New Phase II safety data supports enpatoran’s move to Phase III for cutaneous lupus
Merck KGaA presented new Phase II safety and tolerability data for enpatoran at SLEuro 2026, supporting the drug’s move into Phase III clinical trials for cutaneous lupus erythematosus and systemic lupus erythematosus.
New Phase II safety and tolerability data presented at SLEuro 2026 support enpatoran’s transition into Phase III clinical trials for cutaneous lupus erythematosus and systemic lupus erythematosus.
Key facts
- Merck KGaA presented new Phase II safety and tolerability data for enpatoran at SLEuro 2026.
- The data support enpatoran’s move into Phase III clinical trials for both CLE and SLE.
- Enpatoran is an oral toll-like receptor 7/8 inhibitor targeting type 1 interferon and inflammatory cytokines.
- The oral formulation may become the drug’s main differentiator versus other late-stage injectable biologics in CLE.
At SLEuro 2026, Merck KGaA (Merck; known as EMD Serono in the US and Canada) presented new safety and tolerability data for enpatoran (M5049) in development for cutaneous lupus erythematosus (CLE) and systemic lupus erythematosus (SLE). Enpatoran is an orally administered toll-like receptor 7/8 inhibitor, which targets type 1 interferon and inflammatory cytokines, to alleviate inflammatory symptoms and achieve skin remissions in CLE and SLE patients.
The safety data presented were derived from secondary endpoints of the Phase II trial (NCT05162586; Willow), supporting enpatoran’s move into Phase III clinical trials for both SLE and CLE. The move is significant, given the lack of approved treatment options and the sparse late-stage pipeline for CLE.
Additionally, Merck had already published the drug’s efficacy results in May 2025 from the Phase II trial (NCT05162586; Willow), which indicated that over 60% of patients had achieved Cutaneous Lupus Erythematosus Disease Area and Severity Index (CLASI) improvement in over 70% of the disease versus only about 11%–12% on placebo at week 16, showing a large separation from placebo and suggesting promising efficacy.
Phase II safety and efficacy data support Phase III plans
With enpatoran soon entering Phase III clinical trials (NCT07332481; ELOWEN-1 and NCT07355218; ELOWEN-2), the Phase II safety and efficacy results support the drug’s ongoing development, making the therapy a promising immunosuppressor for the treatment of both SLE and CLE.
The latest update is important because the current treatment landscape for cutaneous lupus erythematosus remains limited and unsatisfactory. Patients with CLE are often treated through off-label use of topical corticosteroids, antimalarials, and broad-spectrum immunosuppressants, despite the absence of therapies specifically approved for CLE.
These treatments are widely known to have low efficacy and are commonly associated with undesirable safety profiles, including risk of severe infections and other complications such as cardiac disease and cancer, which can contribute to poor prognosis and continued unmet medical need in cutaneous lupus.
CLE pipeline remains limited as enpatoran advances
Currently, there are only two drugs in late-stage development for CLE: AstraZeneca’s Saphnelo (anifrolumab) and Biogen’s litifilimab (NCT06015737; LAVENDER and NCT06044337; AMETHYST LTE, respectively). With Saphnelo already approved for SLE, its safety data is well established among clinicians. In addition, the approval of its subcutaneous formulation in December 2025 introduced a more convenient once-weekly self-injection option.
Saphnelo and litifilimab have both already demonstrated efficacy against cutaneous manifestations of lupus comparable to enpatoran, based on their respective Phase II outcomes. That means enpatoran is entering a competitive field, but one that still lacks diversity in mechanism, formulation and patient-friendly delivery options.
Despite the positive outcomes for enpatoran, the oral formulation of the drug may be the primary differentiator from the other late-stage biologics in development, which are all injectables.
Oral delivery may be enpatoran’s key differentiator in lupus treatment
As such, even though efficacy comparisons place enpatoran among the more promising emerging options in lupus, its oral formulation could become the defining advantage if it reaches the market. For many patients and physicians, an oral immunomodulatory therapy may offer practical benefits over injectable biologics, especially in chronic autoimmune diseases that require long-term treatment.
Taken together, the new Phase II safety data, the previously reported efficacy results, and the broader unmet need in cutaneous lupus support enpatoran’s progression into Phase III development. For Merck KGaA, the program now represents one of the more closely watched late-stage opportunities in CLE and SLE, particularly because of the limited treatment landscape and the importance of finding effective therapies with manageable safety profiles and convenient administration.
