argenx Announces U.S. FDA Acceptance of Biologics License Application for Subcutaneous Efgartigimod in Generalized Myasthenia Gravis with Priority Review - Prescription Drug User Fee Act (PDUFA) target action date is

argenx Announces U.S. FDA Acceptance of Biologics

License Application for Subcutaneous

Efgartigimod in Generalized Myasthenia Gravis with Priority Review

- Prescription Drug User Fee Act (PDUFA) target

action date is March 20, 2023

- Submission based on positive results from

the Phase 3 bridging study demonstrating noninferior

total IgG reduction at day 29 with subcutaneously (SC) administered efgartigimod compared to

intravenous (IV) administration

Netherlands - argenx SE (Euronext & Nasdaq: ARGX), a global immunology company committed to improving the lives

of people suffering from severe autoimmune diseases, today announced the U.S. Food and Drug Administration (FDA) has accepted for priority

review a Biologics License Application (BLA) for SC efgartigimod (1000mg efgartigimod-PH20) for the treatment of adult patients with generalized

myasthenia gravis (gMG). The application has been granted a Prescription Drug User Fee Act (PDUFA) target action date of March 20,

SC efgartigimod is co-formulated with recombinant

human hyaluronidase PH20 (rHuPH20), Halozyme's ENHANZE drug delivery technology. ENHANZE facilitates the SC injection

delivery of biologics that are typically administered via IV infusion.

"The FDA's acceptance of our BLA is

an exciting step toward fulfilling our vision of delivering the broadest gMG treatment offering that reflects the unique disease experience

for each patient as they navigate life with this debilitating disease. We're excited about the potential of SC efgartigimod to offer

patients multiple ways to receive treatment through various administrations and an individualized dosing schedule," said Keith Woods,

Chief Operating Officer of argenx. "With an established PDUFA date, we are preparing for our second commercial product launch and

look forward to potentially bringing forth another first-in-class option for gMG patients."

The BLA submission is supported by data from the

Phase 3 ADAPT-SC study evaluating the noninferiority of the pharmacodynamic (PD) effect of SC efgartigimod as compared with IV administered

VYVGART in adult patients with gMG. The majority of enrolled patients were positive for acetylcholine receptor (AChR) antibodies, but

the trial also included patients where AChR antibodies were not detected.

ADAPT-SC met its primary endpoint (p< 0.0001)

of total IgG reduction from baseline at day 29 demonstrating noninferiority of SC efgartigimod to VYVGART. Patients treated with SC efgartigimod

achieved mean total IgG reduction of 66.4% from baseline at day 29, compared to 62.2% reduction with VYVGART. Results were consistent

across the overall population, including those with AChR antibodies and patients where AChR antibodies were not detected. Further, 69.1%

of patients treated with SC efgartigimod were responders on the Myasthenia Gravis Activities of Daily Living (MG-ADL) score. Responders

are defined as having at least a two-point improvement on the MG-ADL score for at least four consecutive weeks. 65.5% of patients treated

with SC efgartigimod were responders on the Quantitative Myasthenia Gravis (QMG) score. Responders are defined as having at least a three-point

improvement on the QMG score for at least four consecutive weeks. Minimal symptom expression (MSE), a measure of symptom-free status,

was achieved in 37% of SC efgartigimod-treated patients after one treatment cycle. Onset of effect was also consistent with the Phase

The safety profile for SC efgartigimod was consistent

with the ADAPT study. It was generally well-tolerated; the most frequent adverse event being injection site reactions (ISRs), commonly

observed with biologics administered subcutaneously. All ISRs were mild to moderate and resolved over time. After completing ADAPT-SC,

95% of participants entered ADAPT-SC+, a three-year open-label extension study evaluating the long-term safety and tolerability of SC

Phase 3 ADAPT-SC Trial Design

The Phase 3 ADAPT-SC trial was a multicenter,

randomized, open-label, parallel-group study evaluating the noninferiority of the pharmacodynamic (PD) effect of SC efgartigimod (1000mg

efgartigimod-PH20) as compared with VYVGART (10mg/kg) in patients with gMG. The pharmacodynamic effect as measured by percent change from

baseline in total IgG levels at day 29, one week after the last dose of IV or SC efgartigimod, served as the primary endpoint in the ADAPT-SC

trial. The correlation between total IgG reduction and clinical benefit in gMG was demonstrated in a Phase 2 trial and the Phase 3 ADAPT

trial, which served as the basis for approval of VYVGART in the U.S., Japan and Europe. Safety, clinical efficacy, immunogenicity and

pharmacokinetics (PK) were also assessed.

