Passage BIO, Inc.

Previous wording

We are a clinical stage genetic medicines company on a mission to improve the lives of patients with neurodegenerative diseases. Our primary focus is the development and advancement of cutting-edge, one-time gene therapies designed to target critical underlying pathologies in these conditions. We believe we have developed a differentiated approach to developing treatments for central nervous system, or CNS, disorders that allows us to select and advance product candidates with a higher probability of technical and regulatory success.

Current wording

We are a clinical stage genetic medicines company focused on improving the lives of patients with neurodegenerative diseases. Our primary focus is the development and advancement of cutting-edge, one-time gene therapies designed to target critical underlying pathologies in these conditions. We believe we have developed a differentiated approach to developing treatments for central nervous system, or CNS, disorders that allows us to select and advance product candidates with a higher probability of technical and regulatory success.

Previous wording

We are currently studying PBFT02 in FTD-GRN, for which there are currently no approved disease-modifying therapies. In addition to the continued clinical development of PBFT02 to treat FTD-GRN, we intend to pursue PBFT02 in additional adult neurodegenerative diseases where we believe increasing PGRN levels could provide benefit. Third-party preclinical studies have shown that increased PGRN levels reduce the pathologic accumulation of TAR DNA binding protein 43, or TDP-43. TDP-43 pathology is a hallmark of multiple neurodegenerative conditions, including FTD due to mutations in theC9orf72 gene, or FTD-C9orf72, approximately 95% of sporadic amyotrophic lateral sclerosis, or ALS, and approximately 50% of sporadic FTD. Additionally, we believe restoration of PGRN has the potential to modulate Alzheimer’s disease, or AD, in patients who are carriers of the PGRN-loweringGRN rs5848 single nucleotide polymorphism, or SNP. Individuals with this polymorphism have reduced PGRN levels and are at an increased risk for AD. We have received positive regulatory feedback on the clinical pathway to treating FTD-C9orf72 patients and ALS patients with PBFT02. We are proceeding with clinical development of PBFT02 in FTD-C9orf72 patients, and plan to begin patient enrollment upon site review and acceptance of the amended upliFT-D clinical trial protocol.

Current wording

We are currently studying PBFT02 in FTD-GRN, for which there are currently no approved disease-modifying therapies. In addition to the continued clinical development of PBFT02 to treat FTD-GRN, we intend to pursue PBFT02 in additional adult neurodegenerative diseases where we believe increasing PGRN levels could provide benefit. Third-party preclinical studies have shown that increased PGRN levels reduce the pathologic accumulation of TAR DNA binding protein 43, or TDP-43. TDP-43 pathology is a hallmark of multiple neurodegenerative conditions, including FTD due to mutations in theC9orf72 gene, or FTD-C9orf72, approximately 95% of sporadic amyotrophic lateral sclerosis, or ALS, and approximately 50% of sporadic FTD. Additionally, we believe restoration of PGRN has the potential to modulate Alzheimer’s disease, or AD, in patients who are carriers of the PGRN-loweringGRN rs5848 single nucleotide polymorphism, or SNP. Individuals with this polymorphism have reduced PGRN levels and are at an increased risk for AD. We have received positive regulatory feedback on the clinical pathway to treating FTD-C9orf72 patients and ALS patients with PBFT02. We are proceeding with clinical development of PBFT02 in FTD-C9orf72 patients, and have opened enrollment in the upliFT-D study for this population.

Previous wording

Prior to the execution of the Outlicense Transaction Agreements, we progressed four product candidates from preclinical to clinical stage development and had one active preclinical program in Huntington’s disease through our research collaboration with the Trustees of the University of Pennsylvania’s, or Penn’s, Gene Therapy Program, or GTP. This collaboration provided access to differentiated scientific expertise for the conduct of rigorous preclinical studies to

Current wording

Prior to the execution of the Outlicense Transaction Agreements, we progressed four product candidates from preclinical to clinical stage development and had one active preclinical program in Huntington’s disease through our research collaboration with the Trustees of the University of Pennsylvania’s, or Penn’s, Gene Therapy Program, or GTP. This collaboration provided access to differentiated scientific expertise for the conduct of rigorous preclinical studies to generate promising product candidates. Gemma is comprised of a core research team from GTP and is continuing the same approach to preclinical development to support the continued development of our preclinical Huntington’s disease program.

