Abstract 4473: WP760, A new highly potent and selective agent against melanoma including BRAFi resistant melanoma
Authors: Rusin Aleksandra , Zielinski Rafal , Fokt Izabela , Nguyen Van , Skora Stanislaw , Jayakumar Arumugam , Priebe Waldemar 
Published: August 2015

Melanoma is expected to be diagnosed in 76,100 patients in the United States, and 9,710 patients are estimated to die of the disease in 2014. Early-stage melanomas can often be treated effectively with surgery alone, but more advanced cancers often require other treatments, including radiation therapy, immunotherapy, chemotherapy and targeted therapy. Targeted therapy with vemurafenib is used to treat approximately 60 percent of melanoma patients with activating mutation in the BRAF gene. V600E mutation in the BRAF gene is detected in over half of the melanoma patients and targeted inhibition of the oncogenic BRAF has shown a very good initial response in melanoma patients, however, this treatment alone turned out to be unsuccessful due to the rapid development of resistance. Development of therapeutics for use in combination with BRAF inhibitors or strategies overcoming the resistance to vemurafenib is a subject of intensive research. Systematic screening of unique DNA bisintercalating agents of our own design using NCI 60 cell line panel led to identification of highly potent and melanoma selective compound WP760.

The main aim of this study was to assess antiproliferative activity of WP760 in a panel of melanoma cell lines including BRAFi resistant cell lines. Here we have shown that WP760 inhibited proliferation of melanoma cell in low nanomolar range and was not toxic to normal fibroblasts. Importantly, WP760 inhibited potently proliferation of cells resistant to BRAF inhibitors and wild type BRAF in low nanomolar range. Moreover, it was equally active in pairs of isogenic cell lines: naïve and those which developed resistance to vemurafenib.

The second aim of this work was preliminary assessment of WP760 toxicity in vivo. In our first attempt to perform in vivo characterization of WP760, we analyzed its solubility and developed formulation in 5% dextrose in a presence of 5% DMSO suitable for intravenous administration. Our preliminary toxicity study performed in CD-1 mice, indicated low or no apparent toxicity symptoms when WP760 was dosed up to 10 mg/kg (rate of death 14%). For multiple dosing, when animals received three IV injections of WP760, the dose of 2.5 mg/kg appeared to be safe and animals did not present abnormal behavior when observed over 30 days period. Mice receiving higher doses of the compound developed toxicity symptoms after 3rd dose and the time they appeared was dose dependent.

The observed melanoma selectivity of WP760 and its low nanomolar range cytotoxic potency in vitro combined with the lack of toxicity in normal fibroblasts were in agreement with results of the in vivo experiments demonstrating relatively high maximum tolerated dose in animals suggesting on the existence of a broad therapeutic window in vivo.

Acknowledgment: This research was supported in part by funds from the University Cancer Foundation via the Sister Institution Network Fund at the UT MD Anderson Cancer Center and Melanoma SPORE (2 P50 CA093459)

Citation Format: Aleksandra Rusin, Rafal Zielinski, Izabela Fokt, Van Nguyen, Stanislaw Skora, Arumugam Jayakumar, Waldemar Priebe. WP760, A new highly potent and selective agent against melanoma including BRAFi resistant melanoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4473. doi:10.1158/1538-7445.AM2015-4473