A total of 110 adult patients with gMG in North

America, Europe and Japan enrolled in the ADAPT-SC trial and were treated. Inclusion criteria of the trial were the same as the Phase

3 ADAPT trial of VYVGART; enrolled patients had a confirmed gMG diagnosis and an MG-ADL total score of at least 5 with greater than 50%

of the total score attributed to non-ocular symptoms, at screening and baseline. Patients were on a stable dose of at least one gMG treatment

prior to randomization, including acetylcholinesterase inhibitors, corticosteroids or nonsteroidal immunosuppressive drugs, and were required

to remain on that stable dose throughout the primary trial. Patients were eligible to enroll in ADAPT-SC regardless of antibody status,

including patients with AChR antibodies (AChR-Ab+) and patients where AChR antibodies were not detected.

Patients were randomized in a 1:1 ratio to receive

SC efgartigimod or IV efgartigimod for one treatment cycle consisting of four doses at weekly intervals. The total study duration was

approximately 12 weeks, including seven weeks of follow-up after the treatment cycle.

full Prescribing Information for VYVGART in the U.S., which includes the below Important Safety Information. For more

information related to VYVGART in Japan, visit argenx.jp.

IMPORTANT SAFETY INFORMATION FOR VYVGART

(efgartigimod alfa-fcab) intravenous (IV) formulation (U.S. PRESCRIBING INFORMATION)

What is VYVGART (efgartigimod alfa-fcab)?

VYVGART is a prescription medicine used to treat

a condition called generalized myasthenia gravis, which causes muscles to tire and weaken easily throughout the body, in adults who are

positive for antibodies directed toward a protein called acetylcholine receptor (anti-AChR antibody positive).

What is the most important information I should know about VYVGART?

VYVGART may cause serious side effects, including:

may increase the risk of infection. In a clinical study, the most common infections were urinary tract and respiratory tract infections.

More patients on VYVGART vs placebo had below normal levels for white blood cell counts, lymphocyte counts, and neutrophil counts. The

majority of infections and blood side effects were mild to moderate in severity. Your health care provider should check you for infections

before starting treatment, during treatment, and after treatment with VYVGART. Tell your health care provider if you have any history

of infections. Tell your health care provider right away if you have signs or symptoms of an infection during treatment with VYVGART such

as fever, chills, frequent and/or painful urination, cough, pain and blockage of nasal passages/sinus, wheezing, shortness of breath,

fatigue, sore throat, excess phlegm, nasal discharge, back pain, and/or chest pain.

reactions (hypersensitivity reactions). VYVGART can cause the immune system to have undesirable reactions such as rashes, swelling

under the skin, and shortness of breath. In clinical studies, the reactions were mild or moderate and occurred within 1 hour to 3 weeks

of administration, and the reactions did not lead to VYVGART discontinuation. Your health care provider should monitor you during and

after treatment and discontinue VYVGART if needed. Tell your health care provider immediately about any undesirable reactions.

Before taking VYVGART, tell your healthcare provider

about all of your medical conditions, including if you:

Have a history of infection or you think you have an infection.

Have received or are scheduled to receive a vaccine

(immunization). Discuss with your health care provider whether you need to receive age-appropriate immunizations before initiation of

a new treatment cycle with VYVGART. The use of vaccines during VYVGART treatment has not been studied, and the safety with live or live-attenuated

vaccines is unknown. Administration of live or live-attenuated vaccines is not recommended during treatment with VYVGART.

Are pregnant or plan to become pregnant and are breastfeeding or plan

Tell your health care provider about all the medicines

you take, including prescription and over-the-counter medicines, vitamins, and herbal supplements.

What are the common side effects of VYVGART?

The most common side effects of VYVGART are respiratory

tract infection, headache, and urinary tract infection.

These are not all the possible side effects of

VYVGART. Call your doctor for medical advice about side effects. You may report side effects to the US Food and Drug Administration at

Please see the full Prescribing Information for VYVGART and talk to

Efgartigimod is an antibody fragment designed

to reduce pathogenic immunoglobulin G (IgG) antibodies by binding to the neonatal Fc receptor and blocking the IgG recycling process.

Efgartigimod is being investigated in several autoimmune diseases known to be mediated by disease-causing IgG antibodies, including neuromuscular

disorders, blood disorders, and skin blistering diseases, in both an intravenous and subcutaneous (SC) formulation. SC efgartigimod is

co-formulated with recombinant human hyaluronidase PH20 (rHuPH20), Halozyme's ENHANZE drug delivery technology.

VYVGART (efgartigimod alfa-fcab)