Abstract 3783: Pharmacokinetics and CNS biodistribution of WP1066, a novel small molecule inhibitor of STAT-3 phosphorylation

Utilizing molecular modeling and medicinal chemistry we have designed and discovered novel, potent small molecule inhibitors of STAT3 activation. WP1066, our lead compound, suppressed several downstream signaling products including c-myc, Bcl-XL and Mcl-1, and induced apoptosis in a panel of malignant gliomas. Further studies demonstrated that WP1066 inhibited, in vivo, the growth of malignant glioma xenografts and decreased levels of phosphorylated STAT3. In order to determine the best dosing schedule for WP1066 we designed a number of in vivo studies to assess the biodistribution of this agent following oral and intravenous administration in a mouse model. For the purposes of this study we developed LC/MS/MS analytical methods capable of quantifying WP1066 extracted from plasma or tissues having a limit of quantification of 1 ng/ml or gm tissue. 80 female mice were assigned to the intravenous arm (16 timepoints, 5 animals per timepoint) and 65 mice to the oral arm (13 timepoints, 5 animals per timepoint). Each mouse received a single administration of 40 mg/kg WP1066 or control vehicle, either orally or intravenously. Blood samples were collected by cardiac puncture under isoflurane anesthesia. At sacrifice blood and brain tissue was collected from groups of animals receiving WP1066. Blood and brain tissue was also collected within 30 minutes of injection in a group of 5 animals receiving control vehicle alone. Blood samples were collected in appropriately labeled heparinized tubes, plasma was generated by centrifugation and frozen at –80°C until analyzed. Brain tissue from all animals was harvested, blotted, weighed, and placed in appropriately labeled cryotubes and frozen at –80°C until analyzed. Following analysis the mean value of 5 measured samples at each timepoint (plasma and brain) were subject to non-compartmental PK analysis. WP1066 showed excellent CNS bioavailability with concurrent brain-to-blood concentration ratios ranging from 10:1 to 100:1, reaching mean CNS and plasma peak concentrations of 57.6 µg/g (162.2 μM) and 0.6 µg /mL (1.8 μM), respectively, following a 40 mg/kg IV bolus administration. CNS penetration following oral administration was similar with tissue and plasma peak concentrations reaching 2.7 µg/g (7.6 μM) and 0.09 µg/mL (0.3 μM), respectively. Oral bioavailability was 36.3% (AUC PO/AUC IV), reaching a mean peak concentration at 0.75 hours postdose with measureable concentrations up to 8 hours after dosing administration. This study demonstrates WP1066 maintains CNS concentrations at many fold higher concentrations than that needed to demonstrate activity in vitro in many cancer cell lines (1 µM). These concentrations were maintained for a significant period of time in this mouse model following a single dose of drug, and support the use of once daily dosing in clinical trials. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3783. doi:1538-7445.AM2012-3783