Abstract
PURPOSE: The RGD-integrin, αvβ6, plays a role in the pathogenesis of pulmonary fibrosis through activation of transforming growth factor beta (TGFβ). This study sought to quantify expression of αvβ6 in the lungs of healthy humans and subjects with pulmonary fibrosis using the αvβ6-selective [(18)F]FB-A20FMDV2 PET ligand. METHODS: [(18)F]FB-A20FMDV2 PET/CT scans were performed in healthy subjects and those with fibrotic lung disease. Standard uptake values (SUV) and volume of distribution (V(T)) were used to quantify αvβ6 expression. In subjects with fibrotic lung disease, qualitative assessment of the relationship between αvβ6 expression and the distribution of fibrosis on high resolution computed tomography was conducted. RESULTS: A total of 15 participants (6 healthy, 7 with idiopathic pulmonary fibrosis (IPF) and 2 with connective tissue disease (CTD) associated PF) were enrolled. V(T) and SUV of [(18)F]FB-A20FMDV2 were increased in the lungs of subjects with pulmonary fibrosis (PF) compared with healthy subjects. Geometric mean V(T) (95% CI) was 0.88 (0.60, 1.29) mL/cm(3) for healthy subjects, and 1.40 (1.22, 1.61) mL/cm(3) for subjects with IPF; and SUV was 0.54 (0.36, 0.81) g/mL for healthy subjects and 1.03 (0.86, 1.22) g/mL for subjects with IPF. The IPF/healthy V(T) ratio (geometric mean, (95% CI of ratio)) was 1.59 (1.09, 2.32) (probability ratio > 1 = 0.988)) and the SUV ratio was 1.91 (1.27, 2.87) (probability ratio > 1 = 0.996). Increased uptake of [(18)F]FB-A20FMDV2 in PF was predominantly confined to fibrotic areas. [(18)F]FB-A20FMDV2 measurements were reproducible at an interval of 2 weeks. [(18)F]FB-A20FMDV2 was safe and well tolerated. CONCLUSIONS: Lung uptake of [(18)F]FB-A20FMDV2, a measure of expression of the integrin αvβ6, was markedly increased in subjects with PF compared with healthy subjects.