argenx Reports Topline Results from ADDRESS Study of Efgartigimod SC in Pemphigus ADDRESS study did not meet primary or secondary endpoints Pemphigus deprioritized as efgartigimod indication Update on BALLAD study GO/NO

argenx Reports Topline Results from ADDRESS Study of

Efgartigimod SC in Pemphigus

study did not meet primary or secondary endpoints

deprioritized as efgartigimod indication

on BALLAD study GO/NO GO decision

Conference call scheduled

for today, December 20, 2023, at 8:30am ET (2:30pm CET)

Regulated Information - Inside Information

December 20, 2023, 7:00am CET

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

lives of people suffering from severe autoimmune diseases, today announced topline results from the ADDRESS study evaluating efgartigimod

subcutaneous (SC) (efgartigimod alfa and hyaluronidase-qvfc) in adults with pemphigus vulgaris (PV) and pemphigus foliaceus (PF). The

ADDRESS results show the proportion of PV patients achieving the primary endpoint of complete remission on a minimal dose of steroids

(CRmin) was not significantly different between efgartigimod SC and placebo.

argenx will not pursue additional development

in pemphigus and plans to prioritize clinical development of efgartigimod in its ongoing severe autoimmune indications.

"We are disappointed by today's results,

particularly for pemphigus patients who have seen little innovation in this treatment space," said Luc Truyen, M.D., Ph.D., Chief

Medical Officer at argenx. "At argenx, we are in the business of transformation, providing new medicines that go beyond incremental

benefit and raise the bar for what patients can expect from a treatment. While we will not move forward into pemphigus, our job today

is the same as yesterday - continue to be execution-focused and data-driven, apply learnings across our ongoing development programs,

and pursue optimal development of efgartigimod, empasiprubart and our earlier stage programs. 2023 was a remarkable year of growth for

argenx across the business and we are poised to build on our success in 2024.

"We are grateful to the pemphigus community

and all involved in the ADDRESS study, including patients, healthcare professionals, and our argenx teams," continued Dr. Truyen.

ADDRESS Study Results

The Phase 3 ADDRESS study enrolled 222 adult

patients with newly diagnosed or relapsing moderate-to-severe PV (n=190) or PF (n=32). Patients were randomized to efgartigimod SC or

placebo with both treatment groups receiving concomitant steroids at a starting dose of 0.5mg/kg, which is a lower dose than recommended

by current treatment guidelines and was tapered according to protocol upon achievement of complete remission.

Update on BALLAD Study

is reviewing the BALLAD study in light of the ADDRESS results and the comparable biology between pemphigus and bullous pemphigoid, and

has decided not to make a GO/NO GO decision at this time but rather wait for learnings from all currently enrolled patients and

consider a new trial design for the path forward.

Conference Call Details

will host a conference call today at 2:30 pm CET (8:30am ET) to discuss the ADDRESS results. A webcast of the live call and replay

may be accessed on the Investors section of the argenx website.

minutes prior to the live call.

About the ADDRESS Study

The ADDRESS study was a randomized, double-blind,

placebo-controlled, multicenter, global trial evaluating the efficacy and safety of efgartigimod SC (efgartigimod alfa and hyaluronidase-qvfc)

in adult patients with pemphigus. Enrolled patients had newly diagnosed or relapsing moderate-to-severe pemphigus vulgaris (PV) or pemphigus

foliaceus (PF) with PDAI scores of 15. Patients were randomized in a 2:1 ratio to receive efgartigimod SC or placebo for a total

of 30 weeks as part of the primary trial. All patients were on concomitant corticosteroids at a starting dose of 0.5mg/kg/day, which

could be tapered according to protocol upon achievement of complete remission (PDAI = 0). The primary endpoint was measured by the proportion

of PV patients who achieved sustained complete remission on a minimal dose of corticosteroids (CRmin) within 30 weeks. Key secondary

endpoints included proportion of overall population (PV and PF) who achieved CRmin, cumulative corticosteroid dose, and time to disease

control and complete remission. At the end of the 30-week study, eligible patients entered a double-blind 8-week follow-up as part of

the ADDRESS open-label extension study during which CRmin off treatment (efgartigimod SC or placebo) was assessed.

