Discovery of Novel Small Molecule Inhibitors of VEGF Expression in Tumor Cells Using a Cell-Based High Throughput Screening Platform.

Current anti-VEGF (Vascular Endothelial Growth Factor A) therapies to treat various cancers indiscriminately block VEGF function in the patient resulting in the global loss of VEGF signaling which has been linked to dose-limiting toxicities as well as treatment failures due to acquired resistance. Accumulating evidence suggests that this resistance is at least partially due to increased production of compensatory tumor angiogenic factors/cytokines. VEGF protein production is differentially controlled depending on whether cells are in the normal "homeostatic" state or in a stressed state, such as hypoxia, by post-transcriptional regulation imparted by elements in the 5' and 3' untranslated regions (UTR) of the VEGF mRNA. Using the Gene Expression Modulation by Small molecules (GEMS™) phenotypic assay system, we performed a high throughput screen to identify low molecular weight compounds that target the VEGF mRNA UTR-mediated regulation of stress-induced VEGF production in tumor cells. We identified a number of compounds that potently and selectively reduce endogenous VEGF production under hypoxia in HeLa cells. Medicinal chemistry efforts improved the potency and pharmaceutical properties of one series of compounds resulting in the discovery of PTC-510 which inhibits hypoxia-induced VEGF expression in HeLa cells at low nanomolar concentration. In mouse xenograft studies, oral administration of PTC-510 results in marked reduction of intratumor VEGF production and single agent control of tumor growth without any evident toxicity. Here, we show that selective suppression of stress-induced VEGF production within tumor cells effectively controls tumor growth. Therefore, this approach may minimize the liabilities of current global anti-VEGF therapies.
Competing Interests: We have the following interests: The authors are employed by and received monetary compensation from PTC Therapeutics, Inc. Liangxian Cao, Marla Weetall, Jenelle Bombard (former employee), Hongyan Qi (former employee), Tamil Arasu (former employee), William Lennox, Jean Hedrick, Josephine Sheedy, Nicole Risher, Panayiota Trifillis, Christopher Trotta, Young-Choon Moon, John Babiak, Neil G Almstead, Joseph M Colacino, Thomas W Davis (former employee) and Stuart W Peltz are or were employed by and hold or held financial interests in PTC Therapeutics, Inc. PTC Therapeutics hold the patents pertaining to the results presented in this paper as below: Liangxian Cao and Panayiota Trifillis, Methods for Identifying Compounds that Modulate Untranslated Region-Based Regulation, CA2514184 and US8460864. Christopher R Trotta and Liangxian Cao, Methods and Agents for Screening for Compounds Capable of Modulating VEGF Expression, CA2567111, EP2400038 and US8426194. Liangxian Cao; William Lennox; Hongyan Qi; Young-Choon Moon and Nadarajan Tamilarasu, Tetra-Cyclic Carboline Derivatives Useful in the Inhibition of Angiogenesis, MX286760 and US8940896. Young-Choon Moon; William Lennox and Hongyan Qi, Tetrahydrocarbazoles as Active Agents for Inhibiting VEGF Production by Translational Control, US8946444 and US9271960. There are no additional patents, products in development or marketed products to declare. This does not alter our adherence to all the PLOS ONE policies on sharing data and materials, as detailed online in the guide for authors.