Post-hoc analyses from Illuminate trial of sepofarsen demonstrate an encouraging efficacy signal when comparing active treatment and sham eyes to their corresponding contralateral eyes across multiple endpoints – Company plans to discuss findings with regulators and provide an update in Q3/early Q4Enrollment is ongoing in Sirius, a Phase 2/3 trial of ultevursen (QR-421a), for USH2A-mediated Usher syndrome and retinitis pigmentosaProQR is accelerating the development of its Axiomer® RNA base-editing technology platform across multiple therapeutic areas and will provide an update on first targets in H2 2022Cash runway into 2025 LEIDEN, Netherlands & CAMBRIDGE, Mass., May 05, 2022 (GLOBE NEWSWIRE) — ProQR Therapeutics N.V. (Nasdaq: PRQR) (the “Company”), a company dedicated to changing lives through the creation of transformative RNA therapies, today reported its financial and operating results for the first quarter ended March 31, 2022, and provided a business update. “In April, we took important steps toward focusing our strategy on accelerating our Axiomer RNA-base editing platform technology, and a select pipeline of RNA therapies for inherited retinal diseases,” said Daniel A. de Boer, Founder and CEO of ProQR Therapeutics. “While we were disappointed by the outcome of the primary analysis in the Illuminate trial of sepofarsen, we believe that the post-hoc analyses and the observation that approximately a third of the patients benefited across multiple concordant endpoints in this trial, in combination with the high unmet need for those with LCA10, warrants a discussion with the regulators. We plan to meet with the regulators in Q3 and will share an update in Q3 or early Q4, depending on timing of the meetings. Additionally, we look forward to sharing details of our development plans for Axiomer in the second half of 2022. ProQR has a strong cash position with runway into 2025, and we look forward to continued progress with the business.” Business Operations and Program Updates Program updates In April, the Company announced that post-hoc analyses from Illuminate trial of sepofarsen demonstrate an encouraging efficacy signal when comparing active treatment and sham eyes to their corresponding contralateral eyes across multiple endpoints. In Q3, the Company plans to meet with the EMA and FDA to discuss these data from the Illuminate trial. Following this discussion, ProQR will share an update in Q3 or early Q4, depending on timing of regulatory meetings. Findings from Illuminate, including examples of individual patient data, were presented at the Seventh Annual Retinal Cell and Gene Therapy Innovation Summit, April 29, 2022, and the Association for Research in Vision and Ophthalmology (ARVO) Annual Meeting, May 1-4, 2022.Based on the recommendation of the sepofarsen Data Safety and Monitoring Committee (DSMC), the Company currently plans to continue Illuminate, which is a 2 year study, the Brighten pediatric study, and Insight, until further regulatory guidance, after which next steps will be determined.Enrollment is ongoing in Sirius, a Phase 2/3 trial of ultevursen (QR-421a), for USH2A-mediated Usher syndrome and retinitis pigmentosa.ProQR is accelerating the development of its Axiomer RNA editing platform and pipeline activities and plans to expand into areas beyond the eye, including initially liver and CNS, which have strong alignment with ProQR’s oligonucleotide delivery approaches. The Company will present further non-clinical data for Axiomer and announce its internal development targets in H2 2022.In April, the Company presented its proprietary RNA base-editing Axiomer technology at the 3rd RNA Editing Summit. Business updates In March, John Maraganore, PhD, was appointed as a strategic advisor to ProQR’s Supervisory Board. Dr. Maraganore is a biopharma industry veteran and the former founding CEO of Alnylam Pharmaceuticals. In April, the Company announced portfolio prioritization and restructuring initiatives expected to extend ProQR’s cash runway into 2025. On May 3, 2022 the Company received written notification from Nasdaq that for the last 30 consecutive business days the Company’s ordinary shares did not maintain a minimum closing bid price of $1.00 per share as required by Nasdaq Listing Rule 5550(a)(2). This notice does not result in the immediate delisting of the Company’s ordinary shares from The Nasdaq Global Market. In accordance with Nasdaq Listing Rule 5810(c)(3)(A) (the “Compliance Period Rule”), the Company has been provided