Discovery of a potent, metabolically stabilized resorcylic lactone as an anti-inflammatory lead H. Du a , T. Matsushima b , M. Spyvee a , M. Goto b , H. Shirota a , F. Gusovsky a , K. Chiba b , M. Kotake b , N. Yoneda b , Y. Eguchi b , L. DiPietro a , J.-C. Harmange a , S. Gilbert a , X.-Y. Li a , H. Davis a , Y. Jiang a , Z. Zhang a , R. Pelletier a , N. Wong a , H. Sakurai b , H. Yang a , H. Ito-Igarashi b , A. Kimura b , Y. Kuboi b , Y. Mizui b , I. Tanaka b , M. Ikemori-Kawada b , Y. Kawakami b , A. Inoue b , T. Kawai b , Y. Kishi c , Y. Wang a, * a Eisai Research Institute of Boston, 4 Corporate Drive, Andover, MA 01810, USA b Eisai Tsukuba Research Laboratories, 1-3, Tokodai 5-chome, Tsukuba-shi, Ibaraki 300-2635, Japan c Scientific Advisory Board, Eisai Co. Ltd., 4-6-10, Koishikawa, Bunkyo-Ku, Tokyo 112-8088, Japan article info Article history: Received 5 August 2009 Revised 26 August 2009 Accepted 31 August 2009 Available online 3 September 2009 Keywords: MEKK1 MEK1 Resorcylic acid Anti-inflammatory ER-803064 abstract With bioactivity-guided phenotype screenings, a potent anti-inflammatory compound f152A1 has been isolated, characterized and identified as the known natural product LL-Z1640-2. Metabolic instability precluded its use for the study on animal disease models. Via total synthesis, a potent, metabolically sta- bilized analog ER-803064 has been created; addition of the (S)-Me group at C4 onto f152A1 has resulted in a dramatic improvement on its metabolic stability, while preserving the anti-inflammatory activities. Ó 2009 Elsevier Ltd. All rights reserved. At Eisai, natural product inspired drug discovery has been one of the key research endeavors in several disease areas. With bioac- tivity-guided phenotype screenings, researchers at Eisai Tsukuba Laboratories detected a potent anti-inflammatory activity in the fraction #152 obtained from the fermentation broth of a fungus, Curvularia verruculosa, in the mid 1990s. They isolated and charac- terized the active metabolite, named as f152A1, thereby establish- ing that f152A1 is identical with a previously reported natural product LL-Z1640-2 1. 1 Several related natural products are known in literature, some of which are listed in Figure 1. 2,3 In 1978, the Lederle group reported that 1 exhibited modest inhibitory activity against growth and motility of ciliated protozoan Tetrahymena Pyr- iformis. 1 More recently, 1 and 2 were reported to exhibit potent inhibition of PDGFR signaling and IL-1b release from inflammatory cells. 4 We became interested in f152A1 (1), because it exhibited po- tent inhibitory activity in cell signaling (IC 50 of 11 nM in a TNFa- PLAP reporter assay), but showed much weaker activity in a coun- ter screen assay designed to assess non-specific cytotoxic effects (IC 50 of 2000–3000 nM in a b-actin-PLAP reporter assay). Despite its poor PK properties, f152A1 showed an in vivo activity indicating its inhibition of LPS-stimulated TNFa production in mice. Our investigations suggested that its pharmacological effects could be attributable to inhibition of two kinases MEKK1 and MEK1 associated with inflammatory signaling. 5 These discoveries were consistent with similar findings reported by a Merck group on a related compound L-783,277 (3). 2b,6 In this Letter, we report a potent and serum stable analog ER-803064 (15) of f152A1 (1), along with some selected SAR studies. In an early phase of study, we recognized that f152A1 (1) exhib- its very potent inhibitory activities in vitro (Table 1). Unfortu- nately, f152A1 was rapidly inactivated in human or mouse microsomes and plasma (Fig. 2). Analysis of the metabolites in mouse plasma indicated that cis-to-trans isomerization of the en- one is the major deactivating process (Supplementary Fig. S1A). The trans-isomer 7 was found to be approximately 50-fold less po- tent (IC 50 = 349 nM) than the parent cis-isomer (Fig. 4). We hypothesized that the cis-to-trans isomerization of the enone takes place via Michael addition/elimination and that glutathione (GSH) and glutathione transferase (GST) in biological fluid are responsible for the isomerization. Indeed, we found that the enone is unstable in the presence of GSH in PBS (Supplementary Fig. S1A) and the deactivation process is accelerated with the combined use of GST 0960-894X/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.bmcl.2009.08.096 * Corresponding author. E-mail address: yuan_wang@eisai.com (Y. Wang). Bioorganic & Medicinal Chemistry Letters 19 (2009) 6196–6199 Contents lists available at ScienceDirect Bioorganic & Medicinal Chemistry Letters journal homepage: www.elsevier.com/locate/bmcl