Proteomics and biomarkers in clinical trials for drug development

Proteomics allows characterization of protein structure and function, protein-protein interactions, and peptide modifications. It has given us insight into the perturbations of signaling pathways within tumor cells and has improved the discovery of new therapeutic targets and possible indicators of response to and duration of therapy. The discovery, verification, and validation of novel biomarkers are critical in streamlining clinical development of targeted compounds, and directing rational treatments for patients whose tumors are dependent upon select signaling pathways. Studies are now underway in many diseases to examine the immune or inflammatory proteome, vascular proteome, cancer or disease proteome, and other subsets of the specific pathology microenvironment. Successful assay verification and biological validation of such biomarkers will speed development of potential agents to targetable dominant pathways and lead to selection of individuals most likely to benefit. Reconsideration of analytical and clinical trials methods for acquisition, examination, and translation of proteomics data must occur before we march further into future of drug development.

Vandetanib, designed to inhibit VEGFR2 and EGFR signaling, had no clinical activity as monotherapy for recurrent ovarian cancer and no detectable modulation of VEGFR2

PURPOSE

To evaluate clinical activity and target modulation of vandetanib in women with recurrent ovarian cancer.

EXPERIMENTAL DESIGN

A phase II trial of orally administered vandetanib 300 mg daily was designed to include analyses of target inhibition through paired biopsies and dynamic imaging. Core 18-gauge needle biopsies and dynamic contrast-enhanced magnetic resonance imaging were obtained before initiation of therapy and 6 weeks into therapy. Biopsy samples were subjected to reverse-phase protein lysate array endpoint analysis. Cytokine concentrations were measured by enzyme-linked immunosorbent assay in serially collected plasma samples.

RESULTS

Twelve patients entered the study, and accrual was terminated in the first stage because of lack of response or disease stabilization beyond 6 months. Adverse events included rash, diarrhea, and prolonged QT interval corrected for heart rate, but not hypertension. Exploratory analyses showed that epidermal growth factor receptor (EGFR) phosphorylation was reduced in the eight paired biopsy sets obtained; vascular endothelial growth factor (VEGF) receptor-2 phosphorylation was not consistently affected nor were dynamic contrast-enhanced MRI permeability and flow parameters. Serial plasma VEGF concentrations were variable and did not significantly change in the 11 patients assessed.

CONCLUSIONS

Vandetanib 300 mg daily monotherapy had no significant clinical benefit in this disease setting. Proteomic analysis of paired biopsies detected both phosphorylated-EGFR and phosphorylated-VEGF receptor-2 in ovarian tumor tissue, but only phosphorylated-EGFR was measurably inhibited by vandetanib.