Discovery of Novel Non-Peptide CCR1 Receptor Antagonists Howard P. Ng, †,1 Karen May,* ,† John G. Bauman, † Ameen Ghannam, † Imadul Islam, † Meina Liang, † Richard Horuk, ‡ Joseph Hesselgesser, ‡ R. Michael Snider, † H. Daniel Perez, ‡ and Michael M. Morrissey † Departments of Discovery Research and Immunology, Berlex Biosciences, 15049 San Pablo Avenue, P.O. Box 4099, Richmond, California 94804-0099 Received June 21, 1999 Ligands for the CCR1 receptor (MIP-1R and RANTES) have been implicated in a number of chronic inflammatory diseases, most notably multiple sclerosis and rheumatoid arthritis. Because these ligands share a common receptor, CCR1, we sought to discover antagonists for this receptor as an approach to treating these disorders. A novel series of 4-hydroxypiperidines has been discovered by high throughput screening (HTS) which potently inhibits the binding of MIP-1R and RANTES to the recombinant human CCR1 chemokine receptor. The structure- activity relationships of various segments of this template are described as the initial HTS lead 1 was optimized synthetically to the highly potent receptor antagonist 6s. This compound has been shown to have at least 200-fold selectivity for inhibition of CCR1 over other human 7-TM receptors, including other chemokine receptors. In addition, data obtained from in vitro functional assays demonstrate the functional antagonism of compound 6s and structurally related analogues against the CCR1 receptor in a concentration dependent manner. The discovery and optimization of potent and selective CCR1 receptor antagonists represented by compound 6s potentially represent a novel approach to the treatment of chronic inflammatory diseases. Introduction Chemokines are chemotactic cytokines that belong to a large family of chemoattractant molecules involved in the directed migration of immune cells. 2 The physi- ological role of chemokines in the immune process is to elicit mobilization of immune cells against pathogenic organisms by direct recruitment and activation. Chemokines are small proteins that are divided into two main classes, based on the position of the first two cysteines. They are the C-X-C and C-C families of chemokines 2 (two smaller branches of this family have been described, the C 3 and CX 3 C 4 subfamilies). To date over 40 chemokines have been identified and character- ized. The chemokines all act by direct interaction with cell surface receptors, known as chemokine receptors. Chemokine receptors are members of the superfamily of seven transmembrane domain proteins that signal across the cellular membrane through coupled G pro- teins. 5 At last count these G-protein coupled receptors (GPCR) number well over 600. Fifteen chemokine receptors have thus far been cloned and identified: five C-X-C, eight C-C, one CX 3 C, and one C receptor. They produce their biological effect through a cascade of intracellular events that begin with binding of the chemokines to their respective receptors and lead ultimately to activation and/or directed migration of the cell. Since the first chemokines were discovered and their receptors cloned, they have been implicated in a number of very important disease states including multiple sclerosis, 6-8 rheumatoid arthritis, 9-11 allograft rejec- tion, 12,13 atherosclerosis, 14 asthma, 15-17 and AIDS. 18 A number of pharmaceutical companies have reported or disclosed significant efforts in discovering chemokine receptor antagonists. 19-24 Our interest in chemokines was an extension of our interest in the treatment of multiple sclerosis (MS). Multiple sclerosis is a debilitating disease affecting over 200 000 people in the United States. It primarily afflicts young adults, temporarily paralyzing parts of their body with remission of disease usually followed by relapses of greater severity and duration resulting ultimately in permanent disability in many cases. One of the hall- marks of MS disease is the infiltration and activation of peripheral blood leukocytes into the brain. This along with central nervous system immune cell activation lead to active demyelination of the central nervous system. To date no approved orally available small molecule therapy exists for the treatment of MS. However, the possibility of utilizing antagonism of binding of a chemokine to its receptor as a novel treatment for inflammatory diseases such as MS was recently dem- onstrated. 7 Studies by Karpus 7 show strong evidence for a role of several chemokines in a mouse experimental autoim- mune encephalomyelitis (EAE) model of MS. More specifically, they reported that a CC chemokine mac- rophage inflammatory protein (MIP-1R) played a key role in the development and progression of rodent EAE disease. Investigators treated the mice with antibodies to MIP-1R and found that both the initial and relapsing paralytic aspects of the disease were significantly reduced. This reduction of clinical disease correlated * To whom correspondence should be addressed: Berlex Biosciences, Department of Discovery Research, 15049 San Pablo Ave., Richmond, CA 94806. E-mail: karen•may@berlex.com. † Department of Discovery Research. ‡ Department of Immunology. 4680 J. Med. Chem. 1999, 42, 4680-4694 10.1021/jm990316l CCC: $18.00 © 1999 American Chemical Society Published on Web 10/08/1999