ProQR Announces Results for the First Quarter of 2017

Key updates
• QR-010 Phase 1b clinical trial on track to present top-line data in cystic fibrosis (CF) patients in mid-2017.
• Investigational new drug (IND) application for QR-110, ProQR’s lead program in ophthalmology, was cleared by the FDA to start a clinical trial in both adult and pediatric LCA 10 patients.
• David M. Rodman, MD was appointed as Chief Development Strategy Officer of ProQR, and will lead the translational development effort to rapidly advance the pipeline programs into the clinic.
• ProQR was granted two key patents, protecting QR-010 for cystic fibrosis in the US and EU.
• Pre-clinical data was presented for three programs in the ophthalmology pipeline targeting LCA 10 and Usher syndrome at the ARVO annual meeting in May 2017

LEIDEN, the Netherlands, May 17, 2017 – ProQR Therapeutics N.V. (Nasdaq:PRQR), today announced results for the first quarter of 2017.
“As we announced earlier this week, we are all devastated by the unexpected passing of our co-founder and vice-chairman of the supervisory board, Henri A. Termeer,” said Daniel de Boer, Chief Executive Officer of ProQR. “Henri was a great mentor, a passionate patient advocate and a key factor in establishing ProQR. His passion to do the right thing in the interest of patients is unparalleled. We are honored to have had the opportunity to work with him so closely and learn from his wealth of experience. He was a true inspiration for all of us, and we will continue to build on the path he helped us to set out. Although he will be deeply missed, our supervisory board, with co-founder and chairman Dinko Valerio, James Shannon, Alison Lawton and Antoine Papiernik, continues to be very strong with broad experience in all aspects of running a biotechnology business and we are extremely motivated to continue to build on the path he helped us set.”
“With that in mind, this is an important phase for the Company in our goal to translate our rich pipeline into a diversified portfolio of development programs. We are very pleased with the clearance of the IND for QR-110, enabling us to now advance our second molecule into clinical development aiming to make a meaningful difference for LCA 10 patients. We are also excited to add Dave Rodman to our team who will further strengthen our development team, with the goal of efficiently and rapidly driving our programs through to patients. Looking forward to the upcoming summer, we are very excited for the expected completion of the Phase 1b trial in our lead program QR-010. We have been treating >64 CF patients with our lead compound QR-010 and are excited to get to the data and progress the compound into next trials.”

Corporate Highlights
• In March, the Company announced that it appointed David M. Rodman, MD as Chief Development Strategy Officer. Dr. Rodman has had a long career in drug development including leadership roles in translational medicine, rare disease drug development, and RNA therapeutics. Dr. Rodman’s experience includes a leadership role in developing two approved medicines for CF at Vertex Pharmaceuticals, as Vice President and head of respiratory drug development. He was also the head of translational medicine at Novartis Institute for Biomedical Research. More recently, he was the Chief Medical Officer at MiRagen and Nivalis. Expansion of the ProQR management team will allow the Company to further realize the potential of RNA therapeutics as well as expand business capabilities needed to advance the development of our product candidates.
Subsequent events
• In April, the Company announced that with the clearance of the investigational new drug (IND) application by the U.S. Food and Drug Administration (FDA), ProQR can now start clinical development of QR-110 in Leber’s congenital amaurosis Type 10 (LCA 10) patients. The trial, named PQ-110-001, is an open-label trial that will include approximately 6 children (age 6-17 years) and 6 adults (≥ 18 years) that have LCA 10 due to one or two copies of the p.Cys998X mutation. During the trial, patients will receive four intravitreal injections of QR-110 into one eye; one every three months for one year and the second eye will serve as a control. The QR-110 trial is expected to be conducted in three centers with significant expertise in genetic retinal disease in the US and Europe. The primary objective will be to assess safety and tolerability of QR-110. Secondary objectives are to evaluate pharmacokinetics and efficacy, which is measured by specialized ophthalmic tests including visual acuity, full field stimulus testing (FST), optical coherence tomography (OCT), pupillary light reflex (PLR) and a mobility course. Fixation stability and changes in quality of life in LCA subjects will also be evaluated. Top-line results from the trial are expected to be available in 2018.
• In April, the Company announced the grant of two key patents protecting QR-010 in the US and EU. These patents provide the Company exclusive rights for QR-010 for the treatment of CF until at least July 2033. US patent no. 9,605,255 is directed to methods of targeting RNA for the most common mutation in CF, called F508del, using oligonucleotides to restore the function of the CFTR protein. Last year, ProQR also received the grant of the equivalent European patent (EP 2 852 668 B1). Apart from these ProQR owned patents, ProQR has an exclusive license to US patent no. 9,617,535 from Massachusetts General Hospital covering QR-010.
• During the 2017 Annual Meeting of the Association for Research in Vision and Ophthalmology (ARVO) held on May 7 – 11, 2017 in Baltimore, MD, USA, the Company presented three abstracts, including additional positive pre-clinical proof-of-concept data for QR-110 in LCA 10 and pre-clinical data for two programs, QRX-411 and QRX-421, each targeting specific mutations that result in Usher syndrome.
• The Company announced that it will host an R&D Day on June 15th in New York where Company executives and external experts will present ProQR’s pipeline of development and early stage programs in detail.

