PARP Inhibitors: Targeted Therapy for BRCA-Related Cancers

Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 2026

PARP inhibitors are a class of targeted therapy drugs used to treat cancers often linked to BRCA gene mutations, such as breast and ovarian cancer. They block the PARP protein, which prevents cancer cells from repairing their damaged DNA and ultimately leads to cell death. Given as daily pills, they can extend survival and improve progression-free survival. They can cause side effects such as fatigue and nausea, and some cancers eventually develop resistance [1].

Quick Answer: What are PARP inhibitors?

PARP inhibitors are targeted cancer treatments that block PARP, a protein cancer cells use to repair damaged DNA, causing the cells to die. They work best in cancers with BRCA mutations and are used for advanced breast, ovarian, prostate and pancreatic cancers. Taken by mouth, they are not a cure but can slow progression. Side effects include fatigue and anemia. [1] [2] [3] [4]

What the research says

• Maintenance olaparib improved long-term survival in BRCA-mutated ovarian cancer. In the SOLO1 trial, 391 women with newly diagnosed advanced ovarian cancer and a BRCA mutation took olaparib (260 women) or placebo (131 women) for up to 2 years. After about 7 years of follow-up, the hazard ratio for death was 0.55 (95% CI, 0.40 to 0.76), and 67.0% of women in the olaparib group were alive versus 46.5% in the placebo group. The authors described the improvement as clinically meaningful but not statistically significant by the prespecified criteria, and reported no new safety signals (DiSilvestro et al., J Clin Oncol, 2023).

• Olaparib after chemotherapy reduced recurrence in high-risk early breast cancer. In the OlympiA trial of 1,836 patients with HER2-negative early breast cancer and a germline BRCA1 or BRCA2 variant, 1 year of olaparib raised 3-year invasive disease-free survival to 85.9%, compared with 77.1% on placebo (difference 8.8 percentage points; hazard ratio 0.58). Distant disease-free survival at 3 years was 87.5% versus 80.4% (Tutt et al., N Engl J Med, 2021).

• Side effects are common, mostly blood-related and digestive. A meta-analysis of 27 randomized trials with 9,542 patients found that olaparib-containing treatment raised the risk of any-grade adverse events (relative risk 1.08; 95% CI, 1.03 to 1.13) and high-grade events (RR 1.45; 95% CI, 1.19 to 1.77), and increased the risk of dose reduction (RR 3.00) and stopping treatment (RR 2.00). Anemia, nausea, and fatigue were the most frequent events (Jin et al., Eur J Clin Pharmacol, 2025).

Research summaries are based on article abstracts retrieved from PubMed.

How do PARP inhibitors work?

The primary mechanism of a PARP inhibitor involves "synthetic lethality." In a healthy body, the PARP protein helps repair damaged DNA. When this protein is blocked by an inhibitor, that damage builds up, and the small breaks turn into more severe double-strand breaks during cell division. For cancer cells that already have a broken repair system, such as those with a BRCA1 or BRCA2 mutation, this additional damage is catastrophic and leads to cell death [1].

What conditions do PARP inhibitors treat, and which types are approved?

Healthcare providers use PARP inhibitors most often for cancers that have spread or reached an advanced stage, including breast, ovarian, fallopian tube, prostate, primary peritoneal, and pancreatic cancers [1]. The FDA and EMA have approved several drugs within this class, each tailored to different diagnostic needs.

Drug Name	Brand Name	Primary Applications
Olaparib	Lynparza	Breast, ovarian, prostate, and pancreatic cancers
Niraparib	Zejula	Ovarian, fallopian tube, and peritoneal cancers
Rucaparib	Rubraca	Ovarian and prostate cancers
Talazoparib	Talzenna	Breast and prostate cancers

These medications are most effective against cancers involving BRCA gene mutations. The BRCA genes normally help prevent tumor growth and repair damaged DNA, so when they are mutated, a key part of the cell's repair system is broken, making the cancer highly susceptible to PARP inhibition [1]. Which drug is used depends on the cancer type, its genetic profile, and approvals in your country, so your oncology team will guide the choice.

What can you expect during treatment with PARP inhibitors?

PARP inhibitors are convenient compared with many other cancer therapies because they are taken by mouth. Patients take a capsule or tablet once or twice every day. Depending on the specific case, this may be the only treatment needed, or it may be used as maintenance therapy after chemotherapy or radiation, which damage cancer cell DNA, to help keep that damage in place so the cells die [1].

The duration of treatment varies significantly. Some patients follow a defined timeline, such as two to three years after chemotherapy, while others continue the medication for as long as it keeps working. Over time, about 40% to 70% of cancers develop resistance to the drug, which requires a change in the treatment plan [1].

What are the benefits and success rates of PARP inhibitors?

PARP inhibitors are not a cure, but they are effective at improving the "progression-free survival rate." This measures how long a person lives without the cancer getting worse. Depending on the diagnosis, they can provide benefits similar to standard chemotherapy and, in some cases, more effective ones, and they are sometimes used together with chemotherapy to improve response [1]. In clinical trials, olaparib has been linked to longer survival without recurrence in selected patients with BRCA-mutated ovarian and breast cancer [2] [3].

What are the possible side effects and risks of PARP inhibitors?

