Emerging Therapies for Palmoplantar Pustulosis with a Focus on IL-23 Inhibitors.

Palmoplantar pustulosis (PPP) is a chronic inflammatory skin disease characterized by recurrent pustules, erythema, and scaling on the palms and soles, leading to a significantly reduced quality of life. Although PPP shares some immunopathological features with psoriasis vulgaris, it is distinguished by unique genetic predispositions, including a higher prevalence in East Asian populations, and a complex immune profile, particularly dysregulation of the IL-23/Th17 axis and IL-36 cytokines. Recent advances in psoriasis treatment have highlighted IL-23 inhibitors, which target the p19 subunit to suppress Th17 activation and inflammatory cytokines. Clinical trials show that IL-23 inhibitors significantly improve disease severity and patient-reported outcomes in PPP while maintaining favorable safety profiles. Notably, guselkumab and risankizumab have recently been approved for PPP treatment in Japan and Korea. In contrast, IL-17 inhibitors and IL-36 blockers have yielded mixed results. A recent phase 3 trial in Japan demonstrated the significant efficacy of apremilast in treating PPP, with a favorable safety profile, suggesting that apremilast may be a promising treatment option for PPP. Due to PPP's lower prevalence compared with psoriasis vulgaris, clinical trials remain limited. Further large-scale, controlled studies are needed to clarify the efficacy and long-term safety of these therapies in diverse populations. This review summarizes emerging evidence on IL-23 inhibitors and other treatments for PPP, detailing their mechanisms of action, clinical efficacy, safety profiles, current challenges, and future perspectives in optimizing therapy.