A double-blind, randomized, placebo-controlled, phase 2 study of maintenance enzastaurin with 5-fluorouracil/leucovorin plus bevacizumab after first-line therapy for metastatic colorectal cancer

BACKGROUND: Enzastaurin and bevacizumab have demonstrated synergistic antitumor effects and, in phase 1 studies, the combination was well tolerated. This phase 2 study assessed enzastaurin with 5-fluorouracil/leucovorin plus bevacizumab as maintenance therapy for metastatic colorectal cancer (MCRC). METHODS: Patients with locally advanced or MCRC and stable or responding disease after completing 6 cycles of first-line chemotherapy randomly received a loading dose of enzastaurin 1125 mg, followed by 500 mg/d subsequent doses or placebo. Both arms received 5-fluorouracil/leucovorin (leucovorin 400 mg/m2 intravenously [IV], 5-fluorouracil 400-mg/m2 bolus, 5-fluorouracil 2400 mg/m2 IV) plus bevacizumab 5 mg/kg IV, every 2 weeks. The primary endpoint was progression-free survival (PFS), from randomization. Overall survival (OS) and PFS were also assessed from start of first-line therapy. Enrollment was stopped, and the final analysis was conducted after 73 PFS events. RESULTS: Fifty-eight patients were randomized to enzastaurin and 59 to placebo. For the enzastaurin and placebo arms, respectively, the median cycles received were 9 and 10, and the median PFS was 5.8 and 8.1 months (hazard ratio [HR], 1.35; 95% confidence interval [CI], 0.84-2.16; P = .896). Median OS was not calculable because of high censoring (77.6% enzastaurin; 91.5% placebo). The median PFS from start of first-line therapy was 8.9 months for enzastaurin and 11.3 months for placebo (HR, 1.39; 95% CI, 0.86-2.23; P = .913). More enzastaurin patients developed thrombosis or embolism compared with placebo (15.8% and 1.7%; P = .008). One possibly enzastaurin-related death occurred because of arrhythmia. CONCLUSIONS: Enzastaurin combined with bevacizumab-based therapy is tolerable, but does not improve PFS during maintenance therapy in patients with MCRC compared with bevacizumab-based therapy alone. Cancer 2012. (c) 2011 American Cancer Society.