Eli Lilly Acquires SiteOne for $1B to Advance Non-Opioid Pain Drug STC-004

Highlights

• Eli Lilly has acquired SiteOne Therapeutics in a deal worth up to $1 billion.
• The acquisition is centered on STC-004, a NaV1.8 inhibitor targeting chronic pain.
• STC-004 has completed a phase 1 trial showing it is well-tolerated and effective in pain management.
• SiteOne secured $100 million in Series C funding in late 2023 to advance its pipeline.
• Lilly is aiming to fill the gap for effective non-opioid pain treatments after previous setbacks, including the discontinued tanezumab program with Pfizer.

Strategic Move Targets Non-Opioid Pain Relief

Eli Lilly and Company has taken a significant step in its pursuit of innovative, non-opioid pain treatments with the acquisition of SiteOne Therapeutics. The deal, announced on May 27, is valued at up to $1 billion and centers around SiteOne’s lead candidate, STC-004. According to Lilly, the acquisition includes an upfront payment and potential milestone payments that could collectively total the billion-dollar figure.

As described in the company’s release, “The global burden of chronic pain continues to increase and an effective non-opioid treatment remains elusive,” stated Dr. Mark Mintun, Vice President of Neuroscience R&D at Lilly. “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.”

Focus on STC-004: A NaV1.8 Inhibitor

The acquisition is primarily aimed at STC-004, a sodium channel inhibitor that targets NaV1.8, a key ion channel found in the peripheral nervous system associated with pain signaling. This next-generation compound is designed to block pain transmission without the addictive potential of opioid-based therapies.

STC-004 recently completed a phase 1 clinical trial that demonstrated promising results. As per SiteOne's February 4 release, “a once-daily dose of the drug candidate was well-absorbed and well-tolerated, while also improving pain tolerance.” With these early signs of clinical viability, the drug is now preparing to enter phase 2 trials.

SiteOne’s Broader R&D Landscape

SiteOne Therapeutics, based in the Bay Area, raised $100 million in a Series C financing round at the end of 2023, led by Novo Holdings. These funds were earmarked for advancing its early pipeline of pain treatments, including other ion channel modulators beyond NaV1.8, such as NaV1.7.

Despite the scientific promise, other NaV1.8 inhibitors have encountered developmental hurdles. Vertex Pharmaceuticals, for instance, discontinued two such assets in 2020. Although a later candidate showed statistically significant results in two phase 3 trials, it ultimately failed to outperform the opioid Vicodin, raising questions about the clinical viability of this drug class.

Lilly's Track Record in Pain Therapeutics

This latest acquisition is not Lilly’s first foray into the pain management space. The pharmaceutical giant previously collaborated with Pfizer on tanezumab, a nerve growth factor inhibitor. Although the compound initially demonstrated efficacy in alleviating osteoarthritis pain, it was ultimately shelved after regulatory authorities in the U.S. and Europe raised concerns about potential joint damage.

Now, with the addition of SiteOne’s expertise and pipeline, Lilly is doubling down on its commitment to deliver safer, non-addictive pain solutions. The collaboration is poised to reinforce Lilly’s position in the growing non-opioid pain treatment market.