Litifilimab Improves Cutaneous Lupus Symptoms Through 52 Weeks

Investigational litifilimab demonstrated sustained improvements in skin manifestations of cutaneous lupus erythematosus (CLE) through 52 weeks, according to findings from the phase 2 portion of the AMETHYST study presented at ACR Convergence 2026 in Orlando, Florida.¹

The results, presented by Joseph Merola, MD, and colleagues, showed continued improvements in skin erythema and other morphological characteristics among patients receiving litifilimab, alongside favorable clinician- and patient-reported assessments of skin changes.

The findings provide additional evidence supporting the potential of litifilimab, a monoclonal antibody targeting blood dendritic cell antigen 2 (BDCA2), as an investigational treatment for patients with active CLE.

Addressing Unmet Needs in Cutaneous Lupus

CLE is a chronic autoimmune disease characterized by inflammatory skin lesions that can result in permanent scarring, dyspigmentation, alopecia, and disfigurement. Disease manifestations may substantially affect patients' quality of life, particularly when visible lesions persist despite treatment.

Litifilimab is designed to inhibit inflammatory pathways associated with CLE by binding to BDCA2, a receptor expressed on plasmacytoid dendritic cells. This mechanism suppresses the production of proinflammatory cytokines and chemokines, including type I interferons, which play an important role in lupus pathogenesis.

The AMETHYST study (NCT05531565) is a randomized, double-blind, placebo-controlled, operationally seamless phase 2/3 trial evaluating subcutaneous litifilimab in patients with active chronic and/or subacute CLE, with or without systemic manifestations.

Study Design and Patient Characteristics

The phase 2 portion of AMETHYST included 93 randomized and treated participants.

During the initial 24-week double-blind, placebo-controlled period, participants received either litifilimab or placebo every 4 weeks.

At week 24, participants originally assigned to placebo transitioned to active litifilimab treatment, while those receiving litifilimab continued therapy through week 52.

At baseline, all participants had moderate-to-severe erythema, defined as a Cutaneous Lupus Activity Investigators' Global Assessment Revised (CLA-IGA-R) erythema score of at least 3.

The mean baseline Cutaneous Lupus Erythematosus Disease Area and Severity Index–Activity (CLASI-A) score was 19.9, indicating substantial inflammatory disease activity.

The primary endpoint evaluated the proportion of participants achieving a CLA-IGA-R erythema score of 0 or 1, corresponding to clear or almost clear skin, at week 16.

Secondary endpoints included CLA-IGA-R erythema scores of 0 or 1 and scores of 0 for other morphological characteristics (OMC) at week 24.

Exploratory endpoints assessed changes in skin manifestations using the Clinician's Global Assessment of Skin (CGA-Skin) and Subject Global Assessment of Skin (SGA-Skin).

Continued Improvement Through Week 52

Among participants who received litifilimab throughout the study, the proportion achieving clear or almost clear erythema increased from 19.0% at week 24 to 27.2% at week 52.

Similarly, the proportion achieving a CLA-IGA-R OMC score of 0 increased from 14.2% to 20.8% during the same period.

Participants who transitioned from placebo to litifilimab at week 24 also experienced improvements.

In this crossover group, clear or almost clear erythema response rates increased from 4.2% at week 24 to 33.7% at week 52.

Responses were observed as early as 4 weeks after initiating active treatment.

The proportion achieving an OMC score of 0 increased from 0% at week 24 to 27.5% at week 52.

These findings suggest that improvements in inflammatory skin manifestations may continue with extended litifilimab treatment, including among patients who begin active therapy after an initial placebo-controlled period.

Clinician- and Patient-Reported Outcomes

Beyond investigator-assessed disease activity, the researchers evaluated whether improvements were reflected in broader assessments of skin appearance.

At week 24, 55.6% of litifilimab-treated participants were rated by clinicians as having moderately or substantially improved skin manifestations on the CGA-Skin assessment, compared with 28.0% of participants receiving placebo.

Among participants who transitioned from placebo to litifilimab, the proportion rated as moderately or substantially improved increased from 28.0% at week 24 to 72.7% at week 52.

Patient-reported assessments demonstrated a similar pattern.

In the placebo-to-litifilimab group, 29.6% of participants reported moderately or substantially improved skin manifestations at week 24, increasing to 75.0% by week 52.

Participants receiving continuous litifilimab also demonstrated continued improvements in clinician- and patient-reported assessments through the extended treatment period.

Together, these findings suggest that improvements in objective measures of CLE activity were accompanied by changes recognized by both clinicians and patients.

Clinical Implications and Future Research

The investigators reported that the study met its primary endpoint and that CLA-IGA-R response rates continued to improve through week 52 among litifilimab-treated participants.

The findings are particularly relevant for dermatologists managing patients with persistent CLE, where treatment goals extend beyond reducing inflammation to preventing irreversible skin damage and improving patients' perceptions of their disease.

However, the 52-week findings should be interpreted in the context of the study design. Because all participants received active litifilimab after week 24, the extended treatment period did not include a concurrent placebo comparison.

Additionally, the clinician- and patient-reported outcomes were exploratory, and the abstract did not provide detailed adverse event findings from the 52-week analysis.

Larger confirmatory studies and comprehensive safety assessments will be important in determining the treatment's long-term benefit-risk profile.

Nevertheless, the findings contribute to growing evidence supporting BDCA2 inhibition as a potential therapeutic strategy for CLE.

As development continues, litifilimab may represent an additional targeted treatment approach for patients with active cutaneous lupus who require improved control of inflammatory skin manifestations.

References

1. Merola J, Chong B, Fivenson D, et al. Litifilimab improves clinician and patient reported skin changes in cutaneous lupus erythematosus: 52-week results from the phase 2 study, AMETHYST Part A. Presented at: ACR Convergence 2026; November 8, 2026; Orlando, FL. Abstract 0872. https://acrabstracts.org/abstract/litifilimab-improves-clinician-and-patient-reported-skin-changes-in-cutaneous-lupus-erythematosus-52-week-results-from-the-phase-2-study-amethyst-part-a/
2. ClinicalTrials.gov. A study to evaluate the efficacy and safety of litifilimab (BIIB059) in participants with active cutaneous lupus erythematosus (AMETHYST). NCT05531565. https://clinicaltrials.gov/study/NCT05531565