A peptide or peptide derivative comprising: (i) WDLYFEIVW； or (ii) a variant amino acid sequence comprising one, two, three or four L-amino acid substitutions in WDLYFEIVW； or (iii) the retro-inverso variant of the peptide or peptide derivative of either one of parts (i) and (ii), wherein said peptide or peptide derivative has procoagulant activity. A peptide or peptide derivative comprising: (i) an amino acid sequence comprising imfwydcye； or (ii) a variant amino acid sequence comprising one, two, three, four, five or six amino acid substitutions in imfwydcye, wherein said peptide or peptide derivative has procoagulant activity.一種胜肽或胜肽衍生物，其包括：(i)WDLYFEIVW；或(ii)包括一個、二個、三個或四個在WDLYFEIVW中的L-胺基酸取代的變異體胺基酸序列；或(iii)第(i)和(ii)部分之任一者之胜肽或胜肽衍生物之反-倒位變異體，其中該胜肽或胜肽衍生物具有促凝血活性。一種胜肽或胜肽衍生物，其包括：(i)包括imfwydcye的胺基酸序列；或(ii)包括一個、二個、三個、四個、五個或六個在imfwydcye的胺基酸取代的變異體胺基酸序列，其中該胜肽或胜肽衍生物具有促凝血活性。
