Ji-Seon Park

Benzimidazole Derivatives as Potent JAK1-Selective Inhibitors.

The Janus kinase (JAK) family comprises four members (JAK1, JAK2, JAK3, and Tyk2) that play a key role in mediating cytokine receptor signaling. JAK inhibition thus modulates cytokine-mediated effects. In particular, selective inhibition of JAK1 or JAK3 may provide an efficient therapeutic agent for the treatment of inflammatory diseases, with minimized side effects. In this study, as part of our continued efforts to develop a selective JAK1 inhibitor, a series of 1,2-disubstituted benzimidazole-5-carboxamide derivatives was prepared and their inhibitory activities against all four JAK isozymes were evaluated. A clear structure-activity relationship was observed with respect to JAK1 selectivity; this highlighted the importance of hydrogen bond donors at both N(1) and R2 positions located within a specific distance from the benzimidazole core. One of the synthesized compounds, 1-(2-aminoethyl)-2-(piperidin-4-yl)-1H-benzo[d]imidazole-5-carboxamide (5c), showed remarkable JAK1 selectivity (63-fold vs JAK2, 25-fold vs JAK3, and 74-fold vs Tyk2). Molecular docking revealed that the 2-aminoethyl and piperidin-4-yl substituents of 5c function as probes to differentiate the ATP-binding site of JAK1 from that of JAK2, resulting in preferential JAK1 binding. A kinase panel assay confirmed the JAK1 selectivity of 5c, which showed no appreciable inhibitory activity against 26 other protein kinases at 10 μM.

Newly developed glycogen synthase kinase-3 (GSK-3) inhibitors protect neuronal cells death in amyloid-beta induced cell model and in a transgenic mouse model of Alzheimer's disease.

Glycogen synthase kinase-3 (GSK-3) is emerging as a prominent therapeutic target of Alzheimers disease (AD). A number of studies have been undertaken to develop GSK-3 inhibitors for clinical use. We report two novel GSK-3 inhibitors (C-7a and C-7b) showing good activity and pharmacokinetic (PK) profiles. IC50 of new GSK-3 inhibitors were in the range of 120-130 nM, and they effectively reduced the Aβ-oligomers induced neuronal toxicity. Also, new GSK-3 inhibitors decreased the phosphorylated tau at pThr231, pSer396, pThr181, and pSer202, and inhibited the GSK-3 activity against Aβ-oligomers induced neuronal cell toxicity. In B6;129-Psen1(tm1Mpm) Tg(APPSwe, tauP301L)1Lfa/Mmjax model of AD, oral administration of C-7a (20 mg/kg, 50 mg/kg) showed increased total arm entries and spontaneous alteration of Y-maze which was regarded as short-term memory. In particular, 50 mg/kg C-7a treated mice significantly decreased the level of phosphorylated tau (Ser396) in brain hippocampus. We suggest that new GSK-3 inhibitor (C-7a) is potential candidates for the treatment of AD.

Synthesis and evaluation of tricyclic derivatives containing a non-aromatic amide as inhibitors of poly(ADP-ribose)polymerase-1 (PARP-1)

Highly potent poly(ADP-ribose)polymerase-1 (PARP-1) inhibitors, including 9-hydroxy-1,2-dihydro-4H-thiopyrano[3,4-c]quinolin-5(6H)-one derivatives with a non-aromatic A-ring, were synthesized. Among the derivatives, 12a showed low nanomolar enzyme and cellular activity (IC(50) = 42 nM, ED(50) = 220 nM) with good water solubility. Further, 12a exhibited microsomal stability in vitro and brain permeability in vivo.

Synthesis and evaluation of 8-amino-[1,2,4]triazolo[4,3-a]pyridin-3(2H)-one derivatives as glycogen synthase kinase-3 (GSK-3) inhibitors

New potent glycogen synthase kinase-3 (GSK-3) inhibitors, 8-amino-[1,2,4]triazolo[4,3-a]pyridin-3(2H)-one derivatives, were designed by modeling, synthesized and evaluated in vitro. Compound 17c showed good potency in enzyme and cell-based assays (IC50=111 nM, EC50=1.78 μM). Moreover, it has demonstrated desirable water solubility, PK profile, and moderate brain penetration.

Development of a Cellular Tau Enzyme-Linked Immunosorbent Assay Method for Screening GSK-3β Inhibitors

Glycogen synthase kinase-3β (GSK-3β), a serine/threonine kinase also known as tau protein kinase I, has been implicated in the pathogenic conditions of Alzheimers disease. Many investigators have focused on GSK-3 inhibitor as a therapeutic drug. In this study, we established a cell-based assay for the screening of novel GSK-3β inhibitors. For this purpose, four-repeat tau cDNAs were stably expressed in human embryonic kidney 293 (HEK293) cells (HEK293-Tau). The proliferation of HEK293-Tau cells was no different from that of HEK293 cells, as measured by the bromodeoxyuridine enzyme-linked immunosorbent assay (BrdU ELISA). The concentration-dependent reduction of tau phosphorylation by GSK-3 inhibitors, LiCl, Chir98023, and SB415286, was examined by immunoblot analysis and Tau ELISA (in situ ELISA). Highly consistent data were obtained, suggesting that this novel ELISA method is highly reproducible. Using this ELISA strategy, we isolated a few candidate compounds, including compounds 114 and 149, from several hundreds of synthetic agents and demonstrated that such candidates protect nerve growth factor-differentiated PC12 cells against amyloid-β-induced cell death. These data indicate that this Tau ELISA method in HEK293-Tau cells may be a suitable cell-based assay system to screen for GSK-3β inhibitors.

