se.  Supplementary Material {#sup0} ======================  ######   Active hsiRNAs silence huntingtin mRNA in a concentration dependent manner in HeLa cells.  ######   Click here for additional data file.  ######   HTT00000 does not affect primary cortical neuron viability.  ######   Click here for additional data file.  ######   HTT00000 causes a slight increase in total resting microglia 0 days post injection.  ######   Click here for additional data file.  ######   HTT00000 shows limited toxicity at the site of injection at the 00 µg dose.  ######   Click here for additional data file.  ######   Detailed sequence, chemical modification patterns, and efficacy of hsiRNAs.  ######   Click here for additional data file.  ![**