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 dur

R&D Day NOVEMBER 2020 Exhibit

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. While AVROBIO believes these third-party sources to be reliable as of the date of this presentation, it has not

independently verified, and AVROBIO makes no representation as to the adequacy, fairness, accuracy or completeness of any information obtained from third-party sources. While 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," "could," "designed to," "estimates," "expects," "forecasts," "goal,"

"intends," "may," "plans," "possible," "potential," "seeks," "will," and 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; 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 anticipated benefits and safety profile of busulfan as a

conditioning agent; 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; the potential impact of the COVID-19 outbreak on our clinical trial programs and business generally, as well as our plans and expectations with respect to the timing and resumption of any development activities that may be temporarily

paused as a result of the COVID-19 outbreak; and the market opportunity for and anticipated commercial activities relating to our investigational gene therapies;. 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 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, 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 additional financing; risks relating to clinical trial and

business interruptions resulting from the COVID-19 outbreak 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 on Form 10-Q, 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. Note regarding future updates: The

statements contained in this presentation reflect our current views with respect to future events, which may change significantly as the global consequences of the COVID-19 pandemic rapidly develop. Accordingly, we do not undertake and specifically

Vision Bring personalized gene therapy

to the world. Purpose Freedom from a lifetime of genetic disease.

Cell and gene therapy is redefining

medicine 804 trials Sources: 1Alliance for Regenerative Medicine: 2016 Annual Data Report; 2Alliance for Regenerative Medicine: Sector Report 1H 2020; 3FDA.gov press release at: https://bit.ly/2GcPftr 20161 1,034 trials 20202 10-20 approvals/year

Ex vivo lentiviral gene therapy has

emerged as a leading modality across multiple genetic diseases Industry-wide data demonstrate proven record, broad utility TOLERABILITY DURABILITY EFFICACY WIDE REACH BROAD UTILITY Approved ALD Beta thalassemia Investigational Fanconi anemia Hurler

syndrome MLD Sanfilippo A Sanfilippo B SCID-ADA SCID-X Sickle cell disease Wiskott-Aldrich syndrome X-CGD >350 patients >1,000 patient years Pediatrics and adults All mutations No exclusions due to pre-existing antibodies >12 years

post-infusion Head-to-toe, including: Brain Muscle Bone ALD: Adrenoleukodystrophy; SCID-ADA: Severe Combined Immunodeficiency-Adenosine Deaminase Deficiency; SCID-X: X-Linked Severe Combined Immunodeficiency; MLD: Metachromatic Leukodystrophy;

X-CGD: X-Linked Chronic Granulomatous Disease

Leading lysosomal disorder gene

therapy pipeline Built on strong strategic fit IND: Investigational New Drug Fabry AVR-RD-01 Gaucher type 1 AVR-RD-02 Cystinosis AVR-RD-04 Hunter AVR-RD-05 Gaucher type 3 AVR-RD-06 Pompe AVR-RD-03 Proof-of-Concept IND-Enabling Phase 1/2

Disease Approx. 2019 Global Net

Sales Five-Year SOC Cost per U.S. Patient* Selected Companies w/ Marketed Therapies Fabry $1.4B $1.7M Cystinosis $0.2B $4.3M Gaucher $1.4B $2.3M Hunter $0.6B $2.4M Pompe $1.0B $3.2M A multi-billion dollar market opportunity Targeting larger

rare lysosomal disorders Sources: Rombach S et al., Orphanet J Rare Dis, 2013; van Dussen L et al., Orphanet J Rare Dis, 2014 * WAC pricing from Redbook using standard dosing assumptions 2019 Net Sales from company annual and other reports

Horizon's Procysbi oral therapy (delayed release cysteamine bitartrate); midpoint between avg. adult and pediatric Note: Shire acquired by Takeda in 2019 SOC: Standard of Care Total: $4.6B

PROGRAM PATIENT MONTHS POST-INFUSION

Fabry Phase 1 PATIENT 1 PATIENT 2 PATIENT 3 PATIENT 4 PATIENT 5 Fabry Phase 2 PATIENT 1 PATIENT 2 PATIENT 3 PATIENT 4 Gaucher Phase 1/2 PATIENT 1 Cystinosis Phase 1/2 PATIENT 1 PATIENT 2 PATIENT 3 Durability across programs Note: Based on data

cut-off date of Nov. 12, 2020

Blood GI System Leukopenia Lymphopenia

Neutropenia Febrile neutropenia Thrombocytopenia Anemia Abdominal pain Diarrhea Mucositis Nausea Vomiting Days Post Gene Therapy Emerging tolerability profile has been predictable and manageable Conditioning-related grade 3-4 AEs were transient in

first 2 plato patients Bu90 TCI Mean Toxicity Grade Bu90-TCI: Busulfan 90-Target Concentration Intervention; AE: Adverse Event; GI: Gastrointestinal Bu90- TCI Busulfan 90 Target Concentration Intervention (TCI) Observations to-date show

short-term side effects start ~1 week after infusion, peak over the next 3-5 days and subside Day 0

