Emerging systemic drugs in the treatment of plaque psoriasis.

INTRODUCTION: Psoriasis is a common, chronic inflammatory skin condition that affects 2-3% of the US population and represents a large psychosocial burden for patients. Over the last decade, highly effective targeted therapies for psoriasis have been developed - namely, those targeting interleukin (IL)-17 and IL-23. The success of biologic agents targeting IL-17 and IL-23 underscores the importance of the IL-23/T helper (Th)17 cell axis in psoriasis pathogenesis. Oral small molecule drugs - such as Janus kinase (JAK) inhibitors, tyrosine kinase 2 (TYK2) inhibitors, and fumaric acid esters (FAEs) - are also being investigated for the treatment of psoriasis. AREAS COVERED: This article reviews systemic biologic and oral small molecule drugs currently undergoing clinical trials for the treatment of plaque psoriasis. EXPERT OPINION: Many patients with psoriasis have mild disease, and many with mild disease do not seek medical care for their condition. Many patients with mild disease could be adequately treated with topical treatments and phototherapy; however, adherence and feasibility have often been an issue with these treatment types. There seems to be limited room for development of novel biologics, as the existing ones are extraordinarily safe, effective, and convenient with few injections. Patients would prefer a safe, effective oral treatment; however, JAK inhibitors seem unlikely to fill this role completely.