Clinical Review

New Systemic Therapies for Psoriasis

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Over the last decade, expanded understanding of psoriasis pathogenesis has led to the development of new systemic agents such as biological drugs that have revolutionized the treatment of psoriasis. Small molecule inhibitors also have been studied and offer patients options for oral administration. This article reviews recently approved and in-the-pipeline biologics (IL-17 inhibitors and IL-23 blockers) as well as small molecule inhibitors (phosphodiesterase 4 [PDE4] and Janus kinase [Jak] inhibitors).

Practice Points

  • ­Secukinumab is an anti–IL-17 antibody approved for the treatment of psoriasis. It is indicated for the treatment of moderate to severe plaque psoriasis in adult patients who are candidates for systemic therapy or phototherapy.
  • ­The new biological agents have shown promising results with some patients achieving psoriasis area and severity index scores of 90 and 100.
  • ­A number of small molecule inhibitors also are in the pipeline, with apremilast the first one to have reached approval for psoriasis.


 

References

Psoriasis is a common chronic inflammatory skin disease affecting 1% to 8% of the world population, depending on the country.1 Psoriasis can greatly impact quality of life in affected individuals, even in those with limited body surface involvement.2 Studies have demonstrated a high degree of psychological distress associated with psoriasis, leading to depression and poor self-esteem.3

Over the last decade, our improved understanding of the autoimmune inflammatory pathways and the associated changing concepts in psoriasis pathogenesis have led to the development of biological drugs targeting specific components of effector immune mechanisms, and these biological drugs have revolutionized the treatment of psoriasis.4 Although response rates of these biological agents are greater compared to those of conventional systemic drugs,5 current biological drugs fail to demonstrate efficacy in some patients or lose their efficacy over time. In addition to the high costs associated with these drugs, these limitations have driven a continued search for alternative therapies.

Helper T cells (TH17) and the proinflammatory cytokine IL-17 have been shown to play a key role in the pathophysiology of psoriasis, bridging innate and adaptive immune responses. IL-17 is involved in the modulation of proinflammatory cytokines, hematopoietic growth factors, antimicrobial peptides, and chemokines. Increased TH17 activity and high levels of IL-17 have been found in psoriatic plaques, and increased levels of TH17 are found in the plasma of psoriasis patients.6 Increased IL-17 induces neutrophilia, inflammation, and angiogenesis.7 Other cytokines that are highly upregulated in involved skin are tumor necrosis factor a (TNF-α), IL-23, IL-22, and IL-21.8 IL-23 is involved in regulating TH17 cells and is a potent activator of keratinocyte proliferation.9 Blockade of IL-12/23 causes downregulation of TH17 and TH22 cell responses.10 As IL-17 has a key role in protecting skin and mucous membranes from bacterial and fungal infections, IL-17 inhibition can potentially interfere with the inflammatory cascade. However, available data suggest that sufficient residual IL-17 activity remains to maintain immunity against infections.11

Currently approved biological agents for psoriasis target proinflammatory cytokines such as TNF-α, or the p40 subunit of IL-12 and IL-23. A number of novel targeted therapies including biologics as well as small molecule inhibitors targeting various cytokines and molecules involved in the pathogenesis of psoriasis are currently in different stages of development (Table). These drugs include 3 IL-17 inhibitors (secukinumab, ixekizumab, and brodalumab); 2 IL-23 blockers (tildrakizumab and guselkumab); and small molecule inhibitors that target the kinase pathway including apremilast (a phosphodiesterase 4 [PDE4] inhibitor), as well as tofacitinib, baricitinib, and ruxolitinib (Janus kinase [Jak] inhibitors). Small molecule inhibitors can be administered orally and are less expensive to produce than biological agents. This article reviews available data on these new systemic agents in the pipeline.

Novel Biologics

Secukinumab

Secukinumab is a fully human monoclonal IgG1k antibody that selectively binds and neutralizes IL-17A.12 It is the first of the IL-17 antibodies to receive approval for the treatment of moderate to severe psoriasis. In 2 phase 3, double-blind, 52-week trials—ERASURE (Efficacy of Response and Safety of Two Fixed Secukinumab Regimens in Psoriasis) and FIXTURE (Full Year Investigative Examination of Secukinumab vs Etanercept Using Two Dosing Regimens to Determine Efficacy in Psoriasis)—participants were randomly assigned to receive subcutaneous secukinumab at doses of 300 mg (n=245 and n=327, respectively) or 150 mg (n=245 and n=327, respectively) once weekly for 5 weeks then every 4 weeks, or placebo (n=248 and n=326, respectively); in the FIXTURE study only, an etanercept group (n=326) was given a 50-mg dose twice weekly for 12 weeks then once weekly.13

In the ERASURE study, the proportion of participants showing a reduction of 75% or more in psoriasis area and severity index (PASI) score from baseline to week 12 was 81.6% with secukinumab 300 mg, 71.6% with secukinumab 150 mg, and 4.5% with placebo.13 Secondary end point results demonstrated the proportion of participants showing a 90% reduction in PASI score was 59.2% with secukinumab 300 mg and 39.1% with secukinumab 150 mg, which were both superior to placebo (1.2%). The proportion of participants who met the criteria for 100% reduction in PASI score at week 12 also was greater with each secukinumab dose than with placebo.13

In the FIXTURE study, the proportion of participants showing a reduction of 75% or more from baseline in PASI score at week 12 was 77.1% with secukinumab 300 mg, 67.0% with secukinumab 150 mg, 44.0% with etanercept, and 4.9% with placebo.13 Secondary end point results demonstrated the proportion of participants showing a 90% reduction in PASI score was 54.2% with secukinumab 300 mg, 41.9% with secukinumab 150 mg, 20.7% with etanercept, and 1.5% with placebo. The speed of response, which was assessed as the median time to a 50% reduction in mean PASI score from baseline, was significantly shorter with both doses of secukinumab (3.0 weeks and 3.9 weeks, respectively) than with etanercept (7.0 weeks)(P<.001 for both).13

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