Argenx Expands Immunology Capabilities with Up-to-$1.15B UNP Acquisition

More than a year after they began partnering to develop oral macrocyclic peptides against multiple historically “undruggable” targets, Argenx has agreed to acquire Unnatural Products (UNP) for up to $1.15 billion, the companies said.

The deal—Argenx’s second planned acquisition announced in nearly four months—is designed to marry UNP’s macrocyclic peptide discovery platform with Argenx’s immunology innovation capabilities to broaden the buyer’s ability to develop oral or long-acting treatments for serious immune-mediated diseases. The buyout would transform Argenx from a minority stakeholder in privately held UNP to the sole owner of its shares.

Argenx is looking to diversify its pipeline beyond its antibody-based portfolio, which is led by the blockbuster franchise consisting of marketed drugs Vyvgart^® (efgartigimod alfa-fcab) injection, indicated to treat adults with generalized myasthenia gravis (gMG); and Vyvgart Hytrulo^® (efgartigimod alfa and hyaluronidase-qvfc), a subcutaneous treatment combination of the neonatal Fc receptor inhibitor (FcRn) and endoglycosidase that is indicated for gMG and chronic inflammatory demyelinating polyneuropathy (CIDP).

The Vygart/Vyvgart Hytrulo franchise generated $4.534 billion in net product sales during the first nine months of 2026—up 58% from $2.866 billion in January-September a year ago. During the third quarter, Argenx racked up $1.721 billion, up 53% from $1.127 billion in Q3 2025.

“Our ambition is to be the leading immunology innovation company, and as Argenx builds its next chapter, we are investing with discipline where it will count the most for patients,” Argenx CEO Karen Massey said in a statement.

‘Shots on goal’

Argenx’s acquisition of UNC builds on a collaboration launched in July 2025 to develop immunology drugs: “What the platform’s about is being able to take smart shots on goal” in order to “find a successful hypothesis to weave your way through that chemical landscape to a development candidate,” Cameron Pye, PhD, UNP’s CEO and co-founder, told GEN.

The partners agreed to apply UNP’s drug discovery platform, which combines AI-guided compound design, massively parallel synthesis, and direct-to-biology screening capabilities. UNP agreed to conduct research and development until IND-enabling studies, with Argenx having the exclusive option to develop and commercialize products against these targets across multiple indications.

The companies have not disclosed details of their progress toward developing new candidates. Argenx is among UNP’s biopharma giant collaboration partners, along with:

• BridgeBio Pharma—Undisclosed value, launched in 2024 to develop macrocyclic peptides for rare diseases and oncology.
• Novartis—Up to $1.8 billion of which $100 million was paid upfront, launched in February to develop an undisclosed cardiovascular disease program.
• Merck & Co.—Undisclosed upfront payment up to $220 million in milestone payments, launched in 2024 to develop macrocyclic candidates against an oncology therapeutic target.

“After working together for more than two years, we also know there is a strong fit in how we work: science first, entrepreneurial and focused on patients,” Massey added. “We want to preserve what has made UNP successful while bringing the strengths of both teams together.”

Argenx shares traded on Euronext Brussels rose modestly on news of the deal, climbing nearly 5% Monday from €815.80 ($906.11) to €853.80 ($948.23). The company’s American depositary shares (ADSs) traded on the Nasdaq Global Select Market rose nearly 4% from $927.21 to $962.27.

On Tuesday, Argenx’ Euronext Brussels shares inched up another 1% to €863.40 ($958.89) as of 11:01 am ET, while its ADSs barely rose 0.21% to $964.27 in morning trading as of 11:15 am ET.

Skittishness and support

The modest stock bounce appeared to reflect lingering skittishness by investors following a pair of setbacks over the past month.

Argenx shares fell more than 10% on October 8 after it announced it was ending the Phase III UNITY trial (NCT06684847)  assessing efgartigimod subcutaneous (SC) in adults with moderate-to-severe Sjögren’s disease. Argenx followed the recommendation of UNITY’s Independent Data Monitoring Committee (IDMC) to stop the trial for futility after concluding that the study would be unable to meet its primary endpoint.

Then on October 23, the FDA jolted Argenx by requesting the company carry out an additional confirmatory registrational trial evaluating efgartigimod SC in dermatomyositis (DM). The agency reasoned that while Argenx showed positive overall results in the Phase II/III ALKIVIA trial (NCT05523167)  assessing the drug in DM, the subgroup of DM patients was too small for the results to achieve statistical significance.

In contrast to the investor reaction, Thomas J. Smith, senior managing director, immunology and metabolism, and a senior research analyst with Leerink Partners, voiced support for the planned acquisition.

“We like this deal for ARGX as it brings engineering and design capabilities to generate macrocyclic peptides (i.e., oral, long-acting, etc.), signaling confidence in oral FcRn potential and expanding on the company’s early-stage pipeline with potential for further modalities beyond specialized antibodies,” Smith wrote Monday in a research note.

“We believe the deal represents potential for longer-term strategic value given both I&I and large pharma’s focus on oral and long-acting therapeutics capable of driving enhanced efficacy with improved convenience vs. conventional biologics,” Smith added.

Pye and Joshua Schwochert, PhD, co-founded UNP in 2016, launching the company in a garage on the west side of Santa Cruz, CA, during their final year of doctoral research in the lab of Scott Lokey, PhD, at the University of California, Santa Cruz. Lokey’s research group focuses on understanding the relationship of stereochemistry and N-Methylation patterns pertaining to cell permeability, as well as applying the relationship to create diverse and permeable drug scaffolds with exquisite selectivity that constrained peptides can offer.

UNP raised $32 million in a Series A financing completed in 2023 and led by Merck Global Health Innovation Fund and TechBio-focused ARTIS Ventures.

Second acquisition

If the deal is completed as planned, UNC would be Argenx’s second acquisition this year. The first is Forte Biosciences, a developer of targeted immunotherapies for autoimmune and autoimmune-related diseases. Argenx on August 27 completed its up to $2.2 billion acquisition of Forte, in a deal also intended to expand the buyer’s immunology portfolio with a pipeline led by FB102, a first-in-class anti-CD122 monoclonal antibody that has shown promising early clinical stage data.

Argenx agreed to acquire UNP for $550 million in upfront cash, plus up to $595 million in payments tied to achieving specified development and regulatory milestones.

The boards of both companies have approved the transaction, which is expected to be completed by year’s end subject to customary closing conditions.

Following closing of the deal, UNP’s staff and leadership will continue to operate from its Santa Cruz, CA, site, which will serve as Argenx’s hub for peptide discovery. UNP will continue to lead its discovery work within a strategic framework agreed upon with Argenx, which will bring clinical development and commercialization capabilities to advance peptide treatments to patients.

“Today is a tremendous milestone for UNP and a testament to the exceptional work of our scientists, employees, collaborators and supporters,” CEO Pye stated. “From the earliest days, we believed our platform had the potential to redefine what is possible in the discovery and design of new medicines. I am so proud of what our team has accomplished and believe Argenx provides the ideal environment to accelerate and amplify that vision to bring innovative therapies to patients.”

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