Characterization of immune-related adverse events (irAEs) in a phase 3 trial of ipilimumab (Ipi) versus placebo (Pbo) in post-docetaxel mCRPC.

Abstract

52 Background: Ipi enhances antitumor immunity by blocking cytotoxic T-lymphocyte antigen-4. We recently reported the results of CA184-043, a phase 3 study of post-docetaxel mCRPC with Ipi vs Pbo, following single-dose radiotherapy (RT). While the study did not meet the primary endpoint of improving overall survival (HR=0.85, p=0.053), Ipi demonstrated antitumor activity in other efficacy endpoints, including progression-free survival. The present analyses further characterize the safety profile of Ipi in this study. Methods: Safety was evaluated for all treated patients (pts; N=393 for Ipi 10 mg/kg, N=396 for Pbo) starting from first study dose and ending 70 days after the last study dose, including maintenance dosing. Results: Any grade (Gr) irAEs occurred in 63.4% and 21.7% of pts in the Ipi and Pbo arms, respectively. Most common Gr 3/4 irAEs were gastrointestinal (GI) (18.1%; mostly diarrhea and colitis). Gr 3/4 liver irAEs (4.6%) were mostly elevations in AST or ALT. Other Gr 3/4 irAEs were uncommon: endocrine (2.0%), skin (1.0%), and neurological (0.3%). Among Ipi-treated pts, there were no meaningful differences in the frequency or severity of GI AEs between those who received baseline pelvic RT and those who did not (n=141 vs 252; any Gr 77.3% vs 69.8%; Gr 3/4 25.5% vs 21.8%, respectively). There were 5 GI perforations in the Ipi arm (3 within 70 days of last dose [2 related, 1 unrelated], 2 after 70 days of last dose, both related), and none in the Pbo arm. Deaths due to study drug toxicity, as per the investigators, occurred in 4 pts (4, Ipi and 0, Pbo). Conclusions: In this study of Ipi in mCRPC, the most frequent severe irAEs were diarrhea and colitis. Most irAEs were manageable using established treatment algorithms. Clinical trial information: NCT00861614. [Table: see text]