argenx reports half year 2019 financial results and second quarter business update · Enrollment on track for Phase 3 ADAPT trial of efgartigimod (ARGX-113) in generalized myasthenia gravis (gMG) patients with toplin

argenx reports half year 2019 financial results and

second quarter business update

Breda, the Netherlands / Ghent, Belgium – argenx (Euronext & Nasdaq: ARGX), a clinical-stage biotechnology company developing a deep pipeline of differentiated antibody-based therapies for the treatment of severe autoimmune diseases and cancer, today announced its financial results for the first half of 2019 and provided its second quarter business update and the outlook for the remainder of the year.

"We continue to execute on accelerating and expanding our robust, late-stage innovative clinical development programs, as we invest in forward integration across our organization to maximize value. Efgartigimod is the most advanced and also the broadest FcRn antagonist program with four indications and both intravenous and subcutaneous formulations. Enrollment for the Phase 3 ADAPT trial in generalized myasthenia gravis is progressing as planned and we are on track to initiate before the end of the year the first of two pivotal Phase 3 trials, ADVANCE, for our global primary immune thrombocytopenia program, as well as a Phase 2 trial in chronic inflammatory demyelinating polyneuropathy. Our Phase 2 trial of efgartigimod in pemphigus vulgaris remains a priority, and we expect to report topline data in the first half of 2020," commented Tim Van Hauwermeiren, CEO of argenx. "As we move towards becoming a fully-integrated biotechnology company, we continue to invest in commercial infrastructure with the build-out of our neuromuscular and hematology franchises and the expansion of our global supply chain through our longstanding collaboration with Lonza, which is expected to support the commercial launch of efgartigimod in generalized myasthenia gravis in 2021."

SECOND QUARTER 2019 AND RECENT HIGHLIGHTS

During its 2019 R&D Day in May, argenx announced its plan to become a fully integrated, global immunology company in accordance with its “argenx 2021” vision, which includes building two successful commercial franchises in neuromuscular and hematological disorders.

Efgartigimod (ARGX-113): Potential to be best-in-class with broad applicability

Efgartigimod is a human IgG1 Fc fragment engineered to increase affinity for FcRn versus endogenous IgG, whilst preserving characteristic pH-dependent binding, which may contribute to efgartigimod's relatively long serum half-life and pharmacodynamic effect, and may promote tissue penetration. Treatment with efgartigimod results in a targeted reduction of IgG autoantibodies and is a rational approach to diseases where IgGs are directly pathogenic. argenx is evaluating efgartigimod as a potential treatment for four high-value indications, including:

argenx entered into a global collaboration with Halozyme in February 2019 to develop a SC formulation of efgartigimod using Halozyme's proprietary ENHANZE® drug delivery technology, gaining exclusive rights to the technology for the FcRn target.

Cusatuzumab (ARGX-110): First-in-class opportunity in acute myeloid leukemia (AML)

Cusatuzumab is a first-in-class monoclonal antibody inhibiting CD70, a target that is uniquely present on both leukemic stem cells and AML blasts but not healthy cells. It is being developed under an exclusive global collaboration and license agreement with Janssen for the treatment of AML, high-risk myelodysplastic syndromes and other hematological malignancies.

Early Development Programs

argenx announced during its R&D Day the expansion of its product pipeline with the addition of two new proprietary therapeutic candidates, ARGX-117 and ARGX-118. Both emerged from argenx's Innovative Access Program, in which it collaborates closely with disease biology experts, bringing the argenx cutting-edge antibody discovery and engineering technologies to the heart of novel target research.

HALF YEAR 2019 FINANCIAL RESULTS (CONSOLIDATED)

On June 30, 2019, cash, cash equivalents and current financial assets totaled €944.3 million, compared to €564.6 million on December 31, 2018. The increase in cash, cash equivalents and current financial assets resulted primarily from the closing of the exclusive global collaboration and license agreement for cusatuzumab with Janssen which resulted in a $300 million upfront payment and a $200 million equity investment in January 2019.

Total operating income increased by €30.8 million for the six months ended June 30, 2019 to reach €51.3 million, compared to €20.5 million for the six months ended June 30, 2018. The increase is primarily related to (i) a €16.0 million increase in the recognition of milestone payments following the initiation of a first-in-human clinical trial with ABBV-151 (formerly named ARGX-115) under the AbbVie collaboration, which triggered a $30 million milestone payment, (ii) an increase of €7.8 million related to the recognition of research and development service fees under the Janssen collaboration and (iii) an increase of €5.2 million, mainly driven by higher payroll tax rebates for employing certain research and development personnel.

Research and development expenses totaled €78.3 million and €34.4 million for the six months ended June 30, 2019 and 2018 respectively. The increase in the first six months of 2019 resulted primarily from higher external research and development expenses and personnel expenses, reflecting higher clinical trials costs and manufacturing expenses related to the development of argenx's product candidate portfolio and the recruitment of additional employees to support research and development activities.

