Send Orders for Reprints to reprints@benthamscience.net 1460 Anti-Cancer Agents in Medicinal Chemistry, 2013, 13, 1460-1466 Discovery of P3971 an Orally Efficacious Novel Anticancer Agent Targeting HIF-1 and STAT3 Pathways Pallavi Godse a , Pramod Kumar a , Nilambari Yewalkar a , Vijaykumar Deore a , Manoj Lohar a , Ramswaroop Mundada a , Amol Padgaonkar b , Sonal Manohar b , Asavari Joshi b , Dimple Bhatia b , Nikesh Desai b , Anagha Damre c , Mandar Bhonde b , Kalpana Joshi b , Rajiv Sharma a and Sanjay Kumar a, * a Department of Medicinal Chemistry, Piramal Healthcare Ltd., 1-Nirlon Complex, Off Western Express Highway, Goregaon (E), Mumbai 400 063, India; b Department of Pharmacology, Piramal Healthcare Ltd., 1-Nirlon Complex, Off Western Express Highway, Goregaon (E), Mumbai 400 063, India; c Department of Drug Metabolism and Pharmacokinetics, Piramal Healthcare Ltd., 1-Nirlon Complex, Off Western Express Highway, Goregaon (E), Mumbai 400 063, India Abstract: Hypoxia-inducible factor-1 (HIF-1) and signal transducer and activator of transcription 3 (STAT3) are transcription factors and are activated in response to hypoxia. Both HIF-1 and STAT3 regulate various aspects of cancer biology such as cell survival, proliferation, angiogenesis etc. and are constitutively expressed in a wide range of human cancers. In the last decade, over expression of HIF-1 and STAT3 has been demonstrated in many common human cancers, thereby emerging as highly compelling anticancer targets for drug discovery. We herein report the design and synthesis of new imidazopyridine based potent dual inhibitors of HIF-1 and STAT3 pathways. The lead compound of this series P3971 has been identified as a potent inhibitor of HIF-1 (200 nM) and STAT3 (350 nM) with significant antiproliferative activity against various cancer cell lines. Moreover, P3971 was also found to be orally efficacious in HCT116 (colon cancer) and H460 (lung cancer) xenograft mice models. Keywords: Anticancer, drug discovery, HIF-1, STAT3, imidazopyridine. INTRODUCTION Hypoxia inducible factor-1 (HIF-1) which is composed of  and  subunits is a key regulator of transcriptional response to oxygen deprivation. HIF-1 plays a significant role in the regulation of various genes involved in tumorigenesis, angiogenesis, glycolysis, survival, growth, invasion, metastasis etc. [1-4]. It has been reported that over expression of HIF-1 is associated with advanced disease stage and poor prognosis in many common human cancers [5]. In normoxic conditions, HIF-1 subunit is rapidly degraded whereas it gets stabilised under hypoxic conditions. HIF-1 subunit is constitutively expressed as a nuclear protein. The signal transducer and activator of transcription 3 (STAT3) belongs to STAT family of proteins and is constitutively active in a wide range of human cancers [6]. When activated by cytokines and growth factors it forms homo- or heterodimers and translocates from cytoplasm to nucleus. In nucleus, the activated STAT3 binds to the promoters of various genes involved in carcinogenesis (anti-apoptosis, proliferation, angiogenesis etc.) [7]. Recently, it has been shown that similar to HIF-1, STAT3 is also activated in response to hypoxia (a common feature of various solid tumors) [8, 9]. Activated STAT3 mediates up-regulation of HIF-1 by increasing its stability and transcriptional activity [10]. In the last decade, HIF- 1 has emerged as a potential target for many common solid tumors [2]. Recently, Boron-containing phenoxyacetanilide based molecule (GN26361), AC1-001 and its benzimidazole derivative AC-004 have been reported as lead molecules targeting HIF-1 [11-13]. Our earlier research work reports the discovery of P2630, imidazopyridine based specific inhibitor targeting HIF-1 [14]. We herein report the design and synthesis of novel hydrazone containing imidazopyridine based dual inhibitors targeting HIF-1 and STAT3. Hayakawa M. et al. have reported the pyrazole containing imidazopyridine based molecules targeting PI3K. *Address correspondence to this author at the Department of Medicinal Chemistry, Piramal Life Sciences Ltd. Mumbai, India- 400063; Tel: +91-22-3081 8317; Fax: +91-22-3081 8036; E-mail: sanjay.kumar@piramal.com However, due to poor stability and efficacy the pyrazole ring was replaced with hydrazone. This modification yielded a stable, potent PI3K inhibitor. Due to poor oral bioavailability the lead molecule was administered intraperitoneally in HeLa human cervical tumor xenograft model [15, 16]. In the quest of discovery of novel orally efficacious anticancer molecules, we designed and synthesized new hydrazone containing imidazopyridine based molecules (9-26) targeting HIF-1 and STAT3 pathways as outlined in Scheme 1. MATERIAL AND METHODS Preparation of P3971 (Compound 10) P3971 was synthesized as per our published patent procedure [17], in brief 2-amino-5-bromopyridine (1) was treated with bromomalonaldehyde in acetonitrile to get 6-bromoimidazo[1,2] pyridine-3-carbaldehyde (2). The resulting compound 2 was treated with pyridine-3-boronic acid using dichlorobis(triphenylphosphine) palladium (II), aqueous Na 2 CO 3 and DMF to get 6-(pyridin-3- yl)imidazo[1,2-a]pyridine-3-carbaldehyde (3). The aldehyde functionality of compound 3 was reacted with methyl hydrazine; the resulting hydrazide was treated with 2-methyl-5-fluoro-phenyl sulfonyl chlorides to get target compound P3971 (5-fluoro-N,2- dimethyl-N'-((6-(pyridin-3-yl)imidazo[1,2-a]pyridin-3-yl)methylene) benzenesulfonohydrazide). 1 H NMR (DMSO-d6, 300 MHz):  9.54 (s, 1 H), 8.91 (d, J = 1.8 Hz, 1 H), 8.68 (dd, J = 5.8 Hz, 1.2 Hz 1 H), 8.32 (s, 1 H), 8.07 (bs, 1 H), 8.04 (s, 1 H), 7.85 (s, 2 H), 7.62- 7.56 (m, 2 H), 7.45-7.35 (m, 2 H), 3.43 (s, 3 H), 2.49 (s, 3 H). 13 C NMR (75 MHz, DMSO-d6):  149.14, 147.38, 146.10, 139.66, 137.07, 136.98, 135.01, 134.35, 133.95, 133.55, 132.10, 126.30, 124.69, 124.17, 124.00, 120.60, 120.25, 117.66, 116.38, 32.04, 19.23. MS: m/e (ES-) 424 (M +1). HPLC purity 99.16 %. HRMS calcd for C 21 H 18 FN 5 O 2 S: 423.1165 found for C 21 H 18 FN 5 O 2 S: 424.122 (M+H). PREPARATION OF OTHER COMPOUNDS 9 & 11-26 All target compounds were made similar to procedure discussed for compound 10 (P3971) using suitable pyridine boronic acid & arylsulfonyl chloride. 187 -5 2/13 $58.00+.00 © 2013 Bentham Science Publishers