Cycloguanil-d6 (Chlorguanide triazine-d6) is the deuterium labeled Cycloguanil (HY-12784). Cycloguanil is a dihydrofolate reductase (DHFR) inhibitor with an IC50 of 10.8 µM against human DHFR. Cycloguanil blocks the folate metabolic pathway, thereby affecting nucleotide synthesis and interfering with DNA replication. Cycloguanil inhibits DHFR in Plasmodium and is thus used in malaria research. Cycloguanil also potently inhibits DHFR in human cancer cells and blocks the transcriptional activity of STAT3, thereby exhibiting anticancer activity[1][2].