AVROBIO, Inc. Reports Third Quarter 2019 Financial Results and Provides Business Update Dosing of first Fabry patient incorporating plato anticipated for fourth quarter 2019 All Fabry patients who discontinued enzyme rep

AVROBIO, Inc. Reports Third Quarter 2019 Financial Results and Provides Business Update

Dosing of first Fabry patient incorporating plato anticipated for fourth quarter

All Fabry patients who discontinued enzyme replacement therapy (ERT) following treatment with

AVR-RD-01 investigational gene therapy remain off ERT

FDA orphan drug designation granted for AVR-RD-02

investigational gene therapy for the

treatment of Gaucher disease

First patient dosed in AVR-RD-04 investigational gene

therapy program for cystinosis

CAMBRIDGE, Mass., November 7, 2019 AVROBIO, Inc. (NASDAQ: AVRO) (the Company ), a Phase 2

clinical-stage gene therapy company, today reported financial results for the third quarter ended September 30, 2019 and provided a business update.

We are thrilled with the progress across our pipeline, including the dosing of the first patient in our cystinosis program and receipt of orphan drug

designation for our investigational gene therapy for Gaucher disease, commented Geoff MacKay, President and Chief Executive Officer of AVROBIO. In our Fabry program, we have now dosed eight patients across two clinical trials and we are

on track to use our optimized lentiviral vector and a conditioning regimen utilizing therapeutic drug monitoring for the first time to dose a patient in our Phase 2 clinical trial for Fabry disease by the end of 2019. While our rapid expansion and

early data have been exciting, we are humbled by the needs of the rare disease communities with whom we engage. They impress a sense of urgency on our work to deliver a new paradigm that we believe can supersede current treatment options and

potentially provide patients freedom from a lifetime of disease.

Program Updates and Milestones

Quarter 2019 Financial Results

AVROBIO reported a net loss of $17.1 million for the third quarter of 2019 as compared to a net loss of

$11.6 million for the comparable period in 2018. This increase was due to increased research and development expenses, as well as increased general and administrative expenses.

Research and development expenses were $13.0 million for the third quarter of 2019 as compared to $9.2 million for the comparable period in 2018.

This increase was driven by increased program development activities related to the advancement of the Company s pipeline, as well as increased personnel-related costs resulting from an increase in employee headcount.

General and administrative expenses were $5.0 million for the third quarter of 2019 as compared to $3.0 million for the comparable period in 2018.

This increase was primarily due to an increase in employee headcount, expenses associated with being a publicly traded company, including consulting expenses, and the impact of non-cash stock-based

As of September 30, 2019, AVROBIO had $206.4 million in cash and cash equivalents, as compared to $126.3 million in cash and

cash equivalents as of December 31, 2018. The cash balance as of September 30, 2019 reflects the receipt of net proceeds of $129.5 million from the Company s July 2019 follow-on equity

offering. Based on the Company s current operating plan, AVROBIO expects its cash and cash equivalents as of September 30, 2019 will enable the Company to fund its operating expenses and capital expenditure requirements into the second

a leading, Phase 2 gene therapy company focused on the development of its investigational gene therapy, AVR-RD-01, in Fabry disease, as well as additional gene

therapy programs in other lysosomal storage disorders including Gaucher disease, cystinosis and Pompe disease. The Company s plato platform includes a proprietary

vector system, automated cell manufacturing solution and refined conditioning regimen deploying therapeutic drug monitoring. AVROBIO is headquartered in Cambridge, MA and has offices in Toronto, ON. For additional information,

visit www.avrobio.com.

Forward-Looking Statements

This press release contains forward-looking statements, including statements made pursuant to the safe harbor provisions of the Private Securities Litigation

Reform Act of 1995. These statements may be identified by words such as aims, anticipates, believes, could, estimates, expects, forecasts,

goal, intends, may, plans, possible, potential, seeks, will, and variations of these words or

similar expressions that are intended to identify forward-looking statements. These forward-looking statements include, without limitation, statements regarding our business strategy, prospective products and goals, the therapeutic potential of our

product candidates, the design, commencement, enrollment and timing of ongoing or planned clinical trials, clinical trial results, product approvals and regulatory pathways, the intended incentives conferred by orphan-drug designation, potential

regulatory approvals and the timing thereof, expected benefits from the appointment of Ms. Verdin to the position of Chief Human Resources Officer and Ms. May to the position of Chief Commercial Officer, anticipated benefits of our gene

therapy platform including potential impact on our commercialization activities, timing and likelihood of success, plans and objectives of management for future operations, future results of anticipated products, and the market opportunity for and

anticipated commercial activities relating to our product candidates, and statements regarding the Company s financial and cash position and expected cash runway. Any such statements in this press release that are not statements of historical

fact may be deemed to be forward-looking statements. Results in preclinical or early stage clinical trials may not be indicative of results from later stage or larger scale clinical trials and do not ensure regulatory approval. You should not place

undue reliance on these statements, or the scientific data presented.

Any forward-looking statements in this press release are based on AVROBIO s

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 AVROBIO s 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 AVROBIO 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 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 AVROBIO s 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, 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 materially and adversely from

those contained in the forward-looking statements, see the section entitled Risk Factors in AVROBIO s Quarterly Report on Form 10-Q for the quarter ended June 30, 2019, 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.

Christopher F. Brinzey

Westwicke, and ICR Company

Ten Bridge Communications

CONDENSED CONSOLIDATED BALANCE SHEETS

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS

(In thousands, except share and per share data)