A randomised, double-blind, dose-finding, phase II multicentre study of ODX in the treatment of patients with castration-resistant prostate cancer and skeletal metastases

Abstract

Aims: This study aimed to assess the efficacy and safety of ODX, a novel, cytotoxic, bone-targeting drug candidate, in castration-resistant prostate cancer bone metastatic disease. Methods: Patients with progressive disease were randomised to ten cycles of ODX, intravenous infusion Q2W (3, 6, and 9 mg/kg, respectively). The primary objective was to assess the relative change from baseline in bone alkaline phosphatase (B-ALP) and serum-aminoterminal-propeptide of Type I procollagen (S-P1NP) at 12 weeks. The inclusion criteria selected were broad, and a double-blind design was used to ensure objective recruitment of patients for the assessment of efficacy. None of the patients received bone-protecting agents during the ODX treatment period. Results: Fifty-five 21,20 and 14) patients were randomised to ODX (3, 6 and 9 mg/kg), respectively. The lower number of patients in arm 3 was due to too low a recruitment rate towards the end of the study. The median treatment time were 14, 13 and 14 weeks, respectively. The decrease in B-ALP at 12 weeks in study arms 3, 6 and 9 mg/kg was seen in 6/15 (40%), 8/12 (67%) and 5/12 (42%) patients, respectively, whereas the corresponding numbers for P1NP were 8/15 (53%), 8/12 (67%), and 4/12 (33%), respectively. The median decrease in B-ALP and P1NP at 12 weeks for study arms 3, 6 and 9 mg/kg were 37%, 14% and 43%, respectively, and 51%, 40% and 64%, respectively. The decrease in serum C-terminal telopeptide at 12 weeks was seen in the vast majority of patients and in about one-third of patients in bone scan index. ODX was well tolerated, and no drug-related serious adverse events occurred. There were no significant differences between study arms regarding efficacy and safety. Conclusions: ODX was well tolerated and demonstrated inhibitory effects on markers related to the vicious cycle in bone at all three doses. The reduction in metastatic burden, assessed with bone scan index, supports this finding. Studies with continued ODX treatment until disease progression are being planned (ClinicalTrials.gov Identifier: NCT02825628).