8-K

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d)

of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): May 14, 2024

PASSAGE BIO, INC.

(Exact name of registrant as specified in its charter)

Delaware	001-39231	82-2729751
(State or other jurisdiction of incorporation)	(Commission File Number)	(IRS Employer Identification No.)

One Commerce Square 2005 Market Street, 39th Floor Philadelphia, PA	19103
(Address of principal executive offices)	(Zip Code)

(267) 866-0311

(Registrant’s telephone number, including area code)

N/A

(Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of each class	Trading symbol(s)	Name of each exchange on which registered
Common Stock, $0.0001 Par Value Per Share	PASG	The Nasdaq Stock Market LLC (Nasdaq Global Select Market)

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company ☒

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Item 2.02 Results of Operations and Financial Condition.

On May 14, 2024, Passage Bio, Inc. (the “Company”) issued a press release announcing its financial results for the quarter ended March 31, 2024. A copy of the press release is attached as Exhibit 99.1 to this report.

The information in this Item 2.02, including Exhibit 99.1 to this report, shall not be deemed to be “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section or Sections 11 and 12(a)(2) of the Securities Act of 1933, as amended (the “Securities Act”). The information contained in this Item 2.02 and in the accompanying Exhibit 99.1 shall not be incorporated by reference into any other filing under the Exchange Act or under the Securities Act, except as shall be expressly set forth by specific reference in such filing.

Item 7.01 Regulation FD Disclosure.

On May 14, 2024, the Company updated its corporate presentation. A copy of the corporate presentation is attached as Exhibit 99.2 to this Current Report on Form 8-K.

The information in this Item 7.01, including Exhibit 99.2 to this Current Report on Form 8-K, shall not be deemed to be “filed” for purposes of Section 18 of the Exchange Act, or otherwise subject to the liabilities of that section or Sections 11 and 12(a)(2) of the Securities Act. The information contained in this Item 7.01 and in the accompanying Exhibit 99.2 shall not be incorporated by reference into any other filing under the Exchange Act or under the Securities Act, except as shall be expressly set forth by specific reference in such filing.

Item 9.01 Financial Statements and Exhibits.

(d)Exhibits

Exhibit No.	Description
99.1	Press release issued by Passage Bio, Inc. regarding its financial results for the quarter ended March 31, 2024, dated May 14, 2024.
99.2	Corporate Presentation.
104	Cover Page Interactive Data File (formatted as Inline XBRL).

2

SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

	PASSAGE BIO, INC.
Date: May 14, 2024	By:	/s/ Kathleen Borthwick
		Kathleen Borthwick
		Chief Financial Officer

3

EX-99.1

‌Ex 99.1

PASSAGE BIO REPORTS FIRST QUARTER 2024 FINANCIAL RESULTS AND PROVIDES RECENT BUSINESS HIGHLIGHTS

● Updated interim data from the upliFT-D trial in FTD-GRN demonstrated that Dose 1 PBFT02 achieved consistent elevation of CSF progranulin at six months post-treatment in the two patients with longest follow-up

● Completed dosing of Cohort 1 (n=5) in upliFT-D trial; on track to deliver 6-month safety and biomarker data from Cohort 1 in 2H 2024

● Plan to continue studying Dose 1 in Cohort 2 of upliFT-D trial; expect to initiate dosing by the end of 1H 2024, as planned

● Initiated regulatory process with FDA to receive feedback on pathway to treating FTD-C9orf72 patients with PBFT02

● Robust balance sheet sufficient to deliver meaningful clinical data, with cash runway into Q4 2025

PHILADELPHIA – May 14, 2024 – Passage Bio, Inc. (Nasdaq: PASG), a clinical stage genetic medicines company focused on improving the lives of patients with neurodegenerative diseases, today reported financial results for the first quarter ended March 31, 2024 and provided recent business highlights.

"The beginning of 2024 has been marked by strong execution as we continue to advance our global upliFT-D clinical trial in FTD-GRN and plan to deliver meaningful data over the next twelve months,” said Will Chou, M.D., president and chief executive officer of Passage Bio. “We are excited to share updated interim data demonstrating continued elevation in CSF progranulin levels at six months after treatment in two patients. This consistent progranulin response underscores the differentiated profile of PBFT02 and gives us confidence in the impact our therapy may have on patients at the current dose. Momentum in our program has been strong since we shared encouraging initial data last year, and we are pleased to have completed dosing of all five patients in Cohort 1.”

