valproic acid + fludarabine

Valproic acid + fludarabine is an investigational combination therapy consisting of valproic acid, a histone deacetylase (HDAC) inhibitor, and fludarabine, a purine nucleoside analogue. This combination has been studied primarily in the context of chronic lymphocytic leukemia (CLL), particularly for patients with resistance to standard therapies. Valproic acid enhances the pro-apoptotic effects of fludarabine by promoting mitochondrial cytochrome c release, activating caspases, increasing reactive oxygen species (ROS), and downregulating anti-apoptotic proteins such as AKT and ATM. The combination induces apoptosis through both intrinsic (mitochondrial) and extrinsic pathways, including upregulation of death receptor DR4 and hyperacetylation of histones. Preclinical studies have shown that this regimen can restore sensitivity to fludarabine in resistant CLL cells[2][3][4].