MECP2

Expanded Phase 1/2 gene therapy trial for Rett syndrome to inform future registrational study design; Company remains on track to share interim clinical data in 4Q:24 Strong financial position with runway into 2H:26 following reverse merger and private financing in December 2023 NEW YORK--(BUSINESS WIRE)-- Neurogene Inc. (Nasdaq: NGNE), a clinical-stage company founded to bring life-changing genetic medicines to patients and families affected by rare neurological diseases, today announced fourth quarter and full year 2023 financial results and highlighted recent corporate updates. “We started the year with strong execution in our Phase 1/2 NGN-401 gene therapy trial for female pediatric patients with Rett syndrome, meeting our goal to expand the trial and add a high-dose cohort. We believe this expanded dataset will support future regulatory discussions to align on the design of a potential registrational study,” said Rachel McMinn, Ph.D., Chief Executive Officer and Founder of Neurogene. “NGN-401 has the potential to be a best-in-class treatment option with a targeted route of administration to deliver full-length, functional copies of the MECP2 gene. We are pleased that NGN-401 has been well-tolerated in all three patients dosed, with no signs of overexpression-related toxicity, demonstrating the potential of our EXACT transgene regulation technology to constrain MECP2 levels within a narrow and therapeutically relevant range. As we look ahead, we remain on track for interim clinical data from the NGN-401 trial in the fourth quarter of this year.” Continued Dr. McMinn, “Our decision to execute a reverse merger, along with the concurrent private financing, provides us with cash runway into the second half of 2026, beyond key inflection points in our NGN-401 program and our NGN-101 program for CLN5 Batten disease. We look forward to sharing data from both programs later this year and continuing to advance our pipeline to enable an additional development candidate using EXACT in 2025.” Fourth Quarter 2023 and Recent Highlights, and Anticipated Milestones Phase 1/2 Trial of NGN-401 Gene Therapy for Treatment of Rett Syndrome As previously planned, amended the protocol, expanding the trial to include more patients in low-dose Cohort 1 and added a high-dose Cohort 2; these updates are expected to provide a robust dataset and inform the design of a future registrational study Remains on track to report interim clinical data from Cohort 1 in the fourth quarter of 2024; additional interim data, including from Cohort 2, are expected in the second half of 2025 Dosed the third patient early in the first quarter of 2024; removed the dosing stagger in Cohort 1, enabling the remaining patients in the cohort to be dosed in parallel Plans to complete enrollment in Cohort 1 in the second half of 2024; enrollment in Cohort 2 is expected to begin in the second quarter of 2024 Reported that NGN-401 has been generally well-tolerated and there have been no treatment-emergent or procedure-related serious adverse events or signs of overexpression-related toxicity observed in any patient Received NGN-401 clinical trial application approval from the United Kingdom (“UK”) Medicines and Healthcare products Regulatory Agency and working to on-board clinical sites in the UK Phase 1/2 Trial of NGN-101 Gene Therapy for Treatment of CLN5 Batten Disease Continuing enrollment in high-dose Cohort 3, and expects to provide interim clinical data and regulatory update in the second half of 2024 Additional Corporate Updates Expanded the leadership team with appointment of Julie Jordan, M.D., as Chief Medical Officer; Dr. Jordan brings more than 20 years of experience to Neurogene, including design and execution of clinical trials for central nervous system disorders and gene therapies Completed reverse merger and concurrent private placement of $95 million, and began trading on the Nasdaq Global Market under “NGNE” in mid-December 2023 Continues to expect to advance one additional product candidate, using EXACT technology, from the discovery stage into the clinic in 2025 Fourth Quarter and Full Year 2023 Financial Results Cash and Cash Equivalents: Cash, cash equivalents and investments as of December 31, 2023 were $197.2 million. Research & Development (“R&D”) Expenses: R&D expenses were $12.2 million and $44.4 million for the three and twelve months ended December 31, 2023, respectively, compared to $11.0 million and $47.5 million for the three and twelve months ended December 31, 2022, respectively. The decrease in R&D expenses for the twelve months ended December 31, 2023 was primarily driven by a decrease in manufacturing and development and pre-clinical costs offset by increased clinical trial costs. General & Administrative (“G&A”) Expenses: G&A expenses were $2.5 million and $11.2 million for the three and twelve months ended December 