Identification of potent 11mer Glucagon-Like Peptide-1 Receptor agonist peptides with novel C-terminal amino acids: Homohomophenylalanine analogs Tasir S. Haque a, *, Ving G. Lee b , Douglas Riexinger b , Ming Lei b , Sarah Malmstrom b , Li Xin c , Songping Han c , Claudio Mapelli b , Christopher B. Cooper a , Ge Zhang b , William R. Ewing a , John Krupinski c a Department of Discovery Chemistry, Bristol-Myers Squibb Pharmaceutical Research Institute, PO Box 4000, Princeton, NJ 08543-4000, USA b Department of Applied Biotechnologies, Bristol-Myers Squibb Pharmaceutical Research Institute, PO Box 4000, Princeton, NJ 08543-4000, USA c Department of Discovery Biology, Bristol-Myers Squibb Pharmaceutical Research Institute, PO Box 4000, Princeton, NJ 08543-4000, USA 1. Introduction The most prevalent form of diabetes is type 2, accounting for 90–95% of the estimated 23.6 million people with diabetes in the United States alone [5]. Initially, patients with type 2 diabetes develop resistance to the effects of insulin, resulting in an elevation of blood glucose levels. The patient’s production of insulin by pancreatic b-cells eventually decreases, leading to an even greater elevation of glucose levels in the blood. Glucagon-Like-Peptide-1 (GLP-1) was first identified in 1983 [3,4], and has since become one of the leading subjects of interest for treatment of type 2 diabetes [14]. GLP-1 is an incretin hormone which is normally secreted in response to food intake and stimulates insulin release in a glucose-dependent manner. GLP- 1 has also been implicated in promoting satiety after meals, preserving pancreatic b-cell mass, and inhibiting gastric emptying, glucagon secretion and hepatic glucose output [10]. The broad, beneficial effects of GLP-1 make it an attractive therapeutic target [7,11,15]. However, the enzyme dipeptidyl peptidase IV (DPP-IV) readily cleaves GLP-1 at the 2-position alanine residue, rapidly inactivating the agonist activity of GLP-1. Consequently, the short plasma half-life of GLP-1 in vivo (less than 5 min) precludes the direct administration of native GLP-1 as a useful treatment for type 2 diabetes unless it is continuously infused via a pump. GLP-1 binds to and activates the GLP-1 receptor (GLP-1R). GLP- 1R is a member of the class B family of G-protein-coupled receptors (GPCRs) [8]. Receptors in this family typically consist of 2 domains; an N-terminal extracellular binding domain (N-domain) and a C- terminal domain of 7 a-helices that span the membrane (juxtamembrane domain, or J-domain). It is believed that high affinity binding of the C-terminal domain of peptide ligands to the receptor occurs at the N-domain, inducing a conformational change that allows the N-terminal domain of the ligand to bind to the J-terminal domain and activate the receptor and intracellular G-protein. With few exceptions the class B GPCRs have proven to be difficult targets for development of small molecule agonist therapeutics; nearly all agonists reported to date consist of peptides of moderate length (30–60 amino acids) [8]. Most of the reported agonists for GLP-1R are closely related in both sequence and length to the endogenous peptide GLP-1(7–37), the sequence of which is shown in Fig. 1, or the other equally biologically active form of the peptide, GLP-1(7–36)amide. A number of organizations are working to develop drugs which act as metabolically stabilized GLP-1R agonists [13]. One example of a potent and relatively stable GLP-1R agonist, approved by the US Food and Drug Administration for use with type 2 diabetes, is exenatide (marketed under the name Byetta TM ). Exenatide is a synthetic version of the naturally occurring peptide exendin-4 (Fig. 1), which is found in Gila Monster lizard saliva. Another Peptides 31 (2010) 950–955 ARTICLE INFO Article history: Received 18 November 2009 Received in revised form 26 January 2010 Accepted 26 January 2010 Available online 4 February 2010 Keywords: GLP-1R (Glucagon-Like Peptide-1) Agonist Homohomophenylalanine ABSTRACT We report the identification of potent agonists of the Glucagon-Like Peptide-1 Receptor (GLP-1R). These compounds are short, 11 amino acid peptides containing several unnatural amino acids, including (in particular) analogs of homohomophenylalanine (hhPhe) at the C-terminal position. Typically the functional activity of the more potent peptides in this class is in the low picomolar range in an in vitro cAMP assay, with one example demonstrating excellent in vivo activity in an ob/ob mouse model of diabetes. ß 2010 Elsevier Inc. All rights reserved. * Corresponding author. Tel.: +1 609 252 4273. E-mail address: tasir.haque@bms.com (T.S. Haque). Contents lists available at ScienceDirect Peptides journal homepage: www.elsevier.com/locate/peptides 0196-9781/$ – see front matter ß 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.peptides.2010.01.008