Orignal Post here ProQR Announces Positive Results from Clinical Trial of QR-421a in Usher Syndrome and Plans to Start Pivotal Trials QR-421a demonstrated a concordant benefit in multiple measures of vision, including best corrected visual activity (BCVA), static perimetry, and retinal imaging (OCT) QR-421a observed to be well tolerated with no serious adverse events reported Two pivotal Phase 2/3 trials are expected to start by the end of 2021 Management to host a conference call today at 8:15am EDT LEIDEN, Netherlands & CAMBRIDGE, Mass.,