Recent Highlights

● Dose 1 PBFT02 achieved consistent elevation of cerebrospinal fluid (CSF) progranulin (PGRN) at six months post-treatment in two patients with the longest follow-up in the global Phase 1/2 upliFT-D clinical trial evaluating PBFT02 for frontotemporal dementia (FTD) with granulin mutations (GRN): Building on interim data shared in December 2023, Dose 1 PBFT02 has now been shown to elevate CSF PGRN levels at six months post-treatment in Patients 2 and 3, with a concentration of 21.7 to 27.3 ng/mL. Consistent with prior findings, Patient 3 plasma PGRN levels remained below levels found in healthy adult controls at up to six months post-treatment. PBFT02 continues to be well-tolerated in participants who received the enhanced immunosuppression regimen at up to eleven months post-treatment.

● Completed dosing of Cohort 1 patients in upliFT-D clinical trial: Completed dosing of Cohort 1, with five patients now having received Dose1 of PBFT02. The company remains on track to deliver 6-month safety and biomarker data from Cohort 1 in the second half of 2024.

● Plan to continue studying Dose 1 in Cohort 2 patients in upliFT-D trial: Based on initial clinical evidence that Dose 1 PBFT02 achieved robust CSF progranulin levels, sustained for up to six months post-treatment (n=2), the company plans to continue studying Dose 1 in Cohort 2, which will consist of three to five patients. Recruitment momentum remains strong, with multiple GRN+ patients identified and being evaluated for study eligibility across seven clinical trial sites in Brazil, Canada, the United States and Europe. The company continues to expect to initiate dosing of Cohort 2 later in the first half of 2024.

● Initiated regulatory process with FDA to receive feedback on the company’s plans to treat FTD-C9orf72 patients with PBFT02: The company expects to receive feedback from the U.S. Food and Drug Administration (FDA) on the clinical development pathway for treating FTD patients with mutations in the C9orf72 gene with PBFT02 in the second half of 2024. FTD-C9orf72, like FTD-GRN, is characterized by TDP-43 pathology, in which the TDP-43 protein abnormally accumulates in the cytoplasm of neurons, contributing to neuronal dysfunction and degeneration. Published, third-party preclinical studies have shown that elevating progranulin levels can reduce TDP-43 pathology and slow neurodegeneration. There are currently no approved disease-modifying therapies for FTD-C9or72, which is estimated to affect approximately 21,000 patients in the U.S. and Europe.

Anticipated Upcoming Milestones:

FTD-GRN

● Initiate dosing for Cohort 2 FTD-GRN patients in 1H 2024

● Report 6-month safety and biomarker data from Cohort 1 patients in 2H 2024

● Announce 12-month follow-up data from Cohort 1 patients in 1H 2025

● Report initial safety and biomarker data from Cohort 2 patients in 1H 2025

FTD-C9orf72 and ALS

● Obtain regulatory feedback on the pathway to treating FTD-C9orf72 and amyotrophic lateral sclerosis (ALS) patients with PBFT02 in 2H 2024

First Quarter 2024 Financial Results

● Cash Position: Cash, cash equivalents and marketable securities were $104.5 million as of March 31, 2024, as compared to $167.8 million as of March 31, 2023. During the quarter ended March 31, 2024, the company raised $8.7 million, net of offering costs, under its ATM Facility. The company expects current cash, cash equivalents and marketable securities to fund operations into Q4 2025.

● Research and Development (R&D) Expenses: R&D expenses were $11.5 million for the quarter ended March 31, 2024, as compared to $16.8 million for the quarter ended March 31, 2023.

● General and Administrative (G&A) Expenses: G&A expenses were $6.5 million for the quarter ended March 31, 2024, as compared to $19.0 million for the quarter ended March 31, 2023. G&A Expenses in the period in 2023 included $11.3 million in non-recurring charges related to the Amended Catalent Agreements.

