AVROBIO Receives Orphan Drug Designation from the U.S. Food and Drug Administration for AVR-RD-05, a Gene Therapy for Mucopolysaccharidosis Type II (MPSII) or Hunter Syndrome

AVR-RD-05 is the fourth AVROBIO gene therapy to receive orphan drug designation

FDA previously granted rare pediatric disease designation for AVR-RD-05

AVROBIO, Inc. (Nasdaq: AVRO), a leading clinical-stage gene therapy company with a shared purpose to free people from a lifetime of genetic disease, today announced that the U.S. Food and Drug Administration (FDA) has granted orphan drug designation for AVR-RD-05, its gene therapy for the treatment of mucopolysaccharidosis type II (MPSII), or Hunter syndrome, a rare and seriously debilitating lysosomal disorder that primarily affects young boys.

Orphan drug designation is granted by FDA to drugs and biologics that are intended for the safe and effective treatment, diagnosis or prevention of rare diseases or conditions that affect fewer than 200,000 people in the U.S. Orphan drug designation provides certain incentives, which may include tax credits towards the cost of clinical trials and prescription drug user fee waivers.

Hunter syndrome is caused by a deficiency in the lysosomal enzyme iduronate-2-sulfatase (IDS), which is essential for breaking down large sugar molecules. The gene therapy uses a patient’s own hematopoietic stem cells (HSCs) that are transduced ex vivo with a lentiviral vector encoding the human IDS enzyme. The company’s planned collaborator-sponsored Phase 1/2 clinical trial for Hunter syndrome is expected to commence in 2023 under the company’s collaboration with the University of Manchester, UK. The program was developed by Brian Bigger, Ph.D., professor of cell and gene therapy at the University of Manchester, who has previously published preclinical data demonstrating that HSC gene therapy deploying an optimized, proprietary tag has the potential to correct peripheral disease and normalize brain pathology.

About Hunter syndrome

Hunter syndrome, which affects an estimated one in 100,000 to one in 170,000 males worldwide, causes devastating complications throughout the body, including severe neurological, cardiac and respiratory dysfunction, skeletal malformations and hearing impairment. Children with severe cases of Hunter syndrome typically show early symptoms of the disease in infancy and childhood and begin to regress developmentally, losing basic motor skills and cognitive function over a few years. The current standard of care is weekly enzyme replacement therapy (ERT), which can delay some health complications but does not halt overall progression of the disease and has not been demonstrated to address the central nervous system (CNS) issues. Even with ERT, people with Hunter syndrome face life-limiting symptoms and a significantly reduced lifespan.

About AVROBIO

Our vision is to bring personalized gene therapy to the world. We aim to prevent, halt or reverse disease throughout the body with a single dose of gene therapy designed to drive durable expression of therapeutic protein, even in hard-to-reach tissues and organs including brain, muscle and bone. AVROBIO’s pipeline is powered by our industry-leading plato^® gene therapy platform, our foundation designed to deliver gene therapy worldwide. It includes clinical programs in cystinosis and Gaucher disease type 1, as well as preclinical programs in Gaucher disease type 3, Hunter syndrome and Pompe disease. We are headquartered in Cambridge, Mass. For additional information, visit avrobio.com, and follow us on Twitter and LinkedIn.

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 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 preclinical and clinical product candidates, including AVR-RD-05 for the treatment of Hunter syndrome, the potential benefits and incentives provided by the FDA’s orphan drug designation for AVR-RD-05, the design, commencement, enrollment and timing of planned clinical trials, preclinical or clinical trial results, product approvals and regulatory pathways, our plans and expectations with respect to interactions with regulatory agencies, anticipated benefits of our gene therapy platform including potential impact on our commercialization activities, timing and likelihood of success, the expected benefits and results of our implementation of the plato platform in our clinical trials and gene therapy programs, and the expected safety profile of our preclinical and investigational gene therapies. 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 successfully recruit or enroll a sufficient number of patients for our clinical trials, 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, 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 enrollment and development timelines 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 materially and adversely 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.

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