pharmacokinetics in rat and are efficacious in pre-clinical models of pain and inflammation.

New indole amide derivatives as potent CRTH2 receptor antagonists.

A new series of indole amide acting as hCRTH2 receptor ligands had been explored and are described herein. Several amide derivatives displaying low nanomolar activity in hCRTH2 binding and whole blood assays were identified. They were found to behave as a full antagonists, exhibiting good selectivity over related prostaglandin receptors. Also, prototypical compounds in this novel series which displayed acceptable CYP profiles and were orally bioavailable in rats were identified.

Impact of passive permeability and gut efflux transport on the oral bioavailability of novel series of piperidine-based renin inhibitors in rodents.

An oral bioavailability issue encountered during the course of lead optimization in the renin program is described herein. The low F(po) of pyridone analogs was shown to be caused by a combination of poor passive permeability and gut efflux transport. Substitution of pyridone ring for a more lipophilic moiety (logD>1.7) had minimal effect on rMdr1a transport but led to increased passive permeability (P(app)>10 × 10(-6) cm/s), which contributed to overwhelm gut transporters and increase rat F(po). LogD and in vitro passive permeability determination were found to be key in guiding SAR and improve oral exposure of renin inhibitors.

Naphthalene/quinoline amides and sulfonylureas as potent and selective antagonists of the EP4 receptor.

Two new series of EP(4) antagonists based on naphthalene/quinoline scaffolds have been identified as part of our on-going efforts to develop treatments for inflammatory pain. One series contains an acidic sulfonylurea pharmacophore, whereas the other is a neutral amide. Both series show subnanomolar intrinsic binding potency towards the EP(4) receptor, and excellent selectivity towards other prostanoid receptors. While the amide series generally displays poor pharmacokinetic parameters, the sulfonylureas exhibit greatly improved profile. MF-592, the optimal compound from the sulfonylurea series, has a desirable overall preclinical profile that suggests it is suitable for further development.

The discovery and synthesis of potent zwitterionic inhibitors of renin.

The incorporation of a carboxylic acid within in a series of 3-amido-4-aryl substituted piperidines (represented by general structure 32) led to the discovery of potent, zwitterionic, renin inhibitors with improved off-target profiles (CYP3A4 time-dependent inhibition and hERG affinity) relative to analogous non-zwitterionic inhibitors of the past (i.e., 3). Strategies to address the oral absorption of these zwitterions are also discussed within.

Renin inhibitors for the treatment of hypertension: design and optimization of a novel series of tertiary alcohol-bearing piperidines.

The design and optimization of a novel series of renin inhibitor is described herein. Strategically, by committing the necessary resources to the development of synthetic sequences and scaffolds that were most amenable for late stage structural diversification, even as the focus of the SAR campaign moved from one end of the molecule to another, highly potent renin inhibitors could be rapidly identified and profiled.

Renin inhibitors for the treatment of hypertension: design and optimization of a novel series of pyridone-substituted piperidines.

An SAR campaign aimed at decreasing the overall lipophilicity of renin inhibitors such as 1 is described herein. It was found that replacement of the northern appendage in 1 with an N-methyl pyridone and subsequent re-optimization of the benzyl amide handle afforded compounds with in vitro and in vivo profiles suitable for further profiling. An unexpected CV toxicity in dogs observed with compound 20 led to the employment of a time and resource sparing rodent model for in vivo screening of key compounds. This culminated in the identification of compound 31 as an optimized renin inhibitor.

The identification of 4,7-disubstituted naphthoic acid derivatives as UDP-competitive antagonists of P2Y14.

A weak, UDP-competitive antagonist of the pyrimidinergic receptor P2RY(14) with a naphthoic acid core was identified through high-throughput screening. Optimization provided compounds with improved potency but poor pharmacokinetics. Acylglucuronidation was determined to be the major route of metabolism. Increasing the electron-withdrawing nature of the substituents markedly reduced glucuronidation and improved the pharmacokinetic profile. Additional optimization led to the identification of compound 38 which is an 8 nM UDP-competitive antagonist of P2Y(14) with a good pharmacokinetic profile.

