In short
ACT-777991 is an investigational substance that blocks the CXCR3 receptor, a protein involved in immune responses. It is being studied in adults with non-segmental vitiligo, a condition where patches of skin lose their colour. One Phase 2 trial, authorised in the EU, is testing ACT-777991 against placebo in 30 participants, measuring how much facial repigmentation occurs after 24 weeks.
Key points
- ACT-777991 is a CXCR3 receptor antagonist, a type of molecule that blocks a specific immune system signal.
- It is being studied in non-segmental vitiligo, a condition causing patches of skin to lose pigment.
- The only registered trial is a Phase 2 study, authorised in the EU.
- The trial compares ACT-777991 with a placebo in 30 participants.
- The main goal is to measure change in facial vitiligo severity after 24 weeks.
- ACT-777991 is taken orally, although the exact dose was not reported in the registry.
What is ACT-777991?
ACT-777991 is an investigational substance, meaning it has not yet been approved as a medicine. It belongs to a class of compounds known as CXCR3 antagonists, which are small molecules designed to block a specific receptor on immune cells. The substance is also referred to by its development code ACT-777991. It is being developed for conditions where the immune system attacks the body's own tissues, including vitiligo.
How does ACT-777991 work?
ACT-777991 blocks the CXCR3 receptor. CXCR3 is a protein found on the surface of certain immune cells, and it normally responds to chemical signals called chemokines, such as CXCL9 and CXCL10. These signals can attract immune cells into tissues and contribute to inflammation. By blocking CXCR3, ACT-777991 aims to reduce this immune cell activity. In vitiligo, immune cells are thought to attack melanocytes, the cells that produce skin pigment. Blocking CXCR3 may help reduce this attack and allow pigment to return.
Which conditions is ACT-777991 studied for?
- Non-segmental vitiligo — a long-term condition where patches of skin lose their colour, often on both sides of the body in a symmetrical pattern. The registered Phase 2 trial is testing ACT-777991 in adults with this form of vitiligo.
How is ACT-777991 given?
ACT-777991 is given orally, meaning it is taken by mouth. The trial registry lists an oral formulation, but the exact dose was not reported in the record. The trial also includes a matching placebo for comparison.
What do the clinical trials show?
One clinical trial of ACT-777991 is registered in the EU Clinical Trials Information System. It is a Phase 2 study, authorised but not yet recruiting, and it plans to enrol 30 adults with non-segmental vitiligo. The trial compares ACT-777991 with a placebo.
The main measure of effect is the change in facial vitiligo severity, scored with a tool called the Facial Vitiligo Area Scoring Index (F-VASI). F-VASI measures both the surface area of affected skin and the degree of depigmentation on the face. Higher scores indicate more severe disease, and a negative change from the start of the study indicates improvement. The primary endpoint is the percentage change in F-VASI at week 24, assessed by independent reviewers who do not know which treatment each participant received.
The trial also looks at whether participants achieve at least 50%, 75%, or 90% improvement in facial vitiligo at weeks 4, 8, 16, and 24. These are called F-VASI50, F-VASI75, and F-VASI90.
What side effects are known?
No side effect data for ACT-777991 were available in the provided sources. As the trial is still in an early phase, safety information will come from the ongoing study.