Dana E. Rathkopf, MD
A number of clinical trials are seeking to identify beneficial therapeutic outcomes in patients with prostate cancer who are resistant to androgen receptor (AR)¬–targeted agents.
First, abiraterone acetate (Zytiga) is being tested in combination with the PARP inhibitor veliparib in a randomized phase II trial of patients with metastatic castration-resistant prostate cancer (mCRPC) who progress on androgen-deprivation therapy (ADT; NCT01576172).
Immunotherapy is also being explored here, too. Results of a phase II study, presented at the 2016 ESMO Congress, showed that the addition of the PD-L1 inhibitor pembrolizumab (Keytruda) to enzalutamide (Xtandi) in patients with mCRPC progressing on the AR-directed therapy may be associated with durable responses.1
Out of the 20 enrolled patients, 4 achieved a confirmed prostate-specific antigen (PSA) reduction ≥50% and remained progression-free after 16 to 61 weeks. Additionally, 2 of the 4 PSA responders had measurable disease in the liver and lymph nodes and are evaluable for objective response; both achieved a partial response.