Incubation with the highest evaluated dose of irinotecan (20 μg/mL) during 24 h significantly decreased mRNA expression of MMP1 (− 30.25 ± 11, p = 0.05, paired t-test) and ACTA2 (− 30 ± 5.4, p = 0.0117, paired t-test) in dermal fibroblasts of SSc patients treated with irinotecan vs. the non-treated condition. The gene discussed is ACTA2; the disease is systemic sclerosis.