Professor and Chair of the Department of Dermatology and Professor of Internal Medicine in the Division of Rheumatic Diseases and in the Peter O'Donnell Jr. School of Public Health at UT Southwestern Medical Center in Dallas

Evolving Research Landscape Drives Progress in CLE at AAD 2026

Cutaneous lupus erythematosus (CLE) is a disease whose therapeutic stagnation has stood in stark contrast to the scientific progress made in understanding its underlying biology. Over the past two decades, advances in immunology have illuminated the central role of plasmacytoid dendritic cells, type I interferon signaling, and innate immune dysregulation in driving the skin inflammation, tissue injury, and scarring that define the disease.¹ That growing mechanistic clarity has not only reframed how clinicians think about CLE pathophysiology but has begun to translate into a new generation of rationally designed therapeutic candidates targeting the specific immunological pathways responsible for disease activity.

Litifilimab is perhaps the clearest example of that translation. Its development as a BDCA2-targeting monoclonal antibody was predicated on the understanding that pDC-driven type I interferon production is a proximal driver of lupus pathogenesis, and its two positive Phase 2 trials in CLE represent the most advanced clinical validation of that mechanistic hypothesis to date.² The progress made in CLE is also inseparable from broader advances in lupus research, where a deepening understanding of immune dysregulation across the spectrum of disease has created shared scientific infrastructure that benefits both systemic and cutaneous manifestations.

For patients who have lived with inadequate treatment options for generations, the convergence of scientific understanding and clinical evidence now underway represents a genuine inflection point. In this final segment, Joseph Merola, MD, MMSc, and Victoria Werth, MD, reflect on how the field's evolving understanding of CLE pathophysiology has shaped the current moment in drug development, and what the trajectory of innovation suggests for the future of care in this long-underserved disease.

Furie R, Werth VP, Merola JF, et al. Monoclonal antibody targeting BDCA2 ameliorates skin lesions in systemic lupus erythematosus. 

 2019;129(3):1359-1371. doi:10.1172/JCI124466

Biogen Inc. Biogen announces second positive Phase 2 litifilimab trial in cutaneous lupus erythematosus at 2026 American Academy of Dermatology Annual Meeting, showing a significant reduction in skin disease activity. Published March 28, 2026. 

https://investors.biogen.com/news-releases/news-release-details/biogen-announces-second-positive-phase-2-litifilimab-trial

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AMETHYST Phase 3 and Remaining Questions Surrounding Litifilimab in CLE

Cutaneous lupus erythematosus (CLE) remains one of dermatology's most consequential unmet needs. Despite its prevalence, chronicity, and capacity for permanent disfigurement, no targeted therapy has ever been approved for the disease, and the clinical trial landscape has historically been sparse. That context makes the emerging litifilimab program not only scientifically significant but unusually anticipated — 2 positive Phase 2 trials in a condition where positive Phase 2 data alone represent a meaningful advance.

With consistent efficacy signals established across the LILAC and AMETHYST Part A studies, attention now turns to AMETHYST Part B, the phase 3 portion of the phase 2/3 trial, which is currently ongoing with results remaining blinded. Part B will be critical in several respects. 

It will need to confirm the efficacy signal observed in Part A in a larger, more powered population, establish the durability of response beyond the 24-week controlled period examined in Phase 2, and provide the robust safety dataset that will ultimately inform regulatory review. Importantly, AMETHYST was designed with a globally representative enrollment strategy, with 74% women and 33% non-white participants in Part A, reflecting the demographic realities of CLE. Whether that representation is maintained and whether the efficacy signal holds across subgroups defined by disease subtype, severity, and background therapy will be among the most closely watched questions as Phase 3 data mature.¹

For clinicians who have long managed CLE with tools borrowed from adjacent indications, the prospect of a purpose-built, mechanism-driven therapy with a Phase 3 program underway is a substantive shift in the trajectory of the field. The Breakthrough Therapy Designation granted to litifilimab by the FDA adds further momentum, signaling regulatory recognition of both the unmet need and the strength of the existing evidence base.

In this segment, Joseph Merola, MD, MMSc, and Victoria Werth, MD, share what they are most anticipating from the AMETHYST Phase 3 program, which data points will be most informative for clinical practice, and what approval of a first targeted therapy for CLE would mean for patients who have been waiting decades for a better option.

Experts share what they anticipate most from the ongoing AMETHYST Phase 3 program and what approval of a first targeted therapy would mean for patients.

Potential of Targeting BDCA2 in Cutaneous Lupus Erythematosus Management

Cutaneous lupus erythematosus (CLE) is driven by a complex interplay of innate and adaptive immune dysregulation, with plasmacytoid dendritic cells (pDCs) occupying a central role in disease pathogenesis. Activated pDCs produce substantial quantities of type I interferon and other pro-inflammatory cytokines and chemokines that perpetuate skin inflammation, drive keratinocyte injury, and contribute to the irreversible tissue damage that defines the most severe presentations of the disease. For a patient population that has long been managed with broadly immunosuppressive agents carrying significant toxicity profiles, a therapy designed to interrupt this pathway at its source represents a meaningful mechanistic departure from the standard of care.

Litifilimab targets BDCA2, a receptor selectively expressed on pDCs. Binding of litifilimab to BDCA2 suppresses pDC activation and downstream production of type I interferon and associated inflammatory mediators, offering a targeted approach to interrupting the immunological cascade thought to underlie CLE pathology. The specificity of this mechanism is clinically relevant: by acting on pDCs rather than broadly suppressing immune function, litifilimab has the potential to attenuate disease-driving inflammation while preserving broader immune competence.

