Antiviral and antitumor compounds from tunicates.

Tunicates provide a rich source of biologically active compounds with potentially useful medicinal properties. The most interesting compounds identified thus far are the didemnins, depsipeptides from a Caribbean Trididemnum species, which are potent inhibitors of L1210 leukemia cells in vitro and are also active in vivo against P388 leukemia and B16 melanoma. In addition the didemnins inhibit growth of a variety of RNA and DNA viruses in vitro and protect mice infected intravaginally with herpes simplex virus type 2. Didemnin B, a derivative of didemnin A, is far more active than A, which argues for the likelihood of further useful chemical modifications in the series.