The severity of hemophilia is measured by how much clotting factor is in the blood. People with severe hemophilia have less than 1 percent of normal. When Addie started the trial, his level was about 0.4 percent, he said.
A month later, his level was up to 10 or 12 percent. A few weeks after that, it had shot up to 50 percent of normal. At its peak, Addie said, his clotting factor level reached 147 percent, before he took a fall and his elbow swelled up.
“It dropped down to 106,” Addie recalled. “The doctor said, ‘Well, that’s because your body is using that factor that’s there.’”
Addie said he took some of his factor replacement after the fall, because his elbow “was so swelled up that it looked like a grapefruit.”
Two weeks later, he fell again.
“But I didn’t take any factor,” he said. “It didn’t swell up as bad or anything. I’m back to whatever my normal is.”
His factor levels, as of two weeks ago, were back up to 127 percent.
Addie’s not the only patient in BioMarin’s clinical trials that have seen a benefit. In an update in May, the company said those taking a high dose had an average factor level of 59 percent two years after their infusion. Those on a lower dose had an average level of 32 percent one year later.
The treatment Addie is helping test is the most advanced in a race that also includes Spark Therapeutics, UniQure, Sangamo and Pfizer. If successful, BioMarin’s treatment could reach the market as soon as 2020, according to Cowen analyst Phil Nadeau.
The companies are not all competing directly: some are focused on hemophilia A, the most common form of the disease, some on hemophilia B, and some on both.
For the winner, the spoils are potentially enormous: Nadeau estimates the total potential revenue for treating all the existing hemophilia patients in the U.S. is $20 billion.
That’s assuming, as most do, an eye-popping price tag: about $1 million per patient.
“Gene therapy’s a one-time treatment; all of the cost of the therapy has to be paid upon that treatment,” Nadeau said. “It’s a different paradigm than what is typically seen in the pharmaceutical industry today, where the patient gets drugs over many days, weeks or years, and so the cost of the therapy is paid out over time.”
Still, $1 million sounds like a lot — until one compares it with the cost of annual treatment for hemophilia with factor replacement therapy.
“These patients can be very expensive,” said McGuinn. “The cost of treating a hemophilia patient can be somewhere like $100,000 all the way up to probably $1 million or $1.5 million for a patient who’s much more complicated.”
That’s per year.
Addie sees it as a bargain. And while it’s not clear yet how long the treatments will last — the goal is patients’ lifetimes, but clinical trials currently have tracked patients for just a few years — he says even a few months without having to take his factor replacement felt like a major benefit.