Povorcitinib Shows Durable Efficacy in HS in Phase 3 STOP-HS Trials

Key Takeaways

• Povorcitinib met primary and secondary endpoints in Phase 3 STOP-HS trials, demonstrating durable efficacy through 54 weeks in moderate-to-severe HS.
• Responses were observed across clinical and patient-reported outcomes, including HiSCR, pain, fatigue, and quality of life.
• JAK1 inhibition is a promising new modality in HS, addressing disease heterogeneity and unmet treatment needs.

Late-breaking results from the Phase 3 STOP-HS1 and STOP-HS2 trials presented at the American Academy of Dermatology (AAD) 2026 Annual Meeting showed that povorcitinib, an oral JAK1-selective inhibitor, achieved sustained efficacy and a manageable safety profile through 54 weeks in patients with moderate-to-severe hidradenitis suppurativa (HS).

Primary author Martina L. Porter, MD, emphasized the importance of expanding therapeutic approaches.

“We have a different modality,” Dr. Porter told Practical Dermatology. “HS is such a heterogeneous disease that for some patients, IL-17 and TNF-alpha is not the main driver. JAK inhibition may address alternative inflammatory pathways.”

The STOP-HS1 and STOP-HS2 studies randomized 1,227 adults to once-daily povorcitinib 45 mg, 75 mg, or placebo for 12 weeks, followed by a 42-week extension. The primary endpoint, HiSCR50 at Week 12, was met for both doses in both trials.

Through Week 54, response rates remained robust, with 57.9%–66.3% achieving HiSCR50, 41.1%–54.3% achieving HiSCR75, and 20.0%–27.2% achieving HiSCR100. Inflammatory lesion clearance (ANdT=0) occurred in up to 19.8% of patients. Greater reductions in draining tunnel counts were observed with the 75 mg dose (up to −65%) compared with 45 mg (up to −51%). Improvements were also seen in patient-reported outcomes, including skin pain, fatigue, and quality of life.

Dr. Porter noted that efficacy aligned with expectations given prior data.

“It was really in line with what I expected,” she said, adding that variability in HS populations can influence response rates across trials.

She also highlighted durability of response, saying, “Those who achieve these very high levels of response really seem to maintain them years out down the road.” 

Responses were observed even among biologic-experienced patients.

“Patients who are already biologic experienced have essentially the same response, even though their disease is more severe at baseline,” Dr. Porter said, suggesting a potential role in difficult-to-treat populations. 

Safety findings through Week 54 were consistent with prior reports. Treatment-emergent adverse events occurred in approximately 80% of patients, with serious adverse events reported in 5.9%–6.5%. Rates of serious infections, herpes zoster, and malignancy were low. Dr. Porter described the safety profile as “quite reassuring,” particularly given concerns around JAK inhibition in comorbid HS populations. 

“This is a very exciting time for HS,” Dr. Porter said. “This is the first Phase 3 trial of a drug that has a very different mechanism of action.