TSU-68 (SU6668,Orantinib)

Ki: Flk-1trans-phosphorylation (2.1 mM), FGFR1 trans-phosphorylation (1.2 mM), and PDGFR autophosphorylation (0.008 mM).

Vascular endothelial growth factor, fibroblast growth factor (FGF), and platelet-derived growth factor (PDGF) and their cognate receptor tyrosine kinases are strongly implicated in angiogenesis associated with solid tumors. TSU-68 is a novel inhibitor of these receptors.

In vitro: Biochemical kinetic studies using isolated Flk-1, FGF receptor 1, and PDGF receptor β kinases revealed that TSU-68 has competitive inhibitory properties with respect to ATP. In cellular systems, TSU-68 inhibited receptor tyrosine phosphorylation and mitogenesis after stimulation of cells by appropriate ligands [1].

In vivo: Oral or i.p. administration of TSU-68 in athymic mice resulted in significant growth inhibition of a diverse panel of human tumor xenografts of glioma, melanoma, lung, colon, ovarian, and epidermoid origin [1].

Clinical trial: Phase I clinical study indicated that TSU-68 can be safely combined with standard doses of carboplatin-paclitaxel, with the combination manifesting promising antitumor activity [2].

References:
[1] Laird AD, Vajkoczy P, Shawver LK et al.  SU6668 is a potent antiangiogenic and antitumor agent that induces regression of established tumors. Cancer Res. 2000 Aug 1;60(15):4152-60.
[2] Okamoto I, Yoshioka H, Takeda K et al.  Phase I clinical study of the angiogenesis inhibitor TSU-68 combined with carboplatin and paclitaxel in chemotherapy-naive patients with advanced non-small cell lung cancer. J Thorac Oncol. 2012 Feb;7(2):427-33.


Inhibition of peritoneal dissemination of ovarian cancer by tyrosine kinase receptor inhibitor SU6668 (TSU-68).[Pubmed:15551349]

Int J Cancer. 2005 Mar 20;114(2):224-9.

SU6668 (TSU-68) is a small-molecule synthetic inhibitor of the angiogenic related receptor tyrosine kinases Flk-1/KDR, PDGFRbeta, and FGFR1. Using a mouse model of peritoneally disseminated ovarian cancer, we investigated whether SU6668 inhibits peritoneal dissemination and prolongs survival time. BALB/c nude mice were intraperitoneally (i.p.) inoculated with SHIN-3 (VEGF-hypersecretory) or KOC-2S (PDGF-hypersecretory) ovarian serous adenocarcinoma cells with marked peritoneal dissemination ability. From the day after i.p. inoculation of tumor cells, SU6668 was orally administered 6 times weekly at a daily dose of 100 mg/kg or 400 mg/kg. The SU6668-administered group and the vehicle-administered control group were compared for the number of tumor vascular endothelial cells, weight of peritoneally disseminated tumors, amount of ascitic fluid and survival time. As a result, these 3 parameters were significantly smaller in the SHIN-3-inoculated, SU6668-administered mice than in the control group (p = 0.03, p = 0.002, and p = 0.02, respectively). The mean survival time was significantly longer, at 58.1 +/- 11.2 days, in the SU6668-administered mice than that (34.5 +/- 8.8 days) in the control group (p = 0.002). Similarly, in the KOC-2S-inoculated mice, the oral administration of SU6668 significantly reduced these 3 parameters (p = 0.04, p = 0.04, and p = 0.03, respectively), and significantly prolonged survival (16.6 +/- 1.7 days vs. 11.0 +/- 0.7 days, p = 0.008). Thus, the oral administration of SU6668 inhibited angiogenesis and peritoneal dissemination and prolonged survival in mice with peritoneally disseminated ovarian cancer. These effects were observed with both the VEGF- and PDGF-hypersecretory cell lines. Our results suggest that molecular targeting with oral SU6668 will become a new therapeutic strategy targeting peritoneally disseminated ovarian cancer.

TSU-68 (SU6668) inhibits local tumor growth and liver metastasis of human colon cancer xenografts via anti-angiogenesis.[Pubmed:16077974]

Oncol Rep. 2005 Sep;14(3):677-82.

