L-4-Oxalysine hydrochloride, a natural product isolated from the culture media of *Streptomyces roseovirdofuscus* in China, has demonstrated antitumor activities.

L-4-Oxalysine counteracts the suppression of spleen lymphocyte proliferation and interleukin-6 production, induced by alpha-fetoprotein (AFP) and a one-way mixed lymphocyte culture in mice with the hepatoma-22 tumor. Additionally, in BEL-7404 human hepatoma cells, which express AFP, L-4-Oxalysine inhibits the expression of AFP mRNA.

L-4-oxalysine effectively suppresses the growth of select mouse-implanted tumors and reduces the spread of pulmonary metastasis in mouse Lewis lung carcinoma. Administering varying doses of L-4-oxalysine (I-677) at 10, 50, and 100 mg/kg over a seven-day period to mice, the most pronounced ultrastructural impacts on hepatocytes were observed on the day following the cessation of treatment. Initial findings include the accumulation of lipid droplets in hepatocytes, which progresses to a reduction in cytoplasmic matrices. However, the total area occupied by lipid droplets does not exceed 25% of the average hepatocyte section area. Notably, damage to mitochondria and rough endoplasmic reticulum (RER) was exclusively observed in groups receiving medium and high doses of L-4-oxalysine.