31, 2023, respectively, compared to $2.0 million and $9.0 million for the three and twelve months ended December 31, 2022, respectively. The increase in G&A expenses for the twelve months ended December 31, 2023 was primarily driven by an increase in personnel costs, increased professional and consulting fees related to the reverse merger, and increased insurance and information technology costs. Due to the timing of the closing of the reverse merger in mid-December 2023, additional transaction-related expenses are expected to be recognized in the first quarter of 2024. Net Income and Net Loss: Net income was $2.4 million and net loss was $36.3 million for the three and twelve months ended December 31, 2023, respectively, compared to net loss of $12.3 million and $55.2 million for the three and twelve months ended December 31, 2022, respectively. Net income for the three months ended December 31, 2023 included a one-time $16.4 million bargain purchase gain related to the reverse merger. Upcoming Events Stifel 2024 Virtual CNS Days: Management will participate in a fireside chat on Wednesday, March 20 at 9:30 a.m. ET About Neurogene The mission of Neurogene is to treat devastating neurological diseases to improve the lives of patients and families impacted by these rare diseases. Neurogene is developing novel approaches and treatments to address the limitations of conventional gene therapy in central nervous system disorders. This includes selecting a delivery approach to maximize distribution to target tissues and designing products to maximize potency and purity for an optimized efficacy and safety profile. The Company’s novel and proprietary EXACT transgene regulation platform technology allows for the delivery of therapeutic levels while limiting transgene toxicity associated with conventional gene therapy. Neurogene has constructed a state-of-the-art gene therapy manufacturing facility in Houston, Texas. CGMP production of NGN-401 was conducted in this facility and will support pivotal clinical development activities. For more information, visit . Cautionary Note Regarding Forward-Looking Statements Statements in this press release which are not historical in nature are intended to be, and hereby are identified as, forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. These statements may discuss goals, intentions and expectations as to future plans, trends, events, results of operations or financial condition, or otherwise, based on current expectations and beliefs of the management of Neurogene, as well as assumptions made by, and information currently available to, management of Neurogene, including, but not limited to, statements regarding: the therapeutic potential and utility, efficacy and clinical benefits of NGN-401; the safety and tolerability pro NGN-401; trial designs, clinical development plans and timing for NGN-401, including anticipated timing of enrollment in and clinical trial results from the Company’s NGN-401 Phase 1/2 trial for Rett syndrome; effects of the removal of staggered dosing in Cohort 1; initiation of new clinical sites for NGN-401 in the UK; expected interactions with the FDA regarding NGN-101; nomination of additional preclinical product candidates; and our expected cash resources and liquidity. Forward-looking statements generally include statements that are predictive in nature and depend upon or refer to future events or conditions, and include words such as “may,” “will,” “should,” “would,” “expect,” “anticipate,” “plan,” “likely,” “believe,” “estimate,” “project,” “intend,” “on track,” and other similar expressions or the negative or plural of these words, or other similar expressions that are predictions or indicate future events or prospects, although not all forward-looking statements contain these words. Forward-looking statements are based on current beliefs and assumptions that are subject to risks, uncertainties and assumptions that are difficult to predict with regard to timing, extent, likelihood, and degree of occurrence, which could cause actual results to differ materially from anticipated results and many of which are outside of Neurogene’s control. Such risks, uncertainties and assumptions include, among other things: risks related to the timing and success of enrolling patients in the expanded cohort of our Phase 1/2 clinical trial of NGN-401 for the treatment of Rett syndrome; the expected timing and results of dosing of patients in our clinical trials, including NGN-401; the potential that we may not be able to expand our Phase 1/2 clinical trial of NGN-401 for the treatment of Rett syndrome into the UK based on a variety of factors, including but not limited to any decisions of regulatory authorities, costs of expanding the trial in the UK, the availability of suitable clinical test sites, and the ability to enroll patients in the UK or other reasons; the