Pemphigus is a rare group of chronic blistering

autoimmune diseases that affect the skin and mucous membranes, and are characterized by painful blisters, erosions and acantholysis,

or disruption of keratinocyte adhesion. Blisters often break open, causing serious pain and increased risk of infection. Pemphigus vulgaris

and pemphigus foliaceous are the most common forms of pemphigus.

About the BALLAD Study

The BALLAD study is a randomized, double-blind,

placebo-controlled, multicenter trial evaluating the efficacy and safety of VYVGART Hytrulo (efgartigimod alfa and hyaluronidase-qvfc)

in adult patients with bullous pemphigoid (BP). Enrolled patients have moderate to severe BP and are a more fragile and older population

than pemphigus patients. Patients were randomized in a 1:1 ratio to receive VYVGART Hytrulo or placebo for a total of 36 weeks as

part of the primary trial. All patients are on concomitant corticosteroids at a starting dose of 0.5 mg/kg/day, which could be tapered

according to protocol upon achievement of complete remission (BPDAI= 0). The primary endpoint is measured at 36 weeks by the proportion

of BP patients who achieved clinical remission while receiving efgartigimod SC or placebo but off corticosteroids therapy for at least

8 weeks. Key secondary endpoints include cumulative dose of corticosteroids from baseline, proportion of patients who achieve an Investigator

Global Assessment of BP (IGA-BP) score of 0 or 1, changes from baseline in the BP Disease Area Index (BPDAI) activity score, proportion

of patients who are in CR on minimal corticosteroids for at least 8 weeks at week 36 and time to control of disease or complete remission.

About Bullous Pemphigus

Bullous pemphigoid is a rare chronic blistering

autoimmune disease and is the most common form of pemphigoid diseases. It is characterized by autoantibodies against structural

proteins of the dermal-epidermal junction and, clinically, by tense blisters and erosions of skin or mucous membranes close to the skin

surface. The disease has a strong impact on a person's quality of life and is associated with a high mortality.

VYVGART Hytrulo (efgartigimod SC)

VYVGART Hytrulo is a

subcutaneous combination of efgartigimod alfa, a human IgG1 antibody fragment marketed for intravenous use as VYVGART ,

and recombinant human hyaluronidase PH20 (rHuPH20), Halozyme's ENHANZE drug delivery technology to facilitate subcutaneous

injection delivery of biologics. In binding to the neonatal Fc receptor (FcRn), VYVGART Hytrulo results in the reduction of circulating

IgG. VYVGART Hytrulo is the proprietary name in the U.S. for subcutaneous efgartigimod alfa and recombinant human hyaluronidase PH20.

It is marketed in Europe as VYVGART and may be marketed under different proprietary names following approval in other regions.

is a global immunology 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 in the U.S., Japan, Israel, the EU, the UK, China and Canada. The Company is evaluating efgartigimod in multiple

serious autoimmune diseases and advancing several earlier stage experimental medicines within its therapeutic franchises. For more information,

For further information, please contact:

This press release contains

inside information within the meaning of Article 7(1) of the EU Market Abuse Regulation (Regulation 596/2014).

Forward-Looking Statements

The contents of this

announcement include statements that are, or may be deemed to be, "forward-looking statements." These forward-looking statements

can be identified by the use of forward-looking terminology, including the terms "plans," "aims," "believes,"

"continues," "hope," "estimates," "anticipates," "expects," "intends,"

"may," "will," "should," or "commitment" and include statements argenx makes concerning

argenx's topline results from the ADDRESS study of efgartigimod SC in adults with PV and PF, our plan to pursue optimal development

of efgartigimod, empasiprubart and our earlier stage programs, and our goal of translating immunology breakthroughs into a world-class

portfolio of novel antibody-based medicines. By their nature, forward-looking statements involve risks and uncertainties and readers

are cautioned that any such forward-looking statements are not guarantees of future performance. argenx's actual results may differ

materially from those predicted by the forward-looking statements as a result of various important factors, including but not limited

to argenx's additional analyses of the dataset from the ADDRESS and BALLAD studies, expectations regarding the inherent uncertainties

associated with development of novel drug therapies, preclinical and clinical trial and product development activities and regulatory

approval requirements, the acceptance of our products and product candidates by our patients as safe, effective and cost-effective, and

the impact of governmental laws and regulations on our business. A further list and description of these risks, uncertainties and other