an initial period of 180 calendar days, or until October 31, 2022, to regain compliance. If, at any time during this 180-day period, the closing bid price for the Company’s ordinary shares closes at $1.00 or more per share for a minimum of 10 consecutive business days, Nasdaq will provide written compliance notification and the ordinary shares will continue to be eligible for listing on The Nasdaq Global Market. In the event the Company does not regain compliance in the required timeframe, the Company may be eligible for an additional 180 calendar day compliance period. The Company’s business operations are not affected by the receipt of this notification. Financial Highlights At March 31, 2022, ProQR held cash and cash equivalents of €167.6 million, compared to €187.5 million at December 31, 2021. Net cash used in operating activities during the three-month period ended March 31, 2022 was €20.5 million, compared to €11.8 million for the same period last year. Research and development (R&D) costs were €13.4 million for the quarter ended March 31, 2022 compared to €8.9 million for the same period last year. General and administrative costs were €4.9 million for the quarter ended March 31, 2022 compared to €3.3 million for the same period last year. Net loss for the three-month period ended March 31, 2022 was €14.5 million, or €0.20 per diluted share, compared to €12.6 million, or €0.25 per diluted share, for the same period last year. For further financial information for the period ending March 31, 2022, please refer to the financial statements appearing at the end of this release. 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 c.2991+1655A>G (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 an investigational RNA therapy designed to restore vision in Leber congenital amaurosis 10 due to the c.2991+1655A>G mutation (p.Cys998X) in the CEP290 gene. The 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 Usher syndrome type 2a and retinitis pigmentosa Usher syndrome is the leading cause of combined deafness and blindness. People with Usher syndrome type 2a are usually born with hearing loss and start to have progressive vision loss during adulthood. The vision loss can also occur without hearing loss in a disease called non-syndromic retinitis pigmentosa. Usher syndrome type 2a and non-syndromic retinitis pigmentosa can be caused by mutations in the USH2A gene. To date, there are no pharmaceutical treatments approved or in clinical development that treat the vision loss associated with mutations in USH2A. About ultevursen Ultevursen (formerly QR-421a) is a first-in-class investigational RNA therapy designed to address the underlying cause of vision loss in Usher syndrome type 2a and non-syndromic retinitis pigmentosa due to mutations in exon 13 of the USH2A gene. QR-421a is designed to restore functional usherin protein by using an exon skipping approach with the aim to stop or reverse vision loss in patients. Ultevursen is intended to be administered through intravitreal injections in the eye and has been granted orphan drug designation in the US and the European Union and received fast-track and rare pediatric disease designations from the FDA. About Axiomer® technology ProQR is pioneering a next-generation RNA technology called Axiomer®, which could potentially yield a new class of medicines for genetic diseases. Axiomer “Editing Oligonucleotides”, or EONs, mediate single nucleotide changes to RNA in a highly specific and targeted way using molecular machinery that is present in human cells. The Axiomer EONs are designed to recruit an endogenously expressed RNA editing system called ADAR, which can direct the change of an Adenosine (A) to an Inosine (I) in the RNA – an Inosine is translated as a Guanosine (G). About ProQR ProQR Therapeutics is dedicated to changing lives through the creation of transformative RNA therapies. ProQR is pioneering a next-generation RNA technology called Axiomer®, which uses a cell’s own editing machinery called ADAR to make specific single nucleotide edits in RNA to reverse a mutation or modulate protein expression and could potentially yield a new class of medicines for genetic diseases. 