Moderate-to-Severe Plaque Psoriasis
Psoriasis is a chronic, complex, immune-mediated disease that requires long-term treatment. It is commonly considered the most prevalent autoimmune disease in the world with a diagnosed U.S. prevalence of approximately 9 million people. In 2013, U.S. sales of biologic therapies for moderate-to-severe plaque psoriasis accounted for approximately $3.7 billion, of which more than $2.8 billion were from biologic tumor necrosis factor (TNF) inhibitors alone.
Approximately 80% of psoriasis patients have plaque psoriasis. These patients typically have symmetrically distributed plaques of thickened, inflamed, red skin covered with silvery scales located on portions of the body including the elbows, knees, scalp or back. Approximately 20% of plaque psoriasis patients have moderate-to-severe disease.
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The symptoms of psoriasis are not limited to the skin, and evidence increasingly suggests that skin symptoms of psoriasis are a dermal manifestation of a systemic autoimmune disorder. Psoriasis often presents with one or more comorbidities associated with inflammatory etiology, such as joint disease or cardiovascular disease. Psoriatic arthritis, which is psoriasis with concomitant joint disease, develops in up to 40% of psoriasis patients, according to the International Federation of Psoriasis Associations. As a result, there is increasing interest in treating psoriasis with products that can address both the skin and other potential systemic manifestations of the autoimmune disorder.
Psoriasis treatments are chosen based on factors including disease severity, comorbidities, patient preference and insurance coverage. Topical treatments, such as steroids, vitamin D derivatives and retinoids, are typically insufficient for patients with moderate-to-severe disease. For decades, moderate-to-severe plaque psoriasis has been treated with light-based or systemic therapies, which are moderately effective and have significant limitations.
The treatment of moderate-to-severe plaque psoriasis has been transformed by the introduction of biologic TNF inhibitors over the past decade. Since their launch into the rheumatology market in the late 1990s, TNF inhibitors have grown to become one of the largest-selling product classes in the pharmaceutical industry with U.S. sales for the treatment of psoriasis of over $2.8 billion in 2013. The TNF inhibitor class has been established as the most frequently used biologic therapy for moderate-to-severe plaque psoriasis. The two self-administered TNF inhibitors approved for psoriasis are Enbrel and Humira. In addition to the TNF inhibitors, Stelara, a biologic product that inhibits two other important inflammatory molecules called interleukin 12 and interleukin 23, was launched for psoriasis in 2009.
While these approved biologics have become useful therapeutic options for dermatologists and their psoriasis patients, they suffer from limitations, including the fact that some patients fail to respond, experience reduced response over time or experience side effects. Accordingly, patients treated with TNF inhibitors and other biologics may rotate between different products, including multiple TNF inhibitors. It is estimated that roughly half of moderate-to-severe plaque psoriasis patients remain unsatisfied with their treatment options.