Abstract
Spleen tyrosine kinase (Syk) mediates B-cell receptor signalling in normal and malignant B cells. Entospletinib is an oral, selective Syk inhibitor. Entospletinib monotherapy was evaluated in a multicentre, phase 2 study of patients with relapsed or refractory indolent non-Hodgkin lymphoma or mantle cell lymphoma (MCL). Subjects received 800 mg entospletinib twice daily. Forty-one follicular lymphoma (FL), 17 lymphoplasmacytoid lymphoma/Waldenström macroglobulinaemia (LPL/WM), 17 marginal zone lymphoma (MZL) and 39 MCL patients were evaluated. The primary endpoint was a progression-free survival (PFS) rate (defined as not experiencing progression or death) at 16 weeks for patients with MCL and at 24 weeks for patients with FL, LPL/WM and MZL. The most common treatment-emergent adverse events were fatigue, nausea, diarrhoea, vomiting, headache and cough. Common laboratory abnormalities were anaemia, neutropenia and thrombocytopenia; aspartate transaminase, alanine transaminase, total bilirubin and serum creatinine were all increased. PFS at 16 weeks in the MCL cohort was 63·9% [95% confidence interval (CI) 45-77·8%]; PFS at 24 weeks in the FL, LPL/WM, MCL and MZL cohorts was 51·5% (95% CI 32·8-67·4%), 69·8% (95% CI 31·8-89·4%), 56·6% (95% CI 37·5-71·8%) and 46·2% (95% CI 18·5-70·2%), respectively. Entospletinib had limited single-agent activity with manageable toxicity in these patient populations.