Independent Auditor’s report

To: the Shareholders and the Board of Directors of argenx SE

Report on the audit of the financial statements 2025 included in the Annual Report

Our opinion

We have audited the accompanying financial statements 2025 of argenx SE based in Amsterdam, the Netherlands.

The financial statements comprise the consolidated financial statements and the company financial statements.

In our opinion:

• The consolidated financial statements give a true and fair view of the financial position of argenx SE as at December 31, 2025 and of its result and its cash flows for 2025 in accordance with IFRS Accounting Standards as adopted in the European Union (IFRS Accounting Standards) and with Part 9 of Book 2 of the Dutch Civil Code
• The company financial statements give a true and fair view of the financial position of argenx SE as at December 31, 2025 and of its result for 2025 in accordance with Part 9 of Book 2 of the Dutch Civil Code

The consolidated financial statements comprise:

• The consolidated statement of financial position as at December 31, 2025
• The following statements for the year ended December 31, 2025: the consolidated statements of profit or loss, comprehensive income or loss, changes in equity and cash flows
• The notes comprising material accounting policy information and other explanatory information

The company financial statements comprise:

• The company balance sheet on December 31, 2025
• The company profit and loss account for the year ended December 31, 2025
• The notes comprising a summary of the accounting policies and other explanatory information

Basis for our opinion

We conducted our audit in accordance with Dutch law, including the Dutch Standards on Auditing. Our responsibilities under those standards are further described in the Our responsibilities for the audit of the financial statements section of our report.

We are independent of argenx SE in accordance with the EU Regulation on specific requirements regarding statutory audit of public-interest entities, the Wet toezicht accountantsorganisaties (Wta, Audit firms supervision act), the Verordening inzake de onafhankelijkheid van accountants bij assurance-opdrachten (ViO, Code of Ethics for Professional Accountants, a regulation with respect to independence) and other relevant independence regulations in the Netherlands. Furthermore, we have complied with the Verordening gedrags- en beroepsregels accountants (VGBA, Dutch Code of Ethics for Professional Accountants).

We believe the audit evidence we have obtained is sufficient and appropriate to provide a basis for our opinion.

Information in support of our opinion

We designed our audit procedures in the context of our audit of the financial statements as a whole and in forming our opinion thereon. The following information in support of our opinion and any findings were addressed in this context, and we do not provide a separate opinion or conclusion on these matters.

Our understanding of the business

argenx SE (“the company”, and, together with its consolidated subsidiaries, “the group”) is a commercial-stage biopharma company developing and marketing therapies for the treatment of severe autoimmune diseases. We paid specific attention in our audit to a number of areas driven by the operations of the group and our risk assessment.

We determined materiality and identified and assessed the risks of material misstatement of the financial statements, whether due to fraud or error in order to design audit procedures responsive to those risks and to obtain audit evidence that is sufficient and appropriate to provide a basis for our opinion.

Materiality

We have also taken into account misstatements and/or possible misstatements that in our opinion are material for the users of the financial statements for qualitative reasons.

We agreed with the Board of Directors that misstatements in excess of $3.65 million, which are identified during the audit, would be reported to them, as well as smaller misstatements that in our view must be reported on qualitative grounds.

Scope of the group audit

argenx SE is at the head of a group of entities. The company has its official seat in the Netherlands. The group’s headquarters and the primary research and development activities are in Belgium. The majority of the group’s product net sales is recognized from the United States. The group relies on contract manufacturing organizations (CMOs) with manufacturing sites in the UK, U.S., Singapore, Switzerland and Denmark. The financial information of this group is included in the financial statements.

We are responsible for planning and performing the group audit to obtain sufficient appropriate audit evidence regarding the financial information of the entities or business units within the group as a basis for forming an opinion on the financial statements. We are also responsible for the direction, supervision, review and evaluation of the audit work performed for purposes of the group audit. We bear the full responsibility for the auditor’s report.

Based on our understanding of the group and its environment, the applicable financial framework and the group’s system of internal control, we identified and assessed risks of material misstatement of the financial statements and the significant accounts and disclosures. Based on this risk assessment, we determined the nature, timing and extent of audit work performed, including the entities or business units within the group (components) at which to perform audit work. For this determination we considered the nature of the relevant events and conditions underlying the identified risks of material misstatements for the financial statements, the association of these risks to components and the materiality or financial size of the components relative to the group.

We performed the (centralized) audit work ourselves at the group’s headquarters in Belgium, including (centralized) audit work for selected components and financial statement account balances such as product net sales and deferred tax assets. For the financial information of argenx B.V., comprising the research and development activities in Belgium, we made use of an EY Firm (component auditor). We communicated the audit work to be performed and identified risks through instructions for the component auditor as well as requesting the component auditor to communicate matters related to the financial information of the component that is relevant to identifying and assessing risks.