● Net Loss: Net loss was $16.7 million, or $0.30 per basic and diluted share, for the quarter ended March 31, 2024, as compared to a net loss of $34.3 million, or $0.63 per basic and diluted share, for the quarter ended March 31, 2023.

About Passage Bio

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: www.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 progress of clinical trials and the availability of clinical data from such trials; our expectations about our collaborators’ and partners’ ability to execute key initiatives; our expectations about manufacturing plans and strategies; our expectations about cash runway; our expectations about potential out-licensing opportunities related to PBGM01, PBKR03 and PBML04; 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.

Passage Bio, Inc.

Balance Sheets

	(Unaudited)
(in thousands, except share and per share data)	March 31, 2024		December 31, 2023
Assets
Current assets:
Cash and cash equivalents	$	36,773	$	21,709
Marketable securities		67,752		92,585
Prepaid expenses and other current assets		1,784		923
Prepaid research and development		1,984		2,742
Total current assets		108,293		117,959
Property and equipment, net		14,489		15,295
Right of use assets - operating leases		17,087		16,858
Other assets		662		433
Total assets	$	140,531	$	150,545
Liabilities and stockholders’ equity
Current liabilities:
Accounts payable	$	1,687	$	1,298
Accrued expenses and other current liabilities		7,483		11,670
Operating lease liabilities		3,671		3,373
Total current liabilities		12,841		16,341
Operating lease liabilities - noncurrent		22,807		22,921
Total liabilities		35,648		39,262
Stockholders’ equity:
Preferred stock, $0.0001 par value: 10,000,000 shares authorized; no shares issued and outstanding at both March 31, 2024 and December 31, 2023		—		—
Common stock, $0.0001 par value: 300,000,000 shares authorized; 61,611,796 shares issued and outstanding at March 31, 2024 and 54,944,130 shares issued and outstanding at December 31, 2023		6		5
Additional paid‑in capital		716,125		705,789
Accumulated other comprehensive income (loss)		(69)		(43)
Accumulated deficit		(611,179)		(594,468)
Total stockholders’ equity		104,883		111,283
Total liabilities and stockholders’ equity	$	140,531	$	150,545

Passage Bio, Inc.

Statements of Operations and Comprehensive Loss

(Unaudited)

	Three Months Ended March 31,
(in thousands, except share and per share data)	2024		2023
Operating expenses:
Research and development	$	11,535	$	16,836
General and administrative		6,515		19,047
Loss from operations		(18,050)		(35,883)
Other income (expense), net		1,339		1,545
Net loss	$	(16,711)	$	(34,338)
Per share information:
Net loss per share of common stock, basic and diluted	$	(0.30)	$	(0.63)
Weighted average common shares outstanding, basic and diluted		56,295,540		54,618,799
Comprehensive loss:
Net loss	$	(16,711)	$	(34,338)
Unrealized gain (loss) on marketable securities		(26)		539
Comprehensive loss	$	(16,737)	$	(33,799)

For further information, please contact:

Investors:

Stuart Henderson

Passage Bio

267.866.0114

shenderson@passagebio.com

Media:

Mike BeyerSam Brown Inc. Healthcare Communications312.961.2502MikeBeyer@sambrown.com

EX-99.2

Exhibit 99.2

Nasdaq: PASG © 2024 Passage Bio. All rights reserved. Corporate Presentation May 2024

2 Forward-Looking Statement This presentation includes “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 progress of clinical trials and the availability of clinical data from such trials; our expectations about our collaborators’ and partners’ ability to execute key initiatives; our expectations about manufacturing plans and strategies; our expectations about cash runway; our expectations about potential outlicensing opportunities related to PBGM01, PBKR03 and PBML04; 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.

