AVROBIO : Investor Presentation March 2023

March 2023

Arianna living with Gaucher disease type 3

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Disclaimer

This presentation has been prepared by AVROBIO, Inc. ("AVROBIO") for informational purposes only and not for any other purpose. Certain information contained in this presentation and statements made orally during this presentation relate to or are based on studies, publications, surveys, and other data obtained from third-party sources and AVROBIO's own internal estimates and research. Although AVROBIO believes these third-party sources to be reliable as of the date of this presentation, they have not been independently verified, and AVROBIO makes no representation as to the adequacy, fairness, accuracy. or completeness of any information obtained from third-party sources. Although AVROBIO believes its internal research is reliable, such research has not been verified by any independent source.

This presentation may contain forward-looking statements made pursuant to the safe harbor provisions of the Private Securities Litigation Reform Act of 1995. These statements may be identified by words and phrases such as "aims," "anticipates," "believes," "continue," "could," "designed to," "estimates," "expects," "forecasts," "goal," "intends," "may," "plans," "possible," "potential," "predicts," "projects," "seeks," "strives," "should," and "will," as well as variations of these words and phrases or similar expressions that are intended to identify forward-looking statements. These forward-looking statements include, without limitation, statements regarding our business strategy for and the potential therapeutic benefits of our current and prospective product candidates; the design, commencement, enrollment, and timing of ongoing or planned clinical trials and regulatory pathways; our plans and expectations with respect to the development of our clinical and preclinical product candidates, including timing, design, and initiation of our potential clinical and registration trials and anticipated interactions with regulatory agencies; the timing of anticipated clinical and regulatory updates; the timing of patient recruitment and enrollment activities,

clinical trial results, and product approvals; the timing and results of our ongoing preclinical studies; the anticipated benefits of our gene therapy platform including the potential impact on our commercialization activities, timing and likelihood of success; the expected benefits and results of our manufacturing technology, including the implementation of our plato® platform in our clinical trials and gene therapy programs; the expected safety profile of our investigational gene therapies; and our financial position and cash runway expectations. Any such statements in this presentation that are not statements of historical fact may be deemed to be forward- looking statements.

Any forward-looking statements in this presentation are based on our current expectations, estimates, and projections about our industry as well as management's current beliefs and expectations of future events only as of today and are subject to a number of risks and uncertainties that could cause actual results to differ materially and adversely from those set forth in or implied by such forward-looking statements. These risks and uncertainties include, but are not limited to, the risk that any one or more of our product candidates will not be successfully developed or commercialized; the risk that regulatory agencies may disagree with our anticipated development approach for any one or more of our product candidates; the risk of cessation or delay of any ongoing or planned clinical trials of AVROBIO or our collaborators; the risk that we may not successfully recruit or enroll a sufficient number of patients for our clinical trials; the risk that we may not realize the intended benefits of our gene therapy platform, including the features of our plato® platform; the risk that our product candidates or procedures in connection with the administration thereof, including our use of busulfan as a conditioning agent or potential use of monoclonal antibody conditioning agents, will not have the safety or efficacy profile that we anticipate; the risk that prior

results, such as signals of safety, activity, or durability of effect, observed from preclinical or clinical trials, will not be replicated or will not continue in ongoing or future studies or trials involving our product candidates; the risk that we will be unable to obtain and maintain regulatory approval for our product candidates; the risk that the size and growth potential of the market for our product candidates will not materialize as expected; risks associated with our dependence on third-party suppliers and manufacturers; risks regarding the accuracy of our estimates of expenses and future revenue; risks relating to our capital requirements and needs for and availability of additional financing; risks relating to clinical trial and business interruptions resulting from the ongoing COVID-19 pandemic or similar public health crises, including that such interruptions may materially delay our development timeline and/or increase our development costs or that data collection efforts may be impaired or otherwise impacted by such crises; and risks relating to our ability to obtain and maintain intellectual property protection for our product candidates. For a discussion of these and other risks and uncertainties, and other important factors, any of which could cause AVROBIO's actual results to differ from those contained in the forward-looking statements, see the section entitled "Risk Factors" in AVROBIO's most recent Quarterly Report, as well as discussions of potential risks, uncertainties and other important factors in AVROBIO's subsequent filings with the Securities and Exchange Commission. AVROBIO explicitly disclaims any obligation to update any forward-looking statements except to the extent required by law.

Note regarding trademarks: plato® is a registered trademark of AVROBIO. Other trademarks referenced in this presentation are the property of their respective owners.

© Copyright 2023 AVROBIO, Inc. All rights reserved.

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Leading hematopoietic stem cell (HSC) gene therapy company

Lysosomal disorder pipeline targeting multi-billion dollar market

Strong data generated to date across two clinical-stage programs

Late-stage trials in Gaucher disease and cystinosis planned for 2023

Unique competitive position with first mover advantage in lead programs

plato® platform delivers unrivaled CMC & analytics capabilities

Multiple clinical and regulatory milestones anticipated over next 12 months

CMC=Chemistry, manufacturing and controls; GT= Gene therapy

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HSC GT approach delivers durable, systemic distribution

Transduction

Viral vector containing

therapeutic gene

Genetically

modified

stem cells

Patient

stem cells

Back	Proliferation and
into body	differentiation

Monocytes/Macrophages

Granulocytes, T cells,

B cells, natural killer cells,

megakaryocytes, erythrocytes

Billions of genetically	Key advantages
modified cells
	Physiological cellular
	enzyme production
	Continuous cellular
	enzyme expression
	Access CNS and periphery
	Predicted durability of
	effect

Capotondo A. et al. 2012; Gordon, S., Plüddemann, A. 2017; HSC=Hematopoietic stem cell; CNS=Central nervous system; GT=Gene therapy

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AVROBIO entering late-stage development

Indication

Gaucher

AVR-RD-02

Cystinosis

AVR-RD-04*

Hunter

AVR-RD-05

Pompe

AVR-RD-03

Preclinical

Early-stage

clinical development

Planned to initiate

in 2023

Late-stage

clinical development

Planned to initiate

in 2023

Planned to initiate

in 2023

Regulatory designations

RPDD; Fast Track; ODD (US, EU); ILAP (UK)

RPDD; Fast Track; ODD (US, EU)

RPDD; ODD (US)

Planned regulatory milestones subject to regulatory agency clearance; *Collaborator-sponsored Phase 1/2 clinical trial of AVR-RD-04 is funded in part by grants to UCSD from the
California Institute for Regenerative Medicine (CIRM), Cystinosis Research Foundation (CRF), and National Institutes of Health (NIH); ILAP=Innovative Licensing and Access	5
Pathway; ODD=Orphan drug designation; RPDD=Rare pediatric drug designation