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 ...

Financial Performance - The company reported net losses of $72.9 million and $56.4 million for the six months ended June 30, 2022 and 2021, respectively, with an accumulated deficit of $381.1 million as of June 30, 2022[67]. - The net loss for the three months ended June 30, 2022, was $37.9 million, compared to a net loss of $30.8 million for the same period in 2021, reflecting a 23.2% increase in losses[87]. - Research and development expenses increased to $28.4 million for the three months ended June 30, 2022, up from $22.7 million in the same period of 2021, representing a 25.2% increase[88]. - General and administrative expenses rose to $10.1 million for the three months ended June 30, 2022, compared to $8.2 million in the same period of 2021, marking a 23.6% increase[90]. - Net cash used in operating activities was $59.0 million for the six months ended June 30, 2022, compared to $48.5 million for the same period in 2021, representing a 21.0% increase[94]. - Net cash used in investing activities was $161.5 million for the six months ended June 30, 2022, primarily due to an increase in purchases of marketable securities[98]. - Net cash provided by financing activities was $3.6 million for the six months ended June 30, 2022, a significant decrease from $213.9 million in the same period of 2021[100]. - The company expects to incur significant expenses and operating losses for the foreseeable future as it continues its research activities and development of programs[93]. - The company believes its existing cash and marketable securities will fund operations into 2025, but additional financing may be required sooner than expected[102]. Capital and Financing - The company completed its IPO in June 2020, issuing 12,105,263 shares of common stock and receiving net proceeds of $210.7 million[66]. - The company had marketable securities amounting to $153.9 million as of June 30, 2022, with no impairment charges recorded during the first half of 2022[109]. - The company is exposed to interest rate market risk, primarily due to investments in short-term securities, but does not currently hedge this exposure[109]. - The company prohibits investment in auction rate securities and does not have direct exposure to losses from mortgage-based securities or related derivatives[110]. - The company may need to significantly curtail or delay research and development programs if sufficient capital is not raised[103]. - The company may have to relinquish valuable rights to future revenue streams if additional funds are raised through collaborations or licensing arrangements[105]. - The company faces risks associated with substantial capital requirements, as detailed in the "Risk Factors" section of its Quarterly Report[106]. Research and Development - The company has focused on building its non-viral genetic medicine platform since its inception in October 2016, with no products approved for sale and no revenue generated from product sales[66]. - The company plans to expand its portfolio to include therapies for rare and prevalent diseases of the skeletal muscle, central nervous system, and oncology[63]. - The company is exploring the development of mRNA-ctLNP and ceDNA-ctLNP vaccines, which could offer more durable antigen expression and greater shelf stability compared to current mRNA-LNP vaccines[62]. - The company achieved a significant increase in scale for ceDNA manufacturing while maintaining high productivity and purity, leading to underutilization of its planned cGMP facility[64]. - The company believes its non-viral genetic medicine platform can deliver antibody genes for long-term production of antibody therapies from a single dose[61]. - The costs and timing of clinical and commercial-scale manufacturing activities are critical to the company's future commercialization efforts[103]. - The company is focused on the continued development of its non-viral genetic medicine platform, which involves significant costs[103]. Administrative and Operational Expenses - The company anticipates that general and administrative expenses will increase as it expands its headcount and incurs costs associated with operating as a public company[85]. - Other income and interest income increased to $0.6 million for the three months ended June 30, 2022, compared to $0.1 million in the same period of 2021, indicating a significant increase[92]. - The company evaluates its estimates and assumptions regarding financial statements on an ongoing basis, which may lead to significant differences in actual results[107]. - The company considers accrued research and development expenses and stock-based compensation as critical accounting policies affecting financial statement preparation[108].

