Focus 1-5 (FS 1-5) : New oral agents: PDE inhibitors and tyrosine kinase inhibitors (TKI) = Focus 1-5 (FS 1-5) : New oral agents: PDE inhibitors and tyrosine kinase inhibitors (TKI)

다국어 초록 (Multilingual Abstract)

A number of novel systemic agents have been developed over the past decade for the treatment of moderate-to-severe psoriasis, including T-cell inhibitors, tumor necrosis factor (TNF)-α inhibitors and interleukin (IL)-12/23 inhibitors. However, these therapies may be limited by some drawbacks such as high cost and administration route; biologics must be delivered either intravenously or subcutaneously. Thus, there is a significant need for more cost-effective drugs that can be orally administered that influence proinflammatory cytokines. The phosphodiesterase 4 inhibitor apremilast is a small molecular inhibitor that acts by increasing cyclic adenosine monophosphate levels, ultimately decreasing production of proinflammatory mediators, such as TNF-α, IL-23, and interferon-γ, and increasing production of anti-inflammatory mediators, such as IL-10. Additionally, apremilast reduced both infiltration of myeloid dendritic cells into the dermis and epidermis and inducible macrophage-type nitric oxide synthase mRNA expression. In a 16-week phase 2b trial, PASI-75 was achieved in five patients (6%) assigned placebo, ten (11%) assigned apremilast 10 mg bid, 25 (29%) assigned 20 mg bid, and 36 (41%) assigned 30 mg bid. Most adverse events (96%) were mild or moderate; at least 5% of patients had nausea, upper respiratory tract infection, diarrhea, nasopharyngitis, headache, arthralgia (placebo), gastroenteritis, or dyspepsia. Also, tofacitinib, an oral Janus kinase (JAK) inhibitor, has proven to be efficacious in moderate to severe psoriasis. The Janus family of kinases is a subset of the protein tyrosine kinases. The JAK family consists of four members: JAK1, JAK2, JAK3, and TYK2. The various combinations of JAK pairs recruit different STAT proteins, of which there are up to six types, and this allows for the wide range of down-stream activities seen in the JAK-STAT pathways. Tofacitinib preferentially inhibits signaling by heterodimeric receptors associated with JAK3 and/or JAK1 with functional selectivity over receptors that signal via JAK2. Inhibition of JAK1 and JAK3 blocks signaling through the common γchain-containing receptor for cytokines including IL-2, -4, -7, -9, -15 and -21 which are crucial to lymphocyte function. Also, in murine models, tofacitinib suppressed the expression of IL-23 receptors, IL-17A, IL-17F, and IL-22 when T cells were stimulated with proinflammatory cytokines such as IL-6 and IL-23. Inhibition of IL-23 receptor expression results in suppression of Th17 cell differentiation,which is a key driving factor in the pathogenesis of psoriasis. Tofacitinib’s inhibition of IL-15 may play an important role in treating psoriasis as IL-15 is highly expressed with enhanced binding activity in psoriatic lesions and associated with increased resistance to keratinocyte apoptosis. Additionally, the suppression of STAT3 phosphorylation reduces IFN-γ expression, which is one of the most potent activation of keratinocyte proinflammatory function. In a 12-week phase 2b trials, PASI 75 response rate were significantly higher for all tofacitinib groups: 25% (2mg bid), 40.8% (5mg bid), and 66.7% (15mg bid) in 197 moderate-to-severe psoriasis patients. The most frequently adverse events were upper respiratory infection, nasopharyngitis and headache.