Study population enrolled and duration of protocol treatment. In dose-finding phase, 12 patients received oral quercetin twice a day for 4 months (16 weeks). An optional 20-month continuation phase at the assigned dosing was offered to those who wished to continue after completion of the first 4 months. In expansion cohort, 18 patients were treated with quercetin for 6 months at the recommended weight-adjusted dose identified in the dose-finding phase 1 study. Those who wished to continue quercetin beyond 6 months were treated for an additional 6 months for a total of up to 1 year. In analysis cohort, 21 patients (last 3 patients from the phase 1 cohort and 18 from the expansion cohort) treated with quercetin at the recommended dosing were included in this cohort. Max, maximum.