3 REDEFINING THE COURSE OF NEURODEGENERATIVE CONDITIONS Advancing potential best-in-class, one-time progranulin raising FTD-GRN gene therapy In-house manufacturing and process analytics to support program execution Strong cash position with runway expected into 4Q 2025* Exploring benefits of elevated progranulin in multiple adult neurodegenerative diseases * Based on cash, cash equivalents and marketable securities as of March 31, 2024

4 Validating the Therapeutic Potential of PBFT02 Promising data from initial clinical study of PBFT02 in FTD-GRN Genetic form of FTD caused by GRN mutations, which lead to progranulin (PGRN) deficiency No approved disease-modifying therapies One-time therapy Proprietary AAV1 construct Nonsurgical injection directly to cerebrospinal fluid (CSF) Durable, elevated CSF PGRN levels* Urgent Patient Need in FTD-GRN Differentiated, Potential Best-in-Class Profile Fast Track and Orphan Drug Designation * Based on interim data.

5 Significant Market Opportunity for PBFT02 Across Multiple Neurodegenerative Diseases ~18,000 ~21,000 ~72,600 ~3.9M FTD-GRN1–3 FTD-C9orf722–4 AMYOTROPHIC LATERAL SCLEROSIS (ALS) 5–6 ALZHEIMER’S DISEASE (GRN SNP)*7–8 * rs5848 single nucleotide polymorphism (SNP) 1. Greaves CV, et al. J Neurol 2019; 266:2075-2086. 2. Galvin JE, et al. Neurology 2017; 89:2049-2056. 3. Onyike CU, et al. Int Rev Psychiatry 2013; 25:130-137. 4. Moore KM, et al. Lancet Neurol 2020; 19: 145–156. 5. Brown et al. Neuroepi 2021; 55:342-353. 6. CDC ALS Registry Dashboard. 7. Sheng J, et al. Gene 2014; 141-145. 8. Alz Assoc. 2023 Alzheimer’s Disease Facts and Figures. Alzheimers Dement 2023;19. Estimated Prevalence (US and EU)

6 Anticipated Upcoming Milestones and Data Readouts 1H 2024 2H 2024 1H 2025 Initiate dosing of Cohort 2 FTD-GRN patients Obtain regulatory feedback on the pathway to treating FTD-C9orf72 and ALS patients Report 6-month safety and biomarker data from Cohort 1 patients Announce 12-month follow-up data from Cohort 1 patients Report initial safety and biomarker data from Cohort 2 patients FTD-GRN Milestones FTD-C9orf72 and ALS Milestones

PBFT02 Frontotemporal Dementia-GRN

8 FTD: A Devastating Adult Disease OVERVIEW • Fatal adult-onset neurodegenerative disease affecting the frontal and temporal lobes of the brain, characterized by a decline in behavior, language and executive function • One of the most common causes of early-onset dementia worldwide, disproportionately affecting individuals aged 40-65 years CLINICAL SYMPTOMS Disease progression is rapid and degenerative, including loss of speech, loss of expression, behavioral changes and immobility On average, people with FTD live 8 years after the onset of symptoms

9 Progranulin Deficiency is the Defining Characteristic of FTD-GRN and Leads to Neurodegeneration Progranulin is critical to maintaining CNS cell homeostasis Rhinn H et al. Trends Pharm Sci. 2022, 43:641-652.

10 Elevated PGRN Increases Potential for Improved Cellular Function • Progranulin is a secreted protein that binds to cell membrane receptors to affect multiple intracellular pathways –Major role is regulating intracellular lysosomal activity –Extracellular PGRN is endocytosed via multiple receptors • Driving elevated PGRN levels in the extracellular space increases the amount of PGRN available to enter target CNS cells Paushter et al., Acta Neuropathol. 2018;136(1):1-17., Rhinn et al., Trends in Pharmacological Sciences 2022; 43.8:641-652.