potential for negative impacts to patients resulting from using a higher dose of NGN-401 in Cohort 2 of the Phase 1/2 clinical trial for the treatment of Rett syndrome; the risk that we may not be able to report our data on the predicted timeline; our limited operating history; the risk that we may not be able to raise adequate additional capital to finance our operations, complete our clinical trials and commercialize our products; risks related to our ability to obtain regulatory approval for, and ultimately commercialize, our product candidates, including NGN-401; risks related to the outcome of non-clinical testing and early clinical trials for our product candidates, including the ability of those trials to satisfy relevant governmental or regulatory requirements; risks related to our limited experience in designing clinical trials and lack of experience in conducting clinical trials; and other risks and uncertainties identified under the heading "Risk Factors" included in our Annual Report on Form 10-K for the year ended December 31, 2023, filed with the Securities and Exchange Commission (“SEC”) on March 18, 2024, and other filings that the Company has made and may make with the SEC in the future. Nothing in this communication should be regarded as a representation by any person that the forward-looking statements set forth herein will be achieved or that the contemplated results of any such forward-looking statements will be achieved. Forward-looking statements in this communication speak only as of the day they are made and are qualified in their entirety by reference to the cautionary statements herein. Except as required by applicable law, Neurogene undertakes no obligation to revise or update any forward-looking statement, or to make any other forward-looking statements, whether as a result of new information, future events or otherwise. This communication contains hyperlinks to information that is not deemed to be incorporated by reference into this communication. - Financial Tables Follow - Neurogene Inc. Condensed Consolidated Balance Sheet Data (In thousands of U.S. dollars) December 31, 2023 December 31, 2022 Assets Cash and cash equivalents $ 148,210 $ 82,021 Other current assets 52,138 2,698 Non-current assets 22,225 24,546 Total assets $ 222,573 $ 109,265 Liabilities Current liabilities $ 22,973 $ 6,651 Non-current liabilities 13,576 3,987 Total liabilities 36,549 10,638 Total convertible preferred stock — 244,366 Stockholders' equity (deficit) 186,024 (145,739) Total liabilities, convertible preferred stock and stockholders' equity (deficit) $ 222,573 $ 109,265 Neurogene Inc. Condensed Consolidated Statements of Operations (In thousands of U.S. dollars, except share information) Year Ended December 31, 2023 2022 Operating expenses: Research and development $ 44,394 $ 47,505 General and administrative 11,189 9,012 Total operating expenses 55,583 56,517 Loss from operations (55,583) (56,517) Other income, net 2,911 1,328 Bargain purchase gain 16,355 — Net loss $ (36,317) $ (55,189) Pre-Merger Post- Merger Pre-Merger Per share information (1): (a) (b) (c) (a) (b) Net income (loss) per share, basic $ (117.28) $ — $ 27.76 $ (139.88) $ — Weighted-average shares outstanding used in computing net income (loss) per share, basic 426,097 — 491,867 394,533 — Net income (loss) per share, diluted $ (117.28) $ — $ 2.93 $ (139.88) $ — Weighted-average shares outstanding used in computing net income (loss) per share, diluted 426,097 — 4,656,947 394,533 — (1) On December 18, 2023, the Company completed its reverse merger, which among other things, resulted in Neurogene OpCo merging with and into a wholly owned subsidiary of Neoleukin Therapeutics, Inc. As the earnings per share information for the pre-merger period is not comparable to the earnings per share information for the post-merger period, the earnings per share information is being presented separately for these periods. See Note 3, Net Income (Loss) Per share, for additional information. (a) Presents information for the pre-merger period for Class A common stock. The pre-merger period is January 1, 2023 through December 17, 2023 for the year ended December 31, 2023 and the full fiscal year ended December 31, 2022. (b) Presents information for the pre-merger period for Class B common stock. The pre-merger period is January 1, 2023 through December 17, 2023 for the year ended December 31, 2023 and the full fiscal year ended December 31, 2022. (c) Presents information for the post-merger period for common stock. The post-merger period is December 18, 2023 through December 31, 2023.

