Quinazolinones and Pyrido[3,4-d]pyrimidin-4-ones as Orally Active and Specific Matrix Metalloproteinase-13 Inhibitors for the Treatment of Osteoarthritis Jie Jack Li,* Joe Nahra, † Adam R. Johnson, Amy Bunker, Patrick O’Brien, Wen-Song Yue, Daniel F. Ortwine, Chiu-Fai Man, Vijay Baragi, Kenneth Kilgore, Richard D. Dyer, and Hyo-Kyung Han Department of Chemistry, Michigan Laboratories, Pfizer Global Research and DeVelopment, 2800 Plymouth Road, Ann Arbor, Michigan 48105 ReceiVed October 10, 2007 Quinazolinones 8 and pyrido[3,4-d]pyrimidin-4-ones 9 as orally active and specific matrix metalloproteinase- 13 inhibitors were discovered for the treatment of osteoarthritis. Starting from a high-through-put screening (HTS) hit thizolopyrimidin-dione 7, we obtained two chemotypes, 8 and 9, using computer-aided drug design (CADD) and methodical structure–activity relationship (SAR) studies. They occupy the unique S 1 ′-specificity pocket and do not bind to the Zn 2+ ion. Some pyrido[3,4-d]pyrimidin-4-ones, such as 10a, possess favorable absorption, distribution, metabolism, and elimination (ADME) and safety profiles. 10a effectively prevents cartilage damage in rabbit animal models of osteoarthritis without inducing musculoskeletal side effects when given at extremely high doses to rats. Introduction Gross and Lapiere discovered the first matrix metallopro- teinase (MMP-1, also known as collagenase 1) from a meta- morphosing tadpole in 1962. 1 Today, matrix metalloproteinases (MMPs) a are elucidated as a family of more than 28 subtypes of zinc- and calcium-dependent endopeptidases that are involved in the degradation of the extracellular matrix (ECM). MMPs have been implicated with many inflammatory diseases, cancers, and other illnesses. 2 Scientists in both academia and industry have carried out an enormous amount of investigations into the use of MMP inhibitors as innovative medicines. 3 Many potent and orally active broad-spectrum MMP inhibitors have been discovered and investigated in clinical trials. MMP inhibitors 1 (marimastat) 4 and 2 (prinomastat) 5 were tested against cancers; MMP inhibitors 3 (cipemastat) 6 and 4 (ilomastat) 7 were tried in the clinics for inflammation. Unfortunately, these broad- spectrum MMP inhibitors have been limited by nonspecificity and the subsequent nonselective toxicity and dose-limiting efficacy. Recognizing that the hydroxamic acid in 1–4 could be a possible culprit for safety issues because of its powerful chelating ability toward the MMP zinc ion, efforts have been made to replace it with milder chelating functional groups. One such group is a carboxylic acid as represented by 5 (tanoma- stat), 8 and another group is a thiol as represented by 6. 9 Regrettably, there is still not a single MMP inhibitor that has emerged on the market thus far. The sole exception is probably doxycycline, which was marketed as an antibiotic but was later found to inhibit MMP-2, -8, -9, and -13. 10 To overcome the nonselective toxicity and dose-limiting efficacy, an industry-wide effort has been undertaken to seek selective MMP inhibitors. In particular, MMP-13 has attracted much attention. 11–15 MMP-13 catalyzes the hydrolysis of type- II collagen at a unique site, which results in 3 / 4 - and 1 / 4 -length polypeptide products. 16–20 MMP-13 is not expressed in normal adult tissues, but it is found in the joints and articular cartilage of osteoarthritis (OA) patients. Therefore, it is a compelling target for the treatment of OA. 21–25 An MMP-13 inhibitor has been shown to block the degradation of explanted human osteoarthritic cartilage. 19 In genetically modified mice, regulated expression of human MMP-13 induces osteoarthritis. 26 On the basis of these findings, it is likely that MMP-13 causes irreversible cartilage damage in OA, and therefore, a selective MMP-13 inhibitor would effectively prevent cartilage degrada- tion without causing musculoskeletal syndrome (MSS) side effects that have plagued many MMP broad-spectrum inhibitors in clinical development. 24,26,27 High-through-put screening (HTS) of our compound collec- tion provided, in addition to all of the broad-spectrum MMP inhibitors, a unique hit, thiazolopyrimidinedione 7, which possessed an astounding selectivity for MMP-13 versus other MMP isoforms (Figure 2). As a matter of fact, it was specific for MMP-13 for all practical purposes. Cocrystallization of 7 with the MMP13-CD (catalytic domain) revealed an unexpected nonzinc-binding mode: instead of binding to the Zn 2+ cation, * To whom correspondence should be addressed: Discovery Chemistry, Bristol-Myers Squibb Company, 5 Research Parkway, Wallingford, CT 06492. Telephone: (203) 677-7255. E-mail: jie.li1@bms.com. † Present address: Discovery Chemistry, Bristol-Myers Squibb Company, P.O. Box 5400, Princeton, NJ 08543-5400. a Abbreviations: ADME, absorption, distribution, metabolism, and elimination; AUC, area under curve; CADD, computer-aided drug design; CD, catalytic domain; CIR, confidence in rationale; ECM, extracellular matrix; HTS, high-through-put screening; IVMN, in Vitro micronucleus; MMP, matrix metalloproteinase; MSS, musculoskeletal syndrome; OA, osteoarthritis; SAR, structure–activity relationship. Scheme 1. Synthesis of Alkynyl Quinazolinones 8 J. Med. Chem. 2008, 51, 835–841 835 10.1021/jm701274v CCC: $40.75  2008 American Chemical Society Published on Web 02/06/2008