Niraparib, sold under the brand name Zejula, is an anti-cancer medication used for the treatment of epithelial ovarian, fallopian tube, or primary peritoneal cancer. It is taken by mouth. It is a PARP inhibitor. The most common side effects include nausea (feeling sick), thrombocytopenia (low blood platelet counts), tiredness and weakness, anemia (low red blood cell counts), constipation, vomiting, abdominal (belly) pain, neutropenia (low levels of neutrophils, a type of white blood cell), insomnia (difficulty sleeping), headache, lack of appetite, diarrhea, dyspnea (difficulty breathing), hypertension (high blood pressure), back pain, dizziness, cough, joint pain, hot flushes and decrease in white blood cells. Niraparib was approved for medical use in the United States and in the European Union in 2017. Medical uses Niraparib is indicated for the maintenance treatment of adults with recurrent epithelial ovarian, fallopian tube, or primary peritoneal cancer who are in complete or partial response to platinum-based chemotherapy. In October 2019, the indication for niraparib was expanded to include people with advanced ovarian, fallopian tube, or primary peritoneal cancer treated with three or more prior chemotherapy regimens and whose cancer is associated with homologous recombination deficiency (HRD)-positive status. HRD is defined by either a deleterious or suspected deleterious BRCA mutation, or genomic instability in patients with disease progression greater than six months after response to the last platinum-based chemotherapy. In April 2020, the indication for niraparib was expanded to include the maintenance treatment of adults with advanced epithelial ovarian, fallopian tube, or primary peritoneal cancer who are in a complete or partial response to first-line platinum-based chemotherapy. In the European Union, niraparib is indicated: as monotherapy for the maintenance treatment of adults with advanced epithelial (FIGO Stages III and IV) high-grade ovarian, fallopian tube or primary peritoneal cancer who are in response (complete or partial) following completion of first-line platinum-based chemotherapy; and as monotherapy for the maintenance treatment of adults with platinum sensitive relapsed high grade serous epithelial ovarian, fallopian tube, or primary peritoneal cancer who are in response (complete or partial) to platinum based chemotherapy. Contraindications No contraindications are listed in the prescribing information. Side effects The most common side effects in studies were low blood cell counts, namely thrombocytopenia (in 61% of patients, severe in 29%), anemia (in 50%, severe in 25%) and neutropenia (in 30%, severe in 20%). Other, mostly mild to moderate side effects included nausea, fatigue, and constipation. In a study running over