Cell permeable sulphonamide. Inhibits p53 binding to mitochondria by reducing its affinity for anti-apoptotic proteins Bcl-2 and Bcl-XL. Pifithrin-u selectively inhibits p53 translocation to mitochondria without affecting the transactivation function of p53. Selectively inhibits HSP70 activity leading to tumour cell death associated with protein aggregation, impaired autophagy and inhibition of lysosomal function.