argenx (AO) | Buy | argenx

Research evidence excerpt

argenx (AO) | Buy | argenx

sts the path may be staged: IMNM first, DM as the larger scale opportunity, and ASyS as

optional longer-term expansion. A strong IMNM outcome alone could still be highly valuable, particularly if it establishes Vyvgart

as the first targeted therapy in a severe rheumatology indication with no approved treatment. DM also remains central to the

upside case, supported by a strong biological rationale and an encouraging Phase 2 signal, even if the small subgroup size limits

firm conclusions ahead of Phase 3.

Disease heterogeneity supports a subtype-specific regulatory path

The most important strategic message from the event is that argenx appears to be prioritising IMNM and DM as two distinct

opportunities rather than relying on a single broad myositis basket claim. In our view, this reflects four factors: disease biology,

opportunity size, regulatory feedback and the practical lessons from the Phase 2 dataset.

Autoimmune myositis is not a single disease, but a group of antibody-defined syndromes with different clinical manifestations,

treatment needs and regulatory arguments. A broad label would maximise theoretical market breadth, but it could also make the

filing package less clean if the evidence is stronger in some subtypes than others. A subtype-driven strategy therefore looks like a

more credible way to access the opportunity, not a retreat from it.

The Phase 2 dataset illustrates this well. Although DM is the larger diagnosed population, with c.40k diagnosed patients in the US

versus c.20k for IMNM, ALKIVIA enrolled a majority of IMNM patients. IMNM represented 61% of the 89 Phase 2 patients, compared

with 29% for DM and 10% for PM. This was not due to a predefined subtype target; the study enrolled on a first-come, first-served