Amgen has put numbers behind the phase 2 discoid lupus result it first flagged in February, disclosing that daxdilimab achieved a 6-point placebo-adjusted drop in disease severity at the lower dose and a 5.7-point drop at the higher dose at Week 24.
The trial enrolled 72 patients with discoid lupus, an autoimmune disease marked by mostly painless sores on the skin, and tested two doses of the ILT7-targeting IgG1 monoclonal antibody. Amgen had already said the study met its primary endpoint. The new abstract fills in the scale of the effect and suggests the lower dose may be sufficient, because it performed slightly better than the higher one on the main efficacy measure.
The data
The primary endpoint was reduction in the Cutaneous Lupus Erythematosus Disease Area and Severity Index score, or CLASI-A, at Week 24. According to the abstract, the low dose delivered the larger benefit, with a 6-point drop versus placebo, while the high dose produced a 5.7-point drop.
Fierce Biotech reported that a 6-point reduction is equivalent to a 50% reduction in lupus disease area and severity, which experts consider meaningful for patients’ quality of life. Both doses also met secondary endpoints.
On the measure of patients achieving a 50% or greater reduction in CLASI-A score, 61.7% of the low-dose group and 62.1% of the high-dose group met the threshold, compared with 23.7% on placebo. On a separate clinician-reported severity scale, 60.3% of low-dose patients and 51.6% of high-dose patients reached a score of 0 or 1 at Week 24, versus 8.9% in the placebo cohort.
The safety profile in the abstract was relatively clean. No serious adverse events or deaths were reported. One patient in the high-dose cohort discontinued because of arthralgia that the study investigator considered related to treatment.
The road here
Daxdilimab came to Amgen through its 2023 acquisition of Horizon Therapeutics. The antibody is designed to target immunoglobulin-like transcript 7 to reduce plasmacytoid dendritic cells, which produce interferons.
Its path has not been straightforward. In a 2023 phase 2 trial run by Horizon, daxdilimab failed to beat placebo in systemic lupus erythematosus, the more common lupus form. Around the same period, Amgen also dropped two of its own midstage systemic lupus programs for futility, leaving the company without an obvious lupus growth story.
That history makes the discoid lupus result strategically important even if it does not reset the broader autoimmune field. The current signal is in a more defined skin-focused indication, and the dose-response pattern may help Amgen shape a registrational plan around a lower exposure level rather than trying to push efficacy with more drug.
Last month, Amgen said it was already taking steps to move daxdilimab into a registrational phase of development. The new data do not answer whether success in discoid lupus can translate beyond this setting, but they do give the company a more credible basis for that next step than the earlier headline-only disclosure did.