Previous wording

In June 2025, we reported biomarker data from patients in our upliFT-D trial. Dose 1 of PBFT02 (3.3e10 genome copies/g estimated brain weight, or 4.5e13 total genome copies) resulted in robust and durable increases in CSF PGRN levels, with concentrations increasing from below 3.0 ng/mL at baseline to a mean of 12.4 ng/mL at one month (n=7), 19.4 ng/mL at six months (n=6), 25.9 ng/mL at 12 months (n=4), and 23.8 ng/mL at 18 months (n=2). These levels of CSF PGRN are higher than the range found in healthy adult controls of 3.3 to 8.2 ng/mL (mean=4.8 ng/mL; n=61). CSF PGRN levels for the first patient treated with Dose 2 of PBFT02 (1.6e10 genome copies/g estimated brain weight, or 2.2e13 total genome copies) increased substantially from 1.5 ng/mL at baseline to 7.6 ng/mL at one month, approaching the upper limit of the range found in healthy adult controls. In contrast, following PBFT02 administration, plasma PGRN levels were unaltered, remaining similar to baseline concentrations and below mean levels found in healthy adult

Current wording

In June 2025, we reported biomarker data from patients in our upliFT-D trial. Dose 1 of PBFT02 (3.3e10 genome copies/g estimated brain weight, or 4.5e13 total genome copies) resulted in robust and durable increases in CSF PGRN levels, with concentrations increasing from below 3.0 ng/mL at baseline to a mean of 12.4 ng/mL at one month (n=7), 19.4 ng/mL at six months (n=6), 25.9 ng/mL at 12 months (n=4), and 23.8 ng/mL at 18 months (n=2). These levels of CSF PGRN are higher than the range found in healthy adult controls of 3.3 to 8.2 ng/mL (mean=4.8 ng/mL; n=61). CSF PGRN levels for the first patient treated with Dose 2 of PBFT02 (1.6e10 genome copies/g estimated brain weight, or 2.2e13 total genome copies) increased substantially from 1.5 ng/mL at baseline to 7.6 ng/mL at one month, approaching the upper limit of the range found in healthy adult controls. In contrast, following PBFT02 administration, plasma PGRN levels were unaltered, remaining similar to baseline concentrations and below mean levels found in healthy adult controls. Dose 1 of PBFT02 resulted in an average 4% increase in plasma neurofilament light chain, or NfL, levels, a biomarker associated with disease progression, compared to baseline at 12 months post-treatment (n=4). This change in plasma NfL after PBFT02 administration contrasts with an expected increase in plasma NfL levels of approximately 28% and 29% per year among untreated, symptomatic FTD-GRN patients, based on analysis of the ALLFTD natural history data and published natural history data (Saracino 2021), respectively.

Previous wording

We have amended the upliFT-D clinical trial protocol to introduce a short course of low dose prophylactic anticoagulation, a decision supported by study investigators and the Independent Data Monitoring Committee, or IDMC. Upon review and acceptance of the amended protocol at study sites, we plan to begin enrollment in Cohort 3, which is expected to consist of five to 10 FTD-GRN patients.

Current wording

We have amended the upliFT-D clinical trial protocol to introduce a short course of low dose prophylactic anticoagulation, a decision supported by study investigators and the Independent Data Monitoring Committee, or IDMC.

