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.

• Phase III trial is larger and longer, with steroid tapering included, aiming for label expansion and long-term leadership in autoimmune myositis.

Clinical and scientific insights

• Autoantibodies are now recognized as pathogenic drivers in myositis, with research showing their direct role in muscle and skin damage.

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

• Clinical improvements in muscle strength and reductions in autoantibody levels were observed, supporting the targeted therapy approach.

• The Total Improvement Score (TIS) is used as a composite endpoint, capturing muscle, skin, and functional outcomes.

• Phase III design includes robust endpoints and is powered to detect meaningful benefit in both IMNM and DM.

Market opportunity and commercial readiness

• IMNM and DM represent sizable markets, with 20,000 and 40,000 diagnosed patients in the U.S., respectively.

• IMNM is seen as a multi-blockbuster opportunity due to high unmet need and lack of approved treatments; DM is larger but more heterogeneous.

• Market research indicates strong willingness among rheumatologists to prescribe VYVGART if approved.

• Commercial strategy leverages prior success in MG and CIDP, with expanded patient support, market access, and education initiatives.

• Anticipated market expansion as awareness, diagnosis, and treatment options increase, similar to trends seen in MG and CIDP.