Thus, AXP2258 treatment alone inhibited fibroblast to myofibroblast differentiation in fibroblasts from slow IPF patients but when this MAP3K19 inhibitor was combined with pirfenidone inhibitory effects on myofibroblast differentiation were observed in both slow and rapid IPF fibroblasts. Here, MAP3K19 is linked to idiopathic pulmonary fibrosis.