Annexon, Inc. announced positive results from the completed pivotal Phase 3 trial of C1q-targeted immunotherapy, ANX005, in Guillain-Barré Syndrome (GBS) at the 2024 Peripheral Nerve Society (PNS) Annual Meeting in Montréal, Canada. Leading global experts in the GBS field highlighted the significant unmet need and opportunity to transform the GBS treatment landscape with a targeted immunotherapy approach, as well as additional Phase 3 analyses of early and durable treatment effects important to patients and the medical community. GBS-Disability Scale (GBS-DS): Primary endpoint at Week 8: 2.41-fold higher likelihood of being in a better state of health with ANX005 vs.

placebo (p = 0.0058). Week 1: 7.22-fold higher likelihood of being in a better state of health with ANX005 vs. placebo (p < 0.0001).

Week 4: 2.49-fold higher likelihood of being in a better state of health with ANX005 vs. placebo (p = 0.0073). Week 26: 2.5 times more patients had fully recovered to a normal /pre-disease state of health (GBS-DS = 0) with ANX005 (21.5%) vs.

placebo (8.6%) (OR 4.14, *p = 0.0092). Week 8 responder analysis (pre-specified sensitivity analysis): 2-times more patients improved 3 points or more with ANX005 (28.2%) vs. placebo (13.6%) (*p = 0.0309).

Week 8 dichotomy analysis (pre-specified sensitivity analysis): 2.5-times more patients were able to run or better ANX005 (29%) vs. placebo (12%) (OR 3.34, p = 0.0065). Functional Measures: Walking 31 days earlier with ANX005 treatment (56 days) vs.

placebo (87 days) (p = 0.0211) and Off ventilation 28 days earlier with ANX005 treatment (20 days) vs. placebo (48 days) (p = 0.0356). Patients with North American and European baseline characteristics: Week 1: 8.8-point improvement in muscle strength measured by Medical Research Council (MRC) sumscore with ANX005 vs.

placebo (p <0.0001). Week 8: 3 times more likely to be in a better state of health on the GBS-DS scale with ANX005 vs. placebo (p = 0.0102).

Key Findings from the Phase 3 GBS Trial of ANX005 30 mg/kg Treatment: Phase 3 trial informed by dose-ranging Phase 1b trial, replicating earlier results. Demonstrated a highly statistically significant effect on primary endpoint of GBS-DS, further supported by multiple prespecified sensitivity analyses. Defined the effective treatment window during the active phase of GBS, an acute disease.

Early, robust and durable treatment effects expedited patient recovery. Single dose administration of ANX005 was generally well-tolerated with mostly mild to moderate adverse events, no increased infection rate while not requiring vaccination or prophylactic antibiotics, and a profile similar to placebo. Annexon?s lead investigational therapy, ANX005, is a first-of-its kind selective, targeted and rapid-acting agent designed to reduce inflammation and nerve damage by fully stopping C1q activity in the peripheral and central nervous systems. In GBS, ANX005 seeks out C1q and selectively blocks it from binding to its target on peripheral nerves.

ANX005 is administered intravenously and has been observed to act almost immediately. In GBS, the aim is to rapidly stop the autoimmune damage of nerve cells, allowing the patient to regain their muscle strength sooner to regain independence and return to pre-illness activities. ANX005 has received both fast track and orphan drug designations from the Food and Drug Administration as well as orphan drug designation by the European Medicines Agency for the treatment of GBS.

GBS is a severe disease resulting from an acute autoantibody attack on peripheral nerves that generally occurs post-infection in otherwise healthy persons following activation of C1q and the classical complement cascade. It is a rapid and acute neurological disease with a narrow therapeutic window that results in hospitalization of over 22,000 people annually in the U.S. and Europe. The peripheral nerve damage progresses rapidly, causing acute neuromuscular paralysis, and may lead to significant morbidity, disability and mortality.

Currently, there are no approved treatments for GBS in the U.S. The long-term disease burden associated with GBS has led to a multi-billion-dollar annual economic cost to the U.S. healthcare system alone.