On Tuesday, Annexon Inc ( ANNX ) released topline results from its Phase 3 trial in patients with Guillain-Barré syndrome (GBS), an autoimmune condition in which the immune system attacks the nerves.

As Guillain-Barre syndrome progresses, muscle weakness can turn into paralysis.

The Phase 3 trial met its primary endpoint, with ANX005 30 mg/kg achieving a statistically significant 2.4-fold improvement on the GBS-disability scale at week 8.

ANX005 30 mg/kg treatment also demonstrated improvements versus placebo on key secondary endpoints, including early gains in muscle strength and a median of fewer days on artificial ventilation.

In a prespecified analysis, ANX005 30 mg/kg demonstrated a 31-day reduction in the median time to walk independently versus placebo.

ANX005 also provided an early reduction in the prespecified analysis of neurofilament light chain serum levels, a nerve damage biomarker (11.2% reduction relative to placebo).

The Phase 3 trial, which enrolled 241 subjects in Bangladesh and the Philippines, evaluated two doses of ANX005-30 mg/kg and 75 mg/kg, which delivered rapid and complete suppression of complement activity but differed in duration of C1q inhibition.

The 30 mg/kg dose suppression lasted one week, and the 75 mg/kg dose suppression lasted two to three weeks.

ANX005 75 mg/kg outperformed the placebo on multiple endpoints. However, it was not statistically significant on the primary endpoint of the GBS-disability scale at week 8.

The GBS Phase 3 study was conducted in Bangladesh and the Philippines due to the high prevalence of the disease.

Based on FDA feedback, Annexon ( ANNX ) has initiated a real-world evidence (RWE) protocol with the International Guillain-Barré Syndrome Outcomes Study (IGOS) to establish comparability between Phase 3 participants and Western patients.

IGOS is a global, prospective, observational, multicenter cohort study that has enrolled 2,000 patients who were followed for one to three years.

RWE data and FDA application submission are expected in the first half of 2025.

Price Action: ANNX shares are up 31.07% at $6.03 at the last check on Tuesday.