argenx signed a definitive agreement to acquire Unnatural Products, Inc., adding a macrocyclic peptide discovery engine to the immunology company’s research capabilities.

The company already holds a minority stake in Unnatural Products and will now acquire all remaining shares in a transaction valuing the company at up to approximately $1.15 billion, combining upfront and milestone-based payments.¹

The acquisition broadens the technical paths available to argenx as it works to develop new treatments for serious immune-mediated diseases. By folding Unnatural Products’ peptide discovery platform into its existing antibody engineering work, argenx aims to pursue novel biological targets and create medicines that can be delivered orally or administered on a long-acting basis, two formats that are often difficult to achieve with antibody-based therapies alone.¹

What are the terms of the transaction?

Under the terms of the agreement, argenx is set to acquire Unnatural Products for an upfront payment of $550 million in cash on hand, with up to an additional $595 million contingent on the achievement of specified development and regulatory milestones.² Combined, the upfront and contingent payments bring the total potential consideration to approximately $1.15 billion.

The boards of directors of both companies approved the transaction and is expected to close by the end of the year, subject to customary closing conditions.¹

Morgan Stanley & Co. LLC is serving as exclusive financial advisor to argenx, with DLA Piper LLP acting as the company’s legal advisor. Latham & Watkins LLP is serving as legal counsel to Unnatural Products.¹

What does the deal add to argenx’s platform?

Unnatural Products brings macrocyclic peptide discovery capabilities that argenx describes as highly complementary to its existing antibody engineering work.² The combination is intended to open up new avenues for addressing biological targets that may not be well suited to antibody-based approaches, while also expanding the range of drug delivery formats argenx can offer patients.

In a conversation with Pharmaceutical Executive, Morten Graugaard, CEO of Orbis Medicines discussed the future of macrocyclic peptide discovery. “As emerging technologies make macrocycle design and development faster and more reliable, the modality is well positioned.”

Karen Massey, chief executive officer of argenx, frames the acquisition as a deliberate, selective investment rather than a broad expansion. “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,” Massey says. “UNP adds macrocyclic peptide capabilities that are highly complementary to our antibody engineering and creates new possibilities for oral and long-acting medicines. 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. We want to preserve what has made UNP successful while bringing the strengths of both teams together.”

The two-year working relationship that stems from argenx’s existing minority stake appears to have influenced the structure of the deal, which is designed to preserve Unnatural Products’ existing operations and culture rather than fully absorb them into argenx’s organization.

How will the two companies work together?

Following the close of the transaction, Unnatural Products’ team and leadership will continue to operate out of its Santa Cruz, California site, which is set to become argenx’s home for peptide discovery work.^1,2 Unnatural Products is expected to continue leading its own discovery efforts, operating within a strategic framework agreed upon with argenx.^1,2 For its part, argenx will contribute its clinical development and commercialization capabilities to help advance any resulting medicines toward patients.

Cameron Pye, Ph.D., chief executive officer and co-founder of Unnatural Products, casts the acquisition as validation of the company’s scientific approach since its founding. “Today is a tremendous milestone for UNP and a testament to the exceptional work of our scientists, employees, collaborators and supporters,” Pye says. “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.”

Sources

1. argenx to Acquire Unnatural Products, Inc., Adding Peptide Discovery Engine to Broaden Immunology Capabilities argenx November 9, 2026, https://argenx.com/news/2026/press-release-3398049.html
2. Unnatural Products to be Acquired by argenx for up to $1.15 Billion to Advance Next-Generation Medicines Unnatural Products Inc. November 9, 2026, https://finance.yahoo.com/healthcare/articles/unnatural-products-acquired-argenx-1-060000461.html?guccounter=1&guce_referrer=aHR0cHM6Ly93d3cuZ29vZ2xlLmNvbS8&guce_referrer_sig=AQAAAM6yps_RbpuYFclVq7uUg4XHXy75jfS28UxezSydxvDyDQjCymJYFizD_6u1WHMmpwX8960pUubsyfBHmIFC24Q7sCkcyJow_GONSrdfpBMOSJq69v6hS_Fj7MZb-5dtW1eWbxwynED4mgcbtjjZVJYEI19FoA0mQZdbVuRDBI3N