Eli Lilly to expand pain portfolio with SiteOne acquisition

Published: 28-May-2025

The acquisition adds a promising a non-opioid treatment option for chronic pain to the company’s pipeline

Eli Lilly has reached a definitive agreement to acquire SiteOne Therapeutics. The company is a major US-based global pharmaceutical company.  

SiteOne is a private biotechnology company focused on developing small molecule inhibitors of sodium channels for the treatment of pain and other neuronal hyperexcitability disorders.

SiteOne Therapeutics is advancing STC-004, a Phase 2-ready Nav1.8 inhibitor designed to address chronic pain through a novel, non-opioid mechanism.

This acquisition aims to bolster Lilly’s neuroscience pipeline, particularly in the area of pain management, by adding a potential next-generation therapeutic alternative to opioids.

The company has reached a definitive agreement to acquire SiteOne Therapeutics

This announcement is another growth step from Lilly, which made a historic announcement to invest $50bn in US manufacturing expansion with four new sites.

Mark Mintun, Group VP of Neuroscience Research and Development at Lilly, said: “The global burden of chronic pain continues to increase, and an effective non-opioid treatment remains elusive. Lilly is eager to continue the development of STC-004 with the outstanding SiteOne team as part of our efforts to advance novel, addiction-free pain therapies. Innovation in pain management is critical to address the unmet needs of millions of patients around the world.”

Under the terms of the agreement, Lilly will acquire SiteOne, with SiteOne shareholders eligible to receive up to $1.0 billion in cash. This sum includes an upfront payment alongside subsequent milestone payments contingent upon regulatory and commercial achievements.

Under the terms of the agreement, Lilly will acquire SiteOne, with SiteOne shareholders eligible to receive up to $1.0 billion in cash

John Mulcahy, PhD, CEO and co-founder of SiteOne Therapeutics, said: “At SiteOne, we’ve spent more than a decade advancing a vision to deliver safer, more effective, non-opioid therapies for patients suffering from pain and other sensory hyperexcitability disorders. 

“Lilly shares our deep commitment to scientific rigour, innovation, and patient-centred drug development. We believe their global capabilities and neuroscience leadership will accelerate our efforts to realise the full potential of STC-004 and our broader platform. This acquisition reflects the expertise and dedication of the SiteOne team and marks an exciting new chapter in our mission to transform pain treatment.”

The acquisition remains subject to customary closing conditions.

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