PASSAGE BIO ANNOUNCES INTERIM DATA FROM UPLIFT-D STUDY IN FTD- GRN AND PROVIDES BUSINESS UPDATES PBFT02 demonstrated durable, elevated CSF PGRN levels and early evidence of reduction in plasma NfL levels, a disease progr

PASSAGE BIO ANNOUNCES INTERIM DATA FROM UPLIFT-D

STUDY IN FTD-GRN AND PROVIDES BUSINESS UPDATES

PBFT02 demonstrated durable, elevated CSF PGRN

levels and early evidence of reduction in plasma NfL levels, a disease progression biomarker, compared to published natural history data

Evaluating Dose 2, 50% lower than Dose 1, in

subsequent FTD-GRN and FTD-C9orf72 patients to allow for dose exploration and support regulatory strategy

Expect to report 12-month data from Dose 1

and interim safety and biomarker data from Dose 2 in 2H 2025; plan to seek regulatory feedback on FTD-GRN pivotal trial design in 1H

Completed process development and scale-up

of a high-productivity, suspension-based manufacturing process for PBFT02

Extended cash runway into 1Q 2027 by moving

to outsourced analytical testing model and reducing operating expenses, allowing for the achievement of meaningful program milestones

PHILADELPHIA - January 10, 2025 - Passage

Bio, Inc. (Nasdaq: PASG), a clinical stage genetic medicines company focused on improving the lives of patients with neurodegenerative

diseases, today reported updated data from the ongoing Phase 1/2 upliFT-D clinical trial evaluating PBFT02 for the treatment of

frontotemporal dementia (FTD) with granulin (GRN) mutations and anticipated upcoming milestones. The company also announced the

successful completion of process development and scale-up of a suspension-based manufacturing process for PBFT02. As the PBFT02 program

continues to advance, the company reviewed its operating needs and will transition to an outsourced analytical testing model. This action,

coupled with an associated workforce reorganization and reductions in operating expenses, extends cash runway through meaningful program

milestones into the first quarter of 2027.

"We are pleased to report updated interim data from our ongoing

upliFT-D clinical trial in FTD-GRN patients showing that Dose 1 PBFT02 consistently increased CSF PGRN expression and that this

elevation translated to early signals of improvement in a disease progression biomarker when compared to published natural history data,"

said Will Chou, M.D., president and chief executive officer of Passage Bio. "Given the robust levels of CSF PGRN achieved with

Dose 1 and to support future discussions with health authorities regarding the registrational pathway, we look forward to introducing

Dose 2, which is fifty percent lower than Dose 1, for subsequent FTD-GRN and FTD-C9orf72 patients. We remain focused on

advancing the upliFT-D study in each of these patient populations and look forward to sharing additional data in the second half of 2025."

"As our PBFT02 program advances, we continue to assess our operating

needs to ensure that we can deliver on meaningful program milestones as we endeavor to bring this promising therapy to the FTD patient

community," Dr. Chou continued. "After careful consideration, we will transition to an outsourced analytical testing

model and have restructured our organization and reduced operating expenses accordingly. Following the implementation of these actions,

we expect existing cash resources will be sufficient to fund operations into the first quarter of 2027, which will allow us to further

validate the potential of PBFT02 and determine the registrational pathway for the program. We want to thank our talented team for their

commitment and important contributions as we continue to pursue our mission of improving the lives of patients with neurodegenerative

Updated interim data from FTD-GRN patients treated with

Safety (patient follow-up up to 18 months as of December 9,

Anticipated Upcoming Milestones:

About upliFT-D (NCT04747431)

upliFT-D is a Phase 1/2 global, multi-center, open-label clinical

trial of PBFT02 administered by single injection into the cisterna magna in patients aged 35 to 75 years with FTD-GRN or FTD-C9orf72.

The clinical trial will sequentially enroll three FTD-GRN cohorts and two FTD-C9orf72 cohorts. Enrollment is currently

ongoing. The primary endpoint of the clinical trial is to evaluate the safety and tolerability of PBFT02. Secondary endpoints

include disease biomarkers and clinical outcome measures. upliFT-D is a two-year clinical trial with a three-year safety extension.

