argenx buys AI-guided peptide platform Unnatural Products for up to $1.15bn

argenx said on 9 November 2026 that it will buy Unnatural Products (UNP), the Santa Cruz, California developer of oral macrocyclic peptides, for $550 million in cash upfront and up to $595 million more in milestones². Including development and regulatory milestones, the deal is worth up to $1.15 billion¹.

The terms and the platform

The Amsterdam-based company already knew the asset well. argenx and UNP signed a multi-target research collaboration and option-to-license agreement in July 2025, valued at up to $1.5 billion, aimed mainly at shelf-stable, once-daily oral pills that mimic the precision of injectable antibodies, an FcRn inhibitor among them³. argenx had also taken a minority stake, which the takeover converts into full ownership²³.

UNP was founded in 2016 by researchers at the University of California, Santa Cruz, and employs more than 50 people¹. Its platform combines AI-guided design with massively parallel synthesis and direct-to-biology screening to produce drug-like macrocycles repeatedly and at scale¹. Macrocyclic peptides are bigger and more complex than conventional small molecules, which helps them bind difficult proteins, yet remain small enough to be taken by mouth². argenx will keep the UNP team in Santa Cruz and turn the site into its macrocyclic peptide discovery hub¹. The companies expect to close before the end of the year, subject to customary conditions³.

Chief executive Karen Massey said the peptide work is "highly complementary to our antibody engineering and creates new possibilities for oral and long-acting medicines"³. Leerink Partners analyst Thomas Smith told clients the purchase "represents potential for longer-term strategic value" and "signals further focus on pipeline growth and diversification"². argenx shares rose nearly 3% by late Monday morning to around $953².

What it means for the market

For argenx, this is the second acquisition in a few months. In July it agreed to buy Forte Biosciences for $2.2 billion, gaining FB102, an anti-CD122 antibody in mid-phase development for vitiligo and coeliac disease¹³. The company is still heavily reliant on Vyvgart, its FcRn antibody fragment for generalised myasthenia gravis and CIDP, which generated $4.5 billion in net product sales in the first nine months of the year¹². Attempts to widen the label have stalled, with a failed trial in Sjögren's disease and an FDA request for a further trial in dermatomyositis³. The UNP deal moves argenx beyond antibodies and into oral modalities¹.

For other AI-enabled discovery platforms, the deal follows a familiar sequence: a platform partners with several large drugmakers and then one of them buys it. UNP signed with Merck in 2024, argenx in 2025 and Novartis in 2026, and pharmaphorum also lists BridgeBio as a partner¹³. Investors will note how those partnerships are handled after the takeover, which none of the sources address.

The price also fits a broader appetite for oral peptides that can reach targets normally hit with intravenous drugs. Fierce Biotech points to Johnson & Johnson's Icotyde and Merck's Lipfendra as proof that the approach works, and to Gilead's $1.28 billion purchase of PepStar Therapeutics' oral IL-23 inhibitor as a recent comparable¹. The FDA has approved several macrocyclic peptide therapies, including UCB's Zilbrysq for generalised myasthenia gravis in 2023, Vyvgart's own indication².

Caveats

More than half of the headline value depends on milestones that have not been met². The sources do not name any UNP candidate or say how far its programmes have advanced, so how soon the platform will produce clinical assets for argenx is still unknown. The analyst view is framed as longer-term value rather than near-term revenue². The next fixed point is completion, which both companies expect before the end of 2026³.