Background:PG545 is a heparan sulfate (HS) mimetic that inhibits tumour angiogenesis by sequestering angiogenic growth factors in the extracellular matrix (ECM), thus limiting subsequent binding to receptors. Importantly, PG545 also inhibits heparanase, the only endoglycosidase which cleaves HS chains in the ECM. The aim of the study was to assess PG545 in various solid tumour and metastasis models.Methods:The anti-angiogenic, anti-tumour and anti-metastatic properties of PG545 were assessed using in vivo angiogenesis, solid tumour and metastasis models. Pharmacokinetic (PK) data were also generated in tumour-bearing mice to gain an understanding of optimal dosing schedules and regimens.Results:PG545 was shown to inhibit angiogenesis in vivo and induce anti-tumour or anti-metastatic effects in murine models of breast, prostate, liver, lung, colon, head and neck cancers and melanoma. Enhanced anti-tumour activity was also noted when used in combination with sorafenib in a liver cancer model. PK data revealed that the half-life of PG545 was relatively long, with pharmacologically relevant concentrations of radiolabeled PG545 observed in liver tumours.Conclusion:PG545 is a new anti-angiogenic clinical candidate for cancer therapy. The anti-metastatic property of PG545, likely due to the inhibition of heparanase, may prove to be a critical attribute as the compound enters phase I clinical trials.

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PG545 is a fully synthetic heparan sulfate (HS) mimetic entering Phase I clinical trials for advanced cancer. PG545 inhibits key processes in tumor progression (a) angiogenesis – by interfering with growth factor binding and (b) metastasis – by inhibition of heparanase activity. The syngeneic 4T1 breast carcinoma murine model is a well known model of spontaneous metastasis and PG545 was assessed for effects on primary tumour growth, metastatic development in lung and overall survival. PG545 and the tyrosine kinase inhibitor (TKI) sorafenib (used as a comparative antiangiogenic agent) were investigated for their effect on primary tumour growth and the number of lung metastases after treatment for two weeks. PG545 significantly inhibited solid tumour growth and potently inhibited the formation of lung metastases when administered on a twice-weekly dosing schedule (2xqw). Although sorafenib inhibited primary tumour growth to a similar extent as PG545, sorafenib significantly increased the number of lung metastases. In a separate study to investigate overall survival, mice had their primary tumours resected (mastectomy) on day 11 post-inoculation and treatment with PG545 (1xqw), sorafenib (1xqd) or cisplatin (1xqw) was administered for 55 days. Interim data on day 30 using satellite animals confirmed the potent antimetastatic activity of PG545 by enumeration of lung metastases. This reduction in metastasis correlated with overall survival in the PG545-treated mice in the main study which was significantly enhanced compared to vehicle control or sorafenib (which had a similar survival profile as control). PG545 also outperformed cisplatin. Mice culled due to clinical signs associated with disease progression correlated with histological assessment of metastatic burden in lung tissue. The antimetastatic effects of PG545 were confirmed by histological assessment at the end of the study on day 55, with very few metastases observed in PG545-treated mice. In conclusion, PG545 has potent anti-metastatic activity that would appear to differentiate it from other antiangiogenic therapies such as TKI's which have also been recently reported by other groups to aggravate metastatic development under certain circumstances. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1461. doi:10.1158/1538-7445.AM2011-1461