What Are PARP Inhibitors and How Are They Used for Ovarian Cancer?

Drugs known as PARP inhibitors are a form of targeted therapy to treat cancer. They are mainly used to treat ovarian, fallopian tube, and peritoneal cancers. They are also being tested in clinical trials as a form of treatment option in other cancers.^1-3

How do PARP inhibitors work?

PARP stands for poly adenosine diphosphate-ribose polymerase. It is an enzyme that is found in human cells. Its job is to repair damaged cells. But in people with cancer, their cells are damaged and have a hard time repairing themselves.¹

PARP inhibitors work on a genetic level within human cells by blocking PARP from doing this repair work. This stops the cancerous cells from trying to repair themselves, which causes them to die.¹

Who benefits from PARP inhibitors?

People who have a mutation in the BRCA1 or BRCA2 genes respond well to targeted therapy with PARP inhibitors. BRCA gene mutations are the most common mutation linked to ovarian cancer. When there is a mutation in either BRCA gene, that puts a person at a greater risk of developing the following cancers:^4,5

• Breast cancer
• Ovarian cancer
• Prostate cancer

People with homologous recombination deficiency (HRD) are also good candidates for treatment with PARP inhibitors. HRD is a genetic condition in which cells cannot repair themselves. PARP inhibitors help prevent the abnormal cancer cells from repairing damaged strands of DNA.⁶

For these reasons, BRCA and HRD testing is becoming more common. It helps guide doctors when forming treatment plans.^4,6

But regardless of whether a person has a BRCA mutation or HRD, nearly all people with ovarian cancer are able to get PARP inhibitor treatment.³

How are PARP inhibitors used to treat ovarian cancer?

People diagnosed with ovarian cancer usually go through a first-line treatment of surgery and chemotherapy. PARP inhibitors are then used as a form of maintenance therapy to help prevent the cancer from coming back. This can help to prolong people’s lives.⁷

PARP inhibitors have been used as maintenance therapy to treat ovarian cancer since 2014. Research now shows that some PARP inhibitors may be used as a first-line therapy for those who are newly diagnosed with advanced ovarian cancer.^2,3

Types of PARP inhibitors

PARP inhibitors are taken in the form of a pill, usually once or twice a day. As of early 2021, the U.S. Food and Drug Administration (FDA) has approved 3 different PARP inhibitor drugs:⁷

• Lynparza® (olaparib)
• Rubraca® (rucaparib)
• Zejula (niraparib)

Some of these drugs are used on their own as maintenance therapy. Others are used in combination with other cancer-fighting drugs. The dosage and length of time you take them depends on the type of cancer you have and which drug you are taking.^7,8

What are the possible side effects of PARP inhibitors?

Side effects can vary depending on the specific drug you are taking. Some side effects may include:⁷

• Low red blood cell count (anemia), which can lead to feeling out of breath, feeling tired, and a greater risk of infection
• Fatigue
• Nausea
• Diarrhea
• Loss of appetite
• Heartburn
• Headaches and dizziness

If you do have any side effects of a PARP inhibitor, tell your doctor. They may be able to adjust the dosage to help reduce symptoms or get rid of them altogether.

An ovarian cancer diagnosis can take its toll, but there are treatment options available. Your doctor and healthcare team can help guide you in deciding if a PARP inhibitor is right for you. Together, you can develop the right treatment plan for you.