GK444 (Compound 15a), a selective HDAC1/2 inhibitor with IC50 values of 100 nM and 92 nM for HDAC1 and HDAC2 respectively, demonstrates an IC50 of 4.1 μM in Caco-2 cell inhibition. Additionally, GK444 attenuates TGF-β1-induced COL1A1 mRNA expression in primary normal human lung fibroblasts and mitigates Bleomycin-induced lung fibrosis in mice [1].