Drimentine B is a terpenylated diketopiperazine antibiotic originally isolated from Actinomycete bacteria. It is active against Gram-positive and Gram-negative bacteria, fungi, and yeast, and has anthelmintic properties. Drimentine B inhibits proliferation of NS-1 murine β lymphocyte myeloma cells by 41 and 59% in vitro when used at concentrations of 50 and 100 μg ml, respectively.