Selling, general and administrative expenses totaled €27.5 million and €11.5 million for the six months ended June 30, 2019 and 2018, respectively. The increase of €16.0 million in selling, general and administrative expenses for the six months ended June 30, 2019 primarily resulted from higher personnel expenses and consulting fees related to the preparation of a possible future commercialization of argenx's lead product candidate efgartigimod.

For the six months ended June 30, 2019, financial income amounted to €7.2 million, compared to €1.3 million for the six months ended June 30, 2018. The increase of €5.9 million in the first six months of 2019 related primarily to an increase in the interest received on cash, cash equivalents and current financial assets.

Exchange gains totaled €2.5 million for the six months ended June 30, 2019, compared to the €4.0 million for the six months ended June 30, 2018 and were mainly attributable to unrealized exchange rate gains on argenx's cash and current financial assets position in U.S. Dollars due to the favorable fluctuation of the EUR/USD exchange rate in the first six months of 2019.

The total comprehensive loss for the six months ended June 30, 2019 was €45.1 million, compared to €20.1 million for the six months ended June 30, 2018.

The 90 day average number of shares outstanding per June 30, 2019 was 38,026,040.

Based on the current objectives of the Company's business plan, argenx expects that its existing cash, cash equivalents and investments will fund planned operating and capital expense requirements into 2021. With the launch of a second global Phase 3 trial for efgartigimod, the execution of the development plan for cusatuzumab, the build-out of the commercial organization, and the expansion of the Company's ambition level within its growing business plan, argenx expects operating and capital expense requirements to continue to increase year-over-year.

U.S. SEC and Statutory Financial Reporting

argenx's primary accounting framework is International Financial Reporting Standards (IFRS) as issued by the International Accounting Standards Board (IASB). Unaudited condensed half yearly interim financial statements prepared in accordance with International Accounting Standards IAS 34 Interim Financial Reporting are available on www.argenx.com.

In addition to reporting financial figures in accordance with IFRS as issued by the IASB, argenx also reports financial figures in accordance with IFRS as adopted by the European Union (EU) for statutory purposes. The unaudited condensed consolidated statement of financial position, the unaudited condensed consolidated statements of profit and loss and other comprehensive income, the unaudited condensed consolidated statements of cashflow, and the unaudited condensed consolidated statement of changes in equity are not affected by any differences between IFRS as issued by the IASB and IFRS as adopted by the EU.

The condensed consolidated statement of profit and loss and other comprehensive income for the six months ended June 30, 2019 presented in this press release is unaudited.

2019 FINANCIAL CALENDAR

CONFERENCE CALL DETAILS

The half year results will be discussed during a conference call and webcast presentation today at 3:00 pm CEST/9:00 am ET. To participate in the conference call and Q&A session, please select your phone number provided below and use the confirmation code 7539308. The live webcast may be accessed on the homepage of the argenx website at www.argenx.com or by clicking here.

argenx is a clinical-stage biotechnology company developing a deep pipeline of differentiated antibody-based therapies for the treatment of severe auto-immune diseases and cancer. The company is focused on developing product candidates with the potential to be either first-in-class

against novel targets or best-in-class against known, but complex, targets in order to treat diseases with a significant unmet medical need. argenx's ability to execute on this focus is enabled by its suite of differentiated technologies. The SIMPLE AntibodyTM Platform, based on the powerful llama immune system, allows argenx to exploit novel and complex targets, and its three complementary Fc engineering technologies are designed to expand the therapeutic index of its product candidates.

For further information, please contact:

Beth DelGiacco, Vice President, Investor Relations

Marieke Vermeersch, Corporate Communications & Investor Relations Consultant

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 “believes,” “estimates,” “anticipates,” “expects,” “intends,” “may,” “will,” or “should” and include statements argenx makes concerning its financial condition, results of operation and business outlook; the sufficiency of its cash, cash equivalents and current financial assets; its 2019 business and financial calendar and related plans; the clinical data of its product candidates; the intended results of its strategy; the momentum of its product candidate pipeline as well as argenx's, and its collaboration partners', advancement of, and anticipated clinical development, data readouts and regulatory milestones and plans, including the timing of planned clinical trials and expected data readouts; and interaction with regulators, including the potential approval of its current or future drug candidates. 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 argenx's expectations regarding its the inherent uncertainties associated with competitive developments, preclinical and clinical trial and product development activities and regulatory approval requirements; argenx's reliance on collaborations with third parties; estimating the commercial potential of argenx's product candidates; argenx's ability to obtain and maintain protection of intellectual property for its technologies and drugs; argenx's limited operating history; and argenx's ability to obtain additional funding for operations and to complete the development and commercialization of its product candidates. A further list and description of these risks, uncertainties and other risks can be found in argenx's U.S. Securities and Exchange Commission (SEC) filings and reports, including in argenx's most recent annual report on Form 20-F filed with the SEC as well as subsequent filings and reports filed by argenx with the SEC. Given these uncertainties, the reader is advised not to place any undue reliance on such forward-looking statements. These forward-looking statements speak only as of the date of publication of this document. argenx undertakes no obligation to publicly update or revise the information in this press release, including any forward-looking statements, except as may be required by law.