Ishitsuka K, Izutsu K, Maruyama D, et al. - Given the involvement of altered EZH2 (enhancer of zeste homolog 2) expression in the causation of non-Hodgkin lymphomas (NHLs), researchers herein described interim outcomes from a phase 1 trial of valemetostat [valemetostat tosylate or DS-3201b: a novel, potent, and selective dual inhibitor of EZH2 and EZH1 (close homolog of EZH2)] in patients (pts) suffering from relapsed or refractory (R/R) NHLs, including peripheral T-cell lymphoma (PTCL) and adult T-cell leukemia/lymphoma (ATL). Until disease progression or intolerance, pts with R/R NHL were treated with valemetostat (dose escalation, 150-300 mg/day; dose expansion, 200 mg/day) given orally once daily in continuous 28-day cycles. At data cutoff (November 2, 2020), treatment was received by 78 pts with R/R NHL; 62 of them were treated with 200 mg. Preliminary efficacy in 45 R/R PTCL cases included an overall response rate (ORR) of 55.6% and median progression-free survival (mPFS) of 52 wk. Preliminary efficacy in R/R ATL cases included an ORR of 50.0%, and mPFS that was not estimable. Findings showed an acceptable safety profile of valemetostat in pts suffering from R/R NHLs as well as revealed its encouraging preliminary efficacy in pts suffering from R/R PTCL or ATL.