PARP Inhibitors

PARP inhibitors are a class of medicines used in select patients with advanced prostate cancer. Patients are eligible for therapy if they have changes (alterations) in certain genes involved in DNA repair. These “DNA damage repair” (DDR) genes include the prostate, breast, and ovarian cancer risk genes BRCA1 and BRCA2, as well as others. PARP inhibitors currently FDA-approved for metastatic castration-resistant prostate cancer (mCRPC) are: olaparib (Lynparza®), rucaparib (Rubraca®), talazoparib (Talzenna®; in combination with enzalutamide) and niraparib (in combination with abiraterone as Akeega®). In 2025, the combination of niraparib and abiraterone (plus prednisone) was approved for patients with metastatic hormone-sensitive prostate cancer and an alteration in the BRCA2 gene.

There are some differences in the use of each drug, such as the specific gene alterations used to select patients, how they may be combined with androgen receptor pathway inhibitors, and when they can be given in the course of advanced prostate cancer. Potentially serious side effects include bone marrow problems, lung inflammation (pneumonitis), and blood clots.

A sizable proportion of patients with metastatic prostate cancer have these gene alterations and thus may be candidates for treatment with PARP inhibitors: Up to 25%–30% have these alterations (inherited or acquired) in their tumor tissue, and about 12% have inherited DDR alterations in the DNA they got from their parents. Cancer cells that already have alterations in BRCA1, BRCA2, or other DDR genes will instead rely on the repair protein called PARP. Blocking PARP with a medication makes the cancer cells unable to repair themselves, and results in cancer cell death. In practice, not all patients will respond to these medications, and response may be linked to the specific type of DDR gene alteration.

Patients with metastatic prostate cancer should strongly consider getting two types of testing: germline genetic testing and somatic testing for specific gene changes. Testing will give you the most complete understanding of your treatment options, including whether you may benefit from PARP inhibitors. Testing may also show whether you carry a genetic alteration that could increase family members’ risk for prostate or other cancers. This information can help you and your family create a plan for cancer prevention and earlier detection. Learn more.

If you have a family history of prostate, breast, ovarian, pancreatic or other cancers, it is important to talk to your doctor about genetic counseling and testing, for you and family members.

Last Reviewed: 12/2025