A number of receptor tyrosine kinases (RTKs) are involved in angiogenesis. TSU-68 (SU-6668) was developed as an inhibitor of RTKs involved in VEGF, bFGF and PDGF signaling, which then inhibits endothelial cell proliferation. We investigated the antitumor effects of TSU-68 against human colon cancer xenografts in male SCID mice and its anti-angiogenic activity using a dorsal air-sac (DAS) assay. TSU-68 was administered orally at a dose of 200 mg/kg twice daily. Mice bearing human colon carcinoma, HT-29, or WiDr xenografts were treated for 16 days. To determine the effect on hepatic metastasis, cell suspensions of HT-29 or WAV-I were injected into the spleen of mice on day 0, and mice treated for 28 days starting from day 1. For the DAS assay, HT-29, WiDr or WAV-I cells suspended in PBS at 2 x 10(7) cells/Millipore chamber were implanted subcutaneously into SCID mice, which were then treated from day 0 to 5, On day 6, the anti-angiogenic effects were assessed. Results indicated that TSU-68 significantly inhibited the growth of subcutaneous tumors. In the hepatic metastasis model, liver weights of the TSU-68-treated group were significantly reduced, compared to those of control mice. In the DAS assay, the angiogenic indices of the treated groups were significantly decreased for HT-29, WiDr and WAV-I tumors, with T/C ratios of 13.4, 50 and 35.3%, respectively. As TSU-68 significantly inhibited tumor growth and liver metastasis formation of human colon cancer xenografts, probably through anti-angiogenic activity, this agent may be useful for the treatment of colon cancer.

Combination therapy of tyrosine kinase receptor inhibitor TSU-68 (SU6668) and paclitaxel inhibits subcutaneous xenografts of endometrial cancer.[Pubmed:21479494]

Mol Med Rep. 2008 Nov-Dec;1(6):843-6.

TSU-68 is a small-molecular-weight synthetic inhibitor of the tyrosine kinase receptors Flk-1/KDR, PDGFRbeta and FGFR1, which are involved in angiogenesis. Using a mouse model in which endometrial cancer was subcutaneously implanted, we investigated the effects of TSU-68 alone or in combination with paclitaxel. We subcutaneously implanted a cell strain of endometrial cancer, HEC1A, into BALB/c nude mice. TSU-68 was orally administered every day, while paclitaxel was intraperitoneally injected once a week, and the rates of subcutaneous tumor proliferation were compared. In a group treated with high-dose (200 mg/kg/day) TSU-68 alone, subcutaneous tumor proliferation was significantly inhibited in comparison with a vehicle-treated control group (p<0.05). In groups treated with low-dose TSU-68 or paclitaxel alone (100 and 10 mg/kg/day, respectively), tumor proliferation was not significantly inhibited. In a low-dose combination therapy group (100 mg/kg/day of TSU-68 + 10 mg/kg/day of paclitaxel), tumor proliferation was significantly inhibited in comparison with the control and low-dose TSU-68 or paclitaxel therapy groups (p<0.01). High-dose monotherapy with TSU-68 inhibited the proliferation of the subcutaneously implanted tumor. Furthermore, a combination of TSU-68 and paclitaxel at a low dose, one at which respective monotherapy was not effective, inhibited tumor proliferation. Combination therapy with the two agents may therefore be useful for treating endometrial cancer.

TSU68 prevents liver metastasis of colon cancer xenografts by modulating the premetastatic niche.[Pubmed:19047154]

Cancer Res. 2008 Dec 1;68(23):9754-62.

The aim of this study was to investigate the inhibitory effect of TSU68 [(Z)-5-[(1,2-dihydro-2-oxo-3H-indol-3-ylidene)methyl]-2,4-dimethyl-1H-pyrrole-3-p ropanoic acid; SU6668], an inhibitor of vascular endothelial growth factor receptor 2, platelet-derived growth factor receptor beta, and fibroblast growth factor receptor 1 (FGFR1), on colon cancer liver metastasis, and to test the hypothesis that TSU68 modulates the microenvironment in the liver before the formation of metastasis. First, we implanted the highly metastatic human colon cancer TK-4 orthotopically into the cecal walls of nude mice, followed by twice-daily administration of TSU68 (400 mg/kg/d) or vehicle. Five weeks of treatment with TSU68 significantly inhibited liver metastasis compared with the control group (P<0.001). Next, we analyzed the gene expression profile in premetastatic liver using microarrays. Microarray and quantitative reverse transcription-PCR analysis showed that mRNA levels for the chemokine CXCL1 were significantly increased in tumor-bearing mice compared with non-tumor-bearing mice. Moreover, CXCL1 expression was significantly decreased by TSU68 treatment. CXCR2 expression was detected predominantly on tumor cells in orthotopic tumors compared with ectopic tumors. The number of migrating neutrophils in premetastatic liver was significantly decreased in the TSU68-treated group (P<0.001). The amount of interleukin-12 (IL-12) p40 in the portal vein was significantly decreased by TSU68 (P=0.02). Blockade of both CXCR2 and IL-12 p40 with a neutralizing antibody significantly inhibited liver metastasis. These results suggest that the CXCL1/CXCR2 axis is important in cancer metastasis and that TSU68 may modulate the premetastatic niche in the target organ through suppression of the inflammatory response, which might be an alternative mechanism used by antiangiogenic agents.

