Development and analytical performance evaluation of an automated chemiluminescent immunoassay for pro-gastrin releasing peptide (ProGRP).

BACKGROUND: Pro-gastrin releasing peptide (ProGRP) concentrations in blood play an important role in the diagnosis and treatment of patients with small cell lung cancer (SCLC). The automated quantitative ARCHITECT ProGRP assay was developed to aid in the differential diagnosis and in the management of SCLC. The purpose of this study was to evaluate the analytical performance of this chemiluminescent microparticle immunoassay at multiple sites. METHODS: ARCHITECT ProGRP measures ProGRP using a two-step sandwich using monoclonal anti-ProGRP antibodies coated on paramagnetic microparticles and labeled with acridinium. Analytical performance of the assay was evaluated at four sites: Abbott Japan, Denka Seiken, the Johns Hopkins University, and the University of Munich. RESULTS: Total precision (%CV) for nine analyte concentrations was between 2.2 and 5.7. The analytical sensitivity of the assay was between 0.20 pg/mL and 0.88 pg/mL. The functional sensitivity at 20% CV was between 0.66 pg/mL and 1.73 pg/mL. The assay was linear up to 50,000 pg/mL using a 1:10 autodilution protocol. The calibration curve was stable for 30 days. Comparison with the Fujirebio microtiter plate enzyme-linked immunosorbent assay (EIA) ProGRP assay gave a slope of 0.93 and a correlation coefficient (r) of 0.99. CONCLUSIONS: These results demonstrate that the ARCHITECT ProGRP assay has excellent sensitivity, precision, and correlation to a reference method. This assay provides a convenient automated method for ProGRP measurement in serum and plasma in hospitals and clinical laboratories.

Challenges in developing a validated biomarker for angiogenesis inhibitors: the motesanib experience.

PURPOSE: We sought to develop placental growth factor as a predictive pharmacodynamic biomarker for motesanib efficacy as first-line therapy in patients with advanced nonsquamous non-small-cell lung cancer. EXPERIMENTAL DESIGN: Placental growth factor was evaluated at baseline and study week 4 (after 3 weeks treatment) in an exploratory analysis of data from a randomized phase 2 study of motesanib 125 mg once daily plus carboplatin/paclitaxel and in a prespecified analysis of data from a randomized, double-blind phase 3 study of motesanib 125 mg once daily plus carboplatin/paclitaxel vs placebo plus carboplatin/paclitaxel (MONET1). Associations between fold-change from baseline in placental growth factor and overall survival were evaluated using Cox proportional hazards models. RESULTS: In the phase 2 study, serum placental growth factor increased from baseline a mean 2.8-fold at study week 4. Patients with ≥2.2-fold change from baseline in placental growth factor (n = 18) had significantly longer overall survival than those with <2.2-fold change (n = 19; 22.9 vs 7.9 months; hazard ratio, 0.30; 95% CI, 0.12-0.74; P = 0.009). Consequently, placental growth factor was investigated as a pharmacodynamic biomarker in the phase 3 MONET1 study. There was no association between log-transformed placental growth factor fold-change from baseline to week 4 (continuous variable) and overall survival (hazard ratio, 0.98; 95% CI, 0.79-1.22; P = 0.868). MONET1 did not meet its primary endpoint of overall survival. Likewise, median overall survival was similar among patients with ≥2.0-fold change in placental growth factor (n = 229) compared with <2.0-fold change (n = 127; 14.8 vs 13.8 months; hazard ratio, 0.88; 95% CI, 0.67-1.15, P = 0.340). CONCLUSIONS: Our results illustrate the challenges of successfully translating phase 2 biomarker results into phase 3 studies. TRIAL REGISTRATION: ClinicalTrials.gov NCT00460317, NCT00369070.