To evaluate the selectivity of 31e towards other cancer cells and normal human cells, the antiproliferative activities against Pc9 (human non-small cell lung cancer cells), Hela (human epithelial cervical cancer cells), SJSA1 (human osteosarcoma cells), LO2 (human normal cells), and HLF (human embryonic lung fibroblast cells) were examined. Here, PCSK9 is linked to cancer.