Lilly takes on Vertex in non-opioid pain with SiteOne buy

Eli Lilly has reached a deal to acquire SiteOne Therapeutics that would give it control of a non-opioid pain drug that would compete with a recently approved therapy from Vertex Pharma.

The all-cash deal, worth up to $1 billion, would give Lilly rights to a sodium channel-targeting therapy for chronic pain called STC-004 that recently generated positive results in a phase 1 trial and is being developed for acute and chronic pain.

Like Vertex's Journavx (suzetrigine), cleared by the FDA in February for moderate-to-severe acute pain, STC-004 is an oral inhibitor of the NaV1.8 sodium channel, blocking a pain-signalling pathway in the peripheral nervous system before the impulses reach the brain.

Vertex also has the ambition to extend the use of suzetrigine into the chronic pain setting, but the results of a phase 2 trial involving patients with lumbosacral radiculopathy, a form of chronic, neuropathic pain, disappointed investors and led to a sell-off in its shares. It is also testing the drug for pain relief in diabetic peripheral neuropathy (DPN).

Nevertheless, Journavx represents the first new class of pain medicine in the US in more than 20 years and sodium channel inhibitors as a group have been held up as potentially important in the fight against the ongoing opioid crisis in the US, as they seem to tackle pain without any evidence that their use can lead to addiction.

Lilly's offer to acquire South San Francisco-based SiteOne includes an undisclosed upfront payment as well as regulatory and commercial milestones and, according to the buyer, will "augment Lilly's efforts to advance non-opioid medicines for pain management" which includes SSTR4 agonist mazisotine, P2X7 inhibitor LY3857210, and epiregulin antibody LY3848575 in mid-stage testing and an AT2R antagonist in phase 1. It hasn't said when it expects the takeover deal to close.

SiteOne said in February that STC-004 was well tolerated at all doses tested in its phase 1 trial, had a profile that suggested it would be suitable for once-daily dosing, and showed preliminary signs of efficacy in an experimental pain model known as the cold pressor test, in which a hand is submerged in ice water to assess physiological responses.

The company is also developing drug candidates against a second sodium channel known as NaV1.7, which could also be a target for pain relief. In something of a twist to the tale, SiteOne has an existing licensing agreement with Vertex for that programme, which dates back to 2022.

The takeover approach also follows a $100 million Series C fundraising that SiteOne completed in December and was led by Novo Holdings. At the time, SiteOne said it was "exploring the potential of sodium channels and other genetically and clinically validated targets to treat pain and sensory hyperexcitability disorders."