argenx Presents New Data at AANEM and MGFA Scientific Session Showcasing Earlier and Sustained Treatment in MG and CIDP with VYVGART and Progress Across its Neuromuscular Pipeline

• New data show deepening improvement in ocular MG and sustained one-year efficacy in anti-AChR antibody-negative MG – broadening VYVGART's potential to treat all MG patients

• Real-world evidence from more than 1,100 U.S. MG patients indicates the value of treating earlier with VYVGART

• Long-term data reinforce VYVGART’s consistent safety and efficacy profile in CIDP, and Phase 4 switch data support the feasibility of a direct, one-week transition from IVIg

• Empasiprubart Phase 2 study results in MMN support its potential as a pathway-selective complement therapy

Amsterdam, the Netherlands – argenx SE (Euronext & Nasdaq: ARGX), a global immunology innovation company, will present new data from across its portfolio and pipeline at the 2026 American Association of Neuromuscular & Electrodiagnostic Medicine (AANEM) Annual Meeting and the Myasthenia Gravis Foundation of America (MGFA) Scientific Session in Orlando, Florida, from September 29 – October 2, 2026. Presentations will include clinical, long-term and real-world data for VYVGART (IV: efgartigimod alfa-fcab and SC or Hytrulo: efgartigimod alfa and hyaluronidase-qvfc) in myasthenia gravis (MG) and chronic inflammatory demyelinating polyneuropathy (CIDP), as well as results for empasiprubart and adimanebart, reflecting argenx’s innovative pipeline across rare neuromuscular diseases.

“The data we are presenting at AANEM and MGFA show how far the evidence for VYVGART now reaches – across years of treatment and into patient populations historically left out of clinical trials,” said Luc Truyen, M.D., Ph.D., Chief Medical Officer, argenx. “Our aim with VYVGART is to benefit as many patients as we can while simplifying treatment decisions for clinicians treating MG and CIDP. In MG, that means one clear treatment choice regardless of a patient's antibody status. We are also seeing growing evidence that starting treatment earlier in MG and CIDP makes a difference. That same ambition to reach more patients drives our pipeline, where empasiprubart and adimanebart target distinct mechanisms in neuromuscular diseases that remain underserved.”

• Continued Improvement with Additional Cycles in Ocular MG. New data from the Phase 3 ADAPT OCULUS study show that improvements in ocular MG among patients treated with VYVGART continue to deepen with additional treatment cycles. After two cycles of VYVGART beyond the placebo-controlled period, mean Myasthenia Gravis Impairment Index (MGII) patient-reported ocular scores improved further from -4.5 to -6.8 points in AChR-Ab-positive patients and from -2.7 to -4.5 points in triple-seronegative patients, indicating that meaningful clinical benefit deepened with continued treatment. These results build on the evidence supporting VYVGART’s potential as the first targeted treatment for patients living with ocular MG. (AANEM Poster #328).

• Sustained Efficacy in anti-AChR antibody-negative MG. One-year ADAPT SERON results show sustained efficacy and consistent safety in patients with generalized MG who do not have detectable anti-AChR antibodies, with mean Myasthenia Gravis Activities of Daily Living (MG-ADL) improvements of approximately 5 points maintained through Week 52 (MGFA Oral #72; AANEM Poster #151). The importance of addressing this historically underrepresented population is further reinforced by real-world evidence from the German Myasthenia Gravis Registry, which found a higher disease burden among patients without detectable anti-AChR antibodies than among AChR-Ab-positive patients, including greater impairment in activities of daily living (mean MG-ADL 6.9 versus 4.8), disease severity, quality of life, and fatigue (MGFA Poster #67).

• Benefits of Earlier Treatment. A real-world analysis of more than 1,100 U.S. MG patients treated with VYVGART showed improvements in MG-ADL scores, steroid burden and exacerbation rates across all sub-cohorts, with the greatest gains among patients who initiated treatment earlier – whether defined by fewer prior treatments or shorter time from diagnosis. Patients treated with VYVGART within a year of diagnosis had a mean MG-ADL reduction of 4.7 points over the first three months, versus 3.5 points among those treated more than three years after diagnosis, and 50% reached minimal symptom expression (p<0.001; MGFA Poster #24).