Previous wording

We received positive regulatory feedback on the clinical pathway to treating FTD-C9orf72 with PBFT02 in the ongoing upliFT-D trial and revised the study to include two cohorts. Cohorts 4 and 5 will consist of three to five symptomatic FTD patients withC9orf72 gene mutations who will initially receive Dose 2 PBFT02. There are no disease modifying therapies approved for the treatment of FTD-C9orf72. Based on available literature, we estimate the prevalence of FTD-

Current wording

We received positive regulatory feedback on the clinical pathway to treating FTD-C9orf72 with PBFT02 in the ongoing upliFT-D trial and revised the study to include two cohorts. Cohorts 4 and 5 will consist of three to five symptomatic FTD patients withC9orf72 gene mutations who will initially receive Dose 2 PBFT02. There are no disease modifying therapies approved for the treatment of FTD-C9orf72. Based on available literature, we estimate the prevalence of FTD-C9orf72 in the United States and Europe is approximately 21,000. We have implemented the amended protocol at initial trial sites and are currently enrolling Cohort 4.

Previous wording

We also have a research program through the Gemma Collaboration Agreement for TLE, which was previously conducted under the research, collaboration and licensing agreement with Penn, as amended, previously the Penn Agreement and now referred to as the Penn License Agreement. In order to reduce operating expenses, we have paused development of this program.

Current wording

We also have a research program through the Gemma Collaboration Agreement for Temporal Lobe Epilepsy, or TLE, which was previously conducted under the research, collaboration and licensing agreement with Penn, as amended, previously the Penn Agreement and now referred to as the Penn License Agreement. In order to reduce operating expenses, we have paused development of this program.

Previous wording

an accumulated deficit of $684.0 million. Our primary use of cash is to fund operating expenses, which consist primarily of research and development expenditures, and to a lesser extent, general and administrative expenditures. Our ability to generate product revenue sufficient to achieve profitability will depend heavily on the successful development and eventual commercialization of one or more of our current or future product candidates. We expect to continue to incur significant expenses and operating losses for the foreseeable future as we advance our product candidates through all stages of development and clinical trials and, ultimately, seek regulatory approval. In addition, if we obtain marketing approval for any of our product candidates, we expect to incur significant commercialization expenses related to product manufacturing, marketing, sales and distribution. Our net losses may fluctuate significantly from quarter to quarter and year to year, depending on the timing of our clinical trials and our expenditures on other research and development activities.

Current wording

We were incorporated in July 2017 under the laws of the State of Delaware. Since inception, our operations have consisted primarily of conducting preclinical studies, developing licensed technology, conducting clinical trials, and manufacturing clinical supply to support clinical trials. We have incurred recurring losses, the majority of which are attributable to research and development activities, and negative cash flows from operations. Historically, we have funded our operations through the sale of convertible preferred stock and public offerings of common stock. Our net losses were $7.7 million and $19.3 million for the three months ended September 30, 2025 and 2024, respectively, and $32.5 million and $52.0 million for the nine months ended September 30, 2025 and 2024, respectively. As of September 30, 2025, we had an accumulated deficit of $691.8 million. Our primary use of cash is to fund operating expenses, which consist primarily of research and development expenditures, and to a lesser extent, general and administrative expenditures. Our ability to generate product revenue sufficient to achieve profitability will depend heavily on the successful development and eventual commercialization of one or more of our current or future product candidates. We expect to continue to incur significant expenses and operating losses for the foreseeable future as we advance our product candidates through all stages of development and clinical trials and, ultimately, seek regulatory approval. In addition, if we obtain marketing approval for any of our product candidates, we expect to incur significant commercialization expenses related to product manufacturing, marketing, sales and distribution. Our net losses may fluctuate significantly from quarter to quarter and year to year, depending on the timing of our clinical trials and our expenditures on other research and development activities.

Previous wording

As of June 30, 2025, we had cash and cash equivalents of $57.6 million. We expect our existing cash and cash equivalents will enable us to fund our operating expenses and capital expenditure requirements into the first quarter of 2027.

Current wording

As of September 30, 2025, we had cash and cash equivalents of $52.8 million. We expect our existing cash and cash equivalents will enable us to fund our operating expenses and capital expenditure requirements into the first quarter of 2027.

