First Line Chemo-Free Therapy with the BRAF Inhibitor Vemurafenib Combined with Obinutuzumab Is Effective in Patients with Hcl

Background: We have previously reported >90% overall response rates of the BRAF inhibitor, vemurafenib, in patients (pts) with relapsed or refractory (R/R) hairy cell leukemia (HCL) (Tiacci and Park et al. NEJM 2015). However, complete response (CR) rate was observed in 35-40% of the pts and 50% relapsed with vemurafenib monotherapy (Park JH et al. Blood 2018, 132;392). Anti-CD20 antibodies such as rituximab and obinutuzumab have demonstrated efficacy in HCL, and the recent data reported improved CR rate when rituximab was added to vemurafenib in R/R HCL (Tiacci et al. NEJM 2021). We therefore initiated a phase II multi-center clinical trial to investigate the efficacy of vemurafenib and obinutuzumab in pts with newly diagnosed HCL (NCT03410875).