Additional Relevant Details Niraparib, formerly known as MK-4827, is an orally active and potent poly (ADP-ribose) polymerase, or PARP, inhibitor. A Phase 1/2 monotherapy study has been completed in more than 100 patients with advanced solid tumors. Based upon the results of the Phase 1/2 study and published data from other trials of PARP inhibitors, TESARO is evaluating niraparib at a dose of 300 milligrams once daily in two Phase 3 studies.