Annexon's Phase III GBS Trial Meets Goal, Prepares for Approval Filing

Annexon has announced encouraging results from a Phase III clinical trial targeting Guillain-Barré syndrome (GBS), suggesting the company may achieve FDA approval in the coming year. The trial involved 241 participants diagnosed with GBS, a rare and serious neurological disorder affecting the peripheral nerves. These individuals were randomized to receive either one of two doses of ANX005, an anti-C1Q antibody, or a placebo.

The primary endpoint of the study focused on the GBS disability score, a measure of functional status in GBS patients. This score helps distinguish between patients requiring assisted ventilation and those capable of walking with assistance. Notably, the group receiving the lower dose of ANX005 demonstrated statistically significant improvements on this score, resulting in a 2.4-fold enhancement compared to the control group. This achievement allowed the study to meet its primary objective.

Secondary endpoints also showed promising results. Participants who received the lower dose of ANX005 exhibited improvements in muscle strength and experienced fewer days on artificial ventilation. These outcomes are crucial for GBS patients, as emphasized by David Cornblath, professor emeritus of neurology at Johns Hopkins University School of Medicine. Cornblath highlighted that the ability to walk independently and to be free from ventilator support are critical steps toward resuming normal daily activities for these patients.

The lower dose of ANX005 was the focal point of Annexon's top-line analysis. Interestingly, the higher dose did not show statistical superiority over the placebo in the primary endpoint assessment. However, Annexon noted that the higher dose did outperform the control group on several other measures. Jamie Dananberg, Annexon's chief medical officer, explained during a conference call that the discrepancy between the two doses might indicate that the 75 milligram per kilogram dose could extend beyond the therapeutic window, thereby limiting C1Q-mediated tissue repair.

Looking ahead, Annexon plans to seek FDA approval in the first half of next year. The company's filing will coincide with the availability of real-world evidence (RWE) comparability data. It's worth noting that the Phase III trial only included sites in Bangladesh and the Philippines. Annexon attributed this decision to the limited access to the standard care treatment of intravenous immunoglobulin in these regions. To support its filing, Annexon is generating additional RWE in Western countries.

The FDA has the authority to approve medications based on foreign clinical data if certain conditions are met. These conditions include the applicability of the results to the U.S. population, the competency of the clinical investigators, and the validity of the data without requiring an on-site inspection. However, it's important to mention that the FDA has sometimes rejected applications that heavily relied on foreign data in recent years, underscoring the need for robust and comprehensive evidence.

Annexon's progress in the GBS clinical trial represents a significant step forward in addressing a debilitating neurological condition. With the company's plans for FDA approval and ongoing efforts to gather comprehensive RWE, there is a cautious optimism for the future availability of ANX005 as a treatment option for patients with Guillain-Barré syndrome.