• Long-term, Consistent Safety and Efficacy. An interim analysis of the ADHERE and ADHERE+ study reinforces the consistent safety profile of VYVGART Hytrulo with follow up of CIDP patients extending beyond five years of treatment. On measures of disability, approximately 40% of responding participants reached an INCAT score of 0 or 1 during the extension, indicating independence in most daily activities with little to no functional disability (AANEM Poster #391).

• Early Grip Strength Improvement. A post hoc analysis shows VYVGART Hytrulo reduced the relative risk of grip strength deterioration in CIDP patients by 71.5% (hazard ratio 0.285; p<0.001), with early improvement detected faster through grip strength assessment than established disability measures (AANEM Poster #343).

• One-week Direct Transition from IVIg. Data from the Phase 4 switch study evaluated the transition from IVIg to VYVGART Hytrulo one week after the last IVIg dose, with 87% of patients remaining on VYVGART Hytrulo through 12 weeks – supporting the feasibility of initiating VYVGART with a one-week interval after concluding treatment with IVIg (AANEM Poster #128).

• Response as a First-Line Treatment. A longitudinal analysis of ADHERE and ADHERE+ shows that 87.5% of treatment-naïve patients treated with VYVGART Hytrulo achieved confirmed evidence of clinical improvement, and 44.4% of these patients improved by 2 or more INCAT points between the start of stage A and Week 36 of ADHERE+ (AANEM Poster #345).

• Sustained Benefit in MMN. Phase 2 ARDA+ results show sustained clinical benefit and consistent safety with empasiprubart in multifocal motor neuropathy (MMN) (AANEM Poster #175), supported by translational data on pathway-selective complement blockade (AANEM Poster #225).

• Digital Gait Outcomes in CMS. The Phase 1b study of adimanebart in adults with DOK7- congenital myasthenic syndrome (CMS) reported in-clinic and real-world improvements in walking performance, measured by digital gait outcomes and informed by qualitative patient interviews (AANEM Posters #130 and #438)

Details for oral and poster presentations at MGFA and AANEM are as follows:

*Session Times:

• Session I: Wednesday, September 30, 6:15-6:45 p.m. ET

• Session II: Thursday, October 1, 9:30-10:00 a.m. ET

• Session III: Thursday, October 1, 2:45-3:15 p.m. ET

More information on the data presented at the 2026 AANEM Annual Meeting and MGFA Scientific Session can be found here.

Important Safety Information What is VYVGART® (efgartigimod alfa-fcab) for intravenous (IV) infusion and what is VYVGART HYTRULO® (efgartigimod alfa and hyaluronidase-qvfc) for subcutaneous injection? VYVGART and VYVGART HYTRULO are both prescription medicines used to treat adults with generalized myasthenia gravis (gMG).

It is not known if VYVGART or VYVGART HYTRULO is safe and effective in children.

IMPORTANT SAFETY INFORMATION Do not take VYVGART if you are allergic to efgartigimod alfa or any of the ingredients in VYVGART. Do not take VYVGART HYTRULO if you are allergic to efgartigimod alfa, hyaluronidase, or any of the ingredients in VYVGART HYTRULO. VYVGART or VYVGART HYTRULO can cause serious allergic reactions and a decrease in blood pressure leading to fainting.

Before taking VYVGART or VYVGART HYTRULO, tell your healthcare provider about all of your medical conditions, including if you:

• have an infection or fever.

• have recently received or are scheduled to receive any vaccinations.

• have any history of allergic reactions.

• have kidney (renal) problems.