That mechanistic rationale is now supported by a pair of positive Phase 2 trials. In the phase 2 portion of the AMETHYST study, litifilimab demonstrated a statistically significant 11.8% higher rate of clear or almost clear skin versus placebo at Week 16 (14.7% vs 2.9%; 95% CI: 1.39, 22.27; P < .05), with separation from placebo observed as early as Week 4. At Week 24, 40.8% of litifilimab-treated participants achieved a CLASI-50 response compared with 21% receiving placebo, and 1 in 6 participants in the litifilimab group achieved a CLASI score of 0 to 3, indicating no or minimal disease activity, compared with none in the placebo group. These results are consistent with the earlier LILAC Phase 2 study and collectively represent the only investigational program with positive efficacy data across multiple CLE trials to date.¹

In this segment, Joseph Merola, MD, MMSc, and Victoria Werth, MD, examine how the mechanism of action of litifilimab maps onto the immunopathology of CLE, what the AMETHYST results reveal about the durability and depth of response, and what these findings may mean for patients who have exhausted current treatment options.

Drenkard C, Barbour KE, Greenlund KJ, Lim SS. The burden of living with cutaneous lupus erythematosus. 

 2022;9:897987. doi:10.3389/fmed.2022.897987

Experts explore how litifilimab's BDCA2-targeting mechanism maps onto CLE pathophysiology.

Navigating Multidisciplinary Care for CLE in an Evolving Landscape

Cutaneous lupus erythematosus (CLE) does not exist in a clinical vacuum. While skin disease is the defining feature, CLE frequently intersects with systemic manifestations, comorbid autoimmune conditions, and the ever-present risk of progression to systemic lupus erythematosus. Managing this complexity has historically required coordination across specialties, with dermatologists, rheumatologists, and primary care clinicians each playing a role in the care of a patient population whose needs often exceed what any single specialty can address alone. Yet in the absence of approved targeted therapies, that collaboration has had limited tools to work with, and management decisions have largely defaulted to the same narrow, off-label options regardless of disease severity or phenotype.

The question of who owns CLE therapeutically is one the field has not fully resolved. Dermatologists are often the first to diagnose and treat, given the primacy of skin involvement, but rheumatologists bring expertise in systemic disease monitoring and immunosuppressive management that is frequently essential. For patients with refractory or severe disease, navigating this divide can translate into fragmented care, delayed escalation, and outcomes that reflect the limitations of the system as much as the limitations of available therapies.

An approved targeted therapy for CLE would not just add a treatment option, it could reframe the clinical conversation. A therapy with a defined mechanism, a validated efficacy profile, and a manageable safety record would give both dermatologists and rheumatologists a shared reference point around which to organize care, set treatment goals, and evaluate response in a more structured and collaborative way. It could also expand access for patients who are currently undertreated because no specialist feels sufficiently equipped to escalate beyond standard of care.

In this segment, Joseph Merola, MD, MMSc, and Victoria Werth, MD, reflect on how CLE patients move through the health care system today, where the gaps in multidisciplinary coordination are most acute, and how the availability of a first approved targeted therapy could reshape not only treatment paradigms but the broader infrastructure of collaborative care for this disease.

Experts discuss how an approved targeted therapy could restructure collaboration between dermatology and rheumatology.

Understanding AMETHYST Design and Patient Needs in CLE

Despite affecting millions of people worldwide, cutaneous lupus erythematosus (CLE) has long posed a clinical challenge that extends beyond diagnosis. For patients with moderate to severe disease, particularly those who are refractory or intolerant to antimalarial therapy, treatment options remain limited, and the consequences of inadequately controlled disease are not merely cosmetic. 

Scarring, alopecia, and dyspigmentation can be permanent, disfiguring, and deeply damaging to quality of life. Selecting endpoints that capture this reality, rather than simply measuring biological activity, is central to evaluating whether a new therapy can meaningfully move the needle for this population.

The AMETHYST Phase 2/3 study evaluated litifilimab, an investigational monoclonal antibody targeting BDCA2 on plasmacytoid dendritic cells, in participants with active subacute or chronic CLE who had failed or could not tolerate antimalarials. The Phase 2 portion of the study employed 2 primary instruments: the CLA-IGA-R, which assessed clear or almost clear skin at Week 16, and the CLASI, a validated composite measure of disease activity and damage that has become a standard tool in CLE clinical research. 

CLASI-50 and CLASI-70 thresholds, representing 50% and 70% reductions in disease activity from baseline, respectively, served as key secondary endpoints, and at Week 24, 1 in 6 participants receiving litifilimab achieved a CLASI score of 0 to 3, defined as no or minimal disease activity, compared with none in the placebo group.¹

These endpoints matter because they align with what patients and clinicians are actually trying to achieve: not incremental reduction in erythema scores, but meaningful, visible, and sustained clearance of skin disease in a patient population accustomed to inadequate responses. The speed of separation, with differences emerging as early as Week 4 on CLASI-50, adds further clinical context to the efficacy signal.

In this segment, Joseph Merola, MD, MMSc, and Victoria Werth, MD, discuss why the endpoint selection in AMETHYST reflects the true burden of CLE, what the observed response thresholds mean in the context of daily clinical practice, and how these data begin to address a treatment gap that has persisted for more than seven decades.

Experts examine why the CLASI and CLA-IGA-R reflect the true burden of CLE.

With no targeted therapies approved in more than 70 years, new phase 2 AMETHYST data for litifilimab may signal a turning point for CLE.

Understanding Unmet Need and Recent Advances in CLE at AAD 2026 

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Latest News

Evolving Research Landscape Drives Progress in CLE at AAD 2026

AMETHYST Phase 3 and Remaining Questions Surrounding Litifilimab in CLE

Potential of Targeting BDCA2 in Cutaneous Lupus Erythematosus Management

Navigating Multidisciplinary Care for CLE in an Evolving Landscape

Understanding AMETHYST Design and Patient Needs in CLE