Argenx to Acquire Biotech Unnatural Products for Up to $1.15 Billion

A Conditional Portion Greater Than the Initial Payment

Argenx announced on November 9, 2026 the signing of a definitive agreement to acquire Unnatural Products (UNP), a biotech based in Santa Cruz, California. The group, which already holds a minority stake in this company, plans to purchase all the shares it does not yet own.

The transaction values UNP at up to approximately $1.15 billion. This total breaks down into two components: an initial payment of $550 million in cash, drawn from the group's available cash, and up to $595 million in conditional payments.

The latter will only be due upon achievement of development and regulatory milestones defined in the agreement. The conditional portion therefore exceeds the initial payment: the amount actually paid will depend on the progress of UNP's programs, the outcome of which remains uncertain, as the risk factors attached to the press release point out.

To put the order of magnitude into perspective, the initial payment remains lower than net product sales for a single quarter. Argenx had published sales of $1,721 million for the third quarter on October 22, 2026, up 54% year over year.

The boards of directors of both companies have approved the transaction. Completion is expected by the end of the year, subject to the usual closing conditions: at this stage, the acquisition has therefore not yet been completed.

The group presented this press release as inside information within the meaning of the European Market Abuse Regulation. It retained Morgan Stanley as exclusive financial advisor and DLA Piper as legal advisor, while UNP is advised by Latham & Watkins.

Macrocyclic Peptides to Target Oral Treatments

The target has developed a medicinal chemistry platform dedicated to macrocyclic peptides, which combines parallel experimentation and machine learning. Founded by researchers whose academic work focused on how natural macrocycles function, UNP has built a portfolio of molecules directed against targets considered difficult to reach with drugs.

For Argenx, the interest lies in the form of future treatments. According to the press release, the acquisition broadens the means to explore new biological mechanisms and to develop oral or long-acting medicines against serious immune-mediated diseases.

“UNP brings macrocyclic peptide capabilities that are highly complementary to our antibody engineering and opens new possibilities for oral and long-acting medicines,” said Karen Massey, Chief Executive Officer of Argenx. She added that the group was investing “with discipline where it will matter most for patients.”

The transaction extends an existing relationship. The executive indicated that the two companies had been working together for more than two years, which, in her view, allowed them to verify their compatibility in operations. Cameron Pye, CEO and co-founder of UNP, considered that Argenx offered an environment enabling the company to “accelerate and amplify” the vision of its platform.

UNP to Remain in Santa Cruz, Argenx to Take Over in the Clinic

Following completion, UNP's teams and management will continue to operate from the Santa Cruz site, which will become Argenx's peptide discovery center. UNP will retain responsibility for its discovery work, within a strategic framework agreed with Argenx.

The division of roles is explicit: Argenx will contribute its clinical development and commercialization capabilities to advance the molecules emerging from the platform. The Dutch group is behind the first approved antibody fragment targeting the neonatal Fc receptor (FcRn), the foundation of a portfolio of programs at various stages.

This approach remains central to its current clinical activity. Argenx had announced on October 19, 2026 that the results of the Phase 3 ALKIVIA study of efgartigimod in autoimmune myositis, whose primary endpoint had been met, would be presented in November.