• are pregnant or plan to become pregnant. It is not known whether VYVGART or VYVGART HYTRULO will harm your unborn baby.

o Pregnancy Exposure Registry. There is a pregnancy exposure registry for women who use VYVGART or VYVGART HYTRULO during pregnancy. The purpose of this registry is to collect information about your health and your baby. Your healthcare provider can enroll you in this registry. You may also enroll yourself or get more information about the registry by calling 1-855-272-6524 or going to VYVGARTPregnancy.com

• are breastfeeding or plan to breastfeed. It is not known if VYVGART or VYVGART HYTRULO passes into your breast milk.

Tell your healthcare provider about all the medicines you take, including prescription and over-the-counter medicines, vitamins, and herbal supplements.

VYVGART or VYVGART HYTRULO can cause side effects which can be serious, including:

• Infection. VYVGART or VYVGART HYTRULO may increase the risk of infection. If you have an active infection, your healthcare provider should delay your treatment with VYVGART or VYVGART HYTRULO until your infection is gone. Tell your healthcare provider right away if you get any of the following signs and symptoms of an infection: fever, chills, frequent and painful urination, cough, pain and blockage of nasal passages, wheezing, shortness of breath, sore throat, excess phlegm, and nasal discharge.

• Allergic reactions (hypersensitivity reactions). VYVGART or VYVGART HYTRULO can cause allergic reactions that can be severe. These reactions can happen during, shortly after, or weeks after your VYVGART infusion or VYVGART HYTRULO injection. Tell your healthcare provider or get emergency help right away if you have any of the following symptoms of an allergic reaction with VYVGART or VYVGART HYTRULO: rash, swelling of the face, lips, throat, or throat, shortness of breath, trouble breathing, low blood pressure, and fainting.

An additional symptom of an allergic reaction with VYVGART HYTRULO can include hives.

• Infusion or injection-related reactions. VYVGART can cause infusion-related reactions. VYVGART HYTRULO can cause infusion or injection-related reactions. These reactions can happen during or shortly after your VYVGART infusion or VYVGART HYTRULO injection. Tell your healthcare provider if you have any of the following symptoms of an infusion or injection-related reaction: high blood pressure, chills, shivering, and chest, stomach, or back pain.

The most common side effects of VYVGART or VYVGART HYTRULO include respiratory tract infection, headache, and urinary tract infection. An additional common side effect with VYVGART HYTRULO includes injection site reactions.

These are not all the possible side effects of VYVGART or VYVGART HYTRULO. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Please see the full Prescribing Information for VYVGART and full Prescribing Information for VYVGART HYTRULO.

About VYVGART and VYVGART Hytrulo VYVGART® (efgartigimod alfa fcab) is a first-in-class human IgG1 antibody fragment that binds to the neonatal Fc receptor (FcRn), resulting in the reduction of circulating IgG autoantibodies. VYVGART Hytrulo® is a subcutaneous combination of efgartigimod alfa (VYVGART) and recombinant human hyaluronidase PH20 (rHuPH20), Halozyme’s ENHANZE® drug delivery technology to facilitate subcutaneous injection delivery of biologics. VYVGART is approved for generalized myasthenia gravis (gMG) and immune thrombocytopenia (Japan only). VYVGART Hytrulo is approved for gMG and chronic inflammatory demyelinating polyneuropathy (CIDP). VYVGART Hytrulo may be marketed under different proprietary names in other regions. About Empasiprubart Empasiprubart (ARGX-117) is a novel humanized monoclonal antibody that binds C2 and blocks activation of both the classical and lectin pathways of the complement cascade. By blocking complement activity upstream of C3 and C5, empasiprubart has the potential to reduce tissue inflammation and cellular damage, representing a broad pipeline opportunity across multiple severe autoimmune indications. In addition to multifocal motor neuropathy, argenx is evaluating empasiprubart in delayed graft function following kidney transplant, and chronic inflammatory demyelinating polyneuropathy (CIDP).

