Annexon had some really positive news to give an update on for investors last week at the AAN Annual Meeting, which took place between April 5th – 9th of 2025 in San Diego California. It gave an oral presentation showcasing its intravenous (IV) monoclonal antibody drug tanruprubart (previously known in its pipeline as ANX005) for the treatment of patients with Guillain-Barre Syndrome (GBS).
Specifically, it highlighted the drug’s capability in a phase 3 placebo-controlled study, whereby patients experienced substantial improvement in multiple clinical measures of it. The bottom line is that the drug performed better than placebo in being able to establish superior functional recovery for them. GBS is a devastating neurological disorder where the immune system targets the body’s nerves.
In turn, this leads to a host of problems that these patients experience, like muscle weakness and tingling effects throughout their bodies. On the one hand, when it comes to less severe disease, a patient at worst may only experience such small effects. However, in severe cases of this disorder, it could lead to a medical emergency. Not all, but a majority of these patients must be treated in a hospital.
The clinical data from the phase 3 placebo-controlled study pretty much speaks for itself in that patients who were given a 30 mg/kg dose of tanruprubart had achieved a statistically significant 2.4x higher likelihood of being in better condition, compared to those who were on placebo at the 8-week mark. Such statistical significance was achieved with a p-value of p=0.0058.
There is a milestone on the horizon that could further boost value for shareholders, which is that the company is expected to hold a pre-BLA meeting with the FDA in the 1st half of 2025. Should the final outcome of this meeting go as planned, then there is a good chance that Annexon should be able to file its Biologics Licensing Application [BLA] of tanruprubart for the treatment of these GBS patients. The timing of such a regulatory application just depends on when the meeting is concluded and how long the company needs to prepare to file this BLA.
The truth is that these GBS patients need some type of treatment option, and the hope is that tanruprubart will be it. Consider that for the time being, there are no FDA approved drugs to treat these patients. The beauty of this biotech comes in its science, whereby like many other companies it targets the complement cascade that causes disease. But it specifically blocks C1q, which is the initiating molecule of the cascade.
In essence, by inhibiting C1q tanruprubart inhibits the complement cascade system at the source, thus leading to the prevention or halting of downstream tissue damage and inflammation. This, in my opinion is a solid approach, and it appears as though the company is at least proving this mechanism of action (MOA) with this indication.
The possibilities here are quite endless, because the targeting of neurological disorders by inhibiting C1q can be applied elsewhere. Annexon is currently in the process of evaluating another drug in its pipeline, known as ANX007, which is a monoclonal antibody antigen-binding fragment (Fab). This particular drug is being given to dry age-related macular degeneration (Dry-AMD) patients via intravitreal injection in the ongoing phase 3 ARCHEER II trial. Completion of enrollment for this late-stage study is expected in the 2nd half of 2025, with topline data expected to be released in the 2nd half of 2026.
