The present invention pertains to an immunostimulant comprising (S)-N-(4-amino-5-(quinolin-3-yl)-6,7,8,9-tetrahydropyrimido[5,4-b]indolizin-8-yl)acrylamide represented by formula (I) or salt thereof, and a pharmaceutical composition for preventing or treating a disease that can be ameliorated through immunostimulation.本發明係關於一種含有下述之式(I)所表示之(S)-N-(4-胺基-5-(喹啉-3-基)-6,7,8,9-四氫嘧啶并[5,4-b]吲哚-8-基)丙烯醯胺或其鹽作為有效成分之免疫賦活化劑、及用於預防或治療可藉由免疫賦活化而改善之疾病之醫藥組合物。
