Elsevier

Bioorganic & Medicinal Chemistry

Volume 19, Issue 18, 15 September 2011, Pages 5490-5499
Bioorganic & Medicinal Chemistry

2-({6-[(3R)-3-amino-3-methylpiperidine-1-yl]-1,3-dimethyl-2,4-dioxo-1,2,3,4-tetrahydro-5H-pyrrolo[3,2-d]pyrimidine-5-yl}methyl)-4-fluorobenzonitrile (DSR-12727): A potent, orally active dipeptidyl peptidase IV inhibitor without mechanism-based inactivation of CYP3A

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Abstract

We report on the identification of 2-({6-[(3R)-3-amino-3-methylpiperidine-1-yl]-1,3-dimethyl-2,4-dioxo-1,2,3,4-tetrahydro-5H-pyrrolo[3,2-d]pyrimidine-5-yl}methyl)-4-fluorobenzonitrile (DSR-12727) (7a) as a potent and orally active DPP-4 inhibitor without mechanism-based inactivation of CYP3A. Compound 7a showed good DPP-4 inhibitory activity (IC50 = 1.1 nM), excellent selectivity against related peptidases and other off-targets, good pharmacokinetic and pharmacodynamic profile, great in vivo efficacy in Zucker-fatty rat, and no safety concerns both in vitro and in vivo.

Introduction

Type 2 diabetes (T2D) is a major metabolic disorder affecting approximately 194 million people worldwide. This number is estimated to reach 366 million by 2030.1 The beneficial effects of anti-diabetic agents currently used, such as sulphonylurea, biguanide, and α-glucosidase inhibitors that can effectively increase insulin secretion or decrease glucose absorption are known to be associated with a number of side effects including hypoglycemia, weight gain, gastrointestinal disorders, and lactic acidosis. Thus, current treatments for T2D are considered to be unsatisfactory in terms of prevention of complications and preservation of quality of life.2 Under these circumstances, intensive effort has been made to find better and safer drugs for T2D.

Glucagon-like peptide 1 (GLP-1), an important incretin hormone that regulates body blood glucose, has recently been receiving great attention as a new target for the development of novel therapies for T2D.3 However, the active state of GLP-1 (7–36) is short-lived as this hormone is quickly cleaved by dipeptidyl peptidase IV (DPP-4).4 This means that DPP-4 inhibition, and consequently increase in GLP-1 level, presents a new approach for the treatment of T2D. DPP-4, a serine protease distributed throughout the body, modulates the activity of a wide variety of regulatory peptides. Based on the report about DPP-4 knockout mice, the use of DPP-4 inhibition in T2D therapy seems to have lots of advantages.5, 6, 7 It is suggested that DPP-4 inhibitors might be able to stimulate production of new β-cell in patients with T2D, and thus prevent deterioration of the disease. In addition, DPP-4 inhibition is unlikely to cause serious hypoglycemia, because GLP-1 is strictly glucose-dependent.

In recent years, a number of DPP-4 inhibitors,8 such as 1 (sitagliptin),9 2 (vildagliptin),10 3 (saxagliptin),11 4 (alogliptin),12 and 5 (linagliptin),13 (Fig. 1) have been marketed or are under clinical development, and have shown great efficacy in patients with T2D.

In our research about DPP-4 inhibitors, we found compound 6,14 which showed excellent inhibitory activity against DPP-4 (0.34 nM), however, had two pharmacokinetic drawbacks. One is reversible inhibition of Cytochrome P450 (CYP) 3A4 (IC50 = 1.6 μM), CYP1A2 (IC50 = 14.7 μM), and CYP2D6 (IC50 = 7.5 μM) caused by the parent drug. The other is potent mechanism-based inactivation (MBI)15 which is irreversible inhibition of CYP3A. MBI is time- and concentration-dependent CYP enzymes inhibition, and caused by metabolites of original compounds. Some specific structures, such as nitroso species, to coordinate with the Fe-center of CYP enzymes or bind covalently with it have been reported as the cause of MBI, however, few examples to prevent or alleviate potent MBI have been reported.16 Our investigation about metabolites of compounds having the (R)-3-aminopiperidine unit, which includes 6, revealed that metabolism of these compounds mainly undergo at the uracil structure to give demethylated compounds, at the piperidine moiety to give hydroxylated derivatives and at the (R)-3-amino position of the piperidine unit to give hydroxyl amine. Among them, hydroxyl amine is supposed to give nitroso species, which is believed to form a metabolic intermediate complex and cause MBI.16, 17

We have previously reported new chemotype DPP-4 inhibitors having (R)-3-amino-3-methylpiperidine as a pharmacophore and showed that these inhibitors have good in vitro activity and pharmacokinetic/pharmacodynamic (PK/PD) profiles.18 In addition to those results, a methyl substitution seemed to have good influence on CYP enzymes inhibition because the reported compounds hardly had strong inhibition of CYP enzymes. Thus, it was expected that compound 6 strong inhibition of CYP3A4 would be alleviated by it. As for MBI, we assumed that introduction of a small alkyl substituent at the 3-position of piperidine unit could prevent metabolism at the amino group and/or coordinate of reactive metabolites with the Fe-center of CYP3A to avoid MBI. We therefore considered that compound 7a, having a methyl instead of a hydrogen at 3-position of compound 6 piperidine unit, would become an ideal DPP-4 inhibitor. In addition, to compare the effects of a small alkyl substituent on the inhibitory activity and potent MBI, the ethyl substituted compound 7b was also prepared and evaluated (Fig. 2). Here, we disclosed our evaluation of these compounds, and the identification of 2-({6-[(3R)-3-amino-3-methylpiperidine-1-yl]-1,3-dimethyl-2,4-dioxo-1,2,3,4-tetrahydro-5H-pyrrolo[3,2-d]pyrimidine-5-yl}methyl)-4-fluorobenzonitrile (DSR-12727) (7a) as a potent and orally active DPP-4 inhibitor without mechanism-based inactivation of Cytochrome P450 3A.

Section snippets

Chemistry

The 3-amino-3-alkyl-piperidine structures 13ab were synthesized in four steps.18 The intermediate 9b was prepared from ethyl nipecotate 8 same as 9a.19 The nitrogen-atom of 9ab was protected by a carbobenzyloxy (Cbz) to give 10ab, which were hydrolyzed to afford the carboxylic acid 11ab. After Curtius rearrangement using diphenylphosphoric azide (DPPA), the crude solution was first washed with water to remove by-products, and then treated with an excess amount of tert-butyl alcohol and a

Experimental section

All reagents and solvents were obtained from commercial suppliers and used without further drying or purification. Other DPP-4 inhibitors were synthesized in our laboratory based on the reported ways. All reactions were performed under nitrogen atmosphere. Normal-phase column chromatography was carried out on a Yamazen W-prep system with pre-packed SiO2 columns or Amino-SiO2 columns. Visualization was performed under UV light (254 nm) or ninhydrine. 1H NMR spectra were recorded on Brucker AVANCE

Acknowledgments

We are thankful to Mr. H. Hochigai for providing compound 6, Mr. S. Suetsugu for making the metabolite of compounds, K. Bando for performing the elemental analysis, and Ms. I. Taoka for recording MS spectra.

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