A Phase 2 interventional study of ACT-777991 and Placebo in Non-Segmental Vitiligo, sponsored by Idorsia Pharmaceuticals Ltd.. Recruiting at 5 sites in 2 countries. Open to participants aged 18 Years to 65 Years. Per ClinicalTrials.gov, last updated 2026-11-02.
Sponsored by Idorsia Pharmaceuticals Ltd. · Phase 2, Interventional, and Treatment
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:
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:
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.
343 studies on the registry are indexed under Vitiligo; 96 are open to participants now.
This study's planned enrollment of 30 is below the median of 36 across 265 interventional studies indexed under Vitiligo.
Browse Vitiligo studies →Idorsia Pharmaceuticals Ltd. is the lead sponsor of 103 studies on the registry; 4 are open to participants now.
Of its 29 completed or terminated interventional studies of FDA-regulated products, 9 (31%) have results posted.
Counted across the registry records on this site, refreshed daily.
The criteria were revised on the registry on Nov 2, 2026. See what changed
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Clinical diagnosis of either active or stable non segmental vitiligo for at least 3 months prior to Screening and meet all the following criteria:
Applicable only to EU: In addition to the above, participants must not have discontinued, reduced, or modified a vitiligo treatment/ procedure for the purpose of meeting trial eligibility criteria or a wash out requirement.
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
A condition in which the immune system attacks the body’s own tissues, such as rheumatoid arthritis, lupus, psoriasis, type 1 diabetes or inflammatory bowel disease.
Immunotherapy studies often leave out active autoimmune disease, and some name exceptions, such as thyroid disease on replacement hormone. Check the exceptions this study lists.
GFR (glomerular filtration rate) is how much blood the kidneys filter each minute. It is usually estimated from a blood test — eGFR, by formulas such as CKD-EPI or MDRD — and some studies ask for it to be measured directly instead. Usually given in mL/min/1.73 m².
Check the method, the units and the minimum the study states. A value of 90 or above is in the normal-or-high range, but kidney damage can show in other tests too.
Cancer (malignancy)
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Autoimmune disease
A condition in which the immune system attacks the body’s own tissues, such as rheumatoid arthritis, lupus, psoriasis, type 1 diabetes or inflammatory bowel disease.
Immunotherapy studies often leave out active autoimmune disease, and some name exceptions, such as thyroid disease on replacement hormone. Check the exceptions this study lists.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
GFR and eGFR (kidney filtering)
GFR (glomerular filtration rate) is how much blood the kidneys filter each minute. It is usually estimated from a blood test — eGFR, by formulas such as CKD-EPI or MDRD — and some studies ask for it to be measured directly instead. Usually given in mL/min/1.73 m².
Check the method, the units and the minimum the study states. A value of 90 or above is in the normal-or-high range, but kidney damage can show in other tests too.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Participants will receive ACT-777991 tablets orally for 24 weeks.
Drug: ACT-777991
Participants will receive placebo tablets orally for 24 weeks.
Drug: Placebo
ACT-777991 tablets
ACT-777991-matching placebo tablets
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.
Time frame: Baseline; Week 24
Supplementary primary outcome measure: Percentage change from baseline in F-VASI based on investigator assessment at Week 24
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: Baseline; Week 4; Week 8; Week 16; Week 24
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.
Time frame: 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.
Time frame: Baseline; Week 4; Week 8; Week 16; Week 24
Adverse events (AEs) leading to premature discontinuation of trial intervention
Time frame: 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).
Time frame: 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)
Time frame: 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
Time frame: 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
Time frame: 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.
Time frame: 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.
Time frame: 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
Time frame: 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
Time frame: 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
Time frame: 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
Time frame: 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
Time frame: From start of trial intervention up to 37 days after last dose of trial intervention (Follow-up visit)
Plan to share: No
No publications or documents are linked to this record.
Started Oct 2026 (actual). Primary completion is estimated for Jun 2027, 8 months after the start.
Of 44 phase 2 interventional studies under Vitiligo, half reached primary completion within 19 months of starting (the median), counting those still running; a quarter within 16 and three quarters within 26. This study's planned 8 months is below that.
Start moved once since we started tracking on Sep 25, 2026: Jun 2026 → Oct 2026, on Nov 2, 2026.
Earlier changes are on the record history on ClinicalTrials.gov ↗
How these figures are worked out, and which studies are left out of them.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
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