11 Preclinical: AAV1 Achieved the Highest Levels of CSF PGRN in NHPs AAV1 increased CSF PGRN levels ~5x more than AAV5 and AAVhu68 (proprietary AAV9 variant) vectors, without further elevating peripheral levels Production of Human PGRN in Plasma AAV1 transgene delivery led to highest hPGRN levels in CSF CSF PGRN (ng/mL) 0 10 20 30 40 CSF 0.1 1 10 100 LLOQ Normal Day RA2981 RA2982 RA3027 RA3153 RA3151 RA3170 RA3155 RA3160 AAVhu68 AAVhu68 (v2) AAV1 AAV5 RA2981 RA2982 RA3027 RA3153 RA3151 RA3170 RA3155 RA3160 AAVhu68 AAVhu68 (v2) AAV1 AAV5 RA2981 RA2982 RA3027 RA3153 RA3151 RA3170 RA3155 RA3160 AAVhu68 AAVhu68 (v2) AAV1 AAVhu68 AAV5 AAVhu68 (v2) AAV5 AAV1 Normal LLOQ Plasma Plasma PGRN (ng/mL) 0 10 20 30 40 0.1 1 10 100 Normal Day 1,000 Left, right: Two adult rhesus macaques per treatment received ICM AAV.hPGRN High dose, 3.0 x 1013 GC / 3.3 x 1011 GC/g brain) on study day 01 .. Shading: Reference range for healthy adult controls’ PGRN levels in CSF (n = 61) and plasma (n = 56) (Passage Bio data).

12 Preclinical: Higher CSF PGRN May Confer Reduction in Inflammatory Response • Microgliosis: inflammatory response to pathogenic insults in the CNS • CD68: marker of activated microglia Thalamus data shown above. Thalamic atrophy is a key feature commonly found in FTD PBFT02 reduced lipofuscin at all doses, suggesting correction of underlying mechanism of disease • Lipofuscin: increased levels associated with lysosomal dysfunction • Correlated with underlying mechanism of FTD-GRN Microgliosis reduction strongest at highest PBFT02 dose / PGRN level Murine FTD Model Murine FTD Model *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001, one-way ANOVA followed by Tukey’s multiple comparisons test

13 upliFT-D: Global Phase 1/2 Trial with PBFT02 DURATION 2 years; with additional 3 years of follow-up for safety and durability of effect PRIMARY ENDPOINTS Safety and tolerability SECONDARY ENDPOINTS Biomarkers • Progranulin (CSF, plasma) • GFAP (CSF, plasma) • vMRI • Retinal nerve fiber layer and retinal lipofuscin deposits via OCT • NfL (CSF, plasma) Clinical • CDR + NACC FTLD sum of boxes EXPLORATORY BIOMARKERS • Cathepsin D (CSF) • LAMP 1 (CSF) • Lys-GL1 (CSF) COHORT 1 Dose 1 (3.3e10 GC/g)* COHORT 2 Dose 2 (1.1e11 GC/g)* OPTIONAL COHORT 3 Optional dose 3 Recruiting IDMC review Phase 1/2 Multicenter Open-label Dose escalation study Up to 15 patients across 3 cohorts 1/2 TRIAL DESIGN COHORT 1 (n=5) Dose 1 COHORT 2 (n=3-5) Dose 1 OPTIONAL COHORT 3 IDMC review Phase Multicenter Open-label Dose escalation study Up to 15 patients across 3 cohorts 1/2 Complete Dose 1: 3.3e10 GC/g estimated brain weight.

14 Intra-Cisterna Magna (ICM) Administration • Directly deliver vector into the CSF via a single injection to reach both CNS and peripheral tissues1 –Allows for broad CNS biodistribution –Lower doses compared to IV systemic delivery –Reduced impact of neutralizing antibodies • Brief (<60 min), non-surgical, CT-guided procedure to allow for precise delivery to the cisterna magna –Infusion catheter does not enter brain tissues Cisterna magna 1. Hinderer et. al, Human Gene Therapy. 2018 Jan; 29(1):15-24​.

15 upliFT-D: Interim Data from First 3 Treated Patients • Patient 1 experienced two SAEs consistent with an immune response; study protocol was revised to increase steroid regimen • Patient 2 and Patient 3 received a higher level of steroid immunosuppression and did not experience SAEs; only mild-to-moderate treatment emergent AEs were reported • No evidence of DRG toxicity, as measured by nerve conduction studies • No complications related to ICM administration observed Safety* Efficacy / Target Engagement • Interim data demonstrates PBFT02 potential for best-in-class efficacy at Dose 1 • Dose 1 showed continued elevation of CSF PGRN levels at up to six months post-treatment: 21.7 – 27.3 ng/mL (n=2) SAE: serious adverse event; AE: adverse event; DRG: dorsal root ganglion; ICM: intracisterna magna *Patient safety follow-up ranged from 2 to 11 months post-dosing as of data cutoff of May 1, 2024

