TGFB1 and systemic sclerosis: In this study, we show that inhibition of the ER stress‐induced IRE1α signaling pathway, using the inhibitor 4μ8C, blocks TGFβ‐induced activation of myofibroblasts in vitro, reduces liver and skin fibrosis in vivo, and reverts the fibrotic phenotype of activated myofibroblasts isolated from patients with systemic sclerosis.