This resulted in a coverage of 100% of operating profit/(loss), 88% of total operating income and 94% of total assets.

For other components, we performed specified audit procedures and analytical procedures to corroborate that our risk assessment and scoping remained appropriate throughout the audit.

We performed site visits to meet with local management of argenx US, Inc. (USA) and with local management and the component auditor of argenx B.V. (Belgium). These site visits encompassed some, or all, of the following activities: observing the component operations, discussing the group risk assessment and the risks of material misstatements. We frequently communicated with the component team in Belgium, reviewed and evaluated the adequacy of the deliverables and reviewed working papers to address the risks of material misstatement. We held planning meetings, key meetings required based on circumstances and we attended closing meetings with local management and the component team.

By performing the audit work mentioned above at the entities or business units within the group, together with additional work at group level, we have been able to obtain sufficient and appropriate audit evidence about the group’s financial information to provide an opinion on the financial statements.

Teaming, use of specialists and internal audit

We ensured that the audit teams both at group and at component levels included the appropriate skills and competences which are needed for the audit of a listed client in the life sciences industry. We included specialists in the areas of IT audit, forensics, and income tax.

We performed our audit in cooperation with Internal Audit of argenx SE, leveraging their in-depth knowledge of the group and work performed. We agreed on the joint coordination of the audit planning, the nature and scope of the work to be performed, reporting and documentation. We evaluated and tested the relevant work performed by Internal Audit to satisfy ourselves that the work was adequate for our purposes and established what work had to be performed by our own professionals.

Our focus on climate-related risks and the energy transition

Climate change and the energy transition are high on the public agenda. Issues such as CO₂ reduction impact financial reporting, as these issues entail risks for the business operation, the valuation of assets and provisions or the sustainability of the business model and access to financial markets of companies with a larger CO₂ footprint.

The Board of Directors reported in the section 7.2 of the Non-financial information how the company is addressing climate-related and environmental risks.

As part of our audit of the financial statements, we evaluated the extent to which climate-related risks and the effects of the energy transition are taken into account in estimates and significant assumptions as well as in the design of relevant internal control measures. Furthermore, we read the non-financial information in the annual report and considered whether there is any material inconsistency between the non-financial information and the financial statements.

Based on the audit procedures performed, we do not deem climate-related risks to have a material impact on the financial reporting judgements, estimates or significant assumptions as at December 31, 2025.

Our focus on fraud and non-compliance with laws and regulations

Our responsibility

Although we are not responsible for preventing fraud or non-compliance and we cannot be expected to detect non-compliance with all laws and regulations, it is our responsibility to obtain reasonable assurance that the financial statements, taken as a whole, are free from material misstatement, whether caused by fraud or error. The risk of not detecting a material misstatement resulting from fraud is higher than for one resulting from error, as fraud may involve collusion, forgery, intentional omissions, misrepresentations, or the override of internal control.

Our audit response related to fraud risks

We identified and assessed the risks of material misstatements of the financial statements due to fraud. During our audit we obtained an understanding of the company and its environment and the components of the system of internal control, including the risk assessment process and the board of director’s process for responding to the risks of fraud and monitoring the system of internal control, as well as the outcomes.

We refer to Section 2 “Risk Factors” of the Annual Report for the Board of Directors’ (fraud) risk assessment.

We evaluated the design and relevant aspects of the system of internal control and in particular the fraud risk assessment, as well as the argenx Code of Business Conduct and Ethics, Global Speak Up and Anti-Retaliation Policy and incident registration. We evaluated the design and the implementation and, where considered appropriate, tested the operating effectiveness, of internal controls designed to mitigate fraud risks.

As part of our process of identifying fraud risks, we evaluated fraud risk factors with respect to financial reporting fraud, misappropriation of assets and bribery and corruption in close co-operation with our forensic specialists. We evaluated whether these factors indicate that a risk of material misstatement due to fraud is present.

We incorporated elements of unpredictability in our audit. We also considered the outcome of our other audit procedures and evaluated whether any findings were indicative of fraud or non-compliance.

We addressed the risks related to management override of controls, as this risk is present in all organizations. For these risks we have, among other things, performed procedures to evaluate whether the selection and application of accounting policies by the company, particularly those relating to subjective measurements and complex transactions, as disclosed in “Note 3 – Critical accounting judgments and major sources of estimation uncertainty” to the consolidated financial statements, may be indicative to fraudulent financial reporting. We have also used data analysis to identify and address high-risk journal entries and other adjustments made in the financial reporting process. We evaluated the business rationale (or the lack thereof) of significant extraordinary transactions, including those with related parties.

When identifying and assessing fraud risks we presumed that there are risks of fraud in revenue recognition. We evaluated the risk of management manipulating the payor mix assumption for the US Sales rebates and reserves related to Medicare Part D, in particular give rise to such risks. We describe the audit procedures responsive to the risk of fraud in revenue recognition in the description of our audit approach for the key audit matter U.S. Sales Rebates and Reserves – Medicare Part D Claims.

