Phase II trial of panobinostat (LBH589) in patients (pts) with refractory metastatic colorectal cancer (MCRC).

Abstract

582 Background: LBH589 is a novel histone deacetylase inhibitor (HDACi) which induces apoptosis of tumor cells. LBH589 has been shown to cause regression of colon cancer in animal models and phase I trials have shown the agent to be well tolerated, providing rationale for studying this agent in pts with MCRC. Methods: This was a multicenter, open-label phase II study of single agent LBH589 in patients with MCRC who failed at least 2 prior regimens for metastatic disease. Measurable disease, adequate organ function and ECOG performance status of 0-2 were required. Pts received LBH589 30mg po on M/W/F until disease progression. Pts were evaluated for toxicity every 2 weeks and for response every 8 weeks. The primary endpoint was overall survival. Secondary endpoints included response rate, time to progression (TTP), and toxicity. Results: 29 pts were enrolled (16 male, 13 female). The median age was 59 (range 41-76). The median number of prior treatment regimes was 3 (2-11). The median survival was 5.1 months (range 1-24+). There were no objective responses. 3 pts had SD at 8 weeks. The median TTP was 7.7 weeks (range 1-38.). Six pts had grade 4 thrombocytopenia requiring platelet transfusion. Nine pts required dose reductions for toxicity. Conclusions: Single-agent LBH589 was not associated with objective tumor responses in this heavily pre-treated pt population. However, the median survival was comparable to that seen in other trials of single agent targeted therapy in the treatment of refractory MCRC. Thrombocytopenia was significant, and may complicate potential trials of combination therapy.