A Randomized Phase Ii Trial Of Sipuleucel-T With Concurrent Or Sequential Abiraterone Acetate (Aa) Plus Prednisone (P) In Metastatic Castrate-Resistant Prostate Cancer (Mcrpc).

5047^ Background: Sipuleucel-T and AA + P are FDA-approved for asymptomatic/minimally symptomatic mCRPC. Suppression of the androgen axis can be immunostimulatory and AA suppresses circulating androgen levels; AA plus sipuleucel-T may therefore be synergistic. However P used with AA, which may be immunosuppressive, has not been studied with concurrent sipuleucelET and could impair sipuleucel-T production and/or immunologic response. P11-3 (NCT01487863) is the 1st study to evaluate the combination of sipuleucel-T and AA + P Methods: Patients (pts) with asymptomatic/minimally symptomatic mCRPC were randomized (1:1) to sipuleucel-T (3 infusions at approx 2-wk intervals) with up to 26 wks of AA + P (AA 1000mg QD + P 5mg BID) starting 1 day after the 1st sipuleucel-T infusion (concurrent, arm A) or at 10 wks following the 1st sipuleucel-T infusion (sequential, arm B). Endpoints included the effect of AA + P on product (sipuleucel-T) characteristics eg antigen presenting cell (APC) activation, measured as CD54 ...