Chlamydocin is a histone deacetylase (HDAC) inhibitor that was originally isolated from D. chlamydosporia and has anticancer properties.1 It is selective for HDAC1 over HDAC6 (IC50 = 0.15 and 1,100 nM, respectively).2 Chlamydocin increases acetylation of histone H3 and histone H4 in A2780 cells when used at concentrations ranging from 1 to 1,000 nM.1 It inhibits growth of A2780, Malme-3M, MCF-7, HT-29, and HeLa cancer cells (IC50s = 0.36, 45, 5.3, 4.3, and 14 nM, respectively). Chlamydocin increases lifespan by 10% in a P185 mouse allograft model when administered at doses ranging from 20 to 160 mg/kg.3

|1. De Schepper, S., Bruwiere, H., Verhulst, T., et al. Inhibition of histone deacetylases by chlamydocin induces apoptosis and proteasome-mediated degradation of survivin. J. Pharmacol. Exp. Ther. 304(2), 881-888 (2003).|2. Furumai, R., Komatsu, Y., Nishino, N., et al. Potent histone deacetylase inhibitors built from trichostatin A and cyclic tetrapeptide antibiotics including trapoxin. Proc. Natl. Acad. Sci. U.S.A. 98(1), 87-92 (2001).|3. St•helin, H., and Trippmacher, A. Cytostatic activity of chlamydocin, a rapidly inactivated cyclic tetrapeptide. Eur. J. Cancer 10(12), 801-808 (1974).