Health Canada recently approved Zytiga (abiraterone acetate) in combination with prednisone and androgen deprivation therapy (ADT) for the treatment of patients with newly diagnosed, high-risk metastatic hormone-sensitive prostate cancer (mHSPC) who may have previously received up to three months of ADT.
Janssen Pharmaceutical Companies of Johnson & Johnson announced the Canadian approval just one week after the U.S. Food and Drug Administration (FDA) approved Zytiga in the United States, following results of the Phase 3 LATITUDE trial (NCT01715285). That clinical trial showed that the combo therapy reduced the risk of death by 38 percent in newly diagnosed patients compared to placebo.
“Previously men with newly diagnosed metastatic prostate cancer have had limited options for first-line treatments,” Fred Saad, a LATITUDE clinical investigator, said in a press release. “This latest approval for Zytiga is an exciting milestone for men, their caregivers and treating clinicians as it provides a new first-line treatment option for high-risk metastatic hormone-sensitive prostate cancer that improves overall survival and quality of life.”
Zytiga blocks CYP17-mediated androgen production at three sources: in the testes, adrenal glands, and prostate tumor tissue. If left unchecked, androgen production can fuel the growth of prostate cancer.
Findings from the LATITUDE trial were published in The New England Journal of Medicine in a study titled, “Abiraterone plus Prednisone in Metastatic, Castration-Sensitive Prostate Cancer.”
In this study, researchers evaluated the clinical benefit of Zytiga plus prednisone with ADT in patients with newly-diagnosed mHSPC. A total of 1,199 patients were randomized into two groups: an active group in which patients received ADT plus Zytiga (at 1,000 mg daily, given in four 250 mg tablets) plus prednisone (5 mg daily), or the placebo group, in which patients received ADT plus dual placebos. The two primary endpoints were overall survival and radiographic progression-free survival.
After a median follow-up of 30.4 months, median overall survival was significantly longer in the active group than in the placebo group. Median radiographic progression-free survival — the time a patient went without disease progression as seen with radiographic imaging — was 33 months in the active group and 14.8 months in the placebo group.
All secondary endpoints achieved significantly better outcomes in the active group as well. Regarding side effects, rates of grade-3 hypertension and hypokalemia (low levels of potassium in the blood) were higher in the active group.
These results led to a unanimous recommendation by the independent data and safety monitoring committee that crossover be allowed for patients in the placebo group to receive Zytiga.
Overall, the researchers concluded that the addition of Zytiga and prednisone to ADT significantly increased overall survival and radiographic progression-free survival in men with newly diagnosed mHSPC.
Health Canada first approved Zytiga in 2011 to be used with prednisone for the treatment of metastatic castration-resistant prostate cancer (mCRPC) in patients who had undergone chemotherapy with docetaxel after the failure of ADT. In 2013, Zytiga was approved for the same patient population in cases that were asymptomatic or mildly symptomatic after failure of ADT.
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