Background: Gene therapy, successfully used in rare, monogenetic disorders, may prove to be a durable management approach for common, polygenetic conditions, including neovascular age-related macular degeneration (nAMD). Repeated injections, oftentimes monthly, and possibly for decades, of vascular endothelial growth factor antagonists (anti-VEGF), is the standard for nAMD. We hypothesised that an in-office, intravitreal administration of ixoberogene soroparvovec (ixo-vec, formerly ADVM-022), a single-dose gene therapy encoding for the proven anti-VEGF protein, aflibercept, would transform retinal cells to continually produce aflibercept to minimise treatment burden in nAMD., Methods: In this two-year, open-label, prospective, multicentre phase 1 study, patients with nAMD responding to anti-VEGF were assigned to four cohorts differing by ixo-vec dose (2 × 10 11 vs 6 × 10 11 vector genomes (vg/eye)) and prophylactic steroids (oral prednisone vs topical difluprednate). The primary outcome was the type, severity, and incidence of ocular and systemic adverse events (AEs); secondary endpoints included vision, central subfield thickness (CST), and the number of supplemental injections. This study was registered with ClinicalTrials.gov, NCT03748784., Findings: Thirty patients with nAMD were enrolled between November 14, 2018 and June 30, 2020 at nine study sites in the United States. No systemic ixo-vec related AEs were noted. Across both dose groups the most common adverse event was anterior chamber cell, which was reported in 11 participants in the 6 × 10 11 dose group and in 7 participants in the 2 × 10 11 dose group; intraocular inflammation was responsive to topical corticosteroids, with no anterior chamber cells or vitreous cells observed in 2 × 10 11 vg/eye patients at the end of the study. Vision and CST remained stable throughout two years with annualised anti-VEGF injections reduced by 80% (10.0 mean annualised anti-VEGF injections to 1.9) in 2 × 10 11 vg/eye and 98% (9.8 mean annualised anti-VEGF injections to 0.2) in 6 × 10 11 vg/eye cohorts., Interpretation: Ixo-vec was generally well-tolerated, maintained vision, and improved anatomical outcomes in nAMD, with a substantial reduction in anti-VEGF injections. A single administration of an in-office gene therapy, with vectorised protein with an already established clinical benefit, has the potential to revolutionise the management of common ocular disorders requiring ongoing, frequent therapeutic interventions., Funding: Adverum Biotechnologies., Competing Interests: Arshad M Khanani, M.D., M.A.: •Support of present manuscript: Adverum Biotechnologies.•Consultant: Adverum Biotechnologies, 4D Molecular Therapeutics, Genentech, Novartis, Regeneron Pharmaceuticals, Regenxbio,•Research Support: Adverum Biotechnologies, 4D Molecular Therapeutics, Genentech, Novartis, Regenxbio. David S Boyer, M.D.:•4D Molecular Therapeutics, Achillion, Adverum Biotechnologies, Alcon, Aldeyra Therapeutics, Alimera Sciences, Alkahest, Allegro, Allergan, Allgenesis, Amydis, Annexon Biosciences, Apellis Pharmaceuticals, Applied Genetec Technologies Crop (AGTC), Ashvattha, AsclepiX Therapeutics, Aviceda Therapeutics, Bausch & Lomb, Bayer, Biovisics Medical, Boehringer-Ingelheim, Cell Care Therapeutics, Chengdu Kanghong Biotechnology, Clearside Biomedical, Curacle Co LTD, Delsitech, Eyepoint Pharmaceuticals, Genentech, Glaukos, Iveric Bio, jCyte, Kriya Therapeutics, Kyowa Kirin, Lineage Cell, Lumithera, Inc, Nanoscope, NGM Biotherapeutics, Novartis, Ocular Therapeutix, Ocular Therapeutix, Ocugen, Oculis, Ocuphire, OcuTerra, Ocutrx Vision Technologies, Opthea, Optigo Biotechnology, Optos, Oxurion, Palatin, Pfizer, Regeneron Pharmaceuticals, RetinAI Medical AG, Ripple Therapeutics, Roche, Sanofi, Santen, Shenyang XingQi Pharma, Smilebiotek Zhuhai Limited, Stealth Biotherapeutics, Surrozen, Inc, Syneos, Thea Laboratories, UNITY Biotechnology, Vanotech, Verseon Corporation, Vitranu, Virto Biopharma, Viva Vision Biotech. Charles C Wykoff, M.D., Ph.D.:•Consulting fees/honoraria paid to me for ongoing services provided as a Consultant