A Study to Learn How Safe ACT-777991 is and How Well it Works in Adults With Non-segmental Vitiligo

A Phase 2a, Proof of Concept, Multicenter, Double Blind, Randomized, Placebo Controlled, Parallel Group Trial to Assess the Efficacy and Safety of ACT-777991 in Adults With Non-segmental Vitiligo

The purpose of this clinical trial is to learn how well ACT-777991 works, how safe it is and how well it is tolerated by adults with non-segmental vitiligo.

The main question this clinical trial aims to answer is:

• Can ACT-777991 help return color to the skin of the face of adults with non-segmental vitiligo?

Researchers will compare ACT-777991 to placebo (a look-alike inactive treatment that contains no medicine) to see if ACT-777991 works to treat non-segmental vitiligo.

Trial participants will:

• Take the trial intervention (either ACT-777991 or placebo) daily for 24 weeks.
• Visit the clinic 7 times for check-up and tests.

Study Overview

• Status: Not yet recruiting
• Conditions: Non-Segmental Vitiligo
• Intervention / Treatment: Drug: ACT-777991; Drug: Placebo

Detailed Description

The trial includes three trial periods:

Following a Screening period, during which it will be checked if participants are eligible to take part, eligible participants will be randomized in a 2:1 ratio to receive either ACT-777991 or placebo for 24 weeks (Trial intervention period). On completion of treatment, participants will be followed for 30 (+7) days (Follow-up period).

Trial participation will end with a Follow-up visit (Participant Last Visit) at the end of the Follow-up period.

The maximum trial duration for an individual participant is approximately 33 weeks including a screening period of up to 28 days, a treatment period of 24 weeks, and a follow-up period of up to 37 days.

• Study Type: Interventional
• Enrollment (Estimated): 30
• Phase: Phase 2

Contacts and Locations

• Study Contact: Name: Clinical Trial Information USA; Phone Number: +1 856 661 37 21; Email: idorsiaclinicaltrials@idorsia.com
• Study Contact Backup: Name: Clinical Trial Information Europe; Phone Number: +41 58 844 1977; Email: idorsiaclinicaltrials@idorsia.com

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Clinical diagnosis of either active or stable non segmental vitiligo for at least 3 months prior to Screening and meet all the following criteria:

  • F-VASI score ≥ 0.3 based on BICR at Screening.
  • T-VASI score ≥ 5 based on investigator assessment at Screening and Randomization.
  • Total body surface area (BSA) involvement, including the face, ≤ 50% based on investigator assessment at Screening and Randomization.
• Participants must agree not to use therapeutic agents and procedures to treat vitiligo from Screening until Participant Last Visit.

Exclusion Criteria:

• Clinical diagnosis of other forms of vitiligo (e.g., segmental) or other hypo- or depigmentation disorders (e.g., piebaldism, leukoderma, Vogt-Koyanagi-Harada disease, malignancy-induced hypopigmentation).
• Any autoimmune disease, except adequately treated thyroid disease.
• History of systemic immunotherapy treatment, including JAK inhibitors, for any inflammatory disease in the 12 months prior to Randomization.
• History of topical JAK inhibitors for any inflammatory disease in the 6 weeks prior to Screening.
• Use of laser or light-based treatment (phototherapy), including tanning beds, in the 8 weeks prior to Screening.
• eGFR < 90 mL/min/1.73 m2, defined by the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) creatinine equation, at Screening.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Triple

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: ACT-777991; Participants will receive ACT-777991 tablets orally for 24 weeks.	Drug: ACT-777991; ACT-777991 tablets
Placebo Comparator: Placebo; Participants will receive placebo tablets orally for 24 weeks.	Drug: Placebo; ACT-777991-matching placebo tablets

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Main primary outcome measure: Percentage change from baseline in Facial Vitiligo Area Scoring Index (F-VASI) based on Blinded Independent Central Reading (BICR) at Week 24	The vitiligo area scoring index (VASI) is a validated clinician-reported outcome measure that scores both the extent (surface area) and degree (level of depigmentation) of vitiligo lesions over time. The F-VASI describes involvement of the face, with higher scores indicating more severe disease. Negative changes from baseline indicate improvement.	Baseline; Week 24
Supplementary primary outcome measure: Percentage change from baseline in F-VASI based on investigator assessment at Week 24		Baseline; Week 24
Supplementary primary outcome measure: Percentage change from baseline in F-VASI at Week 4, 8 and 16	F-VASI will be assessed by the investigator and by BICR.	Baseline; Week 4, Week 8; Week 16
Supplementary primary outcome measure: Achievement of F-VASI50 at Week 4, 8, 16 and 24	Proportion of patients achieving at least a 50% improvement from baseline in F-VASI.	Baseline; Week 4; Week 8; Week 16; Week 24
Supplementary primary outcome measure: Achievement of F-VASI75 at Week 4, 8, 16 and 24	Proportion of patients achieving at least a 75% improvement from baseline in F-VASI.	Baseline; Week 4; Week 8; Week 16; Week 24
Supplementary primary outcome measure: Achievement of F-VASI90 at Week 4, 8, 16 and 24	Proportion of patients achieving at least a 90% improvement from baseline in F-VASI.	Baseline; Week 4; Week 8; Week 16; Week 24

