TGFB1 and fibrosis: Levels of lung tissue pSmad2 following inhibition of TGFβR1 with SB-525334 in murine and human fibrosis was lower than inhibition by GSK3008348, suggesting that under normal conditions there is a basal level of TGFβ activity in the lungs which was not inhibited by GSK3008348 at the concentrations tested.