Clinical proof-of-concept results with a novel TRPA1 antagonist (LY3526318) in 3 chronic pain states

Transient receptor potential ankyrin 1 (TRPA1) is implicated in physiological and pathological nociceptive signaling, but the clinical benefit of TRPA1 antagonists in chronic pain is not clearly demonstrated. LY3526318 is an oral, potent, and selective novel TRPA1 antagonist. The Chronic Pain Master Protocol was used to evaluate the safety and efficacy of LY3526318 in 3 randomized, placebo-controlled, proof-of-concept studies in knee osteoarthritis pain (OA), chronic low back pain (CLBP), and diabetic peripheral neuropathic pain (DPNP). Participants were randomized (1:2, placebo:LY3526318, 250 mg daily) into an 8-week double-blinded period. At 4 weeks, participants treated with LY3526318 transitioned to a placebo. The primary endpoint was the self-reported daily pain intensity measured using a Numerical Rating Scale (NRS) at 4 weeks. All endpoints were collected for up to 8 weeks. Change from baseline in average weekly NRS was analyzed using Bayesian mixed model repeated measures in the OA (N = 160), CLBP (N = 159), and DPNP (N = 154) studies. Baseline characteristics were balanced between treatment arms. Mean NRS change from baseline to week 4 did not differ significantly between placebo and LY3526318; however, a numerical improvement was observed in the CLBP, not in the OA or DPNP populations. Safety analysis integrated across studies enhanced understanding of the safety profile of LY3526318. LY3526318 showed a potential drug-induced hepatotoxic effect posing a risk for clinical development. No other safety signals were identified. LY3526318 showed potential for different responses among chronic pain indications and patient subpopulations, highlighting challenges in developing TRPA1 antagonists but supporting their value as a target in managing chronic pain.