Spark Therapeutics declares phase 3 gene therapy trial successful

A homegrown start-up is on track to make the first approved gene therapy in the U.S. Spark Therapeutics, a spin-off company of the Children’s Hospital of Philadelphia, announced this week that its phase 3 clinical trial to treat a rare form of inherited blindness was successful.

Patients born with mutations in a key gene, RPE65, have poor vision from birth and eventually go blind as their rod photoreceptors wither and die. The company’s gene therapy technology returns the gene to the remaining cells in the eye through a single injection.

The news sent the company’s stock price soaring, although it has since declined to just above last week’s close. The company’s head is Jeffrey Marrazzo, the son of WHYY’s president and CEO.

“The results are extraordinarily exciting, and demonstrate that the intervention is indeed improving their vision,” said Jean Bennett, a professor of ophthalmology at the University of Pennsylvania and one of the investigators of the trial.

The company released limited information about the preliminary results and the findings have not yet been peer-reviewed. Bennett said the main evaluation assessed how well patients who received the gene therapy moved through an obstacle course in dim light. She does not stand to gain financially from the therapy if it’s approved.

“When I see one of these individuals able to navigate the course, it puts tears in my eyes to be able to actually witness this remarkable improvement,” she said.

Overall, the patients’ visual acuity did not increase, although Bennett said this was not an expected outcome.

Julia Haller, ophthalmologist-in-chief at the Wills Eye Hospital and an unpaid consultant on the project, said the results were extremely exciting.

“It was one thing to have one or two children who are able to see in the early days of the trial showing that maybe that it could work in a couple of cases,” she said. “A phase 3 study is a huge, huge, big leap beyond just the proof of concept studies that were done before.”

Haller cautioned, however, that there were still many regulatory steps to go before patients will be able to see the therapy in the clinic.

“We’re still not telling people that they’re going to be treated tomorrow,” she said. “I think you have to temper your enthusiasm a little bit and keep your expectations in check.”

“I think they have a major breakthrough,” said Elemer Piros, a senior research analyst with ROTH Capital Partners, in an email. “It is extremely positive for patients, for the gene therapy field and for biotechnology in general. No one has been able to succeed to this extent in a controlled clinical trial for any condition with gene therapy.”

The first scientific presentation of the results is set for this weekend in Paris at the Retina Society’s annual meeting.