for: 4DMT, AbbVie, Adverum, Aerie, AGTC, Alcon, Alimera, Allergan, Allgenesis, Alnylam, Annexon, Apellis, Arrowhead, Bausch + Lomb, Bayer, Bionic Vision Technologies, Boehringer Ingelheim, Cholgene, Clearside, Curacle, Eyebiotech, EyePoint, Foresite, Frontera, Genentech, Gyroscope, IACTA, IVERIC Bio, Janssen, Kato, Kiora, Kodiak, Kriya, Merck, Nanoscope, Neurotech, NGM, Notal Vision, Novartis, OccuRx, Ocular Therapeutix, Ocuphire, Ocuterra, OliX, ONL, Opthea, Oxular, Palatin, PerceiveBio, Perfuse, PolyPhotonix, Ray, RecensMedical, Regeneron, RegenXBio, Resonance, Roche, Sandoz, Sanofi, SciNeuro, Stealth, Surrozen, Suzhou Raymon, Takeda, THEA, Therini, TissueGen, Valo, Verana.•Grants paid to my institution for ongoing Research support as a Principal Investigator for trials sponsored by: 4DMT, Adverum, AffaMed, Alexion, Alimera, Alkahest, Allergan, Aldeyra, Allgenesis, Amgen, Annexin, Annexon, Apellis, Asclepix, Bayer, Boehringer Ingelheim, Chengdu Kanghong, Clearside, Curacle, Eyebiotech, EyePoint, Gemini, Genentech, GlaxoSmithKline, Graybug, Gyroscope, IONIS, iRENIX, IVERIC bio, Janssen, Kodiak, LMRI, McMaster University, Nanoscope, Neurotech, NGM, Novartis, Ocular Therapeutix, Ocuphire, OcuTerra, OliX, Ophthotech, Opthea, Oxurion, Oxular, Oyster Point, PerceiveBio, RecensMedical, Regeneron, RegenXBio, Rezolute, Roche, SamChunDang Pharm, Sandoz, Senju, Taiwain Liposome Co., UNITY, Verily, Xbrane.•Participation on a Data Safety Monitoring Board or Advisory Board: Kato, Aerie.•Leadership or fiduciary role in other board, society, committee or advocacy group, paid or unpaid: ASRS, Vit-Buckle Society.•Stock Options (not owner) from Private For-Profit Entities: ONL, PolyPhotonix, RecensMedical, TissueGen, Visgenx, Vitranu. Carl D Regillo, M.D.:•Consulting: 4DMT, Adverum, Allergan, Annexon, Apellis, Aviceda, Bausch and Lomb, Clearside, Cognition, Eyepoint, Genentech, Iveric, Janssen, Kodiak, Lineage, Merck, NGM, Novartis, Ocugen, Ocular Therapeutics, Ocuterra, Ray, RegenXBio, Stealth, Thea, Zeiss.•Research Support: Adverum, Allergan, Annexon, Apellis, Astellas, Eyepoint, Genentech, Gyroscope, Iveric, Janssen, Kodiak, Lineage, NGM, Notal, Novartis, Ocugen, Ocuterra, Opthea, Regeneron, RegenXBio.•Participation on a Data Safety Monitoring Board or Advisory Board: Cognition, Iveric. Brandon G Busbee, M.D.:•Consultant: Genentech.•Speaker: Apellis.•Royalties: Thea. Dante Pieramici, M.D.:•Medical writing support for present manuscript: Adverum Biotechnologies.•Consultant: Genentech, Regeneron, RegenXBio, Adverum, Eyepoint, Unity, Clearside, Gyroscope, Opthea.•Research Funding paid to institution: Regeneron, RegenXBio, Adverum, Ocular Therapeutix, Eyepoint, Clearside, 4DMT, Janssen, Helios, Valo.•Participation on a Data Safety Monitoring Board or Advisory Board: PERCEIVE•Leadership or fiduciary role in other board, society, committee or advocacy group, paid or unpaid: Genentech. Carl J Danzig, M.D.:•Research Grant: Adverum, Genentech/Roche, Regeneron/Bayer, Kodiak, Unity, IvericBio, Gyroscope, Novartis, Curacle, Rezolute, 4DMT.•Consultant: Adverum, Genentech/Roche, Regeneron/Bayer, Novartis, Kodiak, IvericBio.•Speaker: Genentech, IvericBio, Novartis, Regeneron.•Advisory Board or Data Safety Monitoring Board: Abbvie/RegenexBio, Genentech, Adverum. Brian C Joondeph, M.D.:•Payment for expert testimony: Contegrity Expert Group.•Leadership or fiduciary role in other board, society, committee or advocacy group, paid or unpaid: Colorado Retina Executive Committee, unpaid. James C Major, M.D., Ph.D.:•Research Support: Adverum Biotechnologies, Inc.•Leadership or fiduciary role in other board, society, committee or advocacy group, paid or unpaid: ASRS Board of Directors (unpaid). Adam Turpcu, Ph.D.:•Employee and stockholder of Adverum Biotechnologies, Inc. Szilárd Kiss, M.D.:•Consultant/Advisor, Equity: Adverum Biotechnologies•Consulting: Regeneron, Optos, Novartis, Gyroscope, Apellis.•Advisory Board or Data Safety Monitoring Board: Novartis.•Intellectual Property related to gene and cellular therapy: Assigned to Weill Cornell/Cornell University., (© 2023 The Author(s).)