Atopic Dermatitis

Atopic dermatitis (AD) is one of the most common chronic inflammatory skin diseases in developed countries, affecting approximately 20% of children and 3% of adults. Globally, the estimated number of AD patients exceeds 200 million, including about 32 million in the United States, 30~40 million in Europe, and an estimated 1.5~2 million in Taiwan. Its prevalence continues to rise, posing a significant burden on public health and healthcare systems worldwide. Although most AD patients develop the disease in childhood, it often persists into adulthood and is characterized by recurrent flares and remissions.

Clinical manifestations include dry skin, chronic itching, erythematous rashes, edema, recurrent infections, and skin thickening with cracking (lichenification) due to prolonged scratching. These symptoms not only affect appearance but also significantly reduce quality of life, particularly impacting mental health and sleep. In children, AD can affect learning and social interactions, while caregivers face increased familial and psychological burdens.

Current treatments mainly rely on topical corticosteroids, immunosuppressants, and immunomodulators to reduce skin inflammation. However, these therapies often have long-term side effects or insufficient efficacy. Novel targeted therapies, such as JAK inhibitors, act on multiple pathogenic pathways and are considered highly promising treatment strategies, highlighting that atopic dermatitis continues to present substantial unmet medical needs in clinical practice.

Alopecia Areata

Alopecia Areata is an autoimmune disease caused by the immune system abnormally attacking hair follicles, resulting in non-scarring hair loss. It affects approximately 2% of the general population worldwide over their lifetime. In the United States, the prevalence is approximately 0.1–0.2%, affecting an estimated 300,000 to 600,000 individuals.

The clinical presentation of AA varies significantly in severity. It most commonly manifests as patchy alopecia, presenting as smooth, round, or oval bald patches on the scalp or beard area. However, the disease can progress to more severe forms, such as Alopecia Totalis (complete loss of scalp hair) or Alopecia Universalis (complete loss of hair on the scalp and body). While AA is not life-threatening, the unpredictable nature of hair loss and the visible alteration of appearance often lead to profound psychological distress, anxiety, and depression, severely impacting the patient's quality of life.

The pathogenesis of AA is driven by an autoimmune attack on the hair follicle, resulting in the collapse of the follicle's "immune privilege." Research has identified that this process is dependent on the JAK–STAT signaling pathway, specifically involving cytokines such as IFN-γ that recruit CD8+ T cells to attack the hair follicle.

Current standard-of-care treatments include intralesional corticosteroids and, more recently, oral JAK inhibitors. While oral JAK inhibitors have shown efficacy, the long-term use of oral JAK inhibitors carries potential safety concerns, requiring continuous monitoring for risks such as infections, cardiovascular events, and other systemic side effects. Currently, no new topical formulations have been approved for Alopecia Areata. Consequently, there remains a significant unmet clinical and market demand for a topical formulation that offers a safe and effective option for long-term use.

AC-1101 as a topical formulation, aims to address this unmet need by delivering high concentrations of the JAK inhibitor directly to the hair follicle site. This targeted approach is designed to effectively block the inflammatory signaling loops responsible for hair loss while minimizing systemic exposure and safety concerns.