HDAC9 and central nervous system cancer: However, given encouraging preclinical data on HDAC and PI3K inhibition, PNOC016 (NCT03893487) was designed as both a target validation study (the primary objective) and a preliminary efficacy trial to evaluate drug penetration of the pan-HDAC and PI3K inhibitor fimepinostat for newly diagnosed diffuse intrinsic pontine gliomas, recurrent high-grade gliomas, and recurrent MB.