Open-label, single-arm, phase II study of enzastaurin in patients with follicular lymphoma.

This open-label, phase II study investigated whether enzastaurin, a protein kinase C-beta (PKCβ) inhibitor, had activity in patients with grade 1 or 2 follicular lymphoma (FL). Adults with grade 1 or 2 FL who had no more than one prior treatment received oral enzastaurin continuously for up to 3 years. Of the 66 patients who received enzastaurin, 53 were evaluable for response. Overall response rate (ORR, primary efficacy endpoint) was 26.4% (3.8% complete response). Median (95% confidence interval) progression-free survival, time to response, and duration of response were 18.1 (11.5-28.3), 4.9 (2.8-8.1), and 22.3 (8.8-not applicable) months, respectively. In patients with tumour tissue available for biomarker analysis, ORRs in low versus high PKCβ2 expression groups were 41.7% and 8.3%, respectively (P = 0.041). The most common, mainly low-grade drug-related adverse events were fatigue (25.8%), diarrhoea (25.8%), nausea (18.2%), and chromaturia (18.2%). Four (6.1%) patients had Grade 3 toxicity and one (1.5%) patient had Grade 4 toxicity. Enzastaurin demonstrated limited clinical activity in grade 1 or 2 FL. Patients with low PKCβ2 expression in tumours had higher ORR than those with high PKCβ2 expression. Enzastaurin was well tolerated with mostly grade 1 or 2 toxicities. Further studies may be warranted in select patient populations.