Incubation with the highest evaluated dose of SN38 (0.4 μg/mL) during 24 h significantly decreased mRNA expression of COL1A1 (− 61.75 ± 5.8, p = 0.0018, paired t-test), COL1A2 (− 55.75 ± 3.7, p = 0.0007, paired t-test), MMP1 (− 50.75 ± 8,1, p = 0.0084, paired t-test) and ACTA2 (− 54.25 ± 7.6, p = 0.0057, paired t-test) in dermal fibroblasts of SSc patients treated with SN38 vs. the non-treated condition (Fig. 4). Here, COL1A1 is linked to systemic sclerosis.