First five patients in Phase 1/2 trial show systemic gene therapy effect across multiple tissues evaluated, including eyes, skin, gastrointestinal mucosa and neurocognitive system

AVROBIO planning to initiate company-sponsored trial in 2023

AVROBIO, Inc. (Nasdaq: AVRO), a leading clinical-stage gene therapy company working to free people from a lifetime of genetic disease, today announced that the sixth and final patient has been dosed in the collaborator-sponsored, Phase 1/2 clinical trial of an investigational gene therapy for the treatment of cystinosis. Cystinosis is a life-threatening disease that causes progressive multi-organ damage, including early, acute kidney disease progressing to end-stage kidney disease.

The Phase 1/2 clinical trial for cystinosis is evaluating the safety and efficacy of this hematopoietic stem cell (HSC) gene therapy approach in adult patients affected by the most severe and common form of cystinosis who previously had been treated with the current standard of care, cysteamine. Pharmacodynamic and clinical efficacy endpoints include evaluation of the effect of treatment on leukocyte cystine levels, kidney function, corneal cystine crystal accumulation, muscle strength, as well as measures of visual motor integration, visual perception and motor coordination. The first patient was dosed in 2019 in this University of California San Diego (UCSD) trial, 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).

“Completing the dosing of the first and only gene therapy trial for cystinosis represents a major milestone for a patient community living with a devastating genetic disease. Unmet medical needs impact the lives of patients and their family members every day,” said Stephanie Cherqui, Ph.D., lead study investigator and associate professor of Pediatrics at UCSD. “To date, the results from the trial show the potential of this investigational gene therapy to stabilize or reduce the impact of cystinosis on different tissues throughout the body with a one-time dose.”

Preliminary data from this trial suggest that this approach is well tolerated, with no adverse events (AEs) related to the drug product reported to date. All AEs reported were related to myeloablative conditioning, study procedures, the underlying disease or pre-existing conditions. The majority of AEs were mild or moderate and resolved without clinical sequelae. Clinical data to date indicate this investigational gene therapy approach provides therapeutic effect in multiple tissues evaluated, including the eyes, skin, gastrointestinal mucosa and the neurocognitive system.

“With proof-of-concept demonstrated, we continue to lay the groundwork for an AVROBIO-sponsored clinical trial planned to begin in 2023,” said AVROBIO Chief Medical Officer, Essra Ridha, M.D., MRCP, FFPM. “We look forward to our interactions with regulators on our clinical and Chemistry Manufacturing and Controls (CMC) strategy.”

About AVR-RD-04

AVR-RD-04 is designed to genetically modify patients’ own HSCs to express the gene encoding cystinosin, the protein that is critically deficient in people living with cystinosis. AVR-RD-04 has received Rare Pediatric Disease Designation and Fast Track Designation from the U.S. Food and Drug Administration (FDA) and Orphan Drug Designation from FDA and the European Medicines Agency. AVROBIO is planning for regulatory agency interactions to discuss clinical development and regulatory strategy, with the intent of initiating a company-sponsored clinical trial in 2023.

About cystinosis

Cystinosis, a rare, progressive disease that is believed to impact thousands of patients worldwide, including approximately 1,600 patients in the U.S., Europe and Japan, is marked by the accumulation of cystine in cellular organelles known as lysosomes. Untreated cystinosis is fatal at an early age. The current standard of care for cystinosis, a treatment regimen that can require dozens of pills per day, does not prevent overall disease progression and carries side effects, such as breath and body odor and gastrointestinal symptoms, which can impede compliance. More than 90% of treated cystinosis patients require a kidney transplant in the second or third decade of life.

About AVROBIO

Our vision is to bring personalized gene therapy to the world. We target the root cause of genetic disease by introducing a functional copy of the affected gene into patients’ own hematopoietic stem cells (HSCs), with the goal to durably express the therapeutic protein throughout the body, including the central nervous system. Our first-in-class pipeline includes clinical programs for cystinosis and Gaucher disease type 1, as well as preclinical programs for Gaucher disease type 3, Hunter syndrome and Pompe disease. Our proprietary plato® gene therapy platform is designed to be scaled to support late-stage clinical development and commercialization globally. 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-04 for the treatment of cystinosis, the potential benefits and incentives provided by FDA’s rare pediatric disease designation for AVR-RD-04, 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, including in collaborator-sponsored 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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