We considered available information and made enquiries of relevant individuals including the Board of Directors (including the Chair of Audit and Compliance Committee), the Chief Executive Officer, Chief Operating Officer, the Chief Financial Officer, Global Group Controller, Head of Internal Control, Head of Global Ethics and Compliance, General Counsel, and Internal Audit.

The fraud risks we identified, enquiries and other available information did not lead to specific indications for fraud or suspected fraud potentially materially impacting the view of the financial statements.

Our audit response related to risks of non-compliance with laws and regulations

We performed appropriate audit procedures regarding compliance with the provisions of those laws and regulations that have a direct effect on the determination of material amounts and disclosures in the financial statements. Furthermore, we assessed factors related to the risks of non-compliance with laws and regulations that could reasonably be expected to have a material effect on the financial statements from our general industry experience, through discussions with the Board of Directors, reading minutes, inspection of internal audit and compliance reports, and performing substantive tests of details of classes of transactions, account balances or disclosures.

We also inspected lawyers’ letters and correspondence with regulatory authorities. We remained alert to any indication of (suspected) non-compliance throughout the audit. Finally, we obtained written representations that all known instances of non-compliance with laws and regulations have been disclosed to us.

Our audit response related to going concern

As disclosed in “Note 2.1 – Statement of compliance and basis of preparation” to the consolidated financial statements, the financial statements have been prepared on a going concern basis. When preparing the financial statements, the Board of Directors made a specific assessment of the company’s ability to continue as a going concern and to continue its operations for the foreseeable future.

We discussed and evaluated the specific assessment with the Board of Directors exercising professional judgment and maintaining professional skepticism. We considered whether the Board of Directors’ going concern assessment, based on our knowledge and understanding obtained through our audit of the financial statements or otherwise, contains all relevant events or conditions that may cast significant doubt on the company’s ability to continue as a going concern. If we conclude that a material uncertainty exists, we are required to draw attention in our auditor’s report to the related disclosures in the financial statements or, if such disclosures are inadequate, to modify our opinion.

Based on our procedures performed, we did not identify material uncertainties about going concern or the Board of Directors’ use of the going concern basis of accounting. Our conclusions are based on the audit evidence obtained up to the date of our auditor’s report. However, future events or conditions may cause a company to cease to continue as a going concern.

Our key audit matters

Key audit matters are those matters that, in our professional judgment, were of most significance in our audit of the financial statements. We have communicated the key audit matter to the Board of Directors. The key audit matter is not a comprehensive reflection of all matters discussed.

U.S. Sales Rebates and Reserves – Medicare Part D Claims (key audit matter)

Report on other information included in the annual report

The annual report contains other information in addition to the financial statements and our auditor’s report thereon.

Based on the following procedures performed, we conclude that the other information:

• Is consistent with the financial statements and does not contain material misstatements
• Contains the information as required by Part 9 of Book 2 of the Dutch Civil Code for the management report (excluding the sustainability statement) and the other information as required by Part 9 of Book 2 of the Dutch Civil Code and as required by Sections:135b and 2:145 sub‑section 2 of the Dutch Civil Code for the remuneration report.

We have read the other information. Based on our knowledge and understanding obtained through our audit of the financial statements or otherwise, we have considered whether the other information contains material misstatements. By performing these procedures, we comply with the requirements of Part 9 of Book 2 and Section 2:135b sub-Section 7 of the Dutch Civil Code and the Dutch Standard 720. The scope of the procedures performed is substantially less than the scope of those performed in our audit of the financial statements.

The Board of Directors is responsible for the preparation of the other information, including the management report in accordance with Part 9 of Book 2 of the Dutch Civil Code and other information required by Part 9 of Book 2 of the Dutch Civil Code. The Board of Directors is responsible for ensuring that the remuneration report is drawn up and published in accordance with Sections:135b and 2:145 sub‑section 2 of the Dutch Civil Code.

Description of responsibilities regarding the financial statements

Responsibilities of the Board of Directors for the financial statements

The Board of Directors is responsible for the preparation and fair presentation of the financial statements in accordance with IFRS Accounting Standards and Part 9 of Book 2 of the Dutch Civil Code. Furthermore, the Board of Directors is responsible for such internal control as the Board of Directors determines is necessary to enable the preparation of the financial statements that are free from material misstatement, whether due to fraud or error.

As part of the preparation of the financial statements, the Board of Directors is responsible for assessing the company’s ability to continue as a going concern. Based on the financial reporting framework mentioned, the Board of Directors should prepare the financial statements using the going concern basis of accounting unless the Board of Directors either intends to liquidate the company or to cease operations, or has no realistic alternative but to do so. The Board of Directors should disclose events and circumstances that may cast significant doubt on the company’s ability to continue as a going concern in the financial statements.

