Abivax (1K) | Buy | The backbone thesis gets stronger

Research evidence excerpt

Abivax (1K) | Buy | The backbone thesis gets stronger

Abivax Buy | Target Price: EUR180.00

The safety debate largely settles

Following the positive Phase III part 1 maintenance readout, efficacy was no longer the key

question. The investment debate progressively shifted towards one remaining uncertainty:

could the few malignancies reported across the programme ultimately become a meaningful

regulatory or commercial hurdle?

Exposure-adjusted incidence rates tell a different story

The expanded safety database now exceeds 1,700 patient-years, almost doubling cumulative

exposure since the initial maintenance update. More importantly, Abivax presented exposure-

adjusted incidence rates, rather than simply reporting the absolute number of malignancies.

This is the methodology routinely used to assess long-term safety in chronic diseases and, in our

view, the most appropriate framework to interpret yesterday's update.

Chart 1:Malignancy rates remain fully consistent with expected UC background rates

Source: Abivax

Using this approach, both malignancies excluding NMSC and NMSC remained within expected

background rates reported in UC populations, substantially changing how the overall safety

profile should be interpreted.

The reported malignancies deserve context

Not all malignancies carry the same regulatory significance. Regulators primarily focus on

malignancies excluding NMSC, as these represent the most clinically meaningful long-term

safety events. NMSC, by contrast, are relatively common in UC patients, particularly following

thiopurine exposure, are usually detected early and have never historically driven boxed

warnings in IBD. We therefore believe Abivax's decision to analyse both categories separately