Preclinical and translational pipeline program data for AX-0810 for Cholestatic Diseases targeting NTCP and AX-1412 for Cardiovascular Disease targeting B4GALT1 anticipated in 2024, building further momentum toward the clinicAccelerated development of Axiomer™ for CNS applications via new research partnership with Rett Syndrome Research TrustCompleted divestment of sepofarsen and ultevursen ophthalmic programs to Laboratoires Théa€118.9 million cash and cash equivalents as of December 31, 2023 providing runway into mid-2026 LEIDEN, Netherlands & CAMBRIDGE, Mass., March 13, 2024 (GLOBE NEWSWIRE) -- ProQR Therapeutics NV. (Nasdaq: PRQR) (ProQR), a company dedicated to changing lives through transformative RNA therapies based on its proprietary Axiomer™ RNA editing technology platform, today reported its financial and operating results for the year ended December 31, 2023, and provided a business update. “Over the past year as we exclusively focused our strategy on RNA editing, ProQR made important progress with Axiomer, our ADAR-mediated RNA editing technology platform,” said Daniel A. de Boer, Chief Executive Officer of ProQR. “We announced our initial pipeline programs, AX-0810 and AX-1412, targeting NTCP and B4GALT1, respectively, and presented preclinical platform data across a variety of targets. Our platform has demonstrated robust editing, including reporting up to 70% editing of ACTB in the liver of non-human primates, as well as functional protein data with the liver target ANGPTL3 in mice. Additionally, we further strengthened our leading global IP estate for ADAR-mediated RNA editing, which was upheld when challenged by multiple parties in various jurisdictions. We continued to execute and build on the successes achieved during the first two years of our collaboration with Eli Lilly, and formed a new partnership with the Rett Syndrome Research Trust. We also completed the divestment of late-stage ophthalmic assets, sepofarsen and ultevursen, to Laboratoires Théa who will continue the development of these therapies for patients, as ProQR continues to focus exclusively on advancing our RNA editing platform and pipeline.” De Boer continued, “In 2024, we anticipate sharing in vitro, in vivo, and translational data for our initial pipeline programs using Axiomer, and remain on track to enter the clinic in late 2024/early 2025. Along with our extensive body of preclinical proof of concept data for the platform, partnership with Eli Lilly, leading IP position, and strong cash position providing runway into mid-2026, we believe that ProQR is well positioned to continue to execute on our strategy and advance our mission of changing lives through transformative RNA therapies.” Recent Progress In February, ProQR announced that it further strengthened its leading intellectual property estate for ADAR-mediated RNA editing by successfully defending against an opposition filed in Japan by a strawman against ProQR’s granted patent JP 7244922, which is related to the broad concept of using chemically modified oligonucleotides to target specific adenosines within target RNA using endogenous enzymes. The Japanese Patent Office rejected the strawman’s opposition and indicated that all claims were to be maintained as granted to ProQR.In January, ProQR highlighted its continued progress in advancing its Axiomer™ RNA editing technology platform, with new data presented at the 5th International Conference on Base Editing, Prime Editing & Related Enzymes (Deaminet 2024), including: Platform demonstrates robust in vivo editing capabilities reporting up to 70% editing of ACTB in the liver of non-human primates (NHPs) and mice; andFunctional effect demonstrated in mice in vivo via modulation of ANGPLT3 protein properties leading to favorable increase in LPL enzymatic activity and meaningful impact of biomarkers. In January, ProQR and the Rett Syndrome Research Trust (RSRT) formed a partnership focused on utilizing ProQR’s Axiomer™ RNA editing technology platform to design and develop editing oligonucleotides targeting an underlying genetic variant that causes Rett syndrome. RSRT awarded ProQR approximately $1 million as a research grant for the initial phase of the project, which encompasses editing oligonucleotide design and optimization, including evaluation in in vivo models for editing efficiency and MECP2 protein recovery. It is the intent of the partnership to be continued by an expanded co-funding arrangement following the initial discovery work.In December, ProQR completed the divestment of sepofarsen and ultevursen to Laboratoires Théa, who will continue the development of these programs for patients with LCA10 and Usher syndrome. The transaction agreement provided ProQR with an initial payment of €8 million and the Company may be eligible for up to €165 million in further development, regulatory, and commercial earn-out payments upon related achieved milestones, as well as double-digit royalties based on commercial sales in the US and EU. Anticipated Upcoming Events Additional Axiomer™ platform data updates throughout 2024.Preclinical and translational pipeline program data for AX-0810 