A novel orally available Syk/Src/Jak2 inhibitor, SKLB-850, showed potent anti-tumor activities in B cell lymphoma (BCL) models.

B cell lymphoma (BCL) is the most frequently diagnosed type of non-Hodgkin lymphoma (NHL), and accounts for about 4% of all cancers in the USA. Kinases spleen tyrosine kinase (Syk), Src, and Janus kinase 2 (JAK2) have been thought as potential targets for the treatment of BCL. We have recently developed a multikinase inhibitor, SKLB-850, which potently inhibits Syk, Src, and JAK2. The aim of this study is to investigate the anti-BCL activities and mechanisms of action of SKLB-850 both in vitro and in vivo. Our results showed that SKLB-850 significantly inhibited BCL cell proliferation, and induced apoptosis of BCL cells. It could considerably decrease the secretion of chemokines CCL3, CCL4, and CXCL12. Oral administration of SKLB-850 considerably suppressed the tumor growth in BCL xenograft models (Ramos and HBL-1) in a dose-dependent manner. Immunohistochemistry of tumor tissues showed that SKLB-850 efficiently inhibited the activation of Syk/ERK, Src/FAK and JAK2/Stat3 pathways. Collectively, SKLB-850 could be a promising agent for the treatment of BCL, hence deserving further study.

From Lead to Drug Candidate: Optimization of 3-(Phenylethynyl)-1H-pyrazolo[3,4-d]pyrimidin-4-amine Derivatives as Agents for the Treatment of Triple Negative Breast Cancer.

Herein we report the sophisticated process of structural optimization toward a previously disclosed Src inhibitor, compound 1, which showed high potency in the treatment of triple negative breast cancer (TNBC) both in vitro and in vivo but had considerable toxicity. A series of 3-(phenylethynyl)-1H-pyrazolo[3,4-d]pyrimidin-4-amine derivatives were synthesized. In vitro cell-based phenotypic screening together with in vivo assays and structure-activity relationship (SAR) studies finally led to the discovery of N-(3-((4-amino-1-(trans-4-hydroxycyclohexyl)-1H-pyrazolo[3,4-d]pyrimidin-3-yl)ethynyl)-4-methylphenyl)-4-methyl-3-(trifluoromethyl)benzamide (13an). 13an is a multikinase inhibitor, which potently inhibited Src (IC50 = 0.003 µM), KDR (IC50 = 0.032 µM), and several kinases involved in the MAPK signal transduction. This compound showed potent anti-TNBC activities both in vitro and in vivo, and good pharmacokinetic properties and low toxicity. Mechanisms of action of anti-TNBC were also investigated. Collectively, the data obtained in this study indicate that 13an could be a promising drug candidate for the treatment of TNBC and hence merits further studies.

Preclinical Evaluation of a Novel Orally Available SRC/Raf/VEGFR2 Inhibitor, SKLB646, in the Treatment of Triple-Negative Breast Cancer.

Triple-negative breast cancer (TNBC) is the most aggressive and deadly breast cancer subtype. To date, chemotherapy is the only systemic therapy and prognosis remains poor. Herein, we report the preclinical evaluation of SKLB646 in the treatment of TNBC; SKLB646 is a novel multiple kinase inhibitor developed by us recently. This compound potently inhibited SRC and VEGFR2 with IC50 values of 0.002 µmol/L and 0.012 µmol/L, respectively. It also considerably inhibited B-Raf and C-Raf with IC50 values of 0.022 and 0.019 µmol/L, respectively. It exhibited significant antiproliferation and antiviability activities against TNBC cell lines. Studies of mechanism of action indicated that SKLB646 inhibited the activation of SRC signaling and blocked the MAPK signaling through inhibiting the Raf kinases. Interestingly, SKLB646 dose dependently downregulated the expression of Fra1, a transcriptional factor that plays a critical role in the epithelial-to-mesenchymal transition. In addition, SKLB646 could inhibit HUVEC proliferation, migration, and invasion. It effectively blocked the formation of intersegmental vessels in zebrafish embryos and displayed considerable antiangiogenic effects in the tumor-induced neovascularization zebrafish model. In TNBC xenograft models, SKLB646 suppressed the tumor growth in a dose-dependent manner. Moreover, SKLB646 could remarkably inhibit TNBC cell migration and invasion in vitro. Furthermore, in an experimental lung metastasis model, the overall survival time of groups treated with SKLB646 was much longer compared with the control-, dasatinib-, and paclitaxel-treated groups. In a preliminary pharmacokinetic study, SKLB646 showed good pharmacokinetic properties. Taken together, the preclinical data show that SKLB646 could be a promising lead compound for the treatment of TNBC.

SKLB-677, an FLT3 and Wnt/ß-catenin signaling inhibitor, displays potent activity in models of FLT3-driven AML.