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, but are not limited to, statements regarding our product candidates, including sepofarsen (QR-110) and the clinical development and the therapeutic potential thereof, statements regarding ultevursen (QR-421a) and the clinical development and therapeutic potential thereof, statements regarding our pipeline of programs targeting inherited retinal dystrophies, the potential of our technologies and platforms (including Axiomer®), our other programs and business operations, our current and planned partnerships and collaborators and the intended benefits thereof, our planned interactions with regulatory authorities relating to our programs, our updated strategic plans and the intended benefits thereof, and our financial position and cash runway. 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. These risks and uncertainties include, among others, the cost, timing and results of preclinical studies and clinical trials and other development activities by us and our collaborative partners whose operations and activities may be slowed or halted by the ongoing COVID-19 pandemic; the likelihood of our clinical programs being executed on timelines provided and reliance on our contract research organizations and predictability of timely enrollment of subjects and patients to advance our clinical trials and maintain their own operations; our reliance on contract manufacturers to supply materials for research and development and the risk of supply interruption from a contract manufacturer; the potential for later data to alter initial and preliminary results of early-stage clinical trials, including as a result of differences in the trial designs and protocols across different trials; the unpredictability of the duration and results of the regulatory review of applications or clearances that are necessary to initiate and continue to advance and progress our clinical programs; the outcomes of our planned interactions with regulatory authorities; the ability to secure, maintain and realize the intended benefits of collaborations with partners; the possible impairment of, inability to obtain, and costs to obtain intellectual property rights; possible safety or efficacy concerns that could emerge as new data are generated in research and development; our ability to maintain and service our loan facility with Pontifax and Kreos; the possibility that we will not be able to regain compliance with Nasdaq’s Minimum Bid Price Requirement, secure a second period of 180 days to regain compliance, or maintain compliance with any of the other Nasdaq continued listing requirements. general business, operational, financial and accounting risks; and risks related to litigation and disputes with third parties. 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. Cautionary note on future updates The statements contained in this press release reflect our current views with respect to future events, which may change significantly as the global consequences of the ongoing COVID-19 pandemic rapidly develop. Accordingly, we do not undertake and specifically disclaim any obligation to update any forward-looking statements. ProQR Therapeutics N.V. Investor contact:Sarah KielyProQR Therapeutics N.V.T: +1 617 599 6228skiely@proqr.comorHans VitzthumLifeSci AdvisorsT: +1 617 430 7578hans@lifesciadvisors.com Media contact:Robert StanislaroFTI ConsultingT: +1 212 850 5657robert.stanislaro@fticonsulting.com PROQR THERAPEUTICS N.V.Unaudited Condensed Consolidated Statement of Financial Position March 31, December 31, 2022 2021 € 1,000 € 1,000Assets Current assets Cash and cash equivalents 167,612 187,524 Prepayments and other receivables 4,047 3,404 Other taxes 812 555 Total current assets 172,471 191,483 Property, plant and equipment 17,141 17,467 Investments in associates — 8 Investments in financial assets 621 621 Total assets 190,233 209,579 Equity and liabilities Equity Equity attributable to owners of the Company 100,829 113,833 Non-controlling interests (612) (604)Total equity 100,217 113,229 Current liabilities Borrowings 6,394 4,771 Lease liabilities 1,324 1,534 Derivative financial instruments 279 3,995 Trade payables 824 191 Current income tax liability — — Social securities and other taxes 1,216 1,230 Deferred income 5,656 5,115 Other current liabilities 8,022 10,760 Total current liabilities 23,715 27,596 Borrowings 38,368 39,319 Lease liabilities 14,382 14,748 Deferred income 13,551 14,687 Total liabilities 90,016 96,350 Total equity and liabilities 190,233 209,579 PROQR THERAPEUTICS N.V.Unaudited Condensed Consolidated Statement of Profit or Loss and OCI (€ in thousands, except share and per share data) Three month period ended March 31, 2022 2021 € 1,000 € 1,000Revenue 1,234 — Other income 101 141 Research and development costs (13,367) (8,905)General and administrative costs (4,908) (3,339)Total operating costs (18,275) (12,244) Operating result (16,940) (12,103)Finance income and expense (1,259) (293)Results related to associates (8) — Gain on disposal of associate — 514 Results related to financial liabilities measured at fair value through profit or loss 3,764 (729) Result before corporate income taxes (14,443) (12,611)Income taxes (7) (7) Result for the period (14,450) (12,618)Other comprehensive income (foreign exchange differences on foreign operation) 222 396 Total comprehensive income (14,228) (12,222) Result attributable to Owners of the Company (14,442) (12,607)Non-controlling interests (8) (11) (14,450) (12,618)Total comprehensive income attributable to Owners of the Company (14,220) (12,211)Non-controlling interests (8) (11) (14,228) (12,222) Share information Weighted average number of shares outstanding1 71,357,170 50,811,135 Earnings per share attributable to owners of the Company (Euro per share) Basic loss per share1 (0.20) (0.25)Diluted loss per share1 (0.20) (0.25) For these periods the potential exercise of share options is not included in the diluted earnings per share as the Company was loss-making. Due to the anti-dilutive nature of the outstanding options, basic and diluted earnings per share are equal. PROQR THERAPEUTICS N.V.Unaudited Condensed Consolidated Statement of Changes in Equity Attributable to owners of the Company Numberof shares ShareCapital SharePremium Equity settledEmployeeBenefitReserve Option premium onconvertibleloan TranslationReserve AccumulatedDeficit Total Non-controllinginterests TotalEquity € 1,000 € 1,000 € 1,000 € 1,000 € 1,000 € 1,000 € 1,000 € 1,000 € 1,000Balance at January 1, 2021 54,131,553 2,165 288,757 23,825 280 (189) (257,747) 57,091 (545) 56,546 Result for the period — — — — — — (12,607) (12,607) (11) (12,618)Other comprehensive income — — — — — 396 — 396 — 396 Recognition of share-based payments 112,657 5 382 1,248 — — — 1,635 — 1,635 Issuance of ordinary shares 585,398 23 2,629 — — — — 2,652 — 2,652 Treasury shares transferred (180,126) — — — — — — — — — Recognition of equity component of convertible loan — — — — — — — — — — Share options lapsed — — — (89) — — 89 — — — Share options exercised 180,126 — 569 (388) — — 388 569 — 569 Balance at March 31, 2021 54,829,608 2,193 292,337 24,596 280 207 (269,877) 49,736 (556) 49,180 Balance at January 1, 2022 74,865,381 2,995 398,309 28,443 1,426 430 (317,770) 113,833 (604) 113,229 Result for the period — — — — — — (14,442) (14,442) (8) (14,450)Other comprehensive income — — — — — 222 — 222 — 222 Recognition of share-based payments — — — 1,183 — — — 1,183 — 1,183 Issuance of ordinary shares — — — — — — — — — — Treasury shares transferred (71,283) — — — — — — — — — Recognition of equity component of convertible loan — — — — — — — — — — Share options lapsed — — — — — — — — — — Share options exercised / RSUs vested 71,283 — 33 (168) — — 168 33 — 33 Balance at March 31, 2022 74,865,381 2,995 398,342 29,458 1,426 652 (332,044) 100,829 (612) 100,217 PROQR THERAPEUTICS N.V.Unaudited Condensed Consolidated Statement of Cash Flows Three month period ended March 31, 2022 2021 € 1,000 € 1,000Cash flows from operating activities Net result (14,450) (12,618)Adjustments for: — Depreciation 570 631 — Share-based compensation 1,183 1,248 — Financial income and expenses 1,259 293 — Results related to associates 8 107 — Gain on disposal of associate — (621)— Results related to financial liabilities measured at fair value through profit or loss (3,764) 729 — Income tax expenses 7 7 Changes in working capital (4,054) (952)Cash used in operations (19,241) (11,176) Corporate income tax paid (7) (7)Interest received — — Interest paid (1,219) (578) Net cash used in operating activities (20,467) (11,761) Cash flow from investing activities Purchases of property, plant and equipment (244) (32) Net cash used in investing activities (244) (32) Cash flow from financing activities Proceeds from issuance of shares, net of transaction costs — 2,652 Proceeds from exercise of share options 33 569 Proceeds from borrowings — — Proceeds from convertible loans — — Repayment of lease liability (576) (236) Net cash (used in)/generated by financing activities (543) 2,985 Net increase (decrease) in cash and cash equivalents (21,254) (8,808) Currency effect cash and cash equivalents 1,342 848 Cash and cash equivalents, at beginning of the period 187,524 75,838 Cash and cash equivalents at the end of the period 167,612 67,878