Study of TRC105 With Abiraterone and With Enzalutamide in Prostate Cancer Patients Progressing on Therapy

This is a Phase II, open-label study of TRC105 (anti-endoglin antibody) in combination with abiraterone or enzalutamide in metastatic, castration-resistant prostate cancer patients who are taking either abiraterone or enzalutamide and showing signs of biochemical progression without radiographic progression. A patient who is progressing on AR-therapy will continue the same AR-therapy on study with the addition of TRC105. The two arms will accrue in parallel and independently. There will be a 2-week washout of the active AR-targeted therapy prior to initiation of combination therapy. Tumor response should be assessed at a frequency of 8 weeks by CT/MRI chest, abdomen and pelvis as well as bone scan. Patients may continue on therapy until radiographic progression by RECIST 1.1 or PCWG3 criteria.