FLT3 has been identified as a valid target for the treatment of acute myeloid leukemia (AML), and some FLT3 inhibitors have shown very good efficacy in treating AML in clinical trials. Nevertheless, recent studies indicated that relapse and drug resistance are still difficult to avoid, and leukemia stem cells (LSCs) are considered one of the most important contributors. Here, we report the characterization of SKLB-677, a new FLT3 inhibitor developed by us recently. SKLB-677 exhibits low nanomolar potency in biochemical and cellular assays. It is efficacious in animal models at doses as low as 1mg/kg when administrated orally once daily. In particular, SKLB-677 but not first-generation and second-generation FLT3 inhibitors in clinical trials has the ability to inhibit Wnt/ß-catenin signaling; Wnt/ß-catenin signaling is required for the development of LSCs, but not necessary for the development of adult hematopoietic stem cells (HSCs). This compound indeed showed considerable suppression effects on leukemia stem-like cells in in vitro functional assays, but had no influence on normal HSCs. Collectively, SKLB-677 is an interesting lead compound for the treatment of AML, and deserves further investigations.

Design, Synthesis, and Structure-Activity Relationship Studies of 3-(Phenylethynyl)-1H-pyrazolo[3,4-d]pyrimidin-4-amine Derivatives as a New Class of Src Inhibitors with Potent Activities in Models of Triple Negative Breast Cancer.

A series of 3-(phenylethynyl)-1H-pyrazolo[3,4-d]pyrimidin-4-amine derivatives were designed and synthesized. Structure-activity relationship (SAR) analysis of these compounds led to the discovery of compound 1j, which showed the highest inhibitory potency against the Src kinase and the most potent antiviability activity against the typical TNBC cell line MDA-MB-231 among all the synthesized compounds. Further kinase inhibition assays showed that compound 1j was a multikinase inhibitor and potently inhibited Src (IC50 = 0.0009 µM) and MAPK signaling protein kinases B-RAF and C-RAF. In an MDA-MB-231 xenograft mouse model, a once-daily dose of compound 1j at 30 mg/kg for 18 days completely suppressed the tumor growth with a tumor inhibition rate larger than 100% without obvious toxicity. It also displayed good pharmacokinetic properties in a preliminary pharmacokinetic assay. Western blot and immunohistochemical assays revealed that compound 1j significantly inhibited Src and MAPK signaling and markedly induced apoptosis in tumor tissues.

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.

Advanced systems biology methods in drug discovery and translational biomedicine.

Systems biology is in an exponential development stage in recent years and has been widely utilized in biomedicine to better understand the molecular basis of human disease and the mechanism of drug action. Here, we discuss the fundamental concept of systems biology and its two computational methods that have been commonly used, that is, network analysis and dynamical modeling. The applications of systems biology in elucidating human disease are highlighted, consisting of human disease networks, treatment response prediction, investigation of disease mechanisms, and disease-associated gene prediction. In addition, important advances in drug discovery, to which systems biology makes significant contributions, are discussed, including drug-target networks, prediction of drug-target interactions, investigation of drug adverse effects, drug repositioning, and drug combination prediction. The systems biology methods and applications covered in this review provide a framework for addressing disease mechanism and approaching drug discovery, which will facilitate the translation of research findings into clinical benefits such as novel biomarkers and promising therapies.

SC-535, a novel oral multikinase inhibitor, showed potent antitumor activity in human melanoma models.

BACKGROUND: Melanoma is considered as one of the most aggressive and deadliest cancers and current targeted therapies of melanoma often suffer limited efficacy or drug resistance. Discovery of novel multikinase inhibitors as anti-melanoma drug candidates is still needed. METHODS: In this investigation, we assessed the in vitro and in vivo anti-melanoma activities of SC-535, which is a novel small molecule multikinase inhibitor discovered by us recently. We analyzed inhibitory effects of SC-535 on various melanoma cell lines and human umbilical vascular endothelial cells (HUVEC) in vitro. Tumor xenografts in athymic mice were used to examine the in vivo activity of SC-535. RESULTS: SC-535 could efficiently inhibit vascular endothelial growth factor receptor (VEGFR) 1/2/3, B-RAF, and C-RAF kinases. It showed significant antiangiogenic potencies both in vitro and in vivo and considerable anti-proliferative ability against several melanoma cell lines. Oral administration of SC-535 resulted in dose-dependent suppression of tumor growth in WM2664 and C32 xenograft mouse models. Studies of mechanisms of action indicated that SC-535 suppressed the tumor angiogenesis and induced G2/M phase cell cycle arrest in human melanoma cells. SC-535 possesses favorable pharmacokinetic properties. CONCLUSION: All of these results support SC-535 as a potential candidate for clinical studies in patients with melanoma.