Effect of JGK-263 as a new glycogen synthase kinase-3β inhibitor on extrinsic apoptosis pathway in motor neuronal cells

Glycogen synthase kinase-3β (GSK-3β) has been identified as one of the important pathogenic mechanisms in motor neuronal death. GSK-3β inhibitor has been investigated as a modulator of apoptosis and has been shown to confer significant protective effects on cell death in neurodegenerative diseases. However, GSK-3β is known to have paradoxical effects on apoptosis subtypes, i.e., pro-apoptotic in mitochondrial-associated intrinsic apoptosis, but anti-apoptotic in death receptor-related extrinsic apoptosis. In this study, we evaluated the effect of a new GSK-3β inhibitor (JGK-263) on motor neuron cell survival and apoptosis, by using low to high doses of JGK-263 after 48 h of serum withdrawal, and monitoring changes in extrinsic apoptosis pathway components, including Fas, FasL, cleaved caspase-8, p38α, and the Fas-Daxx interaction. Cell survival peaked after treatment of serum-deprived cells with 50 μM JGK-263. The present study showed that treatment with JGK-263 reduced serum-deprivation-induced motor neuronal apoptosis by inactivating not only the intrinsic, but also the extrinsic apoptosis pathway. These results suggest that JGK-263 has a neuroprotective effect through effective modulation of the extrinsic apoptosis pathway in motor neuron degeneration.

Neuroprotective effects of a novel poly (ADP-ribose) polymerase-1 inhibitor, JPI-289, in hypoxic rat cortical neurons

Excessive activation of poly (ADP‐ribose) polymerase‐1 (PARP‐1) is known to develop neuronal apoptosis, necrosis and inflammation after ischaemic brain injury. Therefore, PARP‐1 inhibition after ischaemic stroke has been attempted in successful animal studies. The purpose of present work was to develop a novel water soluble PARP‐1 inhibitor (JPI‐289) and explore its neuroprotective effect on ischaemic injury in an in vitro model. The half‐life of JPI‐289 after intravenous or oral administration in rats was relatively long (1.4‐1.5 hours) with 65.6% bioavailability. The inhibitor strongly inhibited PARP‐1 activity (IC50=18.5 nmol/L) and cellular PAR formation (IC50=10.7 nmol/L) in the nanomolar range. In rat cortical neuronal cells, JPI‐289 did not affect cell viability up to 1 mmol/L as assayed by Trypan blue staining (TBS) and lactate dehydrogenase (LDH) assay. Treatment of JPI‐289 for 2 hours after 2 hours of oxygen glucose deprived (OGD) rat cortical neuron attenuated PARP activity and restored ATP and NAD+ levels. Apoptosis‐associated molecules such as apoptosis inducing factor (AIF), cytochrome C and cleaved caspase‐3 were reduced after JPI‐289 treatment in the OGD model. The present findings suggest that the novel PARP‐1 inhibitor, JPI‐289, is a potential neuroprotective agent which could be useful as a treatment for acute ischaemic stroke.

Abstract 825: The development of a novel PARP inhibitor with potent antitumor activity in various tumor xenograft models

Poly (ADP-ribose) Polymerase (PARP) plays a critical role in DNA repair processes. Small molecule inhibitors of PARP for the treatment of cancer are currently being investigated either single agents or in combination therapy with other DNA damaging agents. Based on recent published data, PARP inhibitors have shown promising results as a powerful therapeutic anticancer agents, especially in tumors deficient in BRCA-1or BRCA-2 function. In this study, we present a novel synthetic inhibitor of poly (ADP-ribose) polymerase (PARP) for their anti-tumor activity in various types of tumor xenograft model. Among new synthetic PARP inhibitors, JPI-283 shows synergistic effects in vitro cell cytotoxicity with DNA damaging agent such as Temozolomide(TMZ), SN-38, and CDDP. Also, JPI-283 represents a potential anticancer activity in BRCA-1 and BRCA-2 mutant cells as a single agent. In tumor xenograft model studies, the combination of JPI-283 with TMZ by oral dosing results in more than 60-70% tumor growth inhibition rate, compared to the control group in CAPAN-1, U87MG, MDA-MB-468 and SW620 tumor xenograft model. In addition, the combination of JPI-283 with CDDP shows superior antitumor activity compared to that of AZD2281 with CDDP in MDA-MB468 triple negative breast tumor xenograft model. The pharmacokinetics of JPI-283 in mouse and rat shows over 50% bioavailability. These findings suggest that JPI-283 would be an attractive therapeutic candidate for the treatment of cancer including DNA repair deficient cancer. Citation Format: Ji-Seon Park, Jang-Hyun Kim, Kwang-Woo Cheon, Bo-Young Cho, Kang-Jeon Kim, Han-Chang Lee, Young-Cheol Kim, Hyung-Chan Oh, Hyun-Ho Lee, Jeong-Min Kim. The development of a novel PARP inhibitor with potent antitumor activity in various tumor xenograft models. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 825. doi:10.1158/1538-7445.AM2014-825