For a study, it was determined that in hidradenitis suppurativa (HS), cytokine signaling mediated by Janus kinase (JAK) contributed to local and systemic inflammation. 2 multicenter phase 2 trials of the JAK1 inhibitor INCB054707 in patients with moderate-to-severe HS were used to summarise the safety and effectiveness results. For 8 weeks, patients were given either open-label 15 mg INCB054707 QD or randomized to 30, 60, or 90 mg INCB054707 QD or placebo (3:1 within each cohort. Patients had to be 18–75 years old, have moderate-to-severe HS (Hurley stage II/III disease), have lesions in at least or equal to 2 anatomic areas, and have a total abscess and inflammatory nodule count of at least or equal to 3. Safety and tolerability were the major endpoints in both investigations. HS Clinical Response (HiSCR) and other efficacy indicators were secondary objectives. In Study 1, 10 patients (15 mg INCB054707) were enrolled, and 35 in Study 2 (INCB054707: 30 mg, n=9; 60 mg, n=9; 90 mg, n=8; placebo: n=9). Overall, 70.0% of patients in Study 1 and 80.8% of patients receiving INCB054707 in Study 2 had more than or equal to 1 treatment-emergent adverse event (TEAE); 30·0% and 42·3% of patients, respectively, had more than or equal to 1 treatment-related TEAE. At Week 8, 3 patients (42∙9%) in Study 1 and 17 patients (overall 65∙4%: 30 mg, 55∙6%; 60 mg, 55∙6%; 90 mg, 87∙5%) receiving INCB054707 versus 4 patients (571%) receiving placebo in Study 2 achieved HiSCR. INCB054707 was well tolerated, and patients with moderate-to-severe HS showed positive results. The outcomes on the safety and efficacy of JAK1 inhibition in HS provide proof of concept.