Pyrazofurin is a pyrimidine nucleoside analogue, inhibits cell proliferation and DNA synthesis in cells by inhibiting UMP synthase. Pyrazofurin is a sensitive orotate-phosphoribosyltransferase inhibitor (IC50s between 0.06-0.37 µM in the cell lines Hep-2,
GPI-15427 is a potent PARP-1 inhibitor capable of crossing the blood-brain barrier, which can significantly increased the antitumor activity of the methylating agent TMZ against malignant melanoma, glioblastoma multiforme, or lymphoma growing at the CNS site. GPI-15427 acts as a potent inhibitor of the enzyme, being capable of inhibiting the activity of purified PARP-1 at nanomolar concentrations. GPI-15427 induced significant sensitization to radiotherapy, representing a promising new treatment in the management of HNSCC.