Utility Of Clinical Biomarkers For Detecting Protein Kinase Ck2 Inhibition: A Report From The Phase I Trial Of Cx-4945

Proceedings: AACR 101st Annual Meeting 2010‐‐ Apr 17‐21, 2010; Washington, DC Introduction: CX-4945 is a first-in-class, orally administered small molecule that potently and selectively inhibits protein kinase CK2, a previously unexploited molecular target with well documented roles in many cancers. In vitro, CX-4945 selectively kills cancer cells by modulating key survival pathways, resulting in cell cycle arrest, inhibition of cell proliferation, and promotion of apoptosis. CK2 hyperactivation of the PI3K/Akt pathway promotes the phosphorylation of several proteins which we have exploited as biomarkers for CX-4945 activity. A validated laser scanning cytometry method has been developed to quantify the phosphorylation of p21 and Akt in cells, and this has been employed to characterize these substrates in circulating blood cells collected from patients in the phase I clinical trial of CX-4945. Procedures: Eligible patients with advanced solid tumors with progressive disease, or for whom there are no available standard therapies, were administered CX-4945 in successive dose cohorts using a standard 3×3 design at: 90, 160, 300, 460, and 700 mg per dose. Oral doses were administered twice daily for twenty-one consecutive days of a four week cycle. Serial plasma samples were collected for pharmacokinetic analysis on the first and final dosing days of Cycle 1 (i.e., Day 1 and Day 21). In addition, whole blood samples were collected at pre-treatment, 4 hours and 8 hours following the first dose of CX-4945 on Day 1 and Day 21, and peripheral blood mononuclear cells (PBMCs) were isolated for pharmacodynamic biomarker evaluations (specifically, total and phosphorylated forms of p21 and Akt). Plasma samples were also collected at these time points for quantification of plasma IL-6. Results: Seventeen patients with advanced solid tumors from five separate dose cohorts have received oral doses of CX-4945 to date, and all patients in the study participated in the collection of PBMCs. Biomarkers from patients in Cohorts 3 and 4 demonstrated changes in their profile consistent with the inhibition of CK2. CX-4945 displays general linearity in PK parameters between the dose cohorts, with a terminal half life of approximately 25 hours at steady state. Conclusions: To date, no DLTs have yet been observed, and the MTD remains to be defined in this Phase I study. Early signals suggest a modulation of the biomarker profile consistent with CK2 inhibition. Patient enrollment will continue, to further characterize CX-4945's safety, tolerance, pharmacokinetics and pharmacodynamic effects. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2763.