The approval makes MyChoice CDx the sole FDA-approved test in the US to identify HRD-positive patients eligible for niraparib maintenance therapy.

Myriad Genetics has received Food and Drug Administration (FDA) approval of its MyChoice CDx Test as a companion diagnostic (CDx) for Zejula (niraparib), a PARP inhibitor developed by GSK, for patients with advanced ovarian cancer. The approval, announced March 17, 2026, establishes MyChoice CDx as the only FDA-approved companion diagnostic for Zejula in the US, according to a release from Myriad Genetics.

The approval is based on final data from the PRIMA trial, in which the MyChoice CDx Test was used to determine homologous recombination deficiency (HRD) status and stratify patients with advanced ovarian cancer.

How the Test Works

MyChoice CDx identifies patients with HRD-positive (HRD+) status by leveraging next-generation sequencing (NGS) technology to assess BRCA1/2 genes—including large rearrangements—alongside a tumor genomic instability score (GIS). The GIS incorporates three genomic signatures: loss of heterozygosity, telomeric allelic imbalance, and large-scale state transitions.

Zejula is indicated as a maintenance treatment for adult patients with advanced epithelial ovarian, fallopian tube, or primary peritoneal cancer whose cancer is associated with HRD+ status, defined by a deleterious or suspected deleterious BRCA mutation and/or genomic instability, following a complete or partial response to first-line platinum-based chemotherapy.

Clinical Significance of HRD Testing

According to Myriad Genetics, nearly 50% of patients with advanced ovarian cancer have HRD+ tumors, making accurate identification of this patient population critical for guiding appropriate use of PARP inhibitor therapy and informing personalized treatment decisions.

Best practices for HRD testing have been a growing focus in the clinical laboratory community, with guidance emphasizing the need for validated, standardized assays that can reliably assess tumor genomic instability alongside BRCA mutation status.

“By enabling precise identification of patients who may benefit from PARP inhibitors, MyChoice CDx helps ensure that treatment decisions are guided by robust genomic insights,” says Brian Donnelly, chief commercial officer, Myriad Genetics, in a release.

Expanding the MyChoice CDx Footprint

This is not the first FDA approval for the MyChoice CDx platform in the companion diagnostic space. The test was previously approved as a companion diagnostic for Lynparza (olaparib), and an earlier iteration of the MyChoice test was approved to identify patients eligible for Zejula treatment. The current approval is based on final PRIMA trial data and expands the test’s regulatory standing for the niraparib indication.

Myriad has also pursued a broader strategic partnership with Illumina in oncology and, more recently, partnered with SOPHiA GENETICS on a global liquid biopsy companion diagnostic, reflecting the company’s continued investment in molecular diagnostics across oncology.

“The FDA approval reinforces Myriad’s long-standing leadership in ovarian cancer diagnostics and underscores the clinical importance of comprehensive HRD testing,” says Donnelly, in a release.

The latest approval adds to a broader landscape of companion diagnostic development in oncology, where NGS-based assays are increasingly being used to match patients with targeted therapies. Research has also explored whole-genome sequencing algorithms for PARP inhibitor selection, indicating that the field continues to investigate broader genomic approaches to treatment stratification.

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