ProQR Announces Virtual Presentation of Phase 1/2 Sepofarsen Extension Trial Data at the Association for Research in Vision and Ophthalmology (ARVO) 2021

LEIDEN, Netherlands & CAMBRIDGE, Mass., April 23, 2021 (GLOBE NEWSWIRE) — ProQR Therapeutics N.V. (Nasdaq:PRQR), a company dedicated to changing lives through the creation of transformative RNA therapies for severe genetic rare diseases, today announced a virtual oral presentation of data from the Company’s Phase 1/2 InSight extension trial of sepofarsen and live Q&A session at the Association for Research in Vision and Ophthalmology (ARVO) held May 1-7, 2021. This is an encore presentation of the InSight study data that was presented during the Expert Perspectives Call in July 2020. We expect to present new data from the InSight study in H2 2021. ProQR’s Presentation Presentation title: Safety and efficacy of sepofarsen in the second treated eye in a Ph1b/2 extension trial in Leber Congenital Amaurosis type 10 (LCA10)Presenter: Stephen R. Russell, MD, Professor and Director of Vitreoretinal Diseases and Surgery Service, Department of Ophthalmology and Visual Sciences, University of Iowa Presentation type: Oral paper presentation followed by a live Q&A session.Session: Stem cells/gene therapy/transplantationDate: May 6, 2021 at 5:15pm EDT About Leber Congenital Amaurosis 10 (LCA10) Leber congenital amaurosis (LCA) is the most common cause of blindness due to genetic disease in children. It consists of a group of diseases of which LCA10 is the most frequent and one of the most severe forms. LCA10 is caused by mutations in the CEP290 gene, of which the p.Cys998X mutation has the highest prevalence. LCA10 leads to early loss of vision causing most people to lose their sight in the first few years of life. To date, there are no treatments approved that treat the underlying cause of the disease. Approximately 2,000 people in the Western world have LCA10 because of this mutation. About Sepofarsen Sepofarsen (QR-110) is being evaluated in the pivotal Phase 2/3 Illuminate trial and is a first-in-class investigational RNA therapy designed to address the underlying cause of Leber congenital amaurosis 10 due to the p.Cys998X mutation (also known as the c.2991+1655A>G mutation) in the CEP290 gene. The p.Cys998X mutation leads to aberrant splicing of the mRNA and non-functional CEP290 protein. Sepofarsen is designed to enable normal splicing, resulting in restoration of normal (wild type) CEP290 mRNA and subsequent production of functional CEP290 protein. Sepofarsen is intended to be administered through intravitreal injections in the eye and has been granted orphan drug designation in the United States and the European Union and received fast-track designation and rare pediatric disease designation from the FDA as well as access to the PRIME scheme by the EMA. About ProQR ProQR Therapeutics is dedicated to changing lives through the creation of transformative RNA therapies for the treatment of severe genetic rare diseases such as Leber congenital amaurosis 10, Usher syndrome and retinitis pigmentosa. Based on our unique proprietary RNA repair platform technologies we are growing our pipeline with patients and loved ones in mind.Learn more about ProQR at www.proqr.com. Forward Looking Statements This press release contains forward-looking statements. All statements other than statements of historical fact are forward-looking statements, which are often indicated by terms such as “anticipate,” “believe,” “could,” “estimate,” “expect,” “goal,” “intend,” “look forward to”, “may,” “plan,” “potential,” “predict,” “project,” “should,” “will,” “would” and similar expressions. Such forward-looking statements include those relating to our presentation at ARVO and statements regarding sepofarsen and its clinical development and therapeutic potential, including statements about the InSight trial and timing of new data from this trial. Forward-looking statements are based on management’s beliefs and assumptions and on information available to management only as of the date of this press release. Our actual results could differ materially from those anticipated in these forward-looking statements for many reasons, including, without limitation, the risks, uncertainties and other factors in our filings made with the Securities and Exchange Commission, including certain sections of our annual report filed on Form 20-F. Given these risks, uncertainties and other factors, you should not place undue reliance on these forward-looking statements, and we assume no obligation to update these forward-looking statements, even if new information becomes available in the future, except as required by law. ProQR Therapeutics N.V. Investor Contact: Sarah Kiely ProQR Therapeutics N.V. T: +1 617 599 6228 [email protected] or Hans Vitzthum LifeSci Advisors T: +1 617 430 7578 [email protected] Media Contact: Cherilyn Cecchini, MD LifeSci Communications T: +1 646 876 5196 [email protected]