(±)-RK-682 (150627-37-5) is a protein tyrosine phosphatase inhibitor (IC50‘s = 54 7 µM for CD45, 2.0 μM for VHR; did not inhibit cdc25B) originally isolated from the fermentation of Streptomyces sp. 88-682. Inhibits cell cycle at G1/S. RK-682 has also been shown to inhibit PLA2 (IC50 = 16 μM), HIV-1 protease (IC50 = 84 μlM), and heparanase (IC50 = 17 μM). Natural RK-682 (R-isomer) and synthetic racemic material have identical phosphatase activity. Care should be taken when using RK-682 in the presence of metal salts – because it readily forms metal complexes that affects its phosphatase inhibitory activity. RK-682 has been identified as a potential promiscuous inhibitor.