PARP Inhibitors

What are PARP inhibitors?

A PARP inhibitor is a cancer treatment that blocks a protein your body makes called PARP. “PARP” is short for “poly (ADP-ribose) polymerase.” PARP has an important job. If the DNA in a cell gets damaged, PARP helps repair it. These repairs are essential because DNA contains the genetic material (genes) that tell your cells how to work properly.

But cancer cells can use PARP to repair their DNA, too. These repairs allow cancer to thrive and spread. But taking a PARP inhibitor prevents cancer cells from accessing this protein. Instead, the cells eventually die.

You may also hear your healthcare provider refer to a PARP inhibitor as a targeted therapy drug. These medications zero in on (target) weaknesses in cancer cells to destroy them. Depending on your diagnosis, they may help you live longer.

Types of PARP inhibitors

PARP inhibitors approved by the U.S. Food and Drug Administration (FDA) and European Medicines Agency (EMA) include:

• Olaparib (Lynparza^®)
• Niraparib (Zejula^®)
• Rucaparib (Rubraca^®)
• Talazoparib (Talzenna^®)

What conditions are treated with PARP inhibitors?

Healthcare providers most often use PARP inhibitors to treat advanced or metastatic cancer (cancer that’s spread). Cancers that PARP inhibitors treat include:

• Breast cancer
• Ovarian cancer
• Fallopian tube cancer
• Prostate cancer
• Primary peritoneal cancer
• Pancreatic cancer

PARP inhibitors are most effective at treating cancers that involve mutations in the BRCA gene. The BRCA gene prevents tumor growth. It also helps repair damaged DNA. On the other hand, having a mutation in this gene means you’re at increased risk of developing cancerous tumors. It also means that a key part of your DNA repair system is broken.

By blocking access to PARP, these drugs make it even harder for cancers that already have a faulty DNA repair system to thrive.

What happens during this treatment?

All PARP inhibitors come in pill form, as either a capsule or tablet. You’ll take them once or twice a day. Depending on the cancer and the type of PARP inhibitor, this may be the only treatment you need. Or you may need it in combination with other cancer treatments.

For example, you may take a PARP inhibitor after getting treatments that damage cancer cell DNA, like chemotherapy and radiation therapy. The PARP inhibitor ensures the damage stays so the cells die.

How long will I need this treatment?

Sometimes, PARP inhibitors are used for a defined period, like two to three years after completing chemotherapy. Other people take PARP inhibitors until the inhibitors stop working. Sometimes, people decide the disadvantages of taking a PARP inhibitor (like side effects) outweigh the benefits.

Discuss your timeline for taking this medication with your healthcare provider. They can help you weigh the pros and cons of potential treatment benefits versus the risks.

What are the potential benefits of PARP inhibitors?

PARP inhibitors can’t cure cancer. Still, they help some people living with certain cancers live longer. Depending on your diagnosis, they can provide benefits similar to more common cancer treatments, like chemotherapy. Sometimes, they’re even more effective. And sometimes, they’re used in combination with chemotherapy to increase your response to treatment and help you live longer.

How successful is this treatment?

PARP inhibitors are excellent at improving what healthcare providers call the “progression-free survival rate” associated with some cancers. This means that they can give you more days without the cancer getting worse.

But after a while, they often stop working. About 40% to 70% of people have cancers that eventually develop resistance to PARP inhibitors. Scientists are researching why this happens. They’re studying new ways to combine PARP inhibitors with other cancer therapies so they work longer.

What are the risks or complications of this treatment?

As with any cancer treatment, PARP inhibitors can cause unpleasant side effects, including:

• Fatigue (often a sign of anemia)
• Bleeding problems (a sign of low platelets)
• Infections (a sign of low white blood cells)
• Nausea and vomiting
• Abdominal pain
• Diarrhea and constipation
• Changes to your sense of taste (dysgeusia)
• Unexplained weight loss
• Dizziness
• Headaches

Some types of PARP inhibitors may increase your risk of developing acute myeloid leukemia, but this is rare.

Is there anything I can do to make this treatment easier on me?

It’s important to take advantage of every resource available to make living with cancer more manageable. This applies whether you’re taking a PARP inhibitor or if you’re getting a different treatment.

It’s especially important to know what side effects to look out for. This includes knowing which ones your healthcare provider needs to know about immediately. Your provider can explain what to expect.

When should I call my healthcare provider?

Always let your provider know if you notice new or worsening side effects. They may need to adjust your dose. And they may be able to prescribe medicines that can reduce common side effects like nausea.

Contact your provider immediately if you’re experiencing signs of:

• Infection (like fever or chills)
• Pneumonitis (like shortness of breath and wheezing)
• Blood clots in your legs or lungs