LM22B-10

LM22B-10 (CAS 342777-54-2) is a non-peptide, blood-brain barrier permeant, triarylmethane small molecule that co-activates tropomyosin-related kinase B (TrkB) and tropomyosin-related kinase C (TrkC) neurotrophin receptors. It was identified by Yang, Massa, and Longo at Stanford University through in silico screening with a brain-derived neurotrophic factor (BDNF) loop-domain pharmacophore, coupled with low-throughput neuronal survival screening, and was first reported in Neuropharmacology in 2016. LM22B-10 is distinguished from prior small-molecule Trk ligands, which typically activate a single receptor subtype, by its dual activation of TrkB (EC50 approximately 1.8 micromolar) and TrkC (EC50 approximately 2.5 micromolar), producing neurotrophic activity with an EC50 for neuronal survival of 200 to 300 nanomolar that exceeds the effects of recombinant BDNF and neurotrophin-3 (NT-3), individually and in combination, in hippocampal neuronal assays. The compound selectively activates TrkB and TrkC without engaging TrkA, and drives downstream Akt and ERK1/2 signaling in vitro and in vivo. Preclinical studies in aged mice demonstrated that LM22B-10 activates hippocampal and striatal TrkB and TrkC signaling, increases dendritic spine density, and supports neuronal integrity. In mouse models of Huntington's disease (R6/2 and Q140), the compound reduced intranuclear huntingtin aggregates, dendritic spine loss, microglial activation, and degeneration of medium spiny neurons while improving motor performance. In a rat controlled cortical impact model of traumatic brain injury, LM22B-10 at 10 mg/kg intraperitoneal reduced cortical cell death by approximately 59 percent and increased hippocampal doublecortin-positive neurogenesis by approximately 65 percent, with concurrent improvement in spatial memory and anxiety-related behavior in injured animals. The compound has also demonstrated corneal nerve regeneration in both healthy and diabetic mouse wound models when delivered as topical eye drops. A derivative, PTX-BD10-2, was developed by PharmatrophiX with improved oral bioavailability and has demonstrated prevention of cholinergic neuron atrophy, restoration of hippocampal long-term potentiation, and normalization of synaptic function in late-stage Alzheimer's disease mouse models (hAPPLond/Swe) following chronic oral dosing. The mechanism of TrkB/TrkC activation by LM22B-10 is not without controversy. An independent validation study using microscale thermophoresis reported weak binding to the TrkB extracellular domain (Kd approximately 83 micromolar) and failure to induce TrkB, Akt, or ERK1/2 phosphorylation in conventional blotting assays, results that contrast with the original characterization. A 2025 review in the Journal of Medicinal Chemistry proposed that LM22B-10 and related putative Trk agonists may function as positive allosteric modulators binding the transmembrane domain rather than as classical orthosteric agonists. The discrepancy remains unresolved and constitutes a significant open question in the field. LM22B-10 has not entered clinical trials; it remains a preclinical research tool. This monograph reviews the chemistry, dual-receptor pharmacology, preclinical evidence base across disease models, the mechanistic controversy, sourcing and handling considerations, and a comparative assessment of five neurotrophin receptor ligands against LM22B-10 on five competency standards.