Curt Krouse's severe hemophilia B is a challenge to manage. The Rose Valley resident treats the bleeding disorder by injecting himself with special proteins called clotting factors once a week. Treatment can range from $350,000 to $1 million a year and, despite his best efforts, can damage joints.

Recent work by several biotech firms including Philadelphia-based Spark Therapeutics could improve the lives of hemophilia sufferers like Krouse. Leveraging advances in gene therapy, these firms are working towards a permanent one-time "cure" that could cost more than $1 million. If successful, the patient's genetic code will be reprogrammed inducing the body to produce proper clotting factors on its own. The firm that does it stands to take a commanding lead over the estimated $5 billion market for hemophilia A and B care.

Spark Therapeutics, a pioneer in gene therapy, was spun-off from the Children's Hospital Of Philadelphia and raised $161 million in an Initial Public Offering in early 2015. The growing firm says its retinal blindness treatment is on track to become the first gene therapy approved by the FDA in 2017.

Spark now hopes to tackle both types of hemophilia though it faces much competition.

While they share the same name, A and B are distinct diseases with different protein mutations.

Hemophilia A, which covers 88 percent of the market, is the harder of the two to treat because the protein is larger and harder to deliver.

The firm is collecting clinical data on hemophilia B with Pfizer, which has already paid Spark $35 million and promises another $245 million if benchmarks are met.

Those studies "give us early confidence in achieving our goal of developing a potential one-time, intravenous treatment that eliminates the need for regular infusions to control and prevent bleeding episodes," said Spark CEO Jeffrey Marrazzo.

Spark's shares have rallied more than 48 percent since the start of 2016. RBC Capital Markets analyst Michael Yee says investors remain enthusiastic about Spark's progress with retinal care and look forward to the company's entering the lucrative hemophilia market.

"Spark has a rich pipeline of therapies that could prove transformational," Yee said, reiterating his positive outlook for the company. RBC is providing Spark with investment banking services.

Since hemophilia represents such a large opportunity, other biotechs are gearing up to deploy therapies. BioMarin Pharmaceutical of Novato, CA. announced that its human trials of a hemophilia A therapy show treated some patients are making as much clotting factor 8 as normal humans.

"This really moved the bar," said Barrie J. Carter, BioMarin's Vice President of Vector Biology. "We've got them in the normal range where they can undergo usual activities and even are fine with cuts, trauma and everything like that."

uniQure also is in the running to produce gene therapies for both kinds of hemophilia. (Like Spark, its B program is further ahead than its A program.)

uniQure interim CEO Matt Kapusta envisioned a market that supported several gene therapies. Given differing immune responses, a therapy that works in one person might not be as effective in another.

Questions of cost persist. While none of the companies has released price information, gene therapy is expected to be costly. For comparison, uniQure's Glybera, the first approved gene therapy by European regulators, costs $1 million.

Hemophilia Federation of America CEO Kim Haugstad warned that such high costs could lead to "the emergence of a have-and-have-not society" among hemophiliacs.

For Krouse, who runs the Eastern Pennsylvania branch of the National Hemophilia Foundation, the answer is clear: "I don't think you can put a price tag on quality of life."

"Everyday I wear braces on both my ankles because I have arthritis due to bleeds I've had over the years," said Krouse, 49. "Any treatment that allows someone to live a normal life without having to infuse regularly is life changing both physically and mentally."

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