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With $90M Round, Stoke Eyes a “Spinraza For Epilepsy” And a 2019 IPO

Xconomy Boston — 

Ed Kaye stepped aside from Sarepta Therapeutics (NASDAQ: SRPT) last year after leading the company through one of the most noteworthy and controversial drug approvals in recent memory, for the Duchenne muscular dystrophy drug eteplirsen (Exondys 51). But his hiatus from a publicly traded biotech could be short-lived.

Kaye’s new startup, Bedford, MA-based Stoke Therapeutics, has just raised another $90 million in funding, meaning the company has bankrolled $130 million this year alone. That cash won’t just help Stoke advance a drug it is developing for a rare form of epilepsy called Dravet Syndrome. It lays the foundation for an IPO that could happen in the first half of 2019, says Kaye (pictured), the company’s CEO.

Kaye is touting the Dravet program as the “Spinraza for genetic epilepsy,” referring to the Biogen (NASDAQ: BIIB) drug that in 2016 became the first-ever approved treatment for spinal muscular atrophy (SMA). Stoke has a long way to go to prove that—human testing likely won’t begin until early 2020—but it isn’t just empty talk. Spinraza’s inventor, Cold Spring Harbor Laboratory scientist Adrian Krainer, is a co-founder of Stoke. And like Spinraza, the company’s Dravet drug is a synthetic RNA molecule that increases the production of a specific protein, and is meant to be infused into a patient’s spinal fluid a few times a year.

Krainer, incidentally, won one of the Breakthrough Prizes in Life Sciences last week for his work on Spinraza, just as Stoke was prepping its announcement. (Krainer shared the $3 million prize with Frank Bennett of Ionis Pharmaceuticals.)

“Every once in a while you get lucky,” Kaye says with a laugh. But he envisions Stoke’s lead program potentially having the type of impact for patients with Dravet that Spinraza provides for SMA patients. SMA can rob people of the ability to walk and function independently, and patients diagnosed with the most severe form of the disease can die before the age of two. Spinraza helps slow the progression of multiple forms of the disease.

Dravet Syndrome, meanwhile, can also be devastating. It is a rare genetic disease that affects an estimated one in every 15,700 babies born in the U.S., according to the nonprofit Dravet Syndrome Foundation. The disease starts in infancy and is characterized by severe, long-lasting seizures that can cause cognitive impairment, developmental delays and other problems. Patients can lose the ability to walk or talk, and the seizures can be fatal.

Several drugs are used to try to prevent seizures or rescue Dravet patients from them when they happen, but the medicines don’t work for everyone. The FDA recently approved cannabidiol (Epidiolex) from GW Pharmaceuticals (NASDAQ: GWPH) for Dravet, and another drug from Zogenix (NASDAQ: ZGNX) could follow. Both are meant to help prevent seizures, but they don’t affect the root cause of the disease or slow the cognitive decline it causes.

Stoke aims to make medicines that do just that. The company is developing RNA drugs that target segments of genes and are meant to precisely dial up the level of a protein the body produces. Stoke is using this approach to go after autosomal dominant diseases, where mutations in just one copy of a gene reduces the amount of a particular protein to cause disease. People with Dravet, for instance, have a genetic mutation that lowers the levels of a protein called Nav1.1. Nav 1.1 helps regulate the chemical balance in brain cells, and mutations in Nav 1.1 upset that balance, causing brain cells to become over-excited, which leads to seizures.

Stoke’s drug is designed to cause cells to produce a normal amount of the protein and thus restore balance in the brain. The hope is that a few infusions per year would slow cognitive impairment.

“If it works as well as we think it should, it could be transformational for genetic epilepsies,” Kaye says. “That’s why we’re moving this very quickly.”

In addition to its Dravet program, Stoke aims to go after other autosomal dominant diseases affecting vision, hearing, and more, but Kaye isn’t disclosing them specifically as of yet. The company will focus on rare diseases, though it hopes to bank more cash by forming partnerships with pharma companies to develop drugs for more common disorders.

RTW Investments led the round. Founding investor Apple Tree Partners also participated and was joined by new backers RA Capital Management, Cormorant Asset Management, Perceptive Advisors, Janus Henderson Investors, Redmile Group, Sphera Funds Management, and Alexandria Venture Investments.