5-Methylthioadenosine-13C5 (5-(Methylthio)-5-deoxyadenosine-13C5) is the 13C--labeled 5-Methylthioadenosine (HY-16938). 5-Methylthioadenosine (5-(Methylthio)-5-deoxyadenosine) is a nucleoside generated from S-adenosylmethionine (SAM) during polyamine synthesis[1]. 5-Methylthioadenosine suppresses tumors by inhibiting tumor cell proliferation, invasion, and the induction of apoptosis while controlling the inflammatory micro-environments of tumor tissue. 5-Methylthioadenosine and its associated materials have striking regulatory effects on tumorigenesis[2].