[PART I – FINANCIAL INFORMATION](index=6&type=section&id=PART%20I%20%E2%80%93%20FINANCIAL%20INFORMATION) [Item 1. Financial Statements (unaudited)](index=6&type=section&id=Item%201.%20Financial%20Statements%20%28unaudited%29) This section presents the unaudited condensed consolidated financial statements for the quarter ended March 31, 2022, highlighting a net loss of **$35.0 million** and a strong cash position of **$337.0 million** sufficient for at least 12 months of operations [Condensed Consolidated Balance Sheets](index=6&type=section&id=Condensed%20Consolidated%20Balance%20Sheets) Condensed Consolidated Balance Sheet Highlights (in thousands) | Account | March 31, 2022 | December 31, 2021 | | :--- | :--- | :--- | | Cash and cash equivalents | $336,978 | $375,145 | | Total assets | $444,026 | $476,771 | | Total liabilities | $91,111 | $95,025 | | Total stockholders' equity | $352,915 | $381,746 | [Condensed Consolidated Statements of Operations and Comprehensive Loss](index=7&type=section&id=Condensed%20Consolidated%20Statements%20of%20Operations%20and%20Comprehensive%20Loss) Statement of Operations Summary (in thousands, except per share data) | Metric | Three Months Ended March 31, 2022 | Three Months Ended March 31, 2021 | | :--- | :--- | :--- | | Research and development | $25,554 | $18,753 | | General and administrative | $9,790 | $6,902 | | **Loss from operations** | **$(35,344)** | **$(25,655)** | | **Net loss** | **$(34,999)** | **$(25,562)** | | Net loss per share | $(0.61) | $(0.46) | [Condensed Consolidated Statements of Cash Flows](index=9&type=section&id=Condensed%20Consolidated%20Statements%20of%20Cash%20Flows) Cash Flow Summary (in thousands) | Activity | Three Months Ended March 31, 2022 | Three Months Ended March 31, 2021 | | :--- | :--- | :--- | | Net cash used in operating activities | $(35,435) | $(23,027) | | Net cash (used in) provided by investing activities | $(2,784) | $113,485 | | Net cash provided by financing activities | $52 | $212,957 | [Notes to Condensed Consolidated Financial Statements](index=10&type=section&id=Notes%20to%20Condensed%20Consolidated%20Financial%20Statements) - The company is an early-stage biotech focused on non-viral genetic medicines using closed-ended DNA (ceDNA) and a cell-targeted lipid nanoparticle (ctLNP) delivery system[24](index=24&type=chunk) - As of March 31, 2022, the company had an accumulated deficit of **$343.1 million**, and management expects existing cash and cash equivalents are sufficient to fund operations and capital expenditures for at least **12 months** from the report's issuance date[27](index=27&type=chunk) - In January 2021, the company raised net proceeds of **$211.3 million** from a follow-on public offering, and an "at-the-market" sales agreement for up to **$250.0 million** was established in August 2021, with no shares sold under it as of May 5, 2022[36](index=36&type=chunk) - Total unrecognized stock-based compensation cost as of March 31, 2022, was **$61.2 million**, expected to be recognized over a weighted-average period of **2.8 years** for stock options and **2.0 years** for restricted stock[48](index=48&type=chunk) [Item 2. Management's Discussion and Analysis of Financial Condition and Results of Operations](index=19&type=section&id=Item%202.%20Management%27s%20Discussion%20and%20Analysis%20of%20Financial%20Condition%20and%20Results%20of%20Operations) Management discusses the company's non-viral genetic medicine focus, increased operating expenses, and strong liquidity with **$337.0 million** cash sufficient into **2024** [Results of Operations](index=28&type=section&id=Results%20of%20Operations) Comparison of Operating Results (in thousands) | Metric | Q1 2022 | Q1 2021 | Change | | :--- | :--- | :--- | :--- | | Research and development | $25,554 | $18,753 | $6,801 | | General and administrative | $9,790 | $6,902 | $2,888 | | **Total operating expenses** | **$35,344** | **$25,655** | **$9,689** | | **Net loss** | **$(34,999)** | **$(25,562)** | **$(9,437)** | - The **$6.8 million** increase in R&D expenses was primarily driven by a **$3.1 million** increase in facilities costs related to the