argenx to Acquire Unnatural Products in Deal Worth Up to $1.15 Billion, Adding Peptide Discovery Platform

argenx (Euronext & Nasdaq: ARGX) announced a definitive agreement to acquire Unnatural Products, Inc. (UNP), a Santa Cruz, California-based biotech whose macrocyclic peptide discovery engine the Amsterdam-based immunology company says will broaden its drug-development capabilities. The transaction values UNP at up to approximately $1.15 billion across upfront and milestone payments, according to argenx's press release.

Deal Structure

Under the terms disclosed by argenx, the company will pay $550 million upfront in cash on hand, with up to $595 million more contingent on the achievement of specified development and regulatory milestones. Adding those two figures together produces the up-to-$1.15 billion total argenx has cited for the deal ($550 million upfront plus $595 million in potential milestones, our calculation based on argenx's disclosed figures). argenx did not detail the specific milestone triggers or a payment timeline beyond describing them as tied to development and regulatory achievement.

argenx already held a minority stake in UNP before this agreement, the company said, following more than two years of collaboration and investment between the two firms. The new transaction covers the acquisition of all remaining shares in UNP.

What UNP Brings to the Table

UNP has built a platform that argenx describes as addressing the complexities of medicinal chemistry in the macrocyclic peptide space through a combination of parallel experimentation and machine learning. Fierce Biotech, in its independent reporting on the deal, described the platform as featuring AI-guided design, massively parallel synthesis and direct-to-biology screening.

According to Fierce Biotech, UNP was founded in 2016 by researchers at the University of California, Santa Cruz, and now employs more than 50 people. The outlet also reported that UNP has existing partnerships with Merck, dating to 2024, and Novartis, from 2026, and that its earlier argenx partnership fell between those two deals. Fierce Biotech further reported that argenx and UNP struck that 2025 partnership, worth up to $1.5 billion in biobucks, under which UNP used its macrocyclic peptide delivery platform to generate drug candidates against undruggable targets selected by argenx. argenx's own release says the acquisition builds on more than two years of collaboration and investment with UNP.

Leadership Comments and Post-Deal Structure

argenx said UNP's team and leadership will continue operating from its Santa Cruz site after the deal closes, and that location will become argenx's hub for peptide discovery. UNP will continue to lead its discovery work within a strategic framework agreed upon with argenx, according to the company's press release.

argenx CEO Karen Massey said in the press release that UNP adds macrocyclic peptide capabilities that are highly complementary to argenx's antibody engineering work and "creates new possibilities for oral and long-acting medicines." UNP CEO and Co-Founder Cameron Pye, Ph.D., called the announcement "a tremendous milestone for UNP and a testament to the exceptional work of our scientists, employees, collaborators and supporters," per the same release.

Timeline and Advisors

The boards of directors of both companies have approved the transaction, and argenx said the acquisition is expected to close by the end of the year, subject to customary closing conditions. The press release did not specify additional regulatory approvals or conditions beyond that general reference.

Morgan Stanley & Co. LLC is serving as exclusive financial advisor to argenx, with DLA Piper LLP acting as argenx's legal advisor. Latham & Watkins LLP is serving as legal counsel to UNP, according to argenx's announcement.

Industry Context

Fierce Biotech placed the deal within a broader industry trend toward oral peptide therapeutics, noting that macrocyclic peptides can enable oral delivery of drugs that have traditionally required intravenous administration, pointing to Johnson & Johnson's Icotyde and Merck's Lipfendra as examples. The outlet also reported that this capability, the ability of such peptides to survive the gut and hit targets usually engaged by IV products, has driven related dealmaking, citing Gilead's recent $1.28 billion acquisition of PepStar Therapeutics' oral IL-23 inhibitor as a comparable transaction.

Fierce Biotech also noted that argenx is best known for Vyvgart, an anti-FcRn antibody fragment approved for generalized myasthenia gravis and chronic inflammatory demyelinating polyneuropathy, and that the company has been active in business development recently. The outlet pointed to argenx's July agreement to acquire Forte Biosciences for $2.2 billion, which brought argenx the anti-CD122 antibody FB102, then in mid-phase development for vitiligo and celiac disease. Taken together, the UNP and Forte transactions suggest argenx has been pursuing a strategy of adding external technology platforms and clinical assets through acquisition over the past several months, though neither company's press materials characterize this as a formal stated strategy.

Bottom Line

argenx's agreement to acquire Unnatural Products marks a shift from minority investor to full owner of a peptide-discovery platform the company has already been using under a prior collaboration. The $550 million upfront payment, with up to $595 million more tied to future milestones, puts total potential consideration at approximately $1.15 billion. The deal is expected to close by year-end, pending customary conditions, after which UNP's Santa Cruz team is set to become argenx's dedicated hub for peptide discovery work.