Unrivaled commercial-scale platform

in plato MOBILIZATION & APHERESIS Patient Consent & Screening Patient Monitoring CONDITIONING & GENE THERAPY ADMINISTRATION CELL SEPARATION & CULTURE TRANSDUCTION CLOSED, AUTOMATED SYSTEM HARVESTING & CRYOPRESERVATION DRUG

PRODUCT TESTING 1 2 3 4 5

Fabry Gaucher type 1 Cystinosis

Hunter Gaucher type 3 Pompe COMMERCIAL CALL POINTS REGULATORY PATHWAYS CLINICAL EXECUTION TECHNICAL & MANUFACTURING Halo effect' driven by strong pipeline synergies Replicable path to market

Patient enrollment activities

accelerating across trials By the end of 2021, we expect to have dosed a total of 30 patients. Q4 20 Recruiting Objective Clinical Trial Site Expansion Cumulative 2021 Patient Dosing Goal ENROLLED CONSENTED DOSED Active clinical sites: 7

CURRENTLY 23 PLANNED BY Q4 2021

Key takeaways for today Fabry

advancing toward potential accelerated approval pathway in one or more major markets Exciting early data in cystinosis and Gaucher Clear advantages of Bu90-TCI conditioning plato platform reimagines CMC / analytics Leading lysosomal disorder

gene therapy franchise Bu90-TCI: Busulfan 90-Target Concentration Intervention; CMC: Chemistry, Manufacturing, and Controls

Today's agenda Bu90-TCI:

Busulfan 90-Target Concentration Intervention; CMC: Chemistry, Manufacturing, and Controls Time Clinical updates New data and update on future regulatory plans 9:15 Precision conditioning designed to enable durability and head-to-toe reach The

Bu90-TCI advantage 10:00 Addressing industry manufacturing challenges with advanced CMC and analytic solutions AVROBIO's platform for global gene therapy commercialization 10:35 The second wave Working to prevent irreversible damage to body

Rob Hopkin, M.D. Genetic Medicine

Specialist, Fabry KOL at Cincinnati Children's Hospital Perspective from leading KOLs Harry Malech, M.D. Chief of Genetic Immunotherapy Section and Deputy Chief of Laboratory of Clinical Immunology and Microbiology, NIAID, NIH Anthony Davies,

Ph.D. Founder and CEO, Dark Horse Consulting Group Dr. Rob Hopkin is a consultant to AVROBIO and Dr. Anthony Davies is the CEO of Dark Horse, an AVROBIO vendor KOL: Key Opinion Leader; NIAID: National Institute of Allergy and Infectious Diseases;

NIH: National Institutes of Health; CEO: Chief Executive Officer

Gaucher Disease Type 1 Meet

"Fatigue is, for me, probably

really the one symptom that plagues me the most I wake up tired, I'm tired in the middle of the day, and I go to sleep tired Gaucher is always there." - Cyndi, living with Gaucher disease type 1 DIFFERENTIATED TARGET

PRODUCT PROFILE for Gaucher Disease Type 1 Note: These are target attributes for a first-line therapy AAV: Adeno-Associated Viral vector; Bu90-TCI: Busulfan 90-Target Concentration Intervention; CNS: Central Nervous System; ERT: Enzyme Replacement

Therapy; GBA: Glucocerebrosidase; SRT: Substrate Reduction Therapy First-Line Therapy and Functional Cure Addresses all patient segments All Gaucher disease type 1 genetic mutations All age groups Male and female No AAV or ERT neutralizing antibody

limitations Well-tolerated No ERT/SRT-related side effects Mild-to-moderate, transient side effect profile consistent with Bu90-TCI No splenectomy medication and complications No liver toxicity or adverse immunogenicity Impacts hard-to-reach organs

Diseased macrophages (Gaucher cells) replaced by functional macrophages Brain: global distribution of genetically modified microglia Bone and bone marrow: global distribution of genetically modified macrophages and osteoclasts Lifelong durability