manufacturing facility lease, a **$2.4 million** increase in personnel costs, and a **$1.3 million** increase in stock-based compensation, partly offset by a **$1.2 million** decrease in external manufacturing costs due to the transition to an in-house process[86](index=86&type=chunk) - The **$2.9 million** increase in G&A expenses was mainly due to a **$1.3 million** rise in stock-based compensation and a **$1.0 million** increase in personnel-related costs, both resulting from higher headcount[88](index=88&type=chunk) [Liquidity and Capital Resources](index=30&type=section&id=Liquidity%20and%20Capital%20Resources) - As of March 31, 2022, the company had cash and cash equivalents of **$337.0 million**[90](index=90&type=chunk) - Management believes that existing cash and cash equivalents will be sufficient to fund operating expenses and capital expenditures into **2024**[67](index=67&type=chunk)[102](index=102&type=chunk) - Net cash used in operating activities increased to **$35.4 million** in Q1 2022 from **$23.0 million** in Q1 2021, primarily due to the higher net loss[91](index=91&type=chunk)[92](index=92&type=chunk)[94](index=94&type=chunk) - Net cash provided by financing activities was only **$0.1 million** in Q1 2022, compared to **$213.0 million** in Q1 2021, which included **$211.9 million** in net proceeds from a follow-on public offering[98](index=98&type=chunk) [Item 3. Quantitative and Qualitative Disclosures About Market Risk](index=36&type=section&id=Item%203.%20Quantitative%20and%20Qualitative%20Disclosures%20About%20Market%20Risk) The company's primary market risk is interest rate sensitivity on its **$337.0 million** cash and cash equivalents, with no marketable securities or hedging instruments used - The company's primary market risk is interest rate sensitivity on its cash and cash equivalents, which totaled **$337.0 million** as of March 31, 2022[108](index=108&type=chunk) - The company did not hold any marketable securities as of March 31, 2022, and does not currently use hedging instruments to manage interest rate risk[108](index=108&type=chunk) [Item 4. Controls and Procedures](index=36&type=section&id=Item%204.%20Controls%20and%20Procedures) Management concluded that the company's disclosure controls and procedures were effective as of March 31, 2022, with no material changes to internal controls during the quarter - Based on an evaluation as of March 31, 2022, the CEO and CFO concluded that the company's disclosure controls and procedures were effective at the reasonable assurance level[110](index=110&type=chunk) - There were no changes in internal control over financial reporting during Q1 2022 that have materially affected, or are reasonably likely to materially affect, these controls[111](index=111&type=chunk) [PART II – OTHER INFORMATION](index=38&type=section&id=PART%20II%20%E2%80%93%20OTHER%20INFORMATION) [Item 1A. Risk Factors](index=38&type=section&id=Item%201A.%20Risk%20Factors) This section directs readers to the detailed discussion of risk factors in the company's Annual Report on Form 10-K, which could materially affect future results - The report directs investors to carefully consider the risk factors discussed in Part I, Item 1A of the company's Annual Report on Form 10-K[112](index=112&type=chunk) [Item 6. Exhibits](index=39&type=section&id=Item%206.%20Exhibits) This section lists all exhibits filed with the quarterly report, including a lease amendment and certifications from the Principal Executive and Financial Officers - Exhibits filed with the report include a Third Amendment to the Lease with BMR-Rogers Street LLC, and certifications from the Principal Executive Officer and Principal Financial Officer pursuant to the Sarbanes-Oxley Act of 2002[114](index=114&type=chunk) [Signatures](index=40&type=section&id=Signatures) The report is formally signed and authorized by the company's principal executive and financial officers - The report was signed on May 5, 2022, by Geoff McDonough, President and Chief Executive Officer, and Matthew Norkunas, Chief Financial Officer[119](index=119&type=chunk)

☒ 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 ...

