The ZEST Study for Patients with HER2 Negative or Triple Negative Breast Cancer

Clinical Trial Title

Randomized phase 3 double-blinded study comparing the efficacy and safety of niraparib to placebo in participants with either HER2-negative BRCA-mutated or triple-negative breast cancer

National Clinical Trial Number:


Contact Information

Rush Cancer Center Clinical Trials Office

Clinical Trial Protocol Description:

The purpose of this study is to evaluate if niraparib will help patients delay or prevent their breast cancer from returning. The study is also looking to answer the following questions:

  • Is niraparib safe and effective to treat people with different types of breast cancer?
  • How well does niraparib work to treat people who have had a blood test that shows small amounts of breast cancer DNA in their bloodstream (circulating tumor DNA, called ctDNA)?

While niraparib is approved for use in people with other types of cancer, niraparib is not yet approved for use in people with breast cancer. For this study, niraparib is considered an investigational medicine. “Investigational” means that it is not approved by the U.S. Food and Drug Administration (FDA) and it must be tested to see if it is a safe an effective treatment for the disease or condition being studied.

If you agree to participate in this study, your participation may last up to 10 years and you will receive the study drug for up to 3 years and may have the option to continue study drug after that time. After you stop treatment, you will be contacted by scheduled phone calls until the study has completed (every 3 months for the first 2 years, then every 6 months after that).

About 800 participants are expected to take part in this global study. About 10 participants are expected to enroll at Rush University Medical Center.

More information can be found on and can be found by searching for the following Clinical Trial Registry Number (NCT#): NCT04915755

Clinical Trial Eligibility Criteria:

In order to participate you must meet the following criteria:

  • Stage I to III breast cancer with surgical resection of the primary tumor that is confirmed to be either: TNBC, irrespective of BRCA status or HR+/HER2- breast cancer with a known and documented tBRCA mutation.
  • Completed prior standard therapy for curative intent including all of the following, if indicated: neoadjuvant treatment, surgery, adjuvant radiotherapy and adjuvant chemotherapy.
  • Participants with HR+ breast cancer must be on a stable regimen of endocrine therapy, if indicated, for at least 3 months prior to enrollment. Ovarian suppression, if indicated, must also have been started at least 3 months prior to enrollment.
  • Detectable ctDNA as measured by central Signatera testing.

You will be excluded from the study if any of the following criteria apply to you:

  • Prior treatment with a Poly Adenosine-diphosphate Ribose Polymerase (PARP) inhibitor.
  • Current treatment with a Cyclin-dependent kinase (CDK)4/6 inhibitor or endocrine therapy other than anastrozole, letrozole, exemestane and tamoxifen.
  • Participants have any sign of metastasis or local recurrence after comprehensive assessment conducted per protocol.
  • Participants have shown no definitive response to preoperative chemotherapy by pathologic or radiographic evaluation, in cases where preoperative chemotherapy was administered.

This is a partial list of inclusion and exclusion criteria.

Study Details

Clinical Trial Investigator

Lydia Usha, MD

Contact Information

Rush Cancer Center Clinical Trials Office

Clinical Trial Location

Rush University Cancer Center


Rush University Cancer Center

1725 W Harrison St
Professional Building - Suite 1010
Chicago, IL 60612

Get Directions

Clinical Trial FAQs

Find out if a clinical trial makes sense for you.

Learn more
Learn more