RG3039 is a brain-penetrant and potent inhibitor against the scavenger mRNA-decapping enzyme DcpS (m7GpppX diphosphatase) in vitro (mouse DcpS IC50 = 3.4 nM) and in mice in vivo (∼90% & ∼80% inhibition of brain DcpS, respectively, 2 h & 72 h post last 3 mg/kg daily ip. from P1 to P10). In a murine severe spinal muscular atrophy (SMA) model, RG3039 (10-20 mg/kg/d ip. from P1 till death) increases SMAΔ7 mice survival (by 26%) and motor function with a ∼50% increase of VGLUT1 synapses number on L3-L5 motor neurons (33.7/WT mice at P13 vs. 17.2/SMA mice without 26.1/SMA mice with RG3039 treatment).