Passage Bio is pursuing several initiatives to support clinical

trial recruitment and enrollment, including a collaborative partnership with InformedDNA to provide no-cost genetic counseling and testing

for adults who have been diagnosed by their physicians with FTD. More information about upliFT-D can be found here.

PBFT02 is a gene replacement therapy that utilizes an AAV1 viral vector

to deliver, through ICM administration, a functional GRN gene that encodes PGRN. This vector construct and delivery approach aim

to elevate PGRN levels in the central nervous system to alter the course of neurodegenerative diseases. Interim clinical data from the

upliFT-D Phase 1/2 study in FTD-GRN participants shows that ICM administration of PBFT02 resulted in robust PGRN elevations in

The potential clinical benefit of PBFT02 is supported by extensive

preclinical studies. In non-human primates, a single ICM administration of PBFT02 led to broad vector distribution throughout the CNS,

and robust, dose-dependent elevations in PGRN levels in CSF. An NHP study also demonstrated that AAV1 was particularly proficient at

transducing ependymal cells. In a murine FTD model, PBFT02 administration improved lysosomal function and reduced neuroinflammation.

Passage Bio (Nasdaq: PASG) is 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 therapies designed to target the underlying pathology of these conditions. Passage Bio's lead product candidate,

PBFT02, seeks to treat neurodegenerative conditions, including frontotemporal dementia, by elevating progranulin levels to restore lysosomal

function and slow disease progression.

To learn more about Passage Bio and our steadfast commitment to protecting

patients and families against loss in neurodegenerative conditions, please visit: passagebio.com.

Forward-Looking Statements

This press release contains "forward-looking statements"

within the meaning of, and made pursuant to the safe harbor provisions of, the Private Securities Litigation Reform Act of 1995, including,

but not limited to: our expectations about timing and execution of anticipated milestones, including the outsource of our analytical

testing model, the initiation of dosing of FTD-C9orf72 patients, timing of feedback from regulatory authorities, the progress

of clinical studies and the availability of clinical data from such trials; our expectations about our collaborators' and partners'

ability to execute key initiatives; the financial impact of the restructuring and reduction in workforce and our expectations about cash

runway; and the ability of our product candidates to treat their respective target CNS disorders. These forward-looking statements may

be accompanied by such words as "aim," "anticipate," "believe," "could," "estimate,"

"expect," "forecast," "goal," "intend," "may," "might," "plan,"

"potential," "possible," "will," "would," and other words and terms of similar meaning.

These statements involve risks and uncertainties that could cause actual results to differ materially from those reflected in such statements,

including: our ability to develop and obtain regulatory approval for our product candidates; the timing and results of preclinical studies

and clinical trials; risks associated with clinical trials, including our ability to adequately manage clinical activities, unexpected

concerns that may arise from additional data or analysis obtained during clinical trials, regulatory authorities may require additional

information or further studies, or may fail to approve or may delay approval of our drug candidates; the occurrence of adverse safety

events; the risk that positive results in a preclinical study or clinical trial may not be replicated in subsequent trials or success

in early stage clinical trials may not be predictive of results in later stage clinical trials; failure to protect and enforce our intellectual

property, and other proprietary rights; our dependence on collaborators and other third parties for the development and manufacture of

product candidates and other aspects of our business, which are outside of our full control; risks associated with current and potential

delays, work stoppages, or supply chain disruptions; and the other risks and uncertainties that are described in the Risk Factors section

in documents the company files from time to time with the Securities and Exchange Commission (SEC), and other reports as filed with the

SEC. Passage Bio undertakes no obligation to publicly update any forward-looking statement, whether written or oral, that may be made

from time to time, whether as a result of new information, future developments or otherwise.

For further information, please contact:

Sam Brown Inc. Healthcare Communications

i Saracino et al, J Neurol Neurosurg Psych 2021;