argenx agrees to buy peptide biotech Unnatural Products for up to USD 1.15bn
The European immunology group is buying the Santa Cruz company it already part-owns, betting that peptides can bring oral and long-acting drugs alongside its antibodies.
argenx announced on 9 November 2026 a definitive agreement to acquire Unnatural Products, Inc. (UNP), a California biotech with a macrocyclic peptide discovery platform. argenx already holds a minority stake and will buy the remaining shares.
The terms are USD 550 million upfront, paid from cash on hand, plus up to USD 595 million tied to development and regulatory milestones, for total potential consideration of up to about USD 1.15 billion. Both boards have approved the deal, which is expected to close by the end of 2026. UNP's own release and Reuters confirmed the transaction.
What argenx is buying
Macrocyclic peptides are ring-shaped molecules built from amino acids. The ring locks the molecule into a stable shape, which can help it resist breakdown in the body and bind targets tightly and selectively. UNP, based in Santa Cruz, combines parallel experimentation with machine learning to tackle the medicinal chemistry of these molecules and is developing a portfolio aimed at targets that have been hard to drug, according to the companies.
For argenx, the attraction is format. Its business is built on antibodies, including the first approved antibody fragment targeting the neonatal Fc receptor (FcRn). Antibodies are typically injected or infused. Peptides open the possibility of oral or long-acting medicines for people with serious immune-mediated diseases, which argenx explicitly cites as the rationale.
Built on a two-year relationship
The deal is not a cold acquisition. The two companies have collaborated for more than two years, and argenx invested in UNP before agreeing to buy it outright. Chief executive Karen Massey said argenx is "investing with discipline where it will count the most for patients" and that UNP's capabilities are "highly complementary" to its antibody engineering. UNP co-founder and CEO Cameron Pye called the agreement "a tremendous milestone" for the company.
After closing, UNP's team and leadership will stay in Santa Cruz, which becomes argenx's home for peptide discovery. UNP will continue to lead discovery work within an agreed strategic framework, while argenx brings clinical development and commercialisation. Morgan Stanley is exclusive financial adviser and DLA Piper legal adviser to argenx; Latham & Watkins advises UNP.
How the deal is structured
Slightly more than half of the headline value is contingent. The USD 595 million in milestones is only payable if specified development and regulatory goals are met, which limits argenx's upfront exposure to an early-stage platform whose medicines have not yet reached patients. argenx flagged the announcement as inside information under the EU Market Abuse Regulation.
Why it matters for European biotech
argenx is one of the few European biotechs to have grown into a commercial-stage company with a global footprint, listed on Euronext and Nasdaq. Its decision to pay up to USD 1.15 billion for platform technology rather than a late-stage asset shows a European company acting as a consolidator in the US innovation market, the reverse of the familiar pattern in which US groups buy European science.
It also adds to a busy autumn for life-science deals touching Europe, after ANI Pharmaceuticals' recommended offer for Sweden's Egetis Therapeutics. For European biotech founders, two signals stand out. Long collaborations with a strategic partner can turn into exits, and buyers are using milestone-heavy structures to share development risk. Founders negotiating with large partners should expect contingent consideration to be a large part of any headline price.
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