MAPK3 and systemic sclerosis: It was interesting to note that cultured untreated SSc fibroblasts showed a significant increase in Erk1/2 phosphorylation after 15 min and 30 min (p < 0.01 vs. time zero (T0) for all time points), whereas ACT-333679 treatment was shown to significantly reduce Erk1/2 phosphorylation after 30 min of treatment (p < 0.05 vs. untreated cells for all tested concentrations) (Fig. 4b).