BIOORGANIC & MEDICINAL CHEMISTRY Bioorganic & Medicinal Chemistry Letters 9 (1999) 2359-2364 LEtteRS Pergamon STRUCTURE-ACTIVITY RELATIONSHIPS OF A NOVEL CLASS OF SRC SH2 INHIBITORS John L. Buchanan,* Chi B. Vu, Taylor J. Merry, Evelyn G. Corpuz, Selvaluxmi G. Pradeepan, Ukti N. Mani, Michael Yang, Hilary R. Plake, Vaibhav M. Varkhedkar, Berkley A. Lynch, Ian A. MacNeil, Kara A. Loiacono, Choi Lai Tiong and Dennis A. Holt ARIAD Pharmaceuticals, Inc. 26 Landsdowne Street, Cambridge, Massachusetts 02139-4234 U. S. A. Received 6 May 1999; accepted 6 July 1999 Abstract: The structure-activity relationships (SAR) of a novel class of Src SH2 inhibitors are described. Variation at the pY+l and pY+3 side chain positions using 2,4- and 2,5-substituted thiazoles and 1,2,4- oxadiazoles as scaffolds resulted in inhibitors that bound as well as the standard tetrapeptide Ac-pYEEINH2. © 1999 ElsevierScienceLtd. All rights reserved. Introduction: As a part of our efforts toward developing signal transduction inhibitors into therapeutic drugs, we have been interested in applications involving inhibitors of the Src homology 2 (SH2) domain 1 of the tyrosine kinase pp60c-Src, which has been implicated as a potential target2,3 for therapeutic intervention for both osteoporosis 4-6 and breast cancer. 7 In the preceding communication, 8 we reported on the structure-based design and synthesis of a novel class of Src SH2 inhibitors, represented by the 2,4-substituted thiazole lb (Figure 1). This class of inhibitors was designed based on structural studies (X-ray, NMR) of the preferred tetrapeptide sequence pTyr-Glu-Glu-Ile (pYEEI) bound to both the Src and Lck SH2 domains. 9-n The heterocycl'e ring was incorporated as a replacement scaffold that would appropriately deliver the pY and pY+3 side chains into their respective pockets while gaining a favorable interaction with the hydrophobic surface resulting from Tyr 13D5.11 It was envisioned that the ready availability of enantiopure amino acids could be exploited for the synthesis of nonracemic heterocycles with diverse pY+l (R 1) and pY+3 (R 3) side chain substitution. Subsequent structural analysis of thiazole lb (IC50 = 26 IxM) in both Src and Lck SH2 provided a new frame of reference for analog design. 8 This communication describes our initial results based on thiazole lb, leading to Src SH2 inhibitors with binding affinities equivalent to that of the standard tetrapeptide, Ac-pYEEI-NH2. Figure 1 H203PO~ H S S S F~]/.~ = R3F~ 1 = R 3 R1 R1 PG= Boc, Cbz R 1 R 3 la H CH2Chx lb CH2CH2CO2H CH2Chx lc CH2CH2CO2H CH2CH(CH3)2 ld CH2CH2CO2H (CH2)2CH(CH3)2 *Fax: (617) 494-8144; Email: john.buchanan@ariad.com 0960-894X/99/$ - see front matter © 1999 Elsevier Science Ltd. All rights reserved. Plh S0960-894X(99)00389-3