16 Following Protocol Update to Increase Steroids, Patients 2 and 3 Had No SAEs or Evidence of Significant Immune Response Patient 1 Patient 2 Patient 3 Immunosuppression1 Days -1-60: 60 mg oral prednisone Days 1-3: 1,000 mg IV methylprednisolone Days 4-60: 60 mg oral prednisone Length of Follow-up (as of May 1, 2024) 2 months (subject withdrew from study at week 10) 11 months 7 months Summary 2 SAEs: both asymptomatic and consistent with immune response 1. Hepatotoxicity (resolved with methylprednisolone) 2. Venous sinus thrombosis • No SAEs • No hepatotoxicity or significant LFT changes from baseline • No venous sinus thrombosis or inflammation on MRIs • No clinically significant immune response requiring adjustment to immunosuppression regimen • All treatment emergent AEs mild to moderate in severity LFT: liver function test; SAE: serious adverse event, AE: adverse event 1. Day minus one refers to the day prior to dosing. Revised

17 • Potential best-in-class PGRN profile at Dose 1 • Continued elevation of CSF PGRN at 6-months (n=2) • Consistent response across first three treated patients Initial Patients Treated with PBFT02 Have Seen a Substantial Increase in CSF PGRN At Dosing D30 D60 D180 Patient 1 1.9 12.7 N/A N/A Patient 2 2.8 17.3 N/A 27.3 Patient 3 2.9 10.7 13.7 21.7 CSF Progranulin (ng/mL) Shading: Reference range for healthy adult controls’ PGRN levels in CSF (range: 3.28 – 8.15 ng/mL, mean: 4.76 ng/mL, n = 61) (Passage Bio data) CSF=Cerebrospinal fluid 0 3 6 9 12 15 18 21 24 27 30 0 30 60 90 120 150 180 CSF PGRN, ng/mL Time (days) Dose 1 Progranulin, CSF Patient 1 Patient 2 Patient 3

18 • Plasma PGRN levels remained below normal levels at up to 6 months post-dose • PGRN increased only in the CSF where it has potential to correct deficit associated with neurodegeneration Plasma PGRN Levels Remained Below Normal Levels Post-Dose Shading: Lower limit of normal reference range for healthy adult controls’ PGRN levels in plasma (91.6 – 372.4 ng/mL, n = 56) (Passage Bio data) 0 10 20 30 40 50 60 70 80 90 100 0 7 14 30 60 90 120 150 180 Plasma PGRN, ng/mL Time (days) Dose 1 Progranulin, Plasma Patient 1 Patient 2 Patient 3

19 Summary SAFETY1 PBFT02 Dose 1 generally well-tolerated to date in Patients 2 and 3, who received revised steroid regimen following protocol amendment • No serious AEs • All AEs mild to moderate in intensity • No evidence of clinically significant immune response, hepatotoxicity or venous sinus thrombosis • No evidence of DRG toxicity • No complications observed related to ICM injection BIOMARKERS • Potential best-in-class PGRN profile at Dose 1 • Continued elevation of CSF PGRN at 6-months (n=2) • Consistent response across first three treated patients •No increase in plasma PGRN levels up to Day 180 (n=3) ANTICIPATED NEXT STEPS •Initiate dosing of Cohort 2 patients in 1H 2024 • 6-month data from Cohort 1 in 2H 2024 • 12-month follow-up data from Cohort 1 patients in 1H 2025 •Initial data from Cohort 2 in 1H 2025 AEs=adverse events; ICM=intra-cisterna magna; DRG=dorsal root ganglia 1. Patient safety follow-up ranged from 2 to 11 months post-dosing as of data cutoff of May 1, 2024

Looking Ahead

21 PBFT02 has Potential to Correct Underlying Pathology in FTD-GRN, FTD-C9orf72 and ALS TDP-43 pathology is a hallmark of multiple neurodegenerative diseases1 • TDP-43 mislocalizes from nucleus to cytoplasm • Forms inclusion bodies associated with neurodegeneration 1. Rhinn H et al. Trends Pharm Sci. 2022, 43:641-652

