A preclinical evaluation of SKLB261, a multikinase inhibitor of EGFR/Src/VEGFR2, as a therapeutic agent against pancreatic cancer.

The clinical prognosis of pancreatic cancer remains rather disappointing despite tremendous efforts in exploring medical treatments in the past two decades. Development of more effective treatment strategies is still desperately needed to improve outcomes in patients with pancreatic cancer. SKLB261 is a multikinase inhibitor obtained recently through a lead optimization. In this investigation, we shall evaluate its anti-pancreatic cancer effects both in vitro and in vivo. SKLB261 is a multikinase inhibitor potently inhibiting EGFR, Src, and VEGFR2 kinases. It could significantly inhibit cell proliferation, migration, and invasion, and induce apoptosis in cellular assays of human pancreatic cancer cells that are sensitive or resistant to dasatinib and/or gemcitabine. Western blot analysis showed that SKLB261 inhibited the activation of EGFR and Src kinases as well as their downstream signaling proteins, including FAK, ERK, and STAT3. SKLB261 also showed potent antiangiogenic effects in transgenic zebrafish models. In vivo, SKLB261 displayed more potent antitumor activities than dasatinib, gemcitabine, or erlotinib in pancreatic cancer xenografts, including BxPC-3, PANC-1, AsPC-1, and HPAC. Furthermore, mice receiving SKLB261 therapy showed significant survival advantage compared with vehicle-treated and gemcitabine-treated groups in an experimental metastasis model of pancreatic cancer. These data, together with the good pharmacokinetic properties and low toxicity of this compound, provide a rationale for the ongoing clinical evaluation of SKLB261 in the treatment of pancreatic cancer.

YLT192, a novel, orally active bioavailable inhibitor of VEGFR2 signaling with potent antiangiogenic activity and antitumor efficacy in preclinical models.

Antagonizing vascular endothelial growth factor receptor 2 (VEGFR2) to block angiogenesis has been applied toward cancer therapy for its role in promoting cancer growth and metastasis. However, most these clinical anticancer drugs have unexpected side effects. Development of novel VEGFR2 inhibitors with less toxicity remains an urgent need. In this study, we describe a novel, well-tolerated, and orally active VEGFR2 inhibitor, YLT192, which inhibits tumor angiogenesis and growth. YLT192 significantly inhibited kinase activity of VEGFR2 and suppressed proliferation, migration, invasion, and tube formation of human umbilical vascular endothelial cells (HUVEC) in vitro. In addition, it inhibited VEGF-induced phosphorylation of VEGFR2 and its downstream signaling regulator in HUVEC. Zebrafish embryonic models and alginate-encapsulated tumor cell assays indicated YLT192 also inhibited angiogenesis in vivo. Moreover, YLT192 could directly inhibit proliferation and induce apoptosis of cancer cells in vitro and in vivo. Oral administration of YLT192 at a dose of 100 mg/kg/day could markedly inhibited human tumor xenograft growth without causing obvious toxicities. It decreased microvessel densities (MVD) in tumor sections. It also shows good safety profiles in the studies with mice and rats. Taken together, these preclinical evaluations suggest that YLT192 inhibits angiogenesis and may be a promising anticancer drug candidate.

Identification of novel anaplastic lymphoma kinase (ALK) inhibitors using a common feature pharmacophore model derived from known ligands crystallized with ALK.

In this investigation, a common feature pharmacophore model of anaplastic lymphoma kinase inhibitors was developed based on several known anaplastic lymphoma kinase inhibitors that were co-crystallized with anaplastic lymphoma kinase. The established pharmacophore model Hypo1 was carefully validated and then adopted to screen two in silico chemical databases, Specs (202 408 compounds) and Enamine (1 105 894 compounds), for retrieving novel anaplastic lymphoma kinase inhibitors. The hit compounds were further filtered using a fast bumping-check tool and molecular docking. Finally, 25 compounds were selected and purchased from market. The bioactivity of these compounds was firstly measured at the cellular level against a typical anaplastic lymphoma kinase mutant-driven cancer cell line, Karpas299. And six of them showed a good anti-viability activity. The kinase inhibitory potency against the recombinant human anaplastic lymphoma kinase kinase was tested to the most active compound at the cellular level, T0508-5181 (from Specs), which gave a half maximal inhibitory concentration (IC(50)) of 5.3 µM.

SKLB1206, a novel orally available multikinase inhibitor targeting EGFR activating and T790M mutants, ErbB2, ErbB4, and VEGFR2, displays potent antitumor activity both in vitro and in vivo.

Anti-epidermal growth factor receptor (EGFR) treatment has been successfully applied in clinical cancer therapy. However, the clinical efficacy of first-generation reversible EGFR inhibitors, such as gefitinib and erlotinib, is limited by the development of drug-resistant mutations, including the gatekeeper T790M mutation and upregulation of alternative signaling pathways. Second-generation irreversible EGFR inhibitors that were designed to overcome the drug resistance due to the T790M mutation have thus far had limited success. Here, we report a novel reversible EGFR inhibitor, SKLB1206, which has potent activity against EGFR with gefitinib-sensitive and -resistant (T790M) mutations. In addition, SKLB1206 has also considerable inhibition potency against some other related oncokinases, including ErbB2, ErbB4, and VEGF receptor 2 (VEGFR2). SKLB1206 exhibited highly antiproliferative activity against a range of EGFR-mutant cell lines, including gefitinib-sensitive and -resistant cell lines, and EGFR or ErbB2-overexpressing cell lines. SKLB1206 also showed a potent antiangiogenesis effect in vitro, in a zebrafish embryonic angiogenesis assay, and in an alginate-encapsulate tumor cell assay. In vivo, oral administration of SKLB1206 showed complete tumor regression in gefitinib-sensitive HCC827 and PC-9 xenograft models and showed a considerable antitumor effect on the gefitinib-resistant H1975 model as well as other EGFR/ErbB2-overexpressing or -dependent tumor models including A431, LoVo, and N87 established in athymic mice. SKLB1206 also showed a very good oral bioavailability (50.1%). Collectively, these preclinical evaluations may support clinical development of SKLB1206 for cancers with EGFR-activating/resistance mutations or EGFR/ErbB2 overexpressed.

