L-Norvaline is a non-proteinogenic amino acid, an isomer of valine, and an inhibitor of arginase and p70 ribosomal S6 kinase 1 (p70S6K1) kinase.^1,2 It inhibits arginase-mediated urea production in J774A.¹ macrophage lysates when used at a concentration of 10 mM and TNF-α-induced p70S6K1 activation in human umbilical vein endothelial cells (HUVECs) at 20 mM.¹ L-Norvaline reduces microgliosis and the level of amyloid-β fibrils in the hippocampus, as well as improves learning and memory in the Morris water maze in the 3xTg mouse model of Alzheimer’s disease.³