22 TDP-43 pathology due to lysosomal dysfunction (GRN/ TMEM106 double knockout, DKO) reduced by AAV.hPGRN1 Elevated PGRN Ameliorates TDP-43 Pathology in Preclinical Models AAV delivered hPGRN to DKO mouse brain TDP-43 pathology in DKO mice reduced by AAV.hPGRN Elevated PGRN reduced insoluble TDP-43 in mouse spinal cord Elevated PGRN extended survival of TDP-43 mutant mice Elevated PGRN ameliorated TDP-43 pathology and disease course in a preclinical model2 • Elevated PGRN also prevented degeneration of large axon fibers in TDP-43 mice • PGRN neuroprotection from pleiotropic effect, not single pathway 1. Reich et al. (2023) bioRxiv preprint 07.14.549089; 2. Beel et al (2018) Mol Neurodegen; Laird et al. (2010) Plos One. DKO=double gene knockout; GRN=granulin gene; PGRN=progranulin; TDP-43=transactive response DNA binding protein 43 kDa. † PGRN increased to >2x endogenous levels

23 GRN rs5848 SNP associated with accelerated disease in FTD-C9orf72 patients Decreased PGRN Associated with Greater Disease Severity in Multiple CNS Conditions GRN rs5848 SNP associated with accelerated disease in FTD-C9orf72 patients 1. van Blitterswijk et al (2014) Mol Neurodegen. AD=Alzheimer’s disease; ALS=amyotrophic lateral sclerosis; GRN=granulin gene; PGRN=progranulin; SNP=single nucleotide polymorphism. PGRN SNPs are genetic risk factors for CNS diseases • GRN rs5848 SNP results in ~15% reduction in PGRN levels • PGRN SNPs increase risk for, and worsen severity of, FTD/ALS-C9orf72 and AD1

24 • GRN SNP rs5848 carriers have reduced PGRN levels and increased risk for AD • AD patients with GRN SNP rs5848 show reduced PGRN levels and increased CSF tau • GRN SNP rs5848 is estimated to occur in 30% of the general population, with a similar prevalence rate among AD patients2 • PGRN ablation exacerbates AD pathology in mice • PGRN overexpression reduces pathology burden in AD models Genetic Risk1 Prevalence Supporting Preclinical Evidence3 PBFT02 has Potential to Modulate Alzheimer’s Disease SNP=single nucleotide polymorphism. Third-party preclinical data. Sources: 1. Chen Y et al. J Neurol. 2015, 262:814-22; Takahashi H et al. Acta Neuropathol. 2017, 133:785-807. 2. Fenoglio C et al. J Alzheimers Dis. 2009, 18:603-612. 3. Hosokawa M et al. J Neuropath Exp Neurol. 2015, 74:158-65; Minami SS et al. Nat Med. 2014, 20:1157-64; Van Kampen JM & Kay DG. PLoS ONE 2017, 12:e0182896.

25 Leading In-House CMC Capabilities to Support PBFT02 Development Proven analytical development capabilities In-House CMC Analytical Capabilities to Support Program Advancement and Future Commercialization of PBFT02 Integrated process development GMP QC capabilities Strong regulatory CMC scientific expertise Scale-up capability

26 TIMING MILESTONE FTD-GRN 1H 2024 Initiate dosing of Cohort 2 patients 2H 2024 6-month safety and biomarker data from Cohort 1 patients 1H 2025 12-month follow-up data from Cohort 1 patients 1H 2025 Initial safety and biomarker data from Cohort 2 patients PBFT02 Additional Indications 2H 2024 Obtain regulatory feedback on clinical pathway for treating FTD-C9orf72 and ALS patients Upcoming Milestones and Corporate Updates PIPELINE • Pursuing outlicensing opportunities to advance pediatric clinical-stage programs (GM1, Krabbe and MLD) • Continuing the Huntington’s disease preclinical program being executed through our Penn GTP partnership BALANCE SHEET • Cash balance of $105 million as of 3/31/24* • Cash as of 3/31/24 expected to fund operations into 4Q 2025* * Cash, cash equivalents and marketable securities