The Audit and Compliance Committee advises the Board of Directors on matters relating to the oversight of the quality, integrity, functioning and effectiveness of the company’s financial reporting, internal risk management and control systems over financial and non-financial matters.

Our responsibilities for the audit of the financial statements

Our objective is to plan and perform the audit engagement in a manner that allows us to obtain sufficient and appropriate audit evidence for our opinion.

Our audit has been performed with a high, but not absolute, level of assurance, which means we may not detect all material misstatements, whether due to fraud or error during our audit.

Misstatements can arise from fraud or error and are considered material if, individually or in the aggregate, they could reasonably be expected to influence the economic decisions of users taken on the basis of these financial statements. The materiality affects the nature, timing and extent of our audit procedures and the evaluation of the effect of identified misstatements on our opinion.

We have exercised professional judgment and have maintained professional skepticism throughout the audit, in accordance with Dutch Standards on Auditing, ethical requirements and independence requirements. The Information in support of our opinion section above includes an informative summary of our responsibilities and the work performed as the basis for our opinion.

Our audit further included among others:

• Performing audit procedures responsive to the risks identified, and obtaining audit evidence that is sufficient and appropriate to provide a basis for our opinion
• Obtaining an understanding of internal control relevant to the audit in order to design audit procedures that are appropriate in the circumstances, but not for the purpose of expressing an opinion on the effectiveness of the company’s internal control
• Evaluating the appropriateness of accounting policies used and the reasonableness of accounting estimates and related disclosures made by management
• Evaluating the overall presentation, structure and content of the financial statements, including the disclosures
• Evaluating whether the financial statements represent the underlying transactions and events in a manner that achieves fair presentation

Communication

We communicate with the Board of Directors regarding, among other matters, the planned scope and timing of the audit and significant audit findings, including any significant findings in internal control that we identify during our audit. In this respect we also submit an additional report to the Audit and Compliance Committee of the Board of Directors in accordance with Article 11 of the EU Regulation on specific requirements regarding statutory audit of public-interest entities. The information included in this additional report is consistent with our audit opinion in this auditor’s report.

We provide the Audit and Compliance Committee of the Board of Directors with a statement that we have complied with relevant ethical requirements regarding independence, and to communicate with them all relationships and other matters that may reasonably be thought to bear on our independence, and where applicable, related safeguards.

From the matters communicated with the Board of Directors, we determine the key audit matters: those matters that were of most significance in the audit of the financial statements. We describe these matters in our auditor’s report unless law or regulation precludes public disclosure about the matter or when, in extremely rare circumstances, not communicating the matter is in the public interest.

Report on other legal and regulatory requirements and ESEF

Engagement

We were appointed by the general meeting as auditor of argenx SE on May 7, 2024, as of the audit for the year 2025.

No prohibited non-audit services

We have not provided prohibited non-audit services as referred to in Article 5(1) of the EU Regulation on specific requirements regarding statutory audit of public-interest entities.

European Single Electronic Reporting Format (ESEF)

argenx SE has prepared the annual report in ESEF. The requirements for this are set out in the Delegated Regulation (EU) 2019/815 with regard to regulatory technical standards on the specification of a single electronic reporting format (hereinafter: the RTS on ESEF).

In our opinion the annual report prepared in the XHTML format, including the (partially) marked-up consolidated financial statements as included in the reporting package by argenx SE, complies in all material respects with the RTS on ESEF.

Management is responsible for preparing the annual report, including the financial statements, in accordance with the RTS on ESEF, whereby management combines the various components into a single reporting package.

Our responsibility is to obtain reasonable assurance for our opinion whether the annual report in this reporting package complies with the RTS on ESEF.

We performed our examination in accordance with Dutch law, including Dutch Standard 3950N, “Assurance-opdrachten inzake het voldoen aan de criteria voor het opstellen van een digitaal verantwoordingsdocument” (assurance engagements relating to compliance with criteria for digital reporting). Our examination included amongst others:

• Obtaining an understanding of the company’s financial reporting process, including the preparation of the reporting package
• Identifying and assessing the risks that the annual report does not comply in all material respects with the RTS on ESEF and designing and performing further assurance procedures responsive to those risks to provide a basis for our opinion, including:

• Obtaining the reporting package and performing validations to determine whether the reporting package containing the Inline XBRL instance document and the XBRL extension taxonomy files, has been prepared in accordance with the technical specifications as included in the RTS on ESEF
• Examining the information related to the consolidated financial statements in the reporting package to determine whether all required mark-ups have been applied and whether these are in accordance with the RTS on ESEF.

Eindhoven, March 19, 2026
EY Accountants B.V.

signed by J. C. F. Lemmens