Orally active aminopyridines as inhibitors of tetrameric fructose-1,6-bisphosphatase Paul Hebeisen a , Wolfgang Haap a , Bernd Kuhn a , Peter Mohr a , Hans Peter Wessel a , Ulrich Zutter a , Stephan Kirchner b , Armin Ruf a , Jörg Benz a , Catherine Joseph a , Rubén Alvarez-Sánchez a , Marcel Gubler a , Brigitte Schott a , Agnes Benardeau a , Effie Tozzo a , Eric Kitas a, ⇑ a F. Hoffmann-La Roche Ltd, Discovery Research Basel, CH-4070 Basel, Switzerland b F. Hoffmann-La Roche Ltd, Non Clinical Safety, CH-4070 Basel, Switzerland a r t i c l e i n f o Article history: Received 23 February 2011 Revised 8 April 2011 Accepted 12 April 2011 Available online 20 April 2011 Keywords: Fructose-1,6-bisphosphatase FBPase Allosteric inhibition Structure–activity studies X-ray crystallography Genotoxicity Glucose reduction db/db Mouse model a b s t r a c t A novel sulfonylureido pyridine series exemplified by compound 19 yielded potent inhibitors of FBPase showing significant glucose reduction and modest glycogen lowering in the acute db/db mouse model for Type-2 diabetes. Our inhibitors occupy the allosteric binding site and also extend into the dyad interface region of tetrameric FBPase. Ó 2011 Elsevier Ltd. All rights reserved. Targeting fructose-1,6-bisphosphatase (FBPase) is a potentially viable approach for glucose control in Type-2 diabetes (T2D). Numerous publications have recently appeared describing FBPase inhibitors 1 and,furthermore,molecules from Metabasis Inc. have been advanced to human clinical trials. 2 Besides its role in gluco- neogenesis control,FBPase has also been implicated in glucose sensing and in regulating insulin secretion in b-cells. 3 We have pre- viously described our aminothiazole class of small molecule inhib- itors of FBPase which were shown to significantly lower fasting glucose levels in a transgenic mouse model of T2D. 4 During the optimization phase we investigated the liability of advanced mol- ecules to be oxidized to thioureas which have been associated with lipidosis.Although,we concluded that the very low level of thio- urea metabolite measured in this study not to be a potential risk, we also identified six-membered (hetero)aromatic bioisosteres of aminothiazoles as potent FBPase inhibitors, which are the subject of this paper. As previously outlined,our series occupy the allosteric AMP binding site and reach through the sulfonylureido linker into a second binding region, at the dyad interface of tetrameric FBPase. 4 In the interface region, there are direct p -stacking interactions between the terminal thiazole rings of two adjacent ligands as well as several strong van der Waals interactions between highly polar- izable ligand substituents, such as –Br,–SMe, or –Cl and the side chains of Met18A/C (Fig. 1, left panel). Activity in the thiazole ser- ies could be increased by up to a factor of 80 by these specific sub- stitutions.In this paper,we will focus on the replacement of the aminothiazole motif while trying to satisfy the main recognition motifs ( p -stacking of aromatic ring, polarizable substituent close to Met18) and discuss the evolving SAR. 5 The structure–activity relationship of the (hetero)aromatic sulfonylureido moiety occu- pying the AMP binding site paralleled that of the aminothiazole series and could be transferred to a considerable extent to the new series reported here. We mainly use 3-Cl substituted phenyl and 5-(2-methoxy-ethyl)-4-methyl substituted thiophenyl(Table 1), which have been identified as high affinity fragments in our previous publication. 4 While both meta-Cl in the phenyl and b-methyl in the thiophene series occupy the back pocket in the AMP binding site,the methoxyethyl substituent in the a-position of the thiophene ring makes additional non-polar interactions with Leu30 and Val160 of human liver FBPase (X-ray structure not shown) further enhancing the binding affinity in this series. 0960-894X/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.bmcl.2011.04.044 ⇑ Corresponding author. Tel.: +41 61 6887618; fax: +41 61 6886459. E-mail address: eric_a.kitas@roche.com (E. Kitas). Bioorganic & Medicinal Chemistry Letters 21 (2011) 3237–3242 Contents lists available at ScienceDirect Bioorganic & Medicinal Chemistry Letters j o u r n a l h o me pa ge : w w w . e l s e v i e r . c o m / l o c a t e / b m c l