Dimension Therapeutics Secures $65 Million in Oversubscribed Series B Financing

Dimension Is Advancing Liver-Directed Gene Therapy Treatments for Rare Metabolic Disorders and Hemophilia Based on Innovative AAV technologies and a Proprietary Manufacturing Platform

CAMBRIDGE, MASS., April 21, 2015 – Dimension Therapeutics, Inc. (“Dimension” or the “Company”), a rare disease company advancing novel, liver-directed treatments for diverse genetic disorders, today announced the successful completion of a Series B financing totaling $65 million. New investor New Leaf Venture Partners led the financing, with participation from additional new investors Jennison Associates (on behalf of investors), Partner Fund Management, RA Capital Management, Rock Springs Capital, and Tourbillon Global Ventures, and another life sciences investor. Dimension’s existing investors Fidelity Biosciences and OrbiMed also participated in the round.

“We are pleased with the substantial support from new and existing investors. The strong demand in our Series B affirms the rapid progress we have achieved to date and reflects continued broad interest in the promise of gene therapy to address compelling unmet needs in the treatment of rare diseases,” said Dimension’s CEO Annalisa Jenkins, MBBS, MRCP. “Over the past year, Dimension has raised more than $100 million, including our Series A round, as well as a $20 million upfront payment we received from partner Bayer HealthCare last June. We are well-capitalized for the next stage of our development as we advance our lead programs into the clinic and continue to expand our R&D pipeline focused on rare diseases associated with the liver.”

Dimension plans to use the proceeds from the financing to further advance the company’s adeno-associated virus (AAV) platform and growing pipeline of gene therapy programs. The company’s first program is expected to enter clinical testing in patients with hemophilia B in the second half of 2015. Additional programs to treat indications in rare diseases are anticipated to enter IND-enabling studies during the next 12 to 18 months, with the objective of advancing three clinic-ready programs next year.

In association with the financing, Mike Dybbs, Ph.D., Partner, New Leaf Venture Partners, has joined Dimension’s Board of Directors. “Mike brings substantial experience advising life sciences firms both in terms of his scientific insights and operational acumen, and we are pleased to welcome him to the Board,” stated Ben Auspitz, Partner, Fidelity Biosciences, and Chairman of Dimension’s Board. The Company also announced that Allan M. Fox of FOXKISER, the founders of REGENXBIO, is leaving his position as a member of the Company’s Board of Directors. “The entire Dimension team and I would also like to recognize the contributions and vision of Allan Fox, a key founder and inspiration behind the formation of Dimension,” Mr. Auspitz added.

Dr. Dybbs said, “Dimension is differentiated in the gene therapy sector both in terms of the company’s focus on liver-associated, rare metabolic diseases and the impressive track record of its highly accomplished leadership team. We believe Dimension’s breakthrough platform has strong potential to transform the lives of patients, and we look forward to further progress of the company’s programs.”

About Dimension Therapeutics
Dimension Therapeutics, Inc., is a rare disease company focused on developing novel treatments for devastating disorders associated with the liver and based on an industry-leading, extensively validated adeno-associated virus (AAV) platform. The company is advancing multiple programs toward clinical development, including a collaboration with Bayer HealthCare in hemophilia A, and a wholly owned program in hemophilia B, which is expected to enter clinical testing in the second half of 2015. Dimension has preferred access to multiple best-in-class AAV vectors from REGENXBIO, which founded Dimension with Fidelity Biosciences in October 2013. The Dimension team and senior advisors include biotech industry veterans and renowned thought leaders in gene therapy and rare diseases. For more information, please visit www.dimensiontx.com.

Justin Jackson, Burns McClellan, on behalf of Dimension Therapeutics
212-213-0006, ext.327
jjackson @burnsmc.com