definiens: means a single stranded chemically modified oligonucleotide and/or analogdesigned to cause target mRNA cleavage via the RISC or RNAi mechanism . For purposes of clarity, an ssRNAicompound does not include oligonucleotides ( or chemically modified oligonucleotide analogs ) designed to workvia other mechanisms such as ( i ) RNase H 1 or 2 ( including any oligonucleotide which has [ * * * ] ) ; ( ii ) alteration ofsplicing ; ( iii ) translation arrest ( excluding RNAi - mediated repression of translation ) ; ( iv ) alteration of processing;(v ) polyadenylation ; ( vi ) capping ; ( vii ) modulation of pre - mRNA processing of the target mRNA ; or(viii ) oligonucleotides ( or chemically modified oligonucleotide analogs ) designed to mimic a known naturallyoccurring microRNA