for Cholestatic Diseases targeting NTCP and AX-1412 for Cardiovascular Disease targeting B4GALT1: In vitro and in vivo data for AX-0810 for Cholestatic Diseases targeting NTCP in mid 2024, and In vitro and in vivo data for AX-1412 for Cardiovascular Diseases targeting B4GALT1 in the second half of 2024. Continue to progress on key steps required to advance AX-0810 and AX-1412 to clinical trials with translational data updates ahead of entry to clinic, which is on track for late 2024/early 2025.Potential initial Trident preclinical data in late 2024 – Trident is ProQR’s early stage RNA editing pseudouridylation platform designed to enable the suppression of nonsense mutations and premature stop codons, which can edit a uridine (U) into a pseudouridine.Potential additional new pipeline target announcements in 2024.Continue to execute on partnership with Eli Lilly and Company (Lilly), with potential data updates to come in 2024 along with potential milestone income from existing partnership, and potential option to exercise for expansion of deal to 15 targets, which would result in a $50 million opt-in payment to ProQR.ProQR may selectively form new partnerships, which could include multi-target discovery alliances, or product alliances on specific programs. Year End 2023 Financial Highlights At December 31, 2023, ProQR held cash and cash equivalents of €118.9 million, compared to €94.8 million at December 31, 2022. Net cash generated by operating activities during the full year ended December 31, 2023 was €21.5 million, compared to €68.5 million net cash used in operating activities for the same period in 2022. The Company experienced a net positive cash flow from operating activities in 2023 primarily due to the receipt of the Lilly up-front payment of $60 million in February 2023. Research and development costs for the year ended December 31, 2023 were €25.1 million, compared to €50.9 million for the same period in 2022. Research and development costs for the year end December 31, 2022 included costs related to the winding down of ophthalmology programs, including the clinical trials. General and administrative costs for the year ended December 31, 2023 were €16.2 million, compared to €18.7 million for the same period in 2022. Net loss for the year ended December 31, 2023 was €27.7 million or €0.35 per diluted share, compared to €64.2 million, or €0.90 per diluted share for the same period ended December 31, 2022. For further financial information for the period ended December 31, 2023, please refer to our 2023 Annual Report on Form 20-F and our Statutory Annual Report which will be available on our website, www. proqr.com under Financials and Filings. About Axiomer™ ProQR is pioneering a next-generation RNA base editing technology called Axiomer™, which could potentially yield a new class of medicines for diverse types of 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 called ADAR (Adenosine Deaminase Acting on RNA). Axiomer™ EONs are designed to recruit and direct endogenously expressed ADARs to change an Adenosine (A) to an Inosine (I) in the RNA – an Inosine is translated as a Guanosine (G) – correcting an RNA with a disease-causing mutation back to a normal (wild type) RNA, modulating protein expression, or altering a protein so that it will have a new function that helps prevent or treat disease. About Biliary Atresia (BA) and Primary Sclerosing Cholangitis (PSC) Cholestatic disorders refer to a group of diseases presenting excessive and toxic buildup of bile acids in the liver due to bile ducts dysfunction. This leads to liver damage and a range of debilitating symptoms. Without treatment, liver damage can progress through various stages, ultimately leading to liver failure and elevated risk of liver malignancy, affecting life expectancy. Cholestatic diseases remain leading causes of liver transplantation. There are no approved therapies for primary sclerosing cholangitis (PSC) for adults and biliary atresia (BA) for pediatrics It is estimated that 80,000 and 20,000 individuals have PSC and BA, respectively, in North America and in Europe. About AX-0810 targeting NTCP The majority of the bile acids present in the liver cells originate from the enterohepatic reuptake cycle. The key transporter responsible for hepatic uptake of bile acids from portal circulation is the sodium (Na+)-taurocholate cotransporting polypeptide (NTCP, SLC10A1 gene) expressed in the liver. AX-0810 is designed to introduce a loss of function variant in SLC10A1 RNA that has been found in human genetics to prevent re-uptake of bile acids in liver via NTCP. Based on its mechanism of action, AX-0810 has the potential to become a disease modifying treatment for PSC and BA primarily among other cholestatic diseases. About Cardiovascular Diseases Cardiovascular diseases (CVDs) are a group of health conditions that affect the heart