IL13 and idiopathic pulmonary fibrosis: Strong preclinical studies have identified pro-inflammatory cytokines (e.g., IL-13, CCL2, and CCR2/CCR5) as fibrosis triggers, and likewise, the phase 2 trials of IL-13 inhibitors alone (NCT01266135, NCT00987545, NCT00581997, NCT01872689, and NCT01629667) or IL-4/IL-13 antibodies (NCT02921971 and NCT01529853) have been conducted in the treatment of IPF, skin keloids, and systemic sclerosis.