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Background: Cilengitide, an antiangiogenic agent that inhibits the binding of integrins alpha(nu)beta(3) and alpha(nu)beta(5) to the extracellular matrix, was studied at two dose levels in cancer patients to determine the optimal biological dose., Patients and Methods: The doses of cilengitide were 600 or 1200 mg/m(2) as a 1-h infusion twice weekly every 28 days. A novel dose escalation scheme was utilized that relied upon the biological activity rate., Results: Twenty patients received 50 courses of cilengitide with no dose-limiting toxic effects. The pharmacokinetic (PK) profile revealed a short elimination half-life of 4 h, supporting twice weekly dosing. Of the six soluble angiogenic molecules assessed, only E-selectin increased significantly from baseline. Analysis of tumor microvessel density and gene expression was not informative due to intrapatient tumor heterogeneity. Although several patients with evaluable tumor biopsy pairs did reveal posttreatment increases in tumor and endothelial cell apoptosis, these results did not reach statistical significance due to the aforementioned heterogeneity., Conclusions: Cilengitide is a well-tolerated antiangiogenic agent. The biomarkers chosen in this study underscore the difficulty in assessing the biological activity of antiangiogenic agents in the absence of validated biological assays.

Background: We previously demonstrated that peak microtubule bundle formation (MBF) in peripheral blood mononuclear cells (PBMCs) occurs at the end of drug infusion and correlates with drug pharmacokinetics (PK). In the current study, a new expanded evaluation of drug target effect was undertaken., Patients and Methods: Patients with advanced solid malignancies were treated with ixabepilone 40 mg/m2 administered as a 1-h i.v. infusion every 3 weeks. Blood, plasma, and tumor tissue sampling was carried out to characterize pharmacodynamics and PK., Results: Forty-seven patients were treated with 141 cycles of ixabepilone. In both PBMCs (n=27) and tumor cells (n=9), peak MBF occurred at the end of infusion; however, at 24-72 h after drug infusion, the number of cells with MBF was significantly greater in tumor cells, relative to PBMCs. A Hill model (EC50=109.65 ng/ml; r2=0.94) was fitted, which demonstrated a relationship between percentage of PBMCs with MBF and plasma ixabepilone concentration. The percentage of PBMCs with MBF at the end of infusion also correlated with severity of neutropenia (P=0.050)., Conclusions: Plasma ixabepilone concentration and severity of neutropenia correlate with the level of MBF in PBMCs. Therefore, this technically straightforward assay should be considered as a complement to the clinical development of novel microtubule-binding agents.