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Percentage change from baseline in Total Body Vitiligo Area Scoring Index (T-VASI) at Week 4, 8, 16 and 24	The T-VASI is calculated using a formula that includes contributions from all body regions, with higher scores indicating more severe disease. The F-VASI is used as the score for the 'face' component , i.e., the face is not be scored again. Negative changes from baseline indicate improvement. T-VASI will be assessed by the investigator.	Baseline; Week 24
Achievement of T-VASI50 at Week 4, 8, 16 and 24	Proportion of patients achieving at least a 50% improvement from baseline in T-VASI.	Baseline; Week 4; Week 8; Week 16; Week 24
Adverse events (AEs) leading to premature discontinuation of trial intervention		From start of trial intervention to last dose of trial intervention, assessed up to Week 24
Treatment-emergent AEs and serious AEs (SAEs)	Treatment-emergent events are AEs and SAEs reported for the first time or as worsening of a pre-existing event after first dose of trial intervention up to 37 days after last dose of trial intervention (Follow-up visit).	From start of trial intervention up to 37 days after last dose of trial intervention (Follow-up visit)
Treatment-emergent AEs of special interest (AESI)		From start of trial intervention up to 37 days after last dose of trial intervention (Follow-up visit)
Change from baseline in vital signs: systolic and diastolic blood pressure		Baseline to all pre-defined time points, up to 37 days after last dose of trial intervention (Follow-up visit)
Change from baseline in vital signs: pulse rate		Baseline to all pre-defined time points, up to 37 days after last dose of trial intervention (Follow-up visit)
Change from baseline in hematology variables	The concentration of hematology variables will be measured and the change from baseline summarized.	Baseline to all pre-defined time points, up to 37 days after last dose of trial intervention (Follow-up visit)
Change from baseline in blood chemistry variables	The concentration of blood chemistry variables will be measured and the change from baseline summarized.	Baseline to all pre-defined time points, up to 37 days after last dose of trial intervention (Follow-up visit)
Change from baseline in ECG parameters: PR interval, QRS duration, QTcF Value		Baseline to all pre-defined time points, up to 37 days after last dose of trial intervention (Follow-up visit)
Change from baseline in ECG parameters: Heart rate		Baseline to all pre-defined time points, up to 37 days after last dose of trial intervention (Follow-up visit)
Number of Participants with treatment-emergent marked abnormalities in vital signs: systolic and diastolic blood pressure, pulse rate		From start of trial intervention up to 37 days after last dose of trial intervention (Follow-up visit)
Number of Participants with treatment-emergent marked abnormalities in clinical laboratory variables: hematology and chemistry		From start of trial intervention up to 37 days after last dose of trial intervention (Follow-up visit)
Number of Participants with treatment-emergent marked abnormalities in ECG parameters: PR interval, QRS duration, QTcF Value, Heart rate		From start of trial intervention up to 37 days after last dose of trial intervention (Follow-up visit)

Collaborators and Investigators

• Sponsor: Idorsia Pharmaceuticals Ltd.
• Investigators: Study Director: Clinical Trials, Idorsia Pharmaceuticals Ltd.

Study record dates

Study Major Dates

• Study Start (Estimated): June 1, 2026
• Primary Completion (Estimated): June 1, 2027
• Study Completion (Estimated): July 1, 2027

Study Registration Dates

• First Submitted: May 11, 2026
• First Submitted That Met QC Criteria: June 24, 2026
• First Posted (Actual): June 25, 2026

Study Record Updates

• Last Update Posted (Actual): June 25, 2026
• Last Update Submitted That Met QC Criteria: June 24, 2026
• Last Verified: June 1, 2026

More Information

Terms related to this study

• Other Study ID Numbers: ID-089B201; 2025-524865-25-00 (Ctis)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: Yes
• Studies a U.S. FDA-regulated device product: No