generation bio | --- | --- | --- | --- | --- | --- | --- | --- | --- | |-------|-------|-------|-------|-------|-------|-------|------------------------------------------------------------------------------------------------|----------| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Leading durable | | | | | | | | | | redosable | scalable | | | | | | | | | non-viral genetic medicines FOR MILLIONS OF PATIENTS LIVING WITH RARE AND PREVALENT DISEASES | | | | | | ...

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, 2021 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 ...

Financial Performance - The company reported net losses of $56.4 million for the six months ended June 30, 2021, compared to $35.4 million for the same period in 2020, with an accumulated deficit of $245.3 million as of June 30, 2021[86]. - The net loss for the three months ended June 30, 2021, was $30.8 million, compared to a net loss of $17.7 million for the same period in 2020, reflecting an increase in losses of 73.7%[108]. - Total operating expenses for the six months ended June 30, 2021, were $56.5 million, up from $35.8 million in 2020, indicating a 57.9% increase[113]. - Cash used in operating activities for the six months ended June 30, 2021, was $48.5 million, compared to $33.3 million in 2020, representing a 45.6% increase[118]. - Interest income for the six months ended June 30, 2021, was $0.1 million, down from $0.4 million in 2020, a decrease of 71.4%[116]. - The company expects to incur significant expenses and operating losses for the foreseeable future as it continues its research and development activities[117]. - Existing cash, cash equivalents, and marketable securities are projected to fund operations into 2024, but additional financing may be required sooner than expected[125]. - The company does not have any committed external sources of funds and will need to seek further funding through various means, which may lead to dilution for stockholders[125]. - If sufficient capital is not raised, the company may need to significantly curtail or discontinue research, development programs, or commercialization efforts[126]. Research and Development - The company plans to submit an IND application for its hemophilia A program in 2023 and expects to report Factor VIII expression data in non-human primates by year-end[81]. - The company is advancing a broad portfolio of programs targeting rare and prevalent diseases, initially focusing on liver and retina diseases[79]. - The company aims to enable patients to produce therapeutic antibodies from their own cells for years from a single dose, with in vivo studies showing a peak antibody concentration of 8µg/ml[80]. - The increase in research and development expenses was primarily due to heightened preclinical activity and increased headcount in the R&D function[114]. - Research and development expenses increased to $22.7 million for the three months ended June 30, 2021, up from $13.5 million in the same period of 2020, representing a 68.3% increase[109]. - The company expects substantial increases in expenses related to ongoing activities, particularly in preclinical and clinical trials for product candidates[125]. Manufacturing and Operations - The company has developed a rapid enzymatic synthesis process (RES) that shortens the ceDNA production cycle time from 28 days to one day, aiming to manufacture drug candidates cost-effectively[83]. - The company plans to invest up to $45 million in a new cGMP-compliant manufacturing facility in Waltham, Massachusetts, expected to be operational in 2023[84]. - The company plans to transition all portfolio programs to the RES manufacturing process to enhance scalability and reduce variability[83]. General and Administrative Expenses - General and administrative expenses rose to $8.2 million for the three months ended June 30, 2021, compared to $4.3 million in 2020, marking an increase of 92.5%[111]. COVID-19 Impact - The company is closely monitoring the impact of the COVID-19 pandemic on its operations and has implemented safety measures for its employees[93]. Accounting Policies - Critical accounting policies related to accrued research and development expenses and stock-based compensation are deemed most critical for financial statement preparation[129]. - There have been no material changes to critical accounting policies and estimates from those disclosed in the Annual Report[129]. - The company currently has no off-balance sheet arrangements[130]. - Recently adopted accounting pronouncements that may impact financial position and results of operations are disclosed in the Quarterly Report[131]. - The company is classified as a smaller reporting company and is not required to provide certain market risk disclosures[132].