Dimension Therapeutics Receives Positive Opinion for European Orphan Drug Designation of DTX401 for the Treatment of Glycogen Storage Disease Type Ia

Dimension Therapeutics, Inc. (NASDAQ:DMTX), a biopharmaceutical company advancing novel, adeno-associated virus (AAV) gene therapies targeting the liver, a key organ for human metabolism, today announced that the European Medicines Agency (EMA) Committee for Orphan Medicinal Products (COMP) has issued a positive opinion recommending DTX401 for designation as an orphan medicinal product for the treatment of Glycogen Storage Disease Type Ia (GSDIa).

The positive opinion for DTX401 is a key milestone for Dimension’s leading and unique program advancing the opportunity for AAV gene therapy for patients with limited treatment options to manage their disease. Designed to address the underlying genetic defect, DTX401 has been shown in multiple in vivo preclinical models to deliver stable expression and activity of the enzyme glucose-6-phosphatase-α (G6Pase-α). DTX401 has also been shown to improve G6Pase-α activity and reduce hepatic glycogen levels, a well-described biomarker of disease progression. Dimension has completed candidate selection for its DTX401 program and is currently in IND-enabling studies.
“We are pleased with the progress of our DTX401 program, which has followed a research pathway that includes studies in highly predictive preclinical in vivo models, application of well-described biomarkers, and the development of a proprietary manufacturing platform,” said Dr. Annalisa Jenkins, MBBS, FRCP, Chief Executive Officer of Dimension. “In our current IND-enabling studies, we are replicating the groundbreaking work of leading researchers, particularly through our cooperative research and development agreement, or CRADA, with Janice Chou, Ph.D., at the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) at the National Institutes of Health (NIH).”
David A. Weinstein, MD, who is joining Connecticut’s UConn School of Medicine and Connecticut Children’s Medical Center in early 2017 and is the chair of Dimension’s GSDIa clinical advisory board, added, “The COMP positive opinion in the EU is an important milestone as it represents a key step forward for a potential treatment for GSDIa. Coupled with recent orphan drug designation for DTX401 in the US, the opinion affirms the substantial need for patients with GSDIa, who currently have limited therapeutic options. Affected individuals are at high risk for hypoglycemia (low blood sugar), coma, and potentially death, and are required to adhere to burdensome dietary regimens in order to maintain blood glucose at an appropriate level. Gene therapy is designed to address these challenges and offer a new option to patients.”
The COMP issues an opinion on the granting of orphan drug designation, after which the opinion is submitted to the European Commission (EC) for endorsement of the opinion. Orphan drug designation by the EC provides regulatory and financial incentives for companies to develop and market therapies that treat a life-threatening or chronically debilitating condition affecting no more than five in 10,000 persons in the European Union (EU), and where no satisfactory treatment is available. In addition to a 10-year period of marketing exclusivity in the EU after product approval, orphan drug designation provides incentives for companies seeking protocol assistance from the EMA during the product development phase, and direct access to the centralized authorization procedure.
Background on GSDIa
GSDIa, the most common genetically inherited glycogen storage disease, has significant unmet needs. Patients have a defective gene for the enzyme glucose-6-phosphatase-α, resulting in the inability to regulate blood sugar (glucose). Hypoglycemia in GSDIa patients can be life-threatening, while the accumulation of the complex sugar glycogen in certain organs and tissues can impair the ability of these tissues to function normally. If chronically untreated, patients develop severe lactic acidosis, can progress to renal failure, and die in infancy or childhood. There are no approved pharmacological therapies, and no ongoing clinical development beyond dietary approaches. An estimated 6,000 or more patients are affected by GSDIa worldwide.
About Dimension Therapeutics, Inc.
Dimension Therapeutics, Inc. (NASDAQ:DMTX) is the leader in discovering and developing new therapeutic products for people living with devastating rare and metabolic diseases associated with the liver, based on the most advanced, mammalian adeno-associated virus (AAV) gene delivery technology. Dimension is actively progressing its broad pipeline, which features programs addressing unmet needs for patients suffering from inherited metabolic diseases, including OTC deficiency, GSDIa, citrullinemia type 1, PKU, Wilson disease, a collaboration with Bayer in hemophilia A, and a wholly owned clinical program in hemophilia B. The company targets diseases with readily identifiable patient populations, highly predictive preclinical models, and well-described, and often clinically validated, biomarkers. Founded in 2013, Dimension maintains headquarters in Cambridge, Massachusetts.
For more information, please visit www.dimensiontx.com.
Cautionary Note Regarding Forward-Looking Statements
This press release contains “forward-looking statements” within the meaning of the Private Securities Litigation Reform Act of 1995, including, but not limited to, statements regarding the clinical and developmental progress of Dimension’s portfolio and lead programs, including DTX401, the timing, scope, or likelihood of regulatory filings and approvals, the progress and results of preclinical studies, and our ability to develop and advance product candidates into, and successfully complete, clinical studies and the continued development of our manufacturing platform. All such forward-looking statements are based on management’s current expectations of future events 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 the risks that Dimension’s product candidates, including its candidate, DTX401, will not successfully be developed or commercialized in the times indicated or at all; and the risks described under the caption “Risk Factors” in Dimension Therapeutics’ Quarterly Report on Form 10-Q for the quarter ended September 30, 2016, which is on file with the Securities and Exchange Commission, as well as other risks detailed in Dimension Therapeutics’ additional filings with the Securities and Exchange Commission. All information in this press release is as of the date of the release, and Dimension Therapeutics undertakes no duty to update this information unless required by law.

Contacts:
Jean Franchi
Chief Financial Officer
Dimension Therapeutics
617-714-0709
jean.franchi@dimensiontx.com
Burns McClellan, on behalf of Dimension Therapeutics
Media: Justin Jackson
212-213-0006, ext.327
jjackson@burnsmc.com