The silencing of specific oncogenes via RNA interference (RNAi) holds great promise for the future of cancer therapy. RNAi is commonly carried out using small interfering RNA (siRNA) composed of a 19 bp duplex region with a 2-nucleotide overhang at each 3' end. This classical siRNA structure, however, can trigger non-specific effects, which has hampered the development of specific and safe RNAi therapeutics. Previously, we developed a novel siRNA structure, called asymmetric shorter-duplex siRNA (asiRNA), which did not cause the non-specific effects triggered by conventional siRNA, such as off-target gene silencing mediated by the sense strand. In this study, we first screened potent asiRNA molecules targeting the human c-MET gene, a promising anticancer target. Next, the activity of a selected asiRNA was further optimized by introducing a locked nucleic acid (LNA) to maximize the gene silencing potency. The optimized asiRNA targeted to c-MET may have potential as a specific and safe anticancer RNAi therapeutic.