Treatment agent

The present invention addresses the problem of providing a treatment agent for Merkel cell carcinoma. According to the present invention, provided is a treatment agent for Merkel cell carcinoma, the treatment agent comprising a liposome having an internal aqueous phase and an aqueous solution that is an external aqueous phase in which the liposome is dispersed, the liposome containing topotecan or a salt thereof, the lipid constituting the liposome comprising a lipid modified with polyethylene glycol, dihydrosphingomyelin, and cholesterol, the inner water phase contains ammonium salt. 本发明的课题在于提供一种默克尔细胞癌的处置剂。根据本发明，提供一种默克尔细胞癌的处置剂，该处置剂具备具有内水相的脂质体和分散脂质体的外水相即水溶液，其中，脂质体中内含托泊替康或其盐，构成脂质体的脂质包括用聚乙二醇修饰的脂质、二氢鞘磷脂及胆固醇，内水相中包含铵盐。