argenx needs a second drug to match its first

The technology

argenx makes antibody drugs for autoimmune disease. Its product, efgartigimod (sold as Vyvgart and, in subcutaneous form, Vyvgart Hytrulo), blocks the FcRn receptor and lowers the level of IgG antibodies in the blood. That approach now has approvals in generalized myasthenia gravis of every serotype and CIDP, plus primary immune thrombocytopenia in Japan, and brought in $1.721 billion in third-quarter sales.

The company is testing the same drug across many antibody-driven diseases, and adding other molecules. It won the ALKIVIA myositis trial in August, filed in ocular myasthenia gravis, and bought FB102, an anti-CD122 antibody, with Forte Biosciences. Empasiprubart, its second clinical-stage antibody, is in phase 3 in multifocal motor neuropathy, with EMPASSION results due in December, and in CIDP.

The odds

argenx has a good record of turning efgartigimod trials into labels, but not a perfect one. In 2026 alone it reported wins in ADAPT SERON, ADAPT OCULUS and ALKIVIA's IMNM group, and it stopped the phase 3 UNITY trial in Sjögren's for futility. The DM group in ALKIVIA missed significance.

Base rates favor the near-term filings. Drugs that reach a filing get approved 90.6% of the time and rare disease filings 93.6%, according to BIO, Informa and QLS data for 2011 to 2020. Ocular MG, pediatric MG and IMNM fit that frame. FB102 in celiac disease is a phase 2 asset, where only 28.9% of programs reach phase 3 across the industry.

The money

argenx is profitable. It posted $486 million in operating profit and $506 million in net income in the third quarter. Cash and current financial assets were $3.7 billion at September 30, down from $5.2 billion at June 30 after the Forte deal. Combined R&D and SG&A is guided at about $4 billion for 2026. The company does not give sales guidance.

The profit comes with heavier spending. Third-quarter R&D was $503 million and SG&A $598 million, up from $359 million and $336 million a year earlier, and the quarter absorbed $150 million in deal costs. The U.S. accounted for about $1.47 billion of Vyvgart sales, so U.S. pricing and reimbursement matter more than any other single market.

The risks

argenx is a one-product company. Every dollar of revenue comes from efgartigimod, so any safety issue, pricing pressure or new competitor hits the whole business. The company's own filing lists competition, reimbursement rules and tariffs among its risks.

Growth is slowing as the base grows. Sales grew about 63% in the first quarter, 60% in the second and 54% in the third. New labels need to arrive on time to keep the curve up.

Pipeline breadth can also mislead. UNITY showed that FcRn blockade does not work in every autoimmune disease, and the Forte deal adds integration risk and an early asset bought at a large premium.

Our read

argenx is one of the few biotechs that has turned a single mechanism into a profitable, fast-growing business, and its 2026 record shows a team that runs trials well. The bull case rests on label count: ocular MG, pediatric MG, IMNM, and later empasiprubart, should keep Vyvgart growing for several more years. The weak spots are concentration and the first signs that efgartigimod's reach has limits. The December EMPASSION readout matters because it is the first phase 3 test of a second molecule, and a win there would make argenx less dependent on one drug.