Previous wording

Upon successful commercialization of a product using the licensed technology, we are obligated to pay to Penn, on a licensed product-by-licensed product and country-by-country basis, tiered royalties (subject to customary reductions) in the mid-single digits percentage on annual worldwide net sales of such licensed product. In addition, other than the Amended Gemma Sublicenses, we are obligated to pay to Penn a percentage of sublicensing income, ranging from the mid-single digits to low double digits, for sublicenses under the Penn License Agreement. The agreement will expire on a licensed product-by-licensed product and country-by-country basis upon the later of (i) the expiration of the last valid claim of the licensed patent rights that covers the exploitation of such licensed product in such country, and (ii) the

Current wording

Upon successful commercialization of a product using the licensed technology, we are obligated to pay to Penn, on a licensed product-by-licensed product and country-by-country basis, tiered royalties (subject to customary reductions) in the mid-single digits percentage on annual worldwide net sales of such licensed product. In addition, other than the Amended Gemma Sublicenses, we are obligated to pay to Penn a percentage of sublicensing income, ranging from the mid-single digits to low double digits, for sublicenses under the Penn License Agreement. The agreement will expire on a licensed product-by-licensed product and country-by-country basis upon the later of (i) the expiration of the last valid claim of the licensed patent rights that covers the exploitation of such licensed product in such country, and (ii) the expiration of the royalty period. Pursuant to the Amended Gemma Sublicenses, Gemma is responsible for the payments to Penn related to the Outlicensed Programs.

Previous wording

In addition, we entered into the Transition Services Agreement, as amended by the First Amendment to the Transition Services Agreement, dated January 31, 2025, pursuant to which, we provided transitional services at cost to Gemma through May 31, 2025, and are entitled to reimbursement for transitional services performed retroactively from March 1, 2024, related to the transfer of the Outlicensed Programs. As of June 30, 2025, we have collected $5.0 million in initial payments and $4.7 million in transition services payments under these agreements. Subsequent to June 30, 2025, we have applied $0.7 million in amounts owed to Gemma for the Huntington’s disease program against amounts due to us for transition services.

Current wording

In addition, we entered into the Transition Services Agreement, as amended by the First Amendment to the Transition Services Agreement, dated January 31, 2025, pursuant to which, we provided transitional services at cost to Gemma through May 31, 2025, and are entitled to reimbursement for transitional services performed retroactively from March 1, 2024, related to the transfer of the Outlicensed Programs. As of September 30, 2025, we have collected $7.5 million in initial payments and $4.8 million in transition services payments under these agreements. In addition, we have applied $1.5 million in amounts owed to Gemma for the Huntington’s disease program against amounts due to us for transition services.

Previous wording

We expect our research and development expenses to decrease in the near future as a result of the reduction of our overall workforce by 55% and cessation of our lab operations in Hopewell, New Jersey in January 2025. We expect that the reduction of expenses related to the Outlicensed Programs pursuant to the Outlicense Transaction Agreements will offset the increased expenses of advancing our remaining product candidates in the near future. If our product candidate

Current wording

We expect that the reduction of expenses related to the Outlicensed Programs pursuant to the Outlicense Transaction Agreements will offset the increased expenses of advancing our remaining product candidates. As such, we expect our research and development expenses to remain consistent in the near future. If our product candidate portfolio progresses into later-stage clinical trials, we expect that our research and development expenses will increase in the future to support continued research and development activities and production of clinical supply.

Previous wording

Impairment of long-lived assets consists of non-cash impairment charges recorded to our assets. We review long-lived assets, such as the right of use assets, or ROU assets, or property and equipment, for impairments when events or changes in circumstances indicate the carrying amount of the assets may not be recoverable. During the six months ended June 30, 2025, we recognized impairment expenses related to property and equipment and certain other assets in connection with the announcement to reduce our workforce by 55% and cease our lab operations in Hopewell, New Jersey. We reassessed asset groups at the lab in Hopewell, New Jersey, and evaluated such asset groups for impairment. We determined the laboratory equipment was a separate asset group based on management’s implemented plans to sell the laboratory equipment and estimated the fair value of the laboratory equipment based on the estimated future cash flows from the sale of such equipment.

