LAUSR

146Background: Heat Shock Protein 27 (Hsp27) is a multi-functional chaperone that regulates cell signaling and survival pathways implicated in cancer progression. In prostate cancer models, Hsp27 chaperones androgen receptor (AR) and enhances transactivation of AR-regulated genes. Apatorsen is a 2nd generation antisense that inhibits Hsp27 expression with clinical activity demonstrated in pts with mCRPC. Methods: mCRPC patients with PSA-only progression on ABI + prednisone (P) 10-20 mg daily were randomized to continuing ABI + P (Control Arm) or ABI + P with Apatorsen 600 mg IV x 3 loading doses then 800 mg IV weekly (Study Arm). Control Arm pts could cross over to receive apatorsen at time of progression. Primary endpoint was the proportion of pts progression free (PSA, clinical and radiologic) at day 60. Assuming a 25% increase in proportion of pts progression free and a null hypothesis of 5%, the planned sample size was 74 patients (type I error 20%, type II error 10%). Results: 72 pts were randomized:...