Rubraca Lengthens Time to Progression in Metastatic Prostate Cancer

Rubraca (rucaparib) lengthened time to disease progression in patients with metastatic castration-resistant prostate cancer compared to standard of care, according to recently released findings from the phase 3 TRITON3 clinical trial.

TRITON3 involved 405 patients with BRCA- or ATM-mutant metastatic castration-resistant prostate cancer that had not been treated with chemotherapy. Patients were randomly assigned to receive Rubraca or a physician’s choice of docetaxel, abiraterone acetate or Xtandi (enzalutamide).

Of note, Rubraca bested the other treatments in radiographic progression-free survival (time from treatment until progression is detected on a CT or bone scan) for patients with BRCA mutations as well as those with ATM mutations, according to Clovis Oncology, the manufacturer of Rubraca, a PARP inhibitor.

Among trial participants with a BRCA mutation, average radiographic progression-free survival was 11.2 months in the Rubraca group and 6.4 months in the chemotherapy or androgen deprivation group. For the entire study population (which included patients with BRCA and/or ATM mutations), the average radiographic progression-free survival was 10.2 months and 6.4 months in the Rubraca and standard-of-care groups, respectively.

“Not only does this provide a potential treatment option for eligible men with earlier stage disease, but it is the first and only PARP inhibitor that has demonstrated superior radiographic (progression-free survival) compared to chemotherapy, which is today the standard of care for these patients,” said Patrick J. Mahaffy, the president and CEO of Clovis Oncology, in a press release.

Side effects for Rubraca were similar to those previously observed with the drug. The most common severe side effects were decreased hemoglobin (anemia); decreased levels of neutrophils, a type of white blood cell; fatigue; decreased platelet count; and increased liver enzymes, which could indicate liver damage.

A total of 14.8% of patients stopped treatment with Rubraca due to side effects, compared to 21.5% in the control group.

Clovis Oncology plans on submitting a supplemental New Drug Application to the Food and Drug Administration (FDA) for Rubraca to be approved for patients with BRCA-mutant metastatic castration-resistant prostate cancer.

In 2020, the FDA approved Rubraca to treat men who have metastatic, treatment-resistant prostate cancer that expresses a BRCA gene mutation and has previously been treated with hormonal therapy and a taxane-based chemotherapy.

“Men with this type of metastatic prostate cancer want to get their genetically targeted therapy as early as possible, and this trial clearly shows the value of rucaparib as a treatment for these men,” said Dr. Alan H. Bryce, chair of the Division of Hematology and Medical Oncology at the Mayo Clinic in Rochester, Minnesota, and principal investigator of the TRITON3 trial.

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