Psoriatic Arthritis: A Growth Industry
By Jennifer Huget
Special to The Washington Post
Tuesday, February 19, 2002; Page HE01
On Jan. 16 the National Psoriasis Foundation announced results of a survey that showed that psoriatic arthritis -- a chronic, progressive, inflammatory form of arthritis associated with the skin disease psoriasis -- is more than three times as common as previously believed. According to the survey, the painful, unsightly and sometimes debilitating disease affects as many as 1 million Americans.
That doesn't help the afflicted, but it's big news for Immunex Corp., a Seattle biotech company that helped fund the survey and announced, on the same day the survey was released, that its drug Enbrel had become the first drug to receive U.S. Food and Drug Administration (FDA) approval for treating psoriatic arthritis. Enbrel, already approved for and often used to treat rheumatoid arthritis, is expected by its maker to reach $1 billion in sales this year. It costs about $12,000 per year to treat a typical user.
The survey (which another biotech firm with a stake in the psoriasis market helped to fund) was done not by epidemiologists but by market research firms. According to the National Psoriasis Foundation, the researchers randomly selected 27,000 Americans and interviewed them by phone. One-half of 1 percent of the survey group self-reported having been diagnosed with psoriatic arthritis; the firm applied this figure to the U.S adult population to come up with the estimate of 1 million adults having the condition. Previous estimates -- which for years stood at 300,000 and were raised to 500,000 by medical consultants just prior to the survey -- were based largely on percentage estimates of the psoriasis population.
Psoriatic arthritis primarily affects people aged 30 to 50, but people much older and much younger (including children) can suffer from it, too. With symptoms that can include joint pain, swelling (particularly in the hands) and thickened and pitted fingernails, the disease is often misdiagnosed or undiagnosed. Because its symptoms are similar to those of rheumatoid arthritis, it is frequently mistaken for that disease. In other instances, its symptoms may seem so minor that patients don't even mention them to their physicians, who, in turn, might overlook them.
The situation is complicated by the fact that psoriasis patients generally are treated by dermatologists, who aren't necessarily focused on recognizing arthritic symptoms. According to the National Psoriasis Foundation, about 4.4 million American adults suffer from psoriasis, a serious skin condition resulting from an overgrowth of skin cells.
The foundation's survey bore out the notion that psoriasis and psoriatic arthritis are closely linked: About 85 percent of those with psoriatic arthritis also reported having psoriasis. Yet about a third of those with psoriasis said they had joint stiffness but had not been diagnosed with psoriatic arthritis. That finding, the foundation notes, suggests that a substantial number of people have psoriatic arthritis and don't even know it. In fact, according to Kenneth Gordon, a dermatologist at the Northwestern University Medical School in Chicago, some people with psoriatic arthritis don't even show any signs of psoriasis.
Gordon and his colleague Eric Ruderman, director of rheumatology at Northwestern, are about to open what is believed to be the first clinic for the treatment of psoriatic arthritis. Their patients will be able to consult simultaneously with the skin doctor and the arthritis expert and to coordinate treatment. (Ruderman and Gordon have served as consultants for Immunex.)
In the absence of any drug specifically approved for treating psoriatic arthritis, doctors have for several years made off-label prescriptions for Immunex's Enbrel, which had already been approved to treat rheumatoid arthritis. But since many insurers won't cover off-label uses of a drug -- particularly one that costs $1,000 a month -- its use for the condition has been limited. Doctors also draw on other drugs usually applied to rheumatoid arthritis: aspirin and ibuprofen to ease some symptoms; systemic, disease-modifying agents such as methotrexate that relieve symptoms and may slow disease progression and minimize joint damage; and the immunosuppressant cyclosporine.
Enbrel, a "tumor necrosis factor-alpha" (TNF-alpha) receptor, is expected to trump these treatments by interrupting the essential mechanics of the disease.
But it will not be immediately available to all comers. Because demand outstrips supply (new manufacturing sites are in the works), prospective patients must apply to be added to the Enbrel waiting list. Once they get the drug, they need to be on the lookout for some serious side effects, including heightened susceptibility to infection and, apparently, the potential onset or exacerbation of multiple sclerosis. (Enbrel carries a prominent label warning.)
If things seem a little cozy between Immunex and the National Psoriasis Foundation, they are, but perhaps no cozier than other drug makers and the nonprofits they give financial support to. Foundation spokesperson Molly Marshall says her organization purposely timed the release of its survey to coincide with the FDA's approval of Enbrel, hoping the coincidence would spark media interest. "Past experience has shown the press doesn't want to talk about psoriasis," Marshall said. (Those of a certain age will remember widely mocked television commercials lamenting "the heartbreak of psoriasis.")
Marshall suggests the survey's numbers may be imperfect, in that they depended on people's accurately reporting their own symptoms and diagnoses. "The only way to know the true incidence or prevalence is to bring people in to see the doctor and diagnose them," she said, adding that chances for funding are remote.
For its part, Immunex says the new numbers, despite the fact that it helped pay for them, won't much affect its marketing plan: Spokesperson Robin Shapiro says, "We always knew the market was several hundreds of thousands of people, so in terms of market projection, there was no substantial change."
In the meantime, watch this space: The Psoriasis Foundation data released in January represent part of a larger survey conducted in December 2001. The other part, dealing with psoriasis itself, is to be released in April. The Boston biotech firm Biogen Inc. anticipates FDA approval for its psoriasis drug, Amevive, by the end of the year. And, yes, Biogen was the survey's other major funder.
Jennifer Huget is a frequent contributor to the Health section.
© 2002 The Washington Post Company