Secondary objectives were to determine the qualitative and quantitative toxicity and reversibility of toxicity of rigosertib administered in this fashion; to investigate the clinical pharmacology of rigosertib when administered in this fashion, including plasma pharmacokinetics at each dose level; to confirm the appropriateness of the RPTD; to document any observed antitumor activity of rigosertib; and, to evaluate the biological effect of rigosertib in biomarkers in serum and/or peripheral blood mononuclear cells.