Domatinostat tosylate (4SC-202) is a selective class I HDAC inhibitor targeting HDAC1/2/3 with IC50 values of 1.20/1.12/0.57 μM, respectively, and also inhibits Lysine-specific demethylase 1 (LSD1).

HDAC10:21 μM, HDAC1:1.2 μM, HDAC5:11.3 μM, HDAC3:0.57 μM, HDAC2:1.12 μM, HDAC9:50 μM, HDAC11:9.7 μM

Domatinostat provokes apoptosis activation in CRC cells, while caspase inhibitors (z-VAD-CHO and z-DVED-CHO) significantly alleviate Domatinostat-exerted cytotoxicity in CRC cells. Meanwhile, Domatinostat induces dramatic G2-M arrest in CRC cells. Further studies show that AKT activation might be an important resistance factor of Domatinostat. Domatinostat-induced cytotoxicity is dramatically potentiated with serum starvation, AKT inhibition (by perifosine or MK-2206), or AKT1-shRNA knockdown in CRC cells. On the other hand, exogenous expression of constitutively active AKT1 (CA-AKT1) decreases the sensitivity by Domatinostat in HT-29 cells. Notably, Domatinostat, at a low concentration, enhances oxaliplatin-induced in vitro anti-CRC activity[2]. Domatinostat obviously reduces the proliferation of all epithelial and mesenchymal UC cell lines (IC50: 0.15-0.51 μM), inhibits clonogenic growth and induces caspase activity[1]. Domatinostat treatment induces potent cytotoxic and proliferation-inhibitory activities against established HCC cell lines (HepG2, HepB3, SMMC-7721) and patient-derived primary HCC cells. Domatinostat induces apoptosis signal-regulating kinase 1 (ASK1) activation, causing it translocation to mitochondria and physical association with Cyp-D[3].

4SC-202 (i.g.) inhibits HT-29 xenograft growth in nude mice, and when combined with oxaliplatin, its activity is further strengthened[2].