Background

Hidradenitis Suppurativa (HS) is a chronic inflammatory disease of the hair follicles and sweat glands, characterized by painful nodules, abscesses, and draining tunnels in the deep layers of the skin. Patients experience not only severe pain but also significant difficulties in social life due to pus and odor. However, due to the unclear cause, existing treatment options are very limited. Commonly prescribed oral antibiotics carry a risk of resistance, and tumor necrosis factor-alpha (TNF-α) or interleukin-17 (IL-17) targeted injectables have limited ease of administration. Some patients do not respond to existing treatments or experience a decrease in efficacy over time. This necessitates the development of a convenient oral treatment that targets the underlying inflammatory pathways.

Key Findings

Povorcitinib, an oral Janus Kinase 1 (JAK1) selective inhibitor developed by Incyte, has demonstrated effective reduction of inflammation in patients with moderate to severe HS in a global phase 3 clinical trial. The research, published in the international journal 'Nature Medicine,' is based on the results of two identically designed phase 3 trials (STOP-HS1, STOP-HS2). In the trial, 1,227 adult patients were divided into a 45mg povorcitinib group, a 75mg group, and a placebo group, and treated for 12 weeks. In terms of the primary endpoint, 'Hidradenitis Suppurativa Clinical Response 50 (HiSCR50),' povorcitinib showed significant improvement compared to the placebo group. HiSCR50 refers to a state in which the number of abscesses and inflammatory nodules is reduced by more than 50% compared to the baseline, and no new abscesses or draining tunnels appear. In the STOP-HS1 trial, the HiSCR50 achievement rates in the 45mg and 75mg povorcitinib groups were 40.2% and 40.6%, respectively, which were higher than the placebo group (29.7%). In the STOP-HS2 trial, the 45mg and 75mg groups also recorded 42.3%, significantly higher than the placebo group (28.6%). Povorcitinib also has the characteristic of contributing to the reduction of draining tunnels. In particular, in the 54-week long-term extension study, the 75mg group showed a reduction in the number of draining tunnels by up to 65%, demonstrating a superior inhibitory effect compared to the 45mg group (up to 51% reduction). Skin pain was rapidly alleviated during treatment, and overall quality of life was also improved. No new safety concerns were observed beyond the adverse effects associated with existing JAK inhibitors, confirming excellent tolerability.

Significance and Prospects

These clinical results suggest that the treatment paradigm for chronic skin inflammation, which has been centered on injectables, can be shifted to oral administration. The mechanism of action, which blocks the JAK1 receptor, a signal transduction pathway inside cells, to regulate the activity of inflammatory cytokines, is a distinguishing feature from existing injectables. The fact that significant effects were also induced in patients with severe disease who had not responded to existing treatments supports this. However, the cardiovascular side effects and infection risks associated with JAK inhibitor drugs need to be addressed in future long-term observational studies. If these concerns can be resolved and regulatory approval is obtained, the convenience of treatment for patients is expected to be greatly improved.