- Design
- Randomised, double-blind, placebo-controlled phase 2 (Part A)
- Population
- Adults with cutaneous lupus erythematosus
- Primary outcome
- CLA-IGA-R erythema 0–1 at week 16
- Effect
- 14.7% vs 2.9% (P = .026); CLASI-70 at week 24 21.7% vs 5.8%
AMETHYST is a randomised, double-blind, placebo-controlled phase 2/3 programme of litifilimab, a monoclonal antibody against BDCA2 on plasmacytoid dendritic cells, in cutaneous lupus erythematosus. Part A randomised participants to litifilimab 225 mg or placebo every four weeks for 24 weeks.
At week 16, 14.7% on litifilimab versus 2.9% on placebo reached clear or almost-clear erythema on the investigator global assessment (P = .026). At week 24, CLASI-70 responses were 21.7% versus 5.8%. The drug was generally well tolerated.
Cutaneous lupus has no approved targeted therapy, and many patients cycle through antimalarials, methotrexate and others. Absolute response rates here are modest, and this is a phase 2 readout; the phase 3 results will decide whether it reaches clinic.
- Continue antimalarials, sun protection and smoking cessation as the foundation of cutaneous lupus care
- Check hydroxychloroquine dosing against body weight and arrange retinal screening
- Consider referral to a trial centre for refractory disease
- Litifilimab is not approved; it is not a treatment option outside trials
Why it matters
A targeted option for cutaneous lupus would fill a real gap if phase 3 confirms this.
Don't overread it
This is phase 2 evidence with modest absolute responses; it does not establish efficacy.
The statistics, in plain English
Fewer than one in six patients reached clear or almost-clear skin on the drug, against about one in thirty-five on placebo. The difference is statistically significant, but the absolute response rate is low and the secondary endpoints were not powered.
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