Discovery of MK-7246, a selective CRTH2 antagonist for the treatment of respiratory diseases.

In this manuscript we wish to report the discovery of MK-7246 (4), a potent and selective CRTH2 (DP2) antagonist. SAR studies leading to MK-7246 along with two synthetic sequences enabling the preparation of this novel class of CRTH2 antagonist are reported. Finally, the pharmacokinetic and metabolic profile of MK-7246 is disclosed.

Addressing time-dependent CYP 3A4 inhibition observed in a novel series of substituted amino propanamide renin inhibitors, a case study.

Time-dependent inhibitors of CYPs have the potential to perpetrate drug-drug interactions in the clinical setting. After finding that several leading compounds in a novel series of substituted amino propanamide renin inhibitors inactivated CYP3A4 in an NADPH-dependent and time-dependent manner, a search to identify the cause of this liability was initiated. Extensive SAR revealed that the amide bridge present in compound 1 as a possible culprit. Through the installation of a metabolic soft spot distal to this moiety, potent renin inhibitors with improved CYP profile were identified.

Discovery of 4-[1-[([1-[4-(trifluoromethyl)benzyl]-1H-indol-7-yl]carbonyl)amino]cyclopropyl]benzoic acid (MF-766), a highly potent and selective EP4 antagonist for treating inflammatory pain.

The discovery of a highly potent and selective EP(4) antagonist MF-766 is discussed. This N-benzyl indole derivative exhibits good pharmacokinetic profile and unprecedented in vivo potency in the rat AIA model.

Discovery of MK-0952, a selective PDE4 inhibitor for the treatment of long-term memory loss and mild cognitive impairment.

The structure-activity relationship of a novel series of 8-biarylnaphthyridinones acting as type 4 phosphodiesterase (PDE4) inhibitors for the treatment of long-term memory loss and mild cognitive impairment is described herein. The manuscript describes a new paradigm for the development of PDE4 inhibitor targeting CNS indications. This effort led to the discovery of the clinical candidate MK-0952, an intrinsically potent inhibitor (IC(50)=0.6 nM) displaying limited whole blood activity (IC(50)=555 nM). Supporting in vivo results in two preclinical efficacy tests and one test assessing adverse effects are also reported. The comparative profiles of MK-0952 and two other Merck compounds are described to validate the proposed hypothesis.

Design and optimization of a substituted amino propanamide series of renin inhibitors for the treatment of hypertension.

The discovery and SAR of a new series of substituted amino propanamide renin inhibitors are herein described. This work has led to the preparation of compounds with in vitro and in vivo profiles suitable for further development. Specifically, challenges pertaining to oral bioavailability, covalent binding and time-dependent CYP 3A4 inhibition were overcome thereby culminating in the identification of compound 50 as an optimized renin inhibitor with good efficacy in the hypertensive double-transgenic rat model.

The discovery of MK-0674, an orally bioavailable cathepsin K inhibitor.

MK-0674 is a potent and selective cathepsin K inhibitor from the same structural class as odanacatib with a comparable inhibitory potency profile against Cat K. It is orally bioavailable and exhibits long half-life in pre-clinical species. In vivo studies using deuterated MK-0674 show stereoselective epimerization of the alcohol stereocenter via an oxidation/reduction cycle. From in vitro incubations, two metabolites could be identified: the hydroxyleucine and the glucuronide conjugate which were confirmed using authentic synthetic standards.

Alkyl-bridged substituted 8-arylquinolines as highly potent PDE IV inhibitors.

Substituted 8-arylquinoline analogs bearing alkyl-linked side chain were identified as potent inhibitors of type 4 phophodiesterase. These compounds address the potential liabilities of the clinical candidate L-454560. The pharmacokinetic profile of the best analogs and the in vivo efficacy in an ovalbumin-induced bronchoconstriction assay in conscious guinea pigs are reported.