Discovery and SAR of a Novel Selective and Orally Bioavailable Nonpeptide Classical Competitive Inhibitor Class of Protein-Tyrosine Phosphatase 1B Henrik Sune Andersen,* ,² Ole H. Olsen, ² Lars F. Iversen, ‡ Anette L. P. Sørensen, ² Steen B. Mortensen, ‡ Michael S. Christensen, § Sven Branner, | Thomas K. Hansen, ² Jesper F. Lau, ² Lone Jeppesen, ² Edmond J. Moran, ⊥ Jing Su, ⊥ Farid Bakir, ⊥ Luke Judge, ⊥ Manou Shahbaz, ⊥ Tassie Collins, ⊥ Todd Vo, ⊥ Michael J. Newman, ⊥ William C. Ripka, ⊥ and Niels Peter H. Møller* ,# Departments of Medicinal Chemistry Research 1, 4, and 5 and Drug Metabolism, Health Care Discovery, Novo Nordisk A/S, Novo Nordisk Park, DK-2760 Ma˚ løv, Denmark, Departments of Protein Structure, Protein Design, and Signal Transduction, Novo Nordisk A/S, Novo Alle´ , DK-2880 Bagsværd, Denmark, and Ontogen Corporation, 2325 Camino Vida Roble, Carlsbad, California 92009 Received April 5, 2002 Reversible phosphorylation and dephosphorylation of key proteins on tyrosine residues are important parts of intracellular signaling triggered by hormones and other agents. Recent knock-out studies in mice have identified PTP1B as a potential target for the treatment of diabetes and obesity. As a consequence, a number of academic and industrial groups are aggressively pursuing the development of selective PTP1B inhibitors. In addition, other protein- tyrosine phosphatases (PTPs) appear to be critically involved in major diseases such as cancer and autoimmunity. Given the diversity of PTPs and their potential as drug targets in different diseases, we have taken a broad approach to develop active site-directed selective inhibitors of specific members of this family of enzymes. Using a high throughput screening, we have previously identified 2-(oxalylamino)benzoic acid 3a as a relatively weak but classical competitive inhibitor of several PTPs. 4 On the basis of our early studies, indicating that 3a might be used as a starting point for the synthesis of selective PTP inhibitors, we now present our efforts in expansion of this concept and provide here a number of new chemical scaffolds for the development of inhibitors of different members of the PTP family. Although the core structure of these inhibitors is charged, good oral bioavailability has been observed in rat for some compounds. Furthermore, we have observed enhancement of 2-deoxy-glucose accumulation in C2C12 cells with prodrug analogues. Introduction Reversible tyrosine phosphorylation plays a pivotal role in most cellular signaling processes. Protein ty- rosine kinases (PTKs) phosphorylate cellular substrates on tyrosine residues, and protein-tyrosine phosphatas- es (PTPs) remove phosphate from tyrosine-phosphory- lated proteins (for reviews, see refs 1 and 2). It is generally believed that low molecular weight selective PTP inhibitors could potentially be used for the treat- ment of a variety of diseases such as diabetes, auto- immunity, and cancer. Recently, it was shown that mice lacking functional PTP1B exhibit increased insulin sensitivity and resistance to diet-induced obesity, thus pointing to this enzyme as an attractive drug target in diabetes and obesity. 3 We have recently identified 2-(oxalylamino)benzoic acid 3a (OBA, Figure 1) as a general inhibitor of PTPs. 4 Importantly, OBA seems to be one of the most potent “minimal unit” phenyl phosphate mimetics identified so far. 5 X-ray protein crystallography of PTP1B cocrystal- lized with OBA revealed that it binds to the highly conserved phosphate binding loop (the PTP loop), thus mimicking part of the binding pattern of the natural substrate. 6,7 In addition, OBA exhibits a novel binding pattern, interacting with other residues (e.g., Lys120) surrounding the active site, which are not directly involved in substrate binding. Recently, Bleasdale et al. demonstrated a similar binding pattern for 2-car- boxymethoxybenzoic acid-based inhibitors, which also show interaction to Lys120. 8 Because of OBA’s low molecular weight and its enzyme kinetic behavior as a classical, time-independent competitive inhibitor, this compound was used as a starting point for structure- based lead optimization to develop selective small molecule inhibitors of PTP1B. To obtain selectivity for PTP1B against the expected ∼40 different human PTPs 9 is a key issue. With the aim of identifying unique combinations of amino acid * To whom correspondence should be addressed. H.S.A.: Tel: +45 4443 4890. Fax: +45 4466 3450. E-mail: HSA@novonordisk.com. N.P.H.M.: Tel: +45 4442 2899. Fax: +45 4442 7484. E-mail: NPHM@ novonordisk.com. ² Department of Medicinal Chemistry Research 1, 4, and 5, Novo Nordisk A/S. ‡ Department of Protein Structure, Novo Nordisk A/S. § Department of Drug Metabolism, Novo Nordisk A/S. | Department of Protein Design, Novo Nordisk A/S. ⊥ Ontogen Corporation. # Department of Signal Transduction, Novo Nordisk A/S. Figure 1. 4443 J. Med. Chem. 2002, 45, 4443-4459 10.1021/jm0209026 CCC: $22.00 © 2002 American Chemical Society Published on Web 08/24/2002