and blood vessels, such as atherosclerosis which can lead to severe problems like heart attacks, heart failure, and stroke. CVDs represent the leading cause of disability and death in the world. Approximately 18 million people die every year from CVDs representing one third of all the global deaths. Despite available lipid lowering therapies and hypertension medications, the risk of CVDs is still projected to increase rapidly over the coming years. About AX-1412 targeting B4GALT1 Gene–based analysis of rare beta-1,4-galactosyltransferase 1 (B4GALT1) missense variant (p.Asn352Ser) is known to lead to B4GALT1 protein loss of function and showed an association with decreased coronary artery disease. These beneficial effects are mediated by hypo-galactosylation of the apolipoprotein B100 and fibrinogen, known – independent – drivers of increased risk of CVDs. AX-1412 introduces a protective variant into B4GALT1 RNA to address the remaining residual risk of developing cardiovascular diseases. ProQR intends to advance AX-1412 targeting B4GALT1 to early clinical proof of concept stage, then would seek to partner this program. 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 both rare and prevalent diseases with unmet need. 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 “continue,” "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 business, preclinical model data, our initial pipeline targets and the upcoming strategic priorities and milestones related thereto, our Axiomer™ platform, including the continued development and advancement of our Axiomer platform, the therapeutic potential of our Axiomer RNA editing oligonucleotides and our ability to expand preclinical in vivo and in vitro data, the timing, progress and results of our preclinical studies and other development activities, including the release of data related thereto, our patent estate, including our anticipated strength and our continued investment in it, as well as the timing of our clinical development, the potential of our technologies and product candidates, the collaboration with Lilly 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 shortage and pressure on supply and logistics on the global market; the likelihood of our preclinical and clinical programs being initiated and 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 future data to alter initial and preliminary results of early-stage clinical 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 ability to secure, maintain and realize the intended benefits of collaborations with partners, including the collaboration with Lilly; 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; general business, operational, financial and accounting risks, and risks related to litigation and disputes with third parties; and risks related to macroeconomic conditions and market volatility resulting from global economic developments, geopolitical instability and conflicts. 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 KielyProQR Therapeutics N.V.T: +1 617 599 6228skiely@proqr.comorPeter KelleherLifeSci AdvisorsT: +1 617 430 7579 pkelleher@lifesciadvisors.com Media contact:Robert StanislaroFTI ConsultingT: +1 212 850 5657robert.stanislaro@fticonsulting.com

Ongoing Phase 1/2 clinical trial for NGN-401 to include additional patients in Cohort 1 and a dose-escalation cohort Both previously planned updates are expected to provide a more robust dataset to inform future registrational trial design Removal of staggered dosing in Cohort 1 expected to enable the anticipated completion of Cohort 1 dosing in the second half of 2024 Third patient dosed in Cohort 1 NEW YORK--(BUSINESS WIRE)-- Neurogene Inc. (NASDAQ: NGNE) (“Neurogene” or “the Company”), a clinical-stage company founded to bring life-changing genetic medicines to patients and families affected by rare neurological diseases, today announced the expansion of its ongoing Phase 1/2 gene therapy clinical trial for NGN-401 for female pediatric patients with Rett syndrome and updates to enable more rapid enrollment in the trial. “We are excited to share that we have met our first 2024 program milestones, including dosing the third patient in the NGN-401 Phase 1/2 trial for Rett syndrome and expansion of the trial to include more patients in the current dosing cohort and the addition of a high dose cohort,” said Founder and Chief Executive Officer, Rachel McMinn, Ph.D. “Our clinical development strategy has been to build flexibility and optionality early in the program with two concurrent dose cohorts designed to generate a more complete data package, which we expect will inform future registration discussions with global health authorities. We expect that expansion of the clinical trial and the removal of staggered dosing in Cohort 1 will enable us to treat more patients in a shorter period of time. Based on this update, we expect