Abstract: An Eastern Indian Ocean marine sponge in the genus Spongia was located in the Republic of the Maldives and found to contain a structurally unprecedented macrocyclic lactone named spongistatin 1. The new perhydropyran-containing structure, as shown below, was found to be remarkably potent and specific, log molar TCI.sub.50 to <-10, against twenty human cancer cell lines in the U.S. National Cancer Institute's panel of sixty.

Abstract: A new-type of macrocyclic lactone denominated "dictyostatin 1" bearing a membered ring system is isolated from a Republic of Maldives marine sponge in the genus Spongia sp. and found to strongly inhibit the growth of an important selection of U.S. National Cancer Institute human cancer cell system and the murine P388 lymphocytic leukemia (PS ED.sub.50 3.8.times.10.sup.-4 mg/ml).

Abstract: A Southwest Indian Ocean marine sponge Spirastrella spinispirulifera (bri colored reds and purples) has been found to contain new and exceptionally active cell (human cancer) growth inhibitors spongistatin 5, spongistatin 7, spongistatin 8 and spongistatin 9. These compositions are related to spongistatin 1, which was found in a black Spongia sp. in the Porifera family. A method of treating human cancer cells with spongistatin 5 and spongistatin 7 is also disclosed.

Abstract: A black Spongia sp. in the Porifera class Demospongiae has been found to contain two new and exceptionally active cell (human cancer) growth inhibitors named spongistatin 2 and spongistatin 3. A bright colored Southwest Indian Ocean sponge Spirastrella spinispirulifera has also been found to contain related human cancer cell growth inhibitors named spongistatin 4 and spongistatin 6. A method of treating human cancer cells with spongistatin 1, spongistatin 2, spongistatin 3, spongistatin 4 and spongistatin 6 is also disclosed. The approximate mean GI.sub.50 of the disclosed compounds in the NCI cell line panel is about 10.sup.-10 .mu.g/ml.