New and emerging biologic therapies for moderate-to-severe plaque psoriasis: mechanistic rationales and recent clinical data for IL-17 and IL-23 inhibitors

The development of effective and well-tolerated biologic therapies has advanced the management of psoriasis by enabling clinicians to treat underlying disease mechanisms. Biologics approved for the treatment of moderate-to-severe psoriasis include three tumor necrosis factor alpha inhibitors and an interleukin-12/interleukin-23 inhibitor. The establishment of the immunological basis of psoriasis has led to the development of biologic agents targeting specific downstream mediators in the psoriatic cascade. These drugs inhibit cytokines and cytokine signaling/transcription mediators like interleukin-17, which plays an important role in immunopathogenesis. Several interleukin-17 inhibitors are undergoing phase 3 clinical studies. In addition, biologics that selectively inhibit interleukin-23 have been assessed in phase 2 studies. This review describes how the dissection of pathways in the immunopathogenesis of psoriasis has led to the development of therapeutic agents and highlights the latest clinical efficacy, safety and tolerability data on new and emerging biologic therapies that selectively target interleukin-17 or interleukin-23.