argenx (ARGX) Status update summary

Strategic update and regulatory pathway

• Focus is on autoimmune myositis, specifically IMNM and DM, as high unmet need indications with strong biology rationale and urgent patient need.

• Phase II data showed statistically significant results in IMNM and a clear signal in DM, leading to Breakthrough Designation for IMNM from the FDA.

• Regulatory strategy now involves separate analysis and potential filings for IMNM and DM, with no further path for PM due to evolving classification and low enrollment.

• Ongoing engagement with the FDA supports the approach of assessing each subtype on its own merits for approval.

• Commercialization efforts include expanded medical and sales teams, proactive payor engagement, and partnerships with advocacy groups.

Clinical and scientific insights

• Autoantibodies are now recognized as pathogenic drivers in myositis, correlating with distinct clinical phenotypes and driving disease progression.

• Efgartigimod demonstrated efficacy in preclinical models and phase II trials, restoring muscle function, reducing muscle necrosis, and improving function.

• Clinical improvements in muscle strength, reductions in autoantibody levels, and improved patient-reported outcomes were observed.

• The Total Improvement Score (TIS) is used as a composite endpoint, capturing muscle, skin, and functional outcomes, with all six core set measures improved.

• Safety profile was consistent with known data, with no new safety signals.

ALKIVIA clinical trial results

• Phase 2 data showed significant improvement in TIS at week 24 for efgartigimod versus placebo (P = .0004).

• IMNM was the key contributor to response, with DM showing a clear signal.

• Efgartigimod led to faster and deeper clinical responses, with higher rates of moderate and major improvement.

• All six core set measures of TIS improved, including muscle strength and patient-reported outcomes.

• Safety profile was consistent with known data, with no new safety signals.