argenx (ARGX) investor relations material

Study Overview and Design

• ALKIVIA was a global, randomized, double-blind, placebo-controlled Phase 2/3 basket trial evaluating VYVGART Hytrulo (efgartigimod) in autoimmune myositis, including IMNM and DM, with a primary endpoint of mean Total Improvement Score (TIS) at 52 weeks.

• The study enrolled 264 patients with active muscle weakness; 175 participated in Phase 3 with a mandatory corticosteroid taper from weeks 16-44 to test treatment robustness.

• Both muscle and skin manifestations were assessed, with a specific skin measure for DM, and prespecified analyses for combined and separate subtypes.

• The trial was conducted across North America, Europe, Middle East, and Asia-Pacific, including China and Japan.

• The design supports regulatory flexibility and reflects a strategy of targeting high unmet need areas and following disease biology.

Key Efficacy Results

• The primary endpoint was met in the combined IMNM and DM population, with a statistically significant and clinically meaningful improvement in TIS (p=0.0011), showing a 15.4-point greater improvement over placebo.

• IMNM subgroup achieved statistical significance (p=0.0048), with a 14.81-point TIS difference favoring VYVGART; DM subgroup showed a 14.5-point difference but did not reach statistical significance due to smaller sample size.

• Consistent, rapid, and sustained treatment effects were observed across all six core set measures and both muscle and skin endpoints through 52 weeks, even during steroid tapering.

• Benefit was consistent across primary and secondary endpoints and aligned with the established efficacy profile of efgartigimod.

• This is the first Phase 3 study to show significant and meaningful improvement in IMNM, a subtype with no approved therapy.

Safety and Tolerability

• Safety and tolerability profile was consistent with previous VYVGART/efgartigimod trials and real-world experience.

• Most common adverse events included nasopharyngitis, upper respiratory tract infection, and injection site reactions.

• No new safety signals emerged; infection rates were slightly increased but not concerning given the background of immunosuppression.

• No fatal adverse events reported; rates of serious adverse events and discontinuations were comparable between groups.

• Benefit-risk profile remains robust, supporting regulatory submission.