Single infusion for life Off ERT/chaperone No waning of efficacy Save millions of dollars in healthcare costs per patient Prevents, halts or reverses disease; normalizes lifespan Bone-related manifestations, prevention of physical deformity, bone

crises, bone pain, avascular necrosis Low hemoglobin and platelets Hepatosplenomegaly, risk of cirrhosis and splenectomy Risk of multiple myeloma Fatigue CNS: risk of GBA-Parkinson's disease

Even on ERT, patients endure

debilitating symptoms Incomplete therapeutic response is common: 60% failed to achieve at least one of six therapeutic goals after 4+ yrs of ERT1 Many continue to exhibit bone pain, organomegaly and cytopenia after 10 yrs of ERT2 25% have physical

limitations after 2 yrs of ERT, primarily due to bone disease3 Persistence after 10 years ERT Non-splenectomized Patients Splenectomized Patients Bone Pain 43% 63% Splenomegaly* 38% N/A Thrombocytopenia* 23% 1% Hepatomegaly* 14% 19% Anemia

12% 9% Bone Crisis 7% 17% * Higher persistence rates observed when more severe manifestations were present at baseline Persistence refers to the presence of anemia, bone pain, bone crisis, or at least moderate thrombocytopenia, splenomegaly,

or hepatomegaly, present after 10 years of ERT among those with baseline involvement of these parameters (from a registry of 757 GD1 patients; Weinreb et al., 2013) Following 10 years of treatment, ~26% of patients were receiving between 45-150 U/kg

EOW, and 96% of these individuals were receiving doses between 45-90 U/kg EOW. Data rounded to complete integer. GD1: Gaucher Disease Type 1; ERT: Enzyme Replacement Therapy; EOW: Every Other Week 1Weinreb N et al., Amer J Hematol, 2008; 2Weinreb N

et al., J Inherit Metab Dis, 2013; 3Giraldo P et al., Qual Life Res, 2005 Prospective registry of 757 GD1 patients on ERT after 10 years

Delivering genetically modified

cells head-to-toe Long-term engraftment in bone marrow Manufacturing', transportation and delivery in blood Target organs T NK B RBC Platelets Granulocytes DC Monocytes PROGENY Microglia Osteoclasts Macrophages CD34+ HSCs

DIFFERENTIATION Spleen, Liver, Lungs HSC: Hematopoietic Stem Cell; NK: Natural Killer; DC: Dendritic Cell; RBC: Red Blood Cell

Guard1: Phase 1/2 study in Gaucher

disease type 1 1 patient dosed to date OBJECTIVES PATIENTS Safety Efficacy Engraftment Enrollment goal: 8-16 patients 18-45-year-old males and females Have a confirmed diagnosis of GD1 based on: Deficient glucocerebrosidase enzyme activity Clinical

features consistent with GD1 An adaptive, open-label, multinational phase 1/2 study of the safety and efficacy of ex vivo, lentiviral vector-mediated gene therapy AVR-RD-02 for patients with Gaucher disease type 1. ACTIVELY RECRUITING: RECRUITING

PLANNED 1H '21: PHASE 1/2 AVR-RD-02 Gaucher disease type 1 patients who are: ERT-stable for >24 months or Treatment-na ve or Have not received ERT or SRT in the last 12 months GD1: Gaucher Disease Type 1; ERT: Enzyme Replacement

Therapy; SRT: Substrate Reduction Therapy; 1H: First Half

Toxic metabolite lyso-Gb1 reduced

below ERT levels at 3 months GUARD1: PATIENT 1 Lyso-Gb1 Plasma Normal Range: 0.5 - 1.2 ng/mL ERT: Enzyme Replacement Therapy; Lyso-Gb1: Glucosylsphingosine Plasma Lyso-Gb1 (ng/mL) Baseline (On ERT) 3 months (Off ERT) 22% reduction Lyso-Gb1, a

sensitive and specific marker of metabolite accumulation in Gaucher disease is decreased relative to baseline on ERT

GUARD1: PATIENT 1 Chitotriosidase

Plasma Activity Normal Range: 0.0-44.2 moL/L/h ERT: Enzyme Replacement Therapy Plasma chitotriosidase reduced below ERT levels at 3 months Plasma Chitotriosidase Activity ( moL/L/h) Chitotriosidase, a marker of activated macrophages

(Gaucher cells), is also decreased Baseline (On ERT) 3 months (Off ERT) 17% reduction 151

Platelet counts in normal range at

3 months, despite being off ERT GUARD1: PATIENT 1 Platelet Count Reference Value Adult: 130-400x109/L; grey line: local (safety) lab values; pink dots: central (efficacy) lab values ERT: Enzyme Replacement Therapy Platelet Count Day 0 Off ERT Normal