Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K (Mark One) ☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2023 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number: 001-39319 GENERATION BIO CO. (Exact name of registrant as specified in its charter) Delaware 81-4301284 (State or othe ...

CAMBRIDGE, Mass., Feb. 27, 2024 (GLOBE NEWSWIRE) -- Generation Bio Co. (Nasdaq:GBIO) a biotechnology company innovating genetic medicines for people living with rare and prevalent diseases, announced that Geoff McDonough, M.D., president and chief executive officer, will present at the 2024 TD Cowen Health Care Conference on Tuesday, March 5, 2024 at 9:10 a.m. ET in Boston. A live webcast of the presentation will be available on the investor section of the company’s website at investors.generationbio.com. A ...

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 10-Q ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30, 2023 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number: 001-39319 GENERATION BIO CO. (Exact name of registrant as specified in its charter) Delaware 81-4301284 (State or other ...

Table of Contents (Exact name of registrant as specified in its charter) UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 10-Q ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2023 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number: 001-39319 GENERATION BIO CO. Delaware 81-4301284 (State or other juris ...

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Table of Contents WASHINGTON, D.C. 20549 FORM 10-Q ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2023 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number: 001-39319 GENERATION BIO CO. (Exact name of registrant as specified in its charter) Delaware 81-4301284 (State or other juri ...

Financial Performance - The company incurred net losses of $136.6 million, $119.2 million, and $80.5 million for the years ended December 31, 2022, 2021, and 2020, respectively, with an accumulated deficit of $444.8 million as of December 31, 2022[307]. - The company has never generated revenue from product sales and does not expect to achieve profitability for many years, if at all[312]. - The company anticipates significant increases in operating expenses as it establishes manufacturing sources, sales infrastructure, and expands its research programs[308]. - The company expects to need substantial additional funding to support ongoing operations and product development efforts[314]. Research and Development Challenges - The company has devoted substantially all financial resources to research and development, with no products approved for sale[307]. - The company has not identified any product candidates for Investigational New Drug (IND)-enabling studies or clinical development, indicating a long timeline before potential commercialization[330]. - The risk of failure for product candidates is high, with significant uncertainties regarding their effectiveness and safety in humans[337]. - The company has not previously conducted any IND-enabling studies or clinical trials, which may limit its ability to successfully develop genetic medicine programs[351]. - The non-viral genetic medicine platform relies on unproven technologies, making it difficult to predict development timelines and costs[357]. Regulatory and Approval Processes - The commencement of clinical trials in the United States is contingent upon FDA acceptance of an IND application and finalizing trial design, which may lead to delays if additional preclinical studies are required[332]. - Regulatory approvals from authorities such as the FDA and EMA are critical for the commercialization of product candidates, and any delays in obtaining these approvals could materially impact the business[336]. - The regulatory approval process for novel product candidates can be more expensive and time-consuming compared to established therapies, particularly for indications like hemophilia A and PKU, where approved therapies exist[360]. - The company must establish and maintain healthcare insurance coverage and adequate reimbursement by payers to ensure the commercial success of its product candidates[335]. Manufacturing and Supply Chain Risks - The company has entered into a lease for a cGMP-compliant manufacturing facility in Waltham, Massachusetts, but may incur ongoing costs if unable to sublease the property[383]. - The actual cost of manufacturing and processing product candidates is currently unknown, which could adversely affect their commercial viability[386]. - The company relies on a limited number of third-party suppliers for raw materials, which poses risks related to pricing, availability, and quality, potentially impacting the ability to manufacture product candidates[415]. - Any supply interruption of sole-sourced raw materials could materially harm the company's ability to manufacture product candidates, delaying development and commercialization[416]. Competition and Market Dynamics - The competitive landscape includes numerous companies developing genetic medicines, posing significant competition for the company's product candidates[443]. - The company faces significant competition from rivals with greater financial resources and expertise in R&D, manufacturing, and marketing, which could hinder its market position[447]. - Mergers and acquisitions in the pharmaceutical industry may concentrate resources among fewer competitors, increasing competitive pressures[448]. Intellectual Property and Licensing - The company’s ability to protect its intellectual property is crucial; failure to do so could allow competitors to develop similar products, adversely affecting its market position[471]. - The patent prosecution process is complex and costly, with potential risks of failing to file necessary applications on time, which could jeopardize patent protection[474]. - The company may face challenges in obtaining and maintaining patent rights due to prior work in the public domain, which could affect its ability to secure competitive advantages[474]. - The company may lose intellectual property rights if it fails to comply with obligations under its license agreements, which could hinder its ability to develop and commercialize products[482]. Collaboration and Partnership Challenges - Collaborations with third parties for research and commercialization may limit the company's control over resources and timelines, impacting revenue generation[429]. - Collaborators may not commit sufficient resources or may abandon product candidates, which could delay development and commercialization efforts[430]. - The company faces challenges in negotiating collaborations due to recent business combinations among large pharmaceutical companies, reducing potential partners[441].

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 Commission File Number: 001-39319 GENERATION BIO CO. (Exact name of registrant as specified in its charter) Delaware 81-4301284 (State or other jurisdiction of incorporation or organization) (I.R.S. Employer Identification Number) 301 Binney Street Cambridge, Massachusetts 02142 (Address of principal executive offices) (Zip Code) FORM 10-Q ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE AC ...

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 10-Q ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2022 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number: 001-39319 GENERATION BIO CO. (Exact name of registrant as specified in its charter) Delaware 81-4301284 (State or other juris ...

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 10-Q ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2022 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to (State or other jurisdiction of incorporation or organization) Delaware 81-4301284 (I.R.S. Employer Identification Number) 301 Binney Street Cambrid ...

☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2021 Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K (Mark One) OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number: 001-39319 GENERATION BIO CO. (Exact name of registrant as specified in its charter) Delaware 81-4301284 (State or othe ...