Systems biology modeling reveals a possible mechanism of the tumor cell death upon oncogene inactivation in EGFR addicted cancers.

Despite many evidences supporting the concept of "oncogene addiction" and many hypotheses rationalizing it, there is still a lack of detailed understanding to the precise molecular mechanism underlying oncogene addiction. In this account, we developed a mathematic model of epidermal growth factor receptor (EGFR) associated signaling network, which involves EGFR-driving proliferation/pro-survival signaling pathways Ras/extracellular-signal-regulated kinase (ERK) and phosphoinositol-3 kinase (PI3K)/AKT, and pro-apoptotic signaling pathway apoptosis signal-regulating kinase 1 (ASK1)/p38. In the setting of sustained EGFR activation, the simulation results show a persistent high level of proliferation/pro-survival effectors phospho-ERK and phospho-AKT, and a basal level of pro-apoptotic effector phospho-p38. The potential of p38 activation (apoptotic potential) due to the elevated level of reactive oxygen species (ROS) is largely suppressed by the negative crosstalk between PI3K/AKT and ASK1/p38 pathways. Upon acute EGFR inactivation, the survival signals decay rapidly, followed by a fast increase of the apoptotic signal due to the release of apoptotic potential. Overall, our systems biology modeling together with experimental validations reveals that inhibition of survival signals and concomitant release of apoptotic potential jointly contribute to the tumor cell death following the inhibition of addicted oncogene in EGFR addicted cancers.

Combined SVM-based and docking-based virtual screening for retrieving novel inhibitors of c-Met.

Aberrant c-Met activation has been demonstrated to be implicated in tumorigenesis and anti-cancer drug resistance. Discovery of c-Met inhibitors has attracted much attention in recent years. In this study, a support vector machine (SVM) classification model that discriminates c-Met inhibitors and non-inhibitors was first developed. Evaluation through screening a test set indicates that combined SVM-based and docking-based virtual screening (SB/DB-VS) considerably increases hit rate and enrichment factor compared with the individual methods. Thus the combined SB/DB-VS approach was adopted to screen PubChem, Specs, and Enamine for c-Met inhibitors. 75 compounds were selected for in vitro assays. Eight compounds display a good inhibitory potency against c-Met. Five of them are found to have novel scaffolds, implying a good potential for further chemical modification.

Discovery of novel Pim-1 kinase inhibitors by a hierarchical multistage virtual screening approach based on SVM model, pharmacophore, and molecular docking.

In this investigation, we describe the discovery of novel potent Pim-1 inhibitors by employing a proposed hierarchical multistage virtual screening (VS) approach, which is based on support vector machine-based (SVM-based VS or SB-VS), pharmacophore-based VS (PB-VS), and docking-based VS (DB-VS) methods. In this approach, the three VS methods are applied in an increasing order of complexity so that the first filter (SB-VS) is fast and simple, while successive ones (PB-VS and DB-VS) are more time-consuming but are applied only to a small subset of the entire database. Evaluation of this approach indicates that it can be used to screen a large chemical library rapidly with a high hit rate and a high enrichment factor. This approach was then applied to screen several large chemical libraries, including PubChem, Specs, and Enamine as well as an in-house database. From the final hits, 47 compounds were selected for further in vitro Pim-1 inhibitory assay, and 15 compounds show nanomolar level or low micromolar inhibition potency against Pim-1. In particular, four of them were found to have new scaffolds which have potential for the chemical development of Pim-1 inhibitors.

SKLB1002, a novel potent inhibitor of VEGF receptor 2 signaling, inhibits angiogenesis and tumor growth in vivo.

PURPOSE: VEGF receptor 2 (VEGFR2) inhibitors, as efficient antiangiogenesis agents, have been applied in the cancer treatment. However, currently most of these anticancer drugs suffer some adverse effects. Discovery of novel VEGFR2 inhibitors as anticancer drug candidates is still needed. EXPERIMENTAL DESIGN: In this investigation, we adopted a restricted de novo design method to design VEGFR2 inhibitors. We selected the most potent compound SKLB1002 and analyzed its inhibitory effects on human umbilical vein endothelial cells (HUVEC) in vitro. Tumor xenografts in zebrafish and athymic mice were used to examine the in vivo activity of SKLB1002. RESULTS: The use of the restricted de novo design method indeed led to a new potent VEGFR2 inhibitor, SKLB1002, which could significantly inhibit HUVEC proliferation, migration, invasion, and tube formation. Western blot analysis was conducted, which indicated that SKLB1002 inhibited VEGF-induced phosphorylation of VEGFR2 kinase and the downstream protein kinases including extracellular signal-regulated kinase, focal adhesion kinase, and Src. In vivo zebrafish model experiments showed that SKLB1002 remarkably blocked the formation of intersegmental vessels in zebrafish embryos. It was further found to inhibit a new microvasculature in zebrafish embryos induced by inoculated tumor cells. Finally, compared with the solvent control, administration of 100 mg/kg/d SKLB1002 reached more than 60% inhibition against human tumor xenografts in athymic mice. The antiangiogenic effect was indicated by CD31 immunohistochemical staining and alginate-encapsulated tumor cell assay. CONCLUSIONS: Our findings suggest that SKLB1002 inhibits angiogenesis and may be a potential drug candidate in anticancer therapy.