Like all potent medical treatments, PARP inhibitors carry risks. Most side effects are manageable, but they require close monitoring by a healthcare team [1] [4].

• Blood-related issues: Fatigue is common and is often a sign of anemia. Low platelet counts can lead to bleeding problems, while low white blood cell counts increase the risk of infection [1].

• Digestive distress: Patients frequently report nausea, vomiting, abdominal pain, diarrhea, or constipation [1].

• General physical changes: These may include headaches, dizziness, unexplained weight loss, and changes in the sense of taste (dysgeusia) [1].

• Rare complications: Some PARP inhibitors may increase the risk of acute myeloid leukemia, but this is rare. Blood clots in the legs or lungs are also a warning sign to report right away [1].

When should you contact your doctor while taking PARP inhibitors?

Patients should keep open communication with their oncology team. Always report new or worsening side effects, because dose adjustments can often ease them and supportive medicines can be prescribed for symptoms such as nausea. Seek immediate medical attention if signs of infection (fever or chills), pneumonitis (shortness of breath or wheezing), or blood clots in the legs or lungs appear [1].

Conclusion and Next Steps

PARP inhibitors have changed the treatment landscape for BRCA-related cancers. By exploiting the genetic flaws of cancer cells, they offer a path to longer disease control and, for some people, longer survival. If you have been diagnosed with a BRCA-mutated cancer, speak with your specialist about whether a PARP inhibitor is a suitable part of your treatment plan [1].

Frequently Asked Questions

What are PARP inhibitors?

PARP inhibitors are targeted cancer treatments that block poly (ADP-ribose) polymerase, a protein essential for DNA repair. By preventing cancer cells from fixing genetic damage, these drugs cause the cells to die, especially in patients with BRCA gene mutations.

How do PARP inhibitors work?

PARP inhibitors work through "synthetic lethality" by blocking the PARP protein from repairing DNA breaks. In cancer cells that already have faulty repair systems (like BRCA mutations), this causes catastrophic DNA damage and cell death.

Which cancers do PARP inhibitors treat?

PARP inhibitors are most commonly used to treat advanced or metastatic breast, ovarian, fallopian tube, prostate, primary peritoneal, and pancreatic cancers, particularly those with BRCA mutations.

What are the common brand names for PARP inhibitors?

FDA-approved PARP inhibitors include olaparib (Lynparza), niraparib (Zejula), rucaparib (Rubraca), and talazoparib (Talzenna).

How is this treatment administered?

PARP inhibitors are taken orally in pill form, either as a capsule or a tablet, typically once or twice per day.

Can PARP inhibitors cure cancer?

No, they are not a cure, but they help many people live longer by improving the progression-free survival rate and keeping the cancer from worsening.

What are the most common side effects?

Common side effects include fatigue, nausea, vomiting, diarrhea, anemia, low white blood cell counts, and changes in the sense of taste.

Do cancers become resistant to PARP inhibitors?

Yes, approximately 40% to 70% of cancers eventually develop resistance to these inhibitors, at which point the healthcare provider will adjust the treatment plan.

When should I call my doctor immediately?

Contact your provider immediately if you show signs of infection (fever or chills), pneumonitis (shortness of breath), or blood clots in your legs or lungs.

Can PARP inhibitors be used with other treatments?

Yes, they are often used in combination with or following chemotherapy and radiation therapy to increase the overall effectiveness of the treatment.

Related Resources

External resource for deeper reading:

• Cleveland Clinic: PARP Inhibitors

Related Reading

BRCA Testing: Who Should Get It, How It Works and What Results Mean explains genetic testing for BRCA changes and what results mean.

Ovarian Cancer: Symptoms, Causes, and Treatment — A Clear Guide to Understanding and Managing the Disease covers ovarian cancer symptoms, staging and treatment options.

Targeted Therapy for Cancer: How It Works, Types, Side Effects and Outlook explains how targeted cancer drugs work and their side effects.

Triple-Negative Breast Cancer (TNBC): Symptoms, Causes, Diagnosis and Treatment — What You Need to Know describes a breast cancer type often linked to BRCA changes.

References

1. Cleveland Clinic. PARP Inhibitors. Cleveland Clinic Health Library. Last updated January 20, 2025. https://my.clevelandclinic.org/health/treatments/parp-inhibitors

2. DiSilvestro P, Banerjee S, Colombo N, et al. Overall survival with maintenance olaparib at a 7-year follow-up in patients with newly diagnosed advanced ovarian cancer and a BRCA mutation: the SOLO1/GOG 3004 trial. J Clin Oncol. 2023;41(3):609-617. PMID: 36082969. DOI: 10.1200/JCO.22.01549

3. Tutt ANJ, Garber JE, Kaufman B, et al. Adjuvant olaparib for patients with BRCA1- or BRCA2-mutated breast cancer. N Engl J Med. 2021;384(25):2394-2405. PMID: 34081848. DOI: 10.1056/NEJMoa2105215

4. Jin W, Yang Q, Zhang Z, et al. Olaparib-associated toxicity in cancer patients: a systematic review and meta-analysis. Eur J Clin Pharmacol. 2025;81(1):65-81. PMID: 39499282. DOI: 10.1007/s00228-024-03771-w

Medical disclaimer

This article is for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have about a medical condition.