to complete enrollment of Cohort 1 in the second half of 2024.” Rett Syndrome Program Update The U.S. Phase 1/2 clinical protocol for NGN-401 has been amended as follows: Cohort 1, which specifies a total dose of 1×1015 total vector genomes delivered via intracerebroventricular (ICV) administration, was expanded from five patients to eight patients. The dosing stagger has been removed from Cohort 1, enabling the remaining patients to be dosed in parallel. Cohort 2, which specifies a total dose of 3×1015 total vector genomes delivered via ICV administration, was added and is expected to include a total of eight patients. The first three patients in Cohort 2 will be dosed in a staggered manner, with first patient dosing expected in the second quarter of 2024; pending Data and Safety Monitoring Board review of the safety data for the first three patients, the protocol will allow parallel enrollment for the remaining patients in Cohort 2. In addition, the protocol includes a targeted immunosuppression regimen for Cohort 2, designed as a preventative measure to aid in avoiding potential adeno-associated virus (AAV)-related immune responses that have been observed with other AAV-based products in this dose range. The immunosuppression regimen includes the use of rituximab and sirolimus, along with a shortened course of corticosteroids. Cohort 1 immunosuppression remains unchanged with corticosteroids alone. A similar protocol amendment was submitted to the UK regulatory authorities. These changes are consistent with the Company’s guidance issued in January 2024. Importantly, in comprehensive nonclinical studies, the EXACT transgene regulation technology embedded in NGN-401 was shown to mechanistically constrain MECP2 transgene expression levels, allowing for the potential to dose escalate and enhance biodistribution to the brain, without the commensurate increase in MECP2 transgene expression observed with conventional gene therapy. Both doses in the updated protocol are below the “no observed adverse effect” level established in rodent and nonhuman primate models. A third patient was dosed in the trial early in the first quarter. NGN-401 has been generally well-tolerated and there have been no treatment-emergent or procedure-related serious adverse events, or signs of overexpression-related toxicity observed in any patient. Neurogene remains on track to report interim clinical data from Cohort 1 in the fourth quarter of 2024 and additional data, including from Cohort 2, in the second half of 2025. About EXACT Neurogene’s novel and proprietary EXACT gene regulation platform technology is a self-contained transgene regulation platform that can be tuned to deliver a desired level of transgene expression within a narrow and therapeutically relevant range, with the goal of avoiding transgene-related toxicities associated with conventional gene therapy. EXACT is compatible with viral and non-viral delivery platforms. About NGN-401 NGN-401 is an investigational AAV9 gene therapy being developed as a one-time treatment for Rett syndrome. It is the first clinical candidate to deliver the full-length human MECP2 gene under the control of Neurogene’s EXACT technology. The EXACT technology utilized in NGN-401 is an important advancement in gene therapy for Rett syndrome, specifically because the disorder requires a treatment approach that enables targeted levels of MECP2 transgene expression without causing overexpression-related toxic effects associated with conventional gene therapy. The robust nonclinical data package for NGN-401 provides evidence of a potentially compelling efficacy and safety pro Rett syndrome. About Neurogene Neurogene’s mission is to treat devastating neurological diseases to improve the lives of patients and families impacted by these rare diseases. Neurogene is developing novel approaches and treatments to address the limitations of conventional gene therapy in central nervous system disorders. This includes selecting a delivery approach to maximize distribution to target tissues and by designing products to maximize potency and purity for an optimized efficacy and safety profile. The Company’s novel and proprietary EXACT transgene regulation platform technology allows for the delivery of therapeutic levels while limiting transgene toxicity associated with conventional gene therapy. Neurogene has constructed a state-of-the-art gene therapy manufacturing facility in Houston, Texas. GMP production of NGN-401 was conducted in this facility and will support pivotal clinical development activities. For more information, visit . Cautionary Note Regarding Forward-Looking Statements Statements in this press release which are not historical in nature are intended to be, and hereby are identified as, forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. These statements may discuss goals, intentions and