27 REDEFINING THE COURSE OF NEURODEGENERATIVE CONDITIONS Advancing potential best-in-class, one-time progranulin raising FTD-GRN gene therapy In-house manufacturing and process analytics to support program execution Strong cash position with runway expected into 4Q 2025* Exploring benefits of elevated progranulin in multiple adult neurodegenerative diseases * Based on cash, cash equivalents and marketable securities as of March 31, 2024

Thank You passagebio.com | NASDAQ: PASG

29 Focused Pipeline Addressing Rare and Prevalent Neurodegenerative Indications Program Indication US/EU prevalence Discovery Preclinical Phase 1/2 Pivotal PBFT02 Frontotemporal dementia - GRN 18,0001-3 Frontotemporal dementia - C9orf72 21,0002-4 Amyotrophic lateral sclerosis 72,6005-6 Alzheimer’s disease with rs5848 SNP 3.9M7-8 Unnamed Huntington’s disease 60,0009 PBGM01 GM1 gangliosidosis PBKR03 Krabbe disease PBML04 Metachromatic leukodystrophy Pursuing outlicensing opportunities 1. Greaves CV, et al. J Neurol 2019; 266:2075-2086. 2. Galvin JE, et al. Neurology 2017; 89:2049-2056. 3. Onyike CU, et al. Int Rev Psychiatry 2013; 25:130-137. 4. Moore KM, et al. Lancet Neurol 2020; 19: 145–156. 5. Brown et al. Neuroepi 2021; 55:342-353. 6. CDC ALS Registry Dashboard. 7. Sheng J, et al. Gene 2014; 141-145. 8. Alz Assoc. 2023 Alzheimer’s Disease Facts and Figures. Alzheimers Dement 2023;19. 9. Crowell et al. Neuroepi. 2021; 55:361-368

30 Demonstrated Leadership LEADERSHIP TEAM Deep experience in rare disease, CNS disorders and genetic medicines Eden Fucci SVP Technical Operations BOARD OF DIRECTORS Maxine Gowen, Ph.D. Chairwoman Athena Countouriotis, M.D. Avenzo Therapeutics Derrell Porter, M.D. cTRL Therapeutics Dolan Sondhi, Ph.D. Weill Cornell Medicine Sandip Kapadia Harmony Biosciences Saqib Islam, J.D. SpringWorks William Chou, M.D. President & Chief Executive Officer Stuart Henderson SVP Corporate Development & Investor Relations Mark Forman, M.D., Ph.D. Chief Medical Officer William Chou, M.D. President & Chief Executive Officer Chip Cale General Counsel & Corporate Secretary Kathleen Borthwick Chief Financial Officer Karl Whitney SVP Global Regulatory Affairs Sue Browne, Ph.D. SVP Research & Development

XML

Document and Entity Information	May 14, 2024
Cover [Abstract]
Document Type	8-K
Document Period End Date	May 14, 2024
Securities Act File Number	001-39231
Entity Registrant Name	PASSAGE BIO, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	82-2729751
Entity Address, Address Line One	One Commerce Square
Entity Address, Address Line Two	2005 Market Street, 39th Floor
Entity Address, City or Town	Philadelphia
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	19103
City Area Code	267
Local Phone Number	866-0311
Written Communications	false
Soliciting Material	false
Pre-commencement Tender Offer	false
Pre-commencement Issuer Tender Offer	false
Title of 12(b) Security	Common Stock, $0.0001 Par Value Per Share
Trading Symbol	PASG
Security Exchange Name	NASDAQ
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Central Index Key	0001787297
Amendment Flag	false

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N-2	May 14, 2024
Cover [Abstract]
Entity Central Index Key	0001787297
Amendment Flag	false
Securities Act File Number	001-39231
Document Type	8-K
Entity Registrant Name	PASSAGE BIO, INC.
Entity Address, Address Line One	One Commerce Square
Entity Address, Address Line Two	2005 Market Street, 39th Floor
Entity Address, City or Town	Philadelphia
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	19103
City Area Code	267
Local Phone Number	866-0311
Entity Emerging Growth Company	true
Entity Ex Transition Period	false