Financial Highlights
At March 31, 2017, ProQR held cash and cash equivalents of €52.1 million, compared to €59.2 million at December 31, 2016. Net cash used in operating activities during the three month period ended March 31, 2017 was €8.8 million, compared to €7.8 million for the same period last year.
Research and development costs increased to €8.0 million for the quarter ended March 31, 2017 from €6.9 million for the same period last year and comprised of allocated employee costs including share-based payments, the costs of materials and laboratory consumables, outsourced activities, license and intellectual property costs and other allocated costs. The increase in expenses was primarily due to the advancement of our pipeline, which included clinical development of QR-010 and QR-110, pre-clinical development of QR-313. The remainder represents increased investments in our other pipeline programs.
General and administrative costs decreased to €2.3 million for the quarter ended March 31, 2017 from €2.6 million for the same period last year.
Net result for the three month period ended March 31, 2017 was a €10.5 million loss or €0.45 per share, compared to a €10.2 million loss or €0.44 per share for the same period last year. For further financial information for the period ending March 31, 2017, please refer to the financial statements appearing at the end of this release.

About ProQR
ProQR Therapeutics is dedicated to changing lives through the creation of transformative RNA medicines for the treatment of severe genetic rare diseases such as cystic fibrosis, Leber’s congenital amaurosis Type 10 and dystrophic epidermolysis bullosa. Based on our unique proprietary RNA repair platform technologies we are growing our pipeline with patients and loved ones in mind.
*Since 2012*

About QR-010
QR-010 is a first-in-class RNA-based oligonucleotide designed to address the underlying cause of the disease by targeting the mRNA in CF patients that have the F508del mutation. The F508del mutation is a deletion of three of the coding base pairs, or nucleotides, in the CFTR gene, which results in the production of a misfolded CFTR protein that does not function normally. QR-010 is designed to bind to the defective CFTR mRNA and to restore CFTR function. QR-010 is designed to be self-administered via an optimized eFlow® Nebulizer (PARI Pharma GmbH). eFlow® is a small, handheld aerosol delivery device which nebulizes QR-010 into a mist inhaled directly into the lungs. QR-010 has been granted orphan drug designation in the United States and the European Union and fast-track status by the FDA. The QR-010 project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 633545.

About QR-110
QR-110 is a first-in-class investigational RNA-based oligonucleotide designed to address the underlying cause of Leber’s congenital amaurosis Type 10 due to the p.Cys998X mutation in the CEP290 gene. The p.Cys998X mutation is a substitution of one nucleotide in the pre-mRNA that leads to aberrant splicing of the mRNA and non-functional CEP290 protein. QR-110 is designed to restore wild-type CEP290 mRNA leading to the production of wild-type CEP290 protein by binding to the mutated location in the pre-mRNA causing normal splicing of the pre-mRNA. QR-110 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.

About QR-313
QR-313 is a first-in-class RNA-based oligonucleotide designed to address the underlying cause of dystrophic epidermolysis bullosa (DEB) due to mutations in exon 73 of the COL7A1 gene. Mutations in this exon can cause loss of functional collagen type VII (C7) protein. Absence of C7 results in the loss of anchoring fibrils that normally link the dermal and epidermal layers of the skin together. QR-313 is designed to exclude exon 73 from the mRNA (exon skipping) and produce truncated but functional C7 protein and thereby restores functionality of the anchoring fibrils.

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. 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. These forward-looking statements include, but are not limited to, statements regarding QR-010, QR-110 and QR-313, and the clinical development and the therapeutic potential thereof, statements regarding our ongoing and planned discovery and development of product candidates and the timing thereof, including those in our innovation pipeline, statements regarding release of clinical data, and statements regarding our patent estate. Our actual results could differ materially from those anticipated in these forward-looking statements for many reasons, including, without limitation, risks associated with our clinical development activities, including that positive results observed in our prior and ongoing studies may not be replicated in later trials or guarantee approval of any product candidate by regulatory authorities, manufacturing processes and facilities, regulatory oversight, product commercialization, intellectual property claims, and 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.