expectations as to future plans, trends, events, results of operations or financial condition, or otherwise, based on current expectations and beliefs of the management of Neurogene, as well as assumptions made by, and information currently available to, management of Neurogene, including, but not limited to, statements regarding the therapeutic potential and utility, efficacy and clinical benefits of NGN-401, the safety and tolerability pro NGN-401, trial designs, clinical development plans and timing for NGN-401, including completion of Cohort 1 dosing, first patient dosing of Cohort 2 and anticipated clinical data results in NGN-401 Phase 1/2 trial for Rett syndrome and anticipated impact of expansion of Phase 1/2 trial and removal of staggered dosing in Cohort 1. Forward-looking statements generally include statements that are predictive in nature and depend upon or refer to future events or conditions, and include words such as “may,” “will,” “should,” “would,” “expect,” “anticipate,” “plan,” “likely,” “believe,” “estimate,” “project,” “intend,” “on track,” and other similar expressions or the negative or plural of these words, or other similar expressions that are predictions or indicate future events or prospects, although not all forward-looking statements contain these words. Forward looking statements are subject to risks, uncertainties, and assumptions that are difficult to predict with regard to timing, extent, likelihood, and degree of occurrence, which could cause actual result to differ materially from anticipated results and many of which are outside of Neurogene’s control. Such risks, uncertainties and assumptions include, among other things, risks related the timing and success of enrolling patients in the expanded cohort of our Phase 1/2 clinical trial of NGN-401 for the treatment of Rett syndrome, the expected timing and results of dosing of patients in our clinical trials, including NGN-401, the potential that we may not be able to expand our Phase 1/2 clinical trial of NGN-401 for the treatment of Rett syndrome into the UK based on a variety of factors, including but not limited to any decisions of regulatory authorities, costs of expanding the trial in the UK, the availability of suitable clinical test sites, the ability to enroll patients in the UK or other reasons, the potential for negative impacts to patients resulting from using a higher dose of NGN-401 in Cohort 2 of the Phase 1/2 clinical trial for the treatment of Rett syndrome, the risk that we may not be able to report our data on the predicted timeline, our limited operating history; the risk that we may not be able to raise adequate additional capital to finance our operations, complete our clinical trials and commercialize our products, risks related to our ability to obtain regulatory approval for, and ultimately commercialize, our product candidates, including NGN-401; risks related to the outcome of non-clinical testing and early clinical trials for our product candidates, including the ability of those trials to satisfy relevant governmental or regulatory requirements; risks related to our limited experience in designing clinical trials and lack of experience in conducting clinical trials; expectations regarding the market and potential for Neurogene’s current product candidates, including NGN-401; the substantial competition we face in discovering, developing, or commercializing products, including NGN-401; expectations regarding the potential tolerability, safety or efficacy for our current product candidates, including NGN-401; our ability to attract, hire, and retain skilled executive officers and employees; our ability to protect our intellectual property and proprietary technologies; risks related to our reliance on third parties, contract manufacturers, and contract research organizations and legislative, regulatory, political and economic developments and general market conditions. These and other risks and uncertainties are identified under the heading "Risk Factors" included in our periodic reports that we the Securities and Exchange Commission. Nothing in this communication should be regarded as a representation by any person that the forward-looking statements set forth herein will be achieved or that the contemplated results of any such forward-looking statements will be achieved. Forward-looking statements in this communication speak only as of the day they are made and are qualified in their entirety by reference to the cautionary statements herein. Except as required by applicable law, we do not undertake any obligation to revise or update any forward-looking statement, or to make any other forward-looking statements, whether as a result of new information, future events or otherwise. This communication contains hyperlinks to information that is not deemed to be incorporated by reference into this communication.