HDAC9 and neuroblastoma: PCI-24781 does not inhibit HDAC11, as do belinostat and trichostatin A. Certainly, PCI-24781 displayed strong cytotoxic effects on neuroblastoma cell lines with an IC50 of less than 200 nanomolar while other pan HDAC inhibitors (sodium butyrate, SAHA and valproic acid) had IC50 values in the ranges of micromolar to millimolar [47].