Gene Therapy Startup Dimension Tx Takes Crossover Cash to IPO Queue

Xconomy Boston — 

Time to add one more recipient of crossover investor cash to the list of official IPO candidates.

Cambridge, MA-based Dimension Therapeutics just filed for an IPO this morning, aiming to raise cash from public investors to support a pipeline of potential gene therapies for hemophilia and rare diseases. Should the company go public, it’ll trade on the Nasdaq under the ticker symbol “DMTX.”

The IPO filing comes roughly five months after Dimension raised $65 million from a group of crossover investors that back both public and private companies. Crossovers have been piling cash into biotech startups over the past few years, and their presence is typically a good sign of a looming IPO. (Check out this recent column from Alex Lash for more.)

For Dimension, the decision to file for an IPO has come less than two years after its October 2013 launch. The company was founded via a deal between Fidelity Biosciences and RegenxBio—another gene therapy upstart eyeing the public markets—and has since nabbed more than $90 million in venture financing and a key partnership with Bayer.

For those unfamiliar with Dimension, it’s one of the startups to emerge over the past few years amidst a renaissance for gene therapy. The startup is tied to the work of one of the field’s pioneers and controversial figures, University of Pennsylvania gene therapy specialist James Wilson (pictured above). Wilson co-led the infamous clinical trial that led to the death of teenager Jesse Gelsinger in 1999, but went on to become a key figure in advancing the gene therapy delivery tool known as an adeno-associated virus, or AAV. Wilson’s AAV work led to RegenX, and Dimension was formed with a license to several of the startup’s vectors.

Dimension aims to use the technology to target rare metabolic disorders associated the liver as well as hemophilia A and B. The two rare diseases Dimension has revealed it’s targeting so far are ornithine transcarbamylase (OTC) deficiency—the disease Gelsinger suffered from—and glycogen storage disease type 1a.

Dimension’s hemophilia B program (DTX-101) is the furthest along so far; the company is expected to begin clinical testing of DTX-101 by the end of this year. That treatment is one of at least seven in development for hemophilia, a disorder that leaves patients without the molecular machinery needed to clot blood. For more on that race—which includes companies like Spark Therapeutics (NASDAQ: ONCE), BioMarin Pharmaceutical (NASDAQ: BMRN), Baxalta (NYSE: BXLT), Biogen (NASDAQ: BIIB), UniQure (NASDAQ: QURE), and Sangamo Biosciences (NASDAQ: SGMO)—and the long history of hemophilia gene therapy development, check out this story from March.

Via its partnership with Bayer, Dimension is also developing a gene therapy (DTX201) for hemophilia A.

Dimension’s most significant shareholders are Beacon Bioventures Fund (a fund managed by Fidelity, 20.5 million shares), OrbiMed (15.2 million shares), and New Leaf Venture Partners (3.2 million shares). Each hold more than 5 percent of Dimension’s stock.

The IPO success, or lack thereof, of both Dimension and RegenX will be a good barometer of investor sentiment for gene therapy. Since the field’s rebirth—characterized by better delivery tools and positive early clinical data—there have once again been some setbacks. A few companies, Avalanche Biotechnologies (NASDAQ: AAVL) and Celladon (NASDAQ: CLDN) have seen their shares crater after disappointing results in clinical testing. Spark is next up, with important data on a gene therapy for a rare form of genetic blindness coming next month.