Evaluating Risk: Clarifying the Safety Data Behind Efgartigimod

Josh Bryson, PhD

Efgartigimod (argenx), a neonatal fragment crystallizable receptor (FcRn) inhibitor, has been on the market as a treatment for myasthenia gravis for several years since its original 2021 approval. Since then, its indication has expanded to treat primary immune thrombocytopenia and patients with chronic inflammatory demyelinating polyneuropathy. To date, there is a subcutaneous formulation of the medication as well as a self-administered pre-filled syringe option for patients.

At the 2025 American Academy of Neurology (AAN) Annual Meeting, held April 5-9 in San Diego, California, a poster using data from the FDA Adverse Event Reporting System (FAERS) revealed that the risk of infections was higher than in those treated with efgartigimod over immunoglobulins, another standard of care. Using a sample of more than 5000 reports, infections represented 37% (n = 557) of the reports for efgartigimod vs 24% (n = 107) of those for immunoglobulins. In addition, patients on efgartigimod were found to be more likely to have serious infectious events (92% vs 70.65%) and to result in hospitalization (52% vs 23.72%) than for immunoglobulins.¹

To offer greater context and clarity on these data, NeurologyLive^® reached out to Josh Bryson, PhD, head of Medical Affairs at argenx, who addressed potential concerns about the infection risk of efgartigimod. In the interview, he clarified the limitations of FAERS-based safety signal data and emphasized that product labeling remains the gold standard for efgartigimod’s risk-benefit profile. Bryson also discussed long-term safety monitoring, the most common infections observed, and how ongoing data generation supports clinical decision-making.

NeurologyLive: Regarding the data from Poluzzi et al, what should clinicians know about the safety profile of efgartigimod?

Josh Bryson, PhD: Yeah, certainly. And thanks for the question. So, you know, one thing we wanted to come back to in this specific abstract by Palozza and colleagues is that it's really anchored on data that comes from the FDA FAERS database. That’s an important portal for pharmacovigilance by the FDA, and it’s a public reporting tool for adverse events and safety signals.

One thing we wanted to really point out—and the FDA makes this very clear on the FAERS portal in their Q&A—is that there are some limitations to that data that should be considered. First, the data isn’t perfect: it's often incomplete, it can contain duplicates, and the events reported aren’t always causally attributable. The FDA has a specific disclaimer stating that this data shouldn't be used to make comparative safety claims versus other products.

So while we respect the FAERS database and its role in pharmacovigilance, those limitations are important in the context of interpreting this abstract. I'd also note that this abstract looked at infections and hospitalizations. We think it's critical that if neurologists or HCPs are making treatment decisions, they refer to the product label, which comprehensively describes the risk-benefit profile—including, but not limited to, infection risk. That should be the foundation of the discussion between patients and their treaters.

Are there any specific reasons why we see a slight increase in infection rates?

Yeah, a few important points there. First, I’ll again point to the label—that’s the foundation of the product’s benefit-risk profile. And this is something we monitor rigorously, both in long-term data and ongoing trials. In terms of infection risk, it’s noted in the label, but importantly, the rates we’ve observed are in line with what’s seen in the broader generalized myasthenia gravis (gMG) population.

To date, we’ve collected over 8000 patient-years of safety data, and this is something we continue to monitor closely, as part of our commitment to regulatory agencies and to patients. The benefit-risk profile of efgartigimod—marketed as Vyvgart—has remained consistent and favorable in both gMG and CIDP populations.

As a clinical community, how can we ensure we’re prescribing this medication in the right ways?

First, we don’t provide direct treatment advice, but we do provide comprehensive data to help support informed clinical decisions. Again, I’ll emphasize that the label should be the primary reference for understanding the safety and efficacy of the therapy.

Beyond that, we’re committed to continued data generation—both in controlled clinical settings and real-world practice. Our hope is that this evolving body of evidence helps guide physicians in how best to manage these serious, chronic autoimmune conditions with this therapy.

Are there certain patients who may be more at risk to experience specific adverse events with efgartigimod?

That’s another good one. I’ll refer back to the label again—there are very clear Warnings and Precautions listed, particularly regarding hypersensitivity and infection risks. Infections, when they occur, tend to be respiratory tract infections and urinary tract infections. But overall, the safety profile has remained consistent across seasons and patient types, even as we continue to collect data globally.

REFERENCE
1. Giunchi V, Fusaroli M, Baquié M, Wissman C, Poluzzi E, et al. Infections-related Safety Profile of Efgartigimod Alpha and Immunoglobulins in Myasthenia Gravis (S34.003). Presented at: 2025 AAN Annual Meeting; April 5-9; San Diego, California. Abstract 34.003.