Total PB ROS levels in patients with FA after quercetin treatment (phase 1 dose-finding cohort and analysis cohort). (A) Total PB ROS levels in individual patients (phase 1 cohort). Seven of 12 patients (58%) experienced decrease in PB ROS at 4 months, and 7 of 9 patients (78%) showed decrease in PB ROS at 1 year (3 patients came off study before 1 year). Note: patients in each cohort received escalating doses of quercetin. The last 3 patients treated at the daily maximum dose of 4000 mg/d achieved the highest and most consistent ROS reduction. (B) Median total PB ROS levels in all patients (phase 1 cohort). As desired, median total PB ROS levels decreased after 4 months of treatment with quercetin (42.5% reduction; P = .23). In 9 patients with available PB ROS results, median ROS levels decreased at 1 year (75% reduction; P = .04). (C) Median total PB ROS levels in all patients (analysis cohort). Median total PB ROS levels decreased by 25% at 6 months (P = .67) and 18% at 1 year (P = .06) compared with baseline after treatment with quercetin.