SU6668 is a potent antiangiogenic and antitumor agent that induces regression of established tumors.[Pubmed:10945623]

Cancer Res. 2000 Aug 1;60(15):4152-60.

Vascular endothelial growth factor, fibroblast growth factor (FGF), and platelet-derived growth factor (PDGF) and their cognate receptor tyrosine kinases are strongly implicated in angiogenesis associated with solid tumors. Using rational drug design coupled with traditional screening technologies, we have discovered SU6668, a novel inhibitor of these receptors. Biochemical kinetic studies using isolated Flk-1, FGF receptor 1, and PDGF receptor beta kinases revealed that SU6668 has competitive inhibitory properties with respect to ATP. Cocrystallographic studies of SU6668 in the catalytic domain of FGF receptor 1 substantiated the adenine mimetic properties of its oxindole core. Molecular modeling of SU6668 in the ATP binding pockets of the FIk-1/KDR and PDGF receptor kinases provided insight to explain the relative potency and selectivity of SU6668 for these receptors. In cellular systems, SU6668 inhibited receptor tyrosine phosphorylation and mitogenesis after stimulation of cells by appropriate ligands. Oral or i.p. administration of SU6668 in athymic mice resulted in significant growth inhibition of a diverse panel of human tumor xenografts of glioma, melanoma, lung, colon, ovarian, and epidermoid origin. Furthermore, intravital multifluorescence videomicroscopy of C6 glioma xenografts in the dorsal skinfold chamber model revealed that SU6668 treatment suppressed tumor angiogenesis. Finally, SU6668 treatment induced striking regression of large established human tumor xenografts. Investigations of SU6668 activity in cancer patients are ongoing in Phase I clinical trials.

Design, synthesis, and evaluations of substituted 3-[(3- or 4-carboxyethylpyrrol-2-yl)methylidenyl]indolin-2-ones as inhibitors of VEGF, FGF, and PDGF receptor tyrosine kinases.[Pubmed:10602697]

J Med Chem. 1999 Dec 16;42(25):5120-30.

Receptor tyrosine kinases (RTKs) have been implicated as therapeutic targets for the treatment of human diseases including cancers, inflammatory diseases, cardiovascular diseases including arterial restenosis, and fibrotic diseases of the lung, liver, and kidney. Three classes of 3-substituted indolin-2-ones containing propionic acid functionality attached to the pyrrole ring at the C-3 position of the core have been identified as catalytic inhibitors of the vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF), and platelet-derived growth factor (PDGF) RTKs. Some of the compounds were found to inhibit the tyrosine kinase activity associated with isolated vascular endothelial growth factor receptor 2 (VEGF-R2) [fetal liver tyrosine kinase 1 (Flk-1)/kinase insert domain-containing receptor (KDR)], fibroblast growth factor receptor (FGF-R), and platelet-derived growth factor receptor (PDGF-R) tyrosine kinase with IC(50) values at nanomolar level. Thus, compound 1 showed inhibition against VEGF-R2 (Flk-1/KDR) and FGF-R1 tyrosine kinase activity with IC(50) values of 20 and 30 nM, respectively, while compound 16f inhibited the PDGF-R tyrosine kinase activity with IC(50) value of 10 nM. Structural models and structure-activity relationship analysis of these compounds for the target receptors are discussed. The cellular activities of these compounds were profiled using cellular proliferation assays as measured by bromodeoxyuridine (BrdU) incorporation. Specific and potent inhibition of cell growth was observed for some of these compounds. These data provide evidence that these compounds can be used to inhibit the function of these target receptors.

Orantinib (SU6668; TSU-68) is a multi-targeted receptor tyrosine kinase inhibitor with Kis of 2.1 μM, 8 nM and 1.2 μM for Flt-1, PDGFRβ and FGFR1, respectively.

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