Annexon had some really positive news to give as part of an update 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 the 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 end up leading to a medical emergency. Not all, but a huge majority of these patients end up being treated in the 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 a 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 patients with GBS. The timing of such a regulatory application just depends on when the meeting is concluded and how long the company needs to prepare in order to file its BLA of this drug candidate for the treatment of these patients.
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 is responsible for driving a host of diseases. 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 evaluated in the phase 3 ARCHER II trial targeting patients with dry age-related macular degeneration (Dry-AMD) and is being given to them via the route of intravitreal injection. Completion of enrollment of this late-stage study is expected in the 2nd half of 2025, with topline data expected in the 2nd half of 2026.