IND 205B: A phase II study of the PI3K inhibitor PX-866 and continued abiraterone/prednisone in patients with recurrent or metastatic castration resistant prostate cancer (CRPC) with PSA progression on abiraterone/prednisone.

279 Background: PX-866 is an irreversible, pan-isoform inhibitor of Class I PI-3K. In part A of this study, PX-866 as a single agent was well tolerated and showed modest activity in CRPC but did not meet a priori benchmarks as a single agent in unselected patients (pts). As androgen receptor inhibition promotes PI3K activity in PTEN-loss PC models, the addition of PX-866 in patients whose PSA is rising on abiraterone acetate …