Tesaro Cancer Drug’s Results May Challenge Need for Myriad Test

  • Drugmaker says patients negative for test saw clinical benefit
  • Companion test maker disagrees, says benefit not meaningful

Trial results from Tesaro Inc.’s experimental drug for ovarian cancer may challenge the need for a companion test made by Myriad Genetics Inc., because patients who tested negative and would have been screened out appeared to benefit from the treatment.

Myriad’s test, called myChoice HRD, looks for a biomarker that’s linked to better outcomes from treatments like Tesaro’s. Yet the drug, niraparib, helped a group of HRD-negative patients live 3.1 months longer without their disease worsening compared to those taking a placebo, according to data presented Saturday at the European Society for Medical Oncology meeting in Copenhagen.

The companies are disagreeing on whether the 3.1-month benefit is enough to justify using the drug in patients. While gains for these patients were much smaller than the 9.1-month benefit seen in similar patients who were positive on Myriad’s HRD test, it’s still “clinically meaningful,” said Lonnie Moulder, Tesaro’s chief executive officer, in an interview.

One-fifth of the HRD-negative patients were still without worsening of their disease 18 months into treatment with niraparib, Moulder said. He declined to say whether Tesaro would seek broad regulatory approval from the U.S. Food and Drug Administration, regardless of a patient’s biomarker status. If it does, Myriad’s test might not be necessary for patients to receive the drug.

The study looked at patients both with and without mutations in BRCA genes that are associated with breast and ovarian cancer.

Patient TypeProgression-Free Survival Benefit
all BRCA+15.5 months
BRCA-, HRD+9.1 months
BRCA-, HRD-3.1 months

Myriad’s chief medical officer, Johnathan Lancaster, disagreed with Moulder, saying in a phone interview that the benefit in HRD-negative patients wasn’t clinically significant. He also pointed out that the FDA didn’t approve AstraZeneca Plc’s competing drug Lynparza in patients who were negative for BRCA, even though the company saw a 3.6-month benefit across all patients in a study, including those who tested positive and negative. Myriad makes a companion diagnostic test for Lynparza.

Questions on the need for tests that accompany specific drugs may increase as drugmakers develop more treatments that target certain genetic mutations or biological markers. This approach to treatment, often referred to as “precision medicine” has given diagnostic test makers an opportunity to create a market by steering patients to the correct medications.

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