GTS-21 (DMXBA or DMXB-A; 3-(2,4-dimethoxybenzylidene)anabaseine) is a synthetic derivative of anabaseine, a nicotinic toxin found in marine animals. It has been characterised as a selective partial agonist at alpha7 nicotinic acetylcholine receptors and, at rat receptors, also as a moderately potent antagonist at alpha4-beta2 receptors. Research has examined it in rodent cognition models, an auditory sensory gating model in DBA/2 mice, a transgenic Alzheimer's disease mouse model and in vitro inflammatory signalling in human and mouse immune cells. It has also been evaluated in a phase 2 clinical trial in schizophrenia.