PROBLEM TO BE SOLVED: To provide MSPL inhibitors that can be effectively used to prevent or treat infections of various viruses, especially highly pathogenic influenza viruses.SOLUTION: Provided is an MSPL inhibitor comprising as an active ingredient at least one compound represented by the following formula (I): (R1) x- (Lys) l- (Gln) m- (Arg) n-R2 (I) (where, R1 represents a modifying group of an amino group at the N-terminal side, R2 represents a modifying group of a carboxyl group of an arginine residue at the C-terminal side, x is 0 or 1, l is an integer from 1 to 3, m is 0 or 1, as well as n is an integer from 1 to 3, and l + m + n = 4； however, when l is 2, m is 0 ).SELECTED DRAWING: NoneCOPYRIGHT: (C)2020,JPO&INPIT【課題】各種ウイルス、特に高病原性インフルエンザウイルスの感染の予防または処置に有効に利用できるＭＳＰＬ阻害剤を提供する。【解決手段】下式（Ｉ）で示される化合物の少なくとも１種を有効成分とするＭＳＰＬ阻害剤：（Ｒ１）ｘ－（Ｌｙｓ）ｌ－（Ｇｌｎ）ｍ－（Ａｒｇ）ｎ－Ｒ２（Ｉ）（式中、Ｒ１はＮ末端側のアミノ基の修飾基、Ｒ２はＣ末端のアルギニン残基のカルボキシル基の修飾基を意味する。ｘは０または１、ｌは１～３の整数、ｍは０または１、及びｎは１～３の整数であって、ｌ＋ｍ＋ｎ＝４である。但し、ｌが２のときｍは０である。）。【選択図】なし
