Clinical Cases in Advanced Prostate Cancer - Episode 16

Case 2: The TRITON2 Trial for Rucaparib in Metastatic CRPC

Mary-Ellen Taplin, MD, presents data from the phase 2 TRITON2 trial of rucaparib in metastatic castration-resistant prostate cancer.

Mary-Ellen Taplin, MD: Next, I’d like to share some data from the TRITON trial. This is a trial of rucaparib, which is another PARP inhibitor. This is phase 2 of the TRITON trial. There’s a phase 3 TRITON, which is a randomized trial that has ongoing accrual. These data were presented at ESMO [European Society for Medical Oncology Congress] and subsequently published. How it differs from the PROfound trial is these patients were post-ABI [abiraterone acetate] or ENZA [enzalutamide] but also post-docetaxel chemotherapy. They all received rucaparib, and the primary end point was progression-free survival.

Here is a summary of the patients who had either germline or somatic BRCA1 or BRCA2 mutations. We know that BRCA2 is much more common in prostate cancer than BRCA1. Here’s also a breakdown of whether they’re biallelic or monoallelic. The significance of that is the patients with biallelic mutations tend to have longer responses to drugs such as PARP inhibitors. I’d also like to note that because the percentage of these mutations is around 20% in the population, it required quite a large number of screening to get the patients filled in to the study. Here are the data in terms of overall response rate and PSA [prostate-specific antigen] response rate for the patients, specifically with the BRCA1 and the BRCA2. There was an overall response rate of 43% with a centrally reviewed target lesion and PSA response rate of close to 55%.

Here is a summary of some treatment-related adverse events. It’s not insignificant with these medications to have to delay dose or reduce dose, again primarily because of bone marrow or some GI [gastrointestinal] toxicity. These are treatment-related events that we’ve come to expect with these medications, and here listed in more detail are the percentage with some fatigue, nausea, and other adverse effects.

Similarly to olaparib, the FDA granted approval for rucaparib for BRCA-mutated metastatic castration-resistant prostate cancer that has been treated with a prior second-generation androgen axis inhibitor and taxane-based chemotherapy.

Transcript edited for clarity.