About Adimanebart Adimanebart (ARGX-119) is a first-in-class humanized agonist monoclonal antibody (mAb) that specifically targets and activates muscle-specific tyrosine kinase (MuSK) to promote maturation and stabilization of the neuromuscular junction (NMJ). It is a mAb derived from llamas and discovered using the argenx SIMPLE Antibody™ platform technology. Adimanebart is being developed for patients with neuromuscular disease, including congenital myasthenic syndromes (CMS) and spinal muscular atrophy (SMA). Adimanebart was developed through argenx’s IIP program in collaboration with the world’s leading key opinion leaders on MuSK and the NMJ, Professor Steven J. Burden from MGH, Professor Shohei Koide from NYU and Professor Jan Verschuuren and Associate Professor Maartje Huijbers from LUMC. About Myasthenia Gravis (MG) Myasthenia gravis (MG) is a rare and chronic autoimmune disease where IgG autoantibodies disrupt communication between nerves and muscles, causing debilitating and potentially life-threatening muscle weakness. MG can present in different forms.

In generalized myasthenia gravis (gMG), weakness extends to muscles throughout the body. Approximately 20% of patients with gMG do not have detectable antibodies against the acetylcholine receptor (AChR-Ab). These patients may have detectable autoantibodies targeting other neuromuscular junction (NMJ) proteins, such as muscle-specific tyrosine kinase (MuSK) and low-density lipoprotein receptor-related protein 4 (LRP4), or others.

Ocular myasthenia gravis (oMG) is characterized by muscle weakness limited to the muscles controlling the eyes and eyelids, with common symptoms including ptosis (drooping eyelids), diplopia (double vision), and fluctuating visual disturbance that can impair daily activities.

About Chronic Inflammatory Demyelinating Polyradiculoneuropathy (CIDP) Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is a rare and serious autoimmune disease of the peripheral nervous system. CIDP is a heterogenous disease involving different yet overlapping pathways and a varied disease course. There is increasing evidence that IgG antibodies and the complement system play a key role in the damage to the peripheral nerves. People with CIDP experience fatigue, muscle weakness and a loss of feeling in their arms and legs that can worsen over time or may come and go. These symptoms can significantly impair a person's ability to function in their daily lives. Without treatment, one-third of people living with CIDP will need a wheelchair.

About Multifocal Motor Neuropathy (MMN) Multifocal motor neuropathy (MMN) is a rare, severe, chronic autoimmune disease of the peripheral nervous system. The disease is characterized by slowly progressive, asymmetric muscle weakness mainly of the hands, forearms and lower legs. MMN is often associated with the presence of anti-GM1 IgM autoantibodies, leading to activation of the classical complement pathway, driving subsequent axon damage. High-dose IVIg is the only approved treatment for MMN and patients typically experience disease progression despite therapy, indicating an unmet need for efficacious and better tolerated therapeutic options.

About Congenital Myasthenic Syndromes (CMS) Congenital Myasthenic Syndromes (CMS) are an ultra-rare and heterogenous group of congenital neuromuscular disorders caused by genetic defects that are essential for the integrity of the neuromuscular junction. Early age of onset and fatigable muscle weakness are considered clinical hallmarks of CMS. Muscle weakness can be debilitating and life-threatening causing difficulties in speaking or swallowing, impaired or absent mobility, proximal arm and leg weakness, and respiratory insufficiency. DOK7 variations are one of the more frequent and severe causes of CMS, accounting for approximately 24% of CMS cases. There are no approved treatments. The prevalence of CMS is estimated to be 5 per 1M (DOK7-CMS estimated to be 1.2 per 1M).

About argenx argenx is the global immunology innovation company committed to improving the lives of people suffering from severe autoimmune diseases. Partnering with leading academic researchers through its Immunology Innovation Program (IIP), argenx aims to translate immunology breakthroughs into a world-class portfolio of novel antibody-based medicines. argenx developed and is commercializing the first approved neonatal Fc receptor (FcRn) blocker and is evaluating its broad potential in multiple serious autoimmune diseases while advancing several earlier stage experimental medicines within its therapeutic franchises. For more information, visit www.argenx.com and follow us on LinkedIn, Instagram, Facebook, and YouTube.

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