Current wording

Impairment of long-lived assets consists of non-cash impairment charges recorded to our assets. We review long-lived assets, such as the right of use assets, or ROU assets, or property and equipment, for impairments when events or changes in circumstances indicate the carrying amount of the assets may not be recoverable. During the nine months ended September 30, 2025, we recognized impairment expenses related to property and equipment and certain other assets in connection with the announcement to reduce our workforce by 55% and cease our lab operations in Hopewell, New Jersey. We reassessed asset groups at the lab in Hopewell, New Jersey, and evaluated such asset groups for impairment. We determined the laboratory equipment was a separate asset group based on management’s implemented plans to sell the laboratory equipment and estimated the fair value of the laboratory equipment based on the estimated future cash flows from the sale of such equipment.

Previous wording

Other income (expense), net decreased by $0.4 million to $1.0 million for the three months ended June 30, 2025 from $1.4 million for the three months ended June 30, 2024. The decrease was primarily due to the following:

Current wording

Other income (expense), net decreased by $0.5 million to $0.9 million for the three months ended September 30, 2025 from $1.4 million for the three months ended September 30, 2024. The decrease was primarily due to the following:

Previous wording

The following table sets forth our results of operations for the six months ended June 30, 2025 and 2024:

Current wording

The following table sets forth our results of operations for the nine months ended September 30, 2025 and 2024:

Previous wording

During the six months ended June 30, 2025, we recorded $2.6 million of impairment expense related to laboratory equipment and certain other assets which were revalued and subsequently sold from the Hopewell Laboratory Space.

Current wording

During the nine months ended September 30, 2025, we recorded $2.6 million of impairment expense related to laboratory equipment and certain other assets which were revalued and subsequently sold from the Hopewell Laboratory Space.

Previous wording

During the three months ended June 30, 2024, we recorded $0.4 million of impairment expenses related to property and equipment for a construction in progress asset.

Current wording

During the nine months ended September 30, 2024, we recorded $5.2 million of impairment expense primarily consisting of $2.5 million and $2.3 million recorded to the ROU assets and property and equipment, net, respectively, related to the Hopewell Laboratory Space. In addition, we recorded $0.4 million of impairment expenses related to property and equipment for a construction in progress asset we no longer planned to deploy.

Previous wording

Other income (expense), net decreased by $0.7 million to $2.0 million for the six months ended June 30, 2025 from $2.7 million for the six months ended June 30, 2024. The decrease was primarily due to the following:

Current wording

Other income (expense), net decreased by $1.2 million to $2.9 million for the nine months ended September 30, 2025 from $4.1 million for the nine months ended September 30, 2024. The decrease was primarily due to the following:

Previous wording

As of June 30, 2025, we had $57.6 million in cash and cash equivalents and had an accumulated deficit of $684.0 million. We expect our existing cash and cash equivalents will enable us to fund our operating expenses and capital expenditure requirements into the first quarter of 2027.

Current wording

As of September 30, 2025, we had $52.8 million in cash and cash equivalents and had an accumulated deficit of $691.8 million. We expect our existing cash and cash equivalents will enable us to fund our operating expenses and capital expenditure requirements into the first quarter of 2027.

Previous wording

During the six months ended June 30, 2024, we used $32.1 million of net cash in operating activities. Cash used in operating activities reflected a net loss of $32.7 million and a net increase in our operating assets of $3.8 million, partially offset by non-cash charges of $4.4 million related to depreciation, amortization, share-based compensation, and amortization of premium and discount, net, and impairment of long-lived assets. The primary use of cash was to fund our operations related to the development of our product candidates.

Current wording

During the nine months ended September 30, 2025, we used $25.0 million of net cash in operating activities. Cash used in operating activities reflected a net loss of $32.5 million and a decrease in our operating assets of $1.8 million and non-cash charges of $5.7 million related to depreciation, amortization, share-based compensation, amortization of premium and discount, net, impairment of long-lived assets, and other non-cash items. The primary use of cash was to fund our operations related to the development of our product candidates.

Previous wording

During the six months ended June 30, 2025, we used $20.2 million of net cash in operating activities. Cash used in operating activities reflected a net loss of $24.8 million and a decrease in our operating assets of $0.3 million, partially offset by non-cash charges of $4.9 million related to depreciation, amortization, share-based compensation, amortization of premium and discount, net, and impairment of long-lived assets. The primary use of cash was to fund our operations related to the development of our product candidates.

Current wording

During the nine months ended September 30, 2024, we used $39.5 million of net cash in operating activities. Cash used in operating activities reflected a net loss of $52.0 million, partially offset by a net decrease in our operating assets of $1.5 million, and net non-cash charges of $11.0 million related to depreciation, amortization, share-based compensation, amortization of premium and discount, net, and impairment of long-lived assets. The primary use of cash was to fund our operations related to the development of our product candidates.

Previous wording

Duringthe six months ended June 30, 2025, we had sales and maturities of $39.0 million in marketable securities and received cash proceeds of $1.2 million related to the sale of property and equipment and certain other assets.

Current wording

Duringthe nine months ended September 30, 2025, we had sales and maturities of $39.0 million in marketable securities and received cash proceeds of $1.2 million related to the sale of property and equipment and certain other assets. We did not make any purchases of property and equipment for the nine months ended September 30, 2025.

Previous wording

During the six months ended June 30, 2024, we purchased $50.8 million in marketable securities, and had sales and maturities of $77.1 million in marketable securities. We did not make any purchases of property and equipment for the six months ended June 30, 2025 and 2024.

Current wording

During the nine months ended September 30, 2024, we purchased $72.6 million in marketable securities, and had sales and maturities of $113.9 million in marketable securities. Purchases of property and equipment were de minimis for the nine months ended September 30, 2024.

Previous wording

During the six months ended June 30, 2025, we received de minimis proceeds from the issuance of common stock under the ESPP.

Current wording

During the nine months ended September 30, 2025, we received de minimis proceeds from the issuance of common stock under the ESPP.

Previous wording

During the six months ended June 30, 2024, we received $8.7 million in net proceeds from the issuance of common stock under the ATM Facility. We also received gross proceeds of $9.0 million, net of offering costs of $0.3 million. We received $0.1 million in proceeds from the issuance of common stock under the ESPP and exercises of employee stock options.

Current wording

During the nine months ended September 30, 2024, we received $8.7 million in net proceeds from the issuance of common stock under the ATM Facility. We received gross proceeds of $9.0 million, net of offering costs of $0.3 million. We received $0.1 million in proceeds from the issuance of common stock under the ESPP and exercises of employee stock options.

Previous wording

The aggregate estimated rent payments due over the remaining terms of our leases and sublease are $39.2 million.

Current wording

The aggregate estimated rent payments due over the remaining terms of our leases and sublease are $38.2 million.

Previous wording

During the six months ended June 30, 2025, there were no material changes to our critical accounting policies and estimates from those described under the heading “Management’s Discussion and Analysis of Financial Condition and Results of Operations—Critical Accounting Policies and Estimates” in our 2024 Annual Report filed on Form 10-K.

Current wording

During the nine months ended September 30, 2025, there were no material changes to our critical accounting policies and estimates from those described under the heading “Management’s Discussion and Analysis of Financial Condition and Results of Operations—Critical Accounting Policies and Estimates” in our 2024 Annual Report filed on Form 10-K.

Previous wording

We will remain an emerging growth company until the earliest of (1) the last day of our first fiscal year (a) in which we have total annual gross revenues of at least $1.235 billion or (b) in which we are deemed to be a large accelerated filer, which means the market value of our common stock that is held by non-affiliates exceeds $700.0 million as of the prior June 30 th, (2) the date on which we have issued more than $1.0 billion in non-convertible debt securities during the prior three-year period and (3) December 31, 2025.

Current wording

We will remain an emerging growth company until December 31, 2025.