Findings Demonstrated Dose-Dependent Durable Gene Expression, and No Apparent Safety Issues Across the Dose Range Tested
Topline Data from First Cohort in Phase 1/2 Trial of DTX101 Expected in the Second Half of 2016

CAMBRIDGE, MA, USA I May 05, 2016 I Dimension Therapeutics, Inc. (DMTX), a biopharmaceutical company advancing novel, adeno-associated virus (AAV) gene therapies targeting the liver, a central organ for devastating rare diseases, today announced positive preclinical results supporting Dimension’s ongoing Phase 1/2 clinical trial of lead candidate DTX101, which commenced in January 2016. DTX101 is designed to deliver Factor IX, or FIX, gene expression, in adult patients with moderate/severe to severe hemophilia B. Preclinical research conducted with Dimension’s collaborators at the University of Pennsylvania (PENN) demonstrated dose-dependent expression of FIX levels and stability of FIX expression after single dose administration across the majority of doses during the 90-day study period. The study also found there were no apparent safety concerns related to the anticipated clinical dosing. These findings were highlighted in a poster, titled “A Dose-Escalating Preclinical Study to Determine the Efficacy, MED, and Safety of a Clinical Candidate Vector in a Mouse Model of Hemophilia B” (Abstract No. 227), presented at the 19th ASGCT Annual Meeting, which is taking place in Washington, DC, May 4-7, 2016.

“In DTX101, we have pre-clinically developed a potent AAVrh10 vector containing a wild-type FIX gene with the goal of achieving approximately 10 percent of normal FIX levels, which we hope will ultimately lead to the achievement of clinically meaningful benefits for patients via gene delivery,” said James M. Wilson, MD, PhD, a professor of Medicine and Pediatrics, and director of the Orphan Disease Center at the Perelman School of Medicine at the University of Pennsylvania. “Our preclinical data provides supporting evidence for this, both in terms of durability and consistent, dose-dependent activity of DTX101, as well as promising initial safety findings. We look forward to the continued progress of the clinical program, which is expected to report interim topline data later this year.” Lili Wang, PhD, a research associate professor in the Wilson lab, is first author on this poster presentation. Dimension’s phase 1/2 clinical trial of DTX101 is a single arm, open-label, multi-center study, designed to evaluate the safety, dose and early efficacy of DTX101 in adult patients with moderate/severe to severe hemophilia B. Additional information about Dimension’s Phase 1/2 study of DTX101 may be found at ClinicalTrials.gov, using Identifier NCT: NCT02618915.

“Dimension’s presentations at this week’s ASGCT conference, as well as at other important medical and scientific conferences throughout this year, demonstrate our commitment to generating and communicating important data that enables the translation of gene therapy science into the clinic,” said Annalisa Jenkins, MBBS, MRCP, Chief Executive Officer of Dimension. “Based on breakthrough AAV technology and key collaborations, as with PENN, we continue to advance our leading portfolio in liver-associated diseases –hemophilia and inherited metabolic diseases – to meet compelling needs for patients.”

PENN and Wilson are each holders of Dimension stock and Wilson also holds stock in REGENXBIO, Inc.  Dimension holds exclusive sublicenses from REGENXBIO, Inc. for certain PENN-owned AAV technologies related to this development program.

About DTX101

Dimension is developing its lead gene therapy product DTX101 for the treatment of moderate/severe to severe hemophilia B. DTX101 is designed to deliver Factor IX, or FIX, gene expression in a durable fashion, preventing the long-term complications of hemophilia B. Preclinical studies completed to date indicate DTX101 has the potential to be a well-tolerated, effective therapy for hemophilia B. A Phase 1/2 study commenced in January 2016, and the company anticipates reporting interim clinical data in the second half of 2016.

About Dimension Therapeutics, Inc.

Dimension Therapeutics, Inc. (DMTX) is the leader in discovering and developing new therapeutic products for people